Human body detection device, bed device and human body detection system

Abstract

The human body detection device comprises: a linear piezoelectric substrate, which is arranged axially along the plate in each of a plurality of regions of the plate intersecting with the direction of pressure received from the human body, and detects the pressure applied in the radial direction; a memory; and a processor connected to the memory, wherein the processor is capable of detecting the output signals of each of the piezoelectric substrates.

Description

Technical Field

[0001] The present disclosure relates to a human body detection device, a bed device, and a human body detection system. Background Art

[0002] In recent years, consideration has arisen for installing pressure-sensitive sensors on beds in hospitals and various nursing facilities to detect the presence or absence of a bedridden patient and changes in their physical condition. For example, Patent Document 1 discloses a bed device in which piezoelectric cables are arranged in a wave pattern and assembled within a mattress, enabling detection of the bedridden patient's body through the piezoelectric cables. Furthermore, Patent Document 2 discloses a biological monitoring device in which long strips of piezoelectric sensors are arranged across the width of the bed's upper surface. These piezoelectric sensors detect the bedridden patient's body and determine the patient's blood pressure and degree of arteriosclerosis.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-351781

[0004] Patent Document 2: Japanese Patent Application Laid-Open No. 10-229973 Summary of the Invention

[0005] Problems to be solved by the invention

[0006] On the other hand, the device of Patent Document 1 uses piezoelectric cables arranged in a wave pattern and assembled within the mattress. Therefore, while it can detect the presence or absence of a bedridden person, it cannot detect any deviation in the bedridden person's position. Furthermore, the device of Patent Document 2 uses long strip-shaped piezoelectric sensors arranged across the width of the bed. While it can detect the presence or absence of a bedridden person, it cannot detect any deviation in the bedridden person's position.

[0007] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a human body detection device, a bed device, and a human body detection system that use a piezoelectric material and can detect the position of a bedridden person on a bed surface.

[0008] Means for solving problems

[0009] Specific means for achieving the above-mentioned objects are as follows.

[0010] <1> A human body detection device comprising:

[0011] a linear piezoelectric substrate disposed axially along the plate in each of a plurality of regions of the plate intersecting with a direction of pressure applied from the human body, and detecting pressure applied in a radial direction;

[0012] Memory; and

[0013] a processor connected to the memory,

[0014] The processor is capable of detecting the output signals of each of the piezoelectric substrates.

[0015] <2> like <1> The human body detection device, wherein the piezoelectric substrate has:

[0016] long strips of conductor; and

[0017] The piezoelectric body is a long strip of material that is spirally wound in one direction relative to the conductor.

[0018] The pressure input to the piezoelectric body is detected based on a potential difference between the conductor and the piezoelectric body.

[0019] <3> like <2> In the human body detection device, the piezoelectric body is made of organic piezoelectric material.

[0020] <4> like <3> In the human body detection device, the piezoelectric body is a helical chiral polymer (A) having optical activity.

[0021] <5> like <4> In the human body detection device, the helical chiral polymer (A) is polylactic acid.

[0022] <6> like <2> to <5> The human body detection device described in any one of the preceding claims, wherein the piezoelectric substrate includes a covering member around the piezoelectric body.

[0023] <7> like <1> to <6> The human body detection device according to any one of the preceding claims comprises:

[0024] a pressurizing portion that contacts the piezoelectric substrate and is disposed along the plate, and is pressurized by contact with the human body; and

[0025] The base portion is adjacent to the piezoelectric substrate and is provided on the opposite side of the pressurizing portion.

[0026] <8> like <7> The human body detection device, wherein the thickness of the pressurizing portion is within the range of 0.005 to 200 mm, and the hardness of the pressurizing portion is within the range of 50 to 200 N when measured according to method A specified in JIS K6400-2.

[0027] <9> like <7> or <8> The human body detection device is characterized in that the pressurizing portion, the piezoelectric substrate, and the base portion are arranged along a pressurizing direction of the pressurizing portion.

[0028] <10> like <7> to <9> The human body detection device described in any one of the above, wherein the base is made of foam plastic.

[0029] <11> like <1> to <10> The human body detection device described in any one of the above, wherein the piezoelectric substrate is a biological information acquisition device.

[0030] <12> like <1> to <11> The human body detection device according to any one of the preceding claims, wherein a cross-sectional shape of the piezoelectric substrate perpendicular to the axial direction is a non-circular cross-sectional shape.

[0031] <13> like <12> In the human body detection device, the piezoelectric substrate has a ratio of a major axis to a minor axis in a cross section perpendicular to the axial direction of the piezoelectric substrate of 1.05 to 10.00.

[0032] <14> A bed device having <1> to <13> The human body detection device described in any one of the preceding claims.

[0033] <15> A human body detection system having:

[0034] <1> to <13> The human body detection device described in any one of the preceding claims;

[0035] The above-mentioned area arranged along a specified direction in the above-mentioned plate; and

[0036] The piezoelectric substrates disposed in the respective regions,

[0037] The processor compares output signals of the piezoelectric substrates adjacent to each other in the predetermined direction to determine movement of the human body on the plate.

[0038] Effects of the Invention

[0039] According to the present disclosure, the position of a bedridden person on the bed surface can be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] [ Figure 1 ] is a disassembled three-dimensional view of the bed device involved in the first embodiment.

[0041] [ Figure 2 ] is a top view of the human body detection device included in the bed device according to the first embodiment.

[0042] [ Figure 3 ] is a cross-sectional view of the detection part of the human body detection device.

[0043] [ Figure 4 ] is a block diagram showing the hardware structure of the information processing unit.

[0044] [ Figure 5 ] is a block diagram showing an example of the functional configuration of a CPU in a processing PC.

[0045] [ Figure 6A ] is a side view showing a specific form A of the piezoelectric substrate involved in the first embodiment.

[0046] [ Figure 6B ] is a cross-sectional view showing a specific form A of the piezoelectric substrate involved in the first embodiment ( Figure 6A XX' line cross-section).

[0047] [ Figure 7 ] is a side view showing a specific form B of the piezoelectric substrate involved in the first embodiment.

[0048] [ Figure 8 ] is a side view showing a specific form C of the piezoelectric substrate involved in the first embodiment.

[0049] [ Figure 9 ] is a top view showing the arrangement of the piezoelectric substrate in the bed device according to the second embodiment.

[0050] [ Figure 10 ] is a top view showing the arrangement of the piezoelectric substrate in the bed device according to the third embodiment.

[0051] [ Figure 11 ] is a top view showing the arrangement of the piezoelectric substrate in the bed device according to the fourth embodiment.

[0052] [ Figure 12 ] is a top view showing the configuration of the piezoelectric substrate in the bed device involved in the fifth embodiment.

[0053] [ Figure 13 ] is a graph showing the measurement results of the voltage output of each piezoelectric substrate in the bed device of Example 1.

[0054] [ Figure 14 ] to show Figure 13 A graph showing the output when the voltage output exceeds the threshold value in the measurement results.

[0055] [ Figure 15A ] is a side view showing the piezoelectric substrate involved in the sixth embodiment.

[0056] [ Figure 15B ] is a cross-sectional view showing a piezoelectric substrate according to the sixth embodiment ( Figure 15A Y-Y' line cross-sectional view).

[0057] [ Figure 16A ] is a graph showing the results of the temperature characteristic evaluation of the piezoelectric substrate of Example 2.

[0058] [ Figure 16B ] is a graph showing the results of the temperature characteristic evaluation of the piezoelectric substrate of Example 3. DETAILED DESCRIPTION

[0059] Hereinafter, embodiments of the present disclosure will be described. However, it should be noted that the present disclosure is not limited to the following embodiments.

[0060] In this specification, the numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0061] In this specification, the "principal surface" of the long flat-plate piezoelectric body (the first piezoelectric body and the second piezoelectric body) refers to the surface perpendicular to the thickness direction of the long flat-plate piezoelectric body (in other words, the surface including the length direction and width direction of the piezoelectric body).

[0062] In this specification, unless otherwise specified, a "surface" of a component refers to a "principal surface" of the component.

[0063] In this specification, thickness, width, and length are as generally defined, and satisfy the relationship of thickness < width < length.

[0064] In this specification, the angle formed by two line segments is expressed in the range of 0° to 90°.

[0065] In this specification, the term "film" is a concept that includes not only articles generally referred to as "films" but also articles generally referred to as "sheets."

[0066] <First embodiment>

[0067] As a first embodiment, based on Figures 1 to 8 , bed device 10 as a human body detection system and human body detection device 30 included in bed device 10 will be described.

[0068] [Composition of bed device]

[0069] like Figure 1 As shown, the bed device 10 of this embodiment includes a bed 20 with legs and a human body detection device 30. The bed 20 includes a frame 22 provided on the bed surface, a pair of bed boards 24 serving as plates covering the center portion of the frame 22, and a mattress 26 placed on the upper surface of the bed boards 24.

[0070] The bed board 24 is a duckboard formed by arranging short grid-shaped plate materials in the bed longitudinal direction of the bed device 10. The bed boards 24 are arranged in parallel in the bed longitudinal direction.

[0071] The mattress 26 is a sheet of polyurethane foam covered with a polyester base material. The mattress 26 is placed on the bed board 24 and the sensor unit 32 (described later), and the person lying in a recumbent position lies on the upper surface of the mattress 26. The mattress 26 of this embodiment is in contact with the piezoelectric substrate 12, which is covered with an insulating member 38 (a covering member), and is pressurized by the person's body contacting the mattress, thus acting as a pressurizing unit.

[0072] It should be noted that the pressure-receiving portion of the mattress 26 of this embodiment is made of polyurethane (polyurethane foam), but is not limited thereto and may also be made of fiber or latex. Furthermore, the pressure-receiving portion need not necessarily be the mattress 26 of the bed 20; a sheet or mat may also be employed. The thickness of the pressure-receiving portion is within the range of 0.005 to 200 mm, and the hardness of the pressure-receiving portion, as measured according to Method A specified in JIS K6400-2, is within the range of 50 to 200 N, preferably 100 to 200 N, and more preferably 110 to 170 N.

[0073] It should be noted that the hardness of the mattress 26 of this embodiment is determined as follows using Method A specified in JIS K6400-2. Specifically, the hardness of the mattress 26 is determined by laying the foam inside the mattress 26 flat, placing a circular pressure plate with a diameter of 200 mm, and pressing it down to 75% of the foam's initial thickness. The plate is then returned to its original position and pressed down again to 40% of the initial thickness. The plate is then left at rest for 30 seconds, and the load value at this point is calculated as N (Newtons).

[0074] As described above, the bed device 10 of this embodiment functions as the bed 20 by means of the frame 22 , the pair of bedboards 24 , and the mattress 26 . The sensor unit 32 is provided between the bedboard 24 and the mattress 26 , thereby being able to detect the position of a human body on the bed surface.

[0075] [Composition of human body detection device]

[0076] The human body detection device 30 of this embodiment includes: a mattress 26 as a pressurizing unit; a sensor unit 32, which is provided between the bed board 24 and the mattress 26 and can detect pressure; and an information processing unit 40, which includes a detection unit for detecting an output signal from the sensor unit 32. The sensor unit 32 is plate-shaped, such as Figure 2 and Figure 3 As shown in FIG. 1 , the sensor unit 32 is installed on the bed board 24 in such a manner that the bed width direction is the longitudinal direction. That is, the sensor unit 32 is installed in a direction intersecting with the human body in the recumbent position. The sensor unit 32 is formed so that: with the installation surface facing the bed board 24 as the reference surface 33, it can detect the pressure (see arrow P) applied in the direction intersecting with the reference surface 33 (see FIG. 1 ). Figure 3 ). In addition, Figure 2As shown, the sensor unit 32 of this embodiment is divided into four regions 34 along its length. In each region 34, a cable-shaped piezoelectric substrate 12 for detecting pressure is disposed along the length of the sensor unit 32 (the bed width). Consequently, the pressure detection range of the mattress 26 is divided into four sections along the bed width. Furthermore, the mattress 26 of this embodiment includes detection regions 27 corresponding to each region 34 (or piezoelectric substrate 12), namely, locations A through D.

[0077] The sensor unit 32 includes a support plate 36 placed on the bed plate 24 (see Figure 3 ); a cushioning material 37 as a base, which covers the upper surface of the support plate 36; and a piezoelectric substrate 12, which is provided on the upper surface of the cushioning material 37 and is surrounded by an insulating member 38. The support plate 36 is a plate-shaped member that supports the piezoelectric substrate 12 and the cushioning material 37. The length of the support plate 36 in the bed width direction is slightly shorter than the width of the bed plate 24. Figure 3 As shown, the support plate 36 of this embodiment is provided on the bed board 24 so as to straddle the bed boards 24 arranged side by side in the bed longitudinal direction.

[0078] The cushioning material 37 is a sponge sheet provided to alleviate the tension applied to the piezoelectric substrate 12. The cushioning material 37 is bonded to the support plate 36 in each region 34. Furthermore, the piezoelectric substrate 12, which is covered with an insulating member 38, is in contact with the upper surface of the cushioning material 37. Thus, in the sensor unit 32 of this embodiment, the mattress 26, the piezoelectric substrate 12, and the cushioning material 37 are arranged in this order along the direction of pressure applied by the bedridden person's body (i.e., the direction of arrow P). With the piezoelectric substrate 12 as the reference, the cushioning material 37 is provided on the opposite side of the mattress 26.

[0079] It should be noted that the cushioning material 37 of the present embodiment is provided in each of the regions 34 , but the present invention is not limited thereto. A single cushioning material 37 may be bonded to the support plate 36 so as to span all of the regions 34 .

[0080] The insulating member 38 may be a commercially available adhesive tape, a flexible and insulating film, an adhesive film, or the like. The piezoelectric substrate 12 of this embodiment is coated with a pair of insulating films. For example, the insulating member 38 may be a member coated with an acrylic or silicone adhesive material using a biaxially oriented nylon film, polyimide film, polyethylene terephthalate film, polyphenylene sulfide film, polysulfone sulfide film, polyester film, polystyrene film, or the like having a Young's modulus of 2.0 to 10 GPa and a thickness of 4 to 50 μm. The member may have an adhesive strength of 5.0 N to 30 N.

[0081] like Figure 4 As shown, the information processing unit 40 includes an AD converter 42 that converts the voltage output, which is an analog signal, from the piezoelectric substrate 12 into a digital signal, and a processing PC 50 that detects the converted digital signal from each piezoelectric substrate 12. The AD converter 42 is provided with a plurality of input terminals for inputting analog signals, and the piezoelectric substrate 12 is electrically connected to each input terminal.

[0082] The processing PC 50 includes a CPU (Central Processing Unit) 50A, a ROM (Read Only Memory) 50B, a RAM (Random Access Memory) 50C, a storage device 50D, a communication I / F (Interface) 50E, and an input / output I / F 50F. The CPU 50A, ROM 50B, RAM 50C, storage device 50D, communication I / F 50E, and input / output I / F 50F are interconnected via a bus 51 so as to be able to communicate with each other.

[0083] Here, the CPU 50A corresponds to a processor, and the RAM 50C corresponds to a memory.

[0084] The CPU 50A is a central processing unit that executes various programs or controls various parts. That is, the CPU 50A reads programs from the ROM 50B or the storage device 50D and uses the RAM 50C as a work area to execute the programs. In this embodiment, the storage device 50D stores execution programs for executing various processes. The CPU 50A executes the execution programs to serve as Figure 5 The detection unit 55, determination unit 56, and notification unit 57 shown here function.

[0085] ROM 50B stores various programs and various data. RAM 50C temporarily stores programs and data as a work area. Storage device 50D, which serves as a storage unit and is composed of a HDD (Hard Disk Drive) or an SSD (Solid State Drive), stores various programs including an operating system and various data.

[0086] The communication I / F 50E is an interface for communicating with a portable terminal such as a smartphone, and uses standards such as Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark).

[0087] The input / output I / F 50F is an interface for communicating with each device constituting the information processing unit 40. The AD converter 42, the monitor 44, and the speaker 46 are connected to the processing PC 50 of this embodiment via the input / output I / F 50F.

[0088] Figure 5 5 is a block diagram showing an example of the functional configuration of the CPU 50A. Figure 5 As shown, the CPU 50A includes a detection unit 55, a determination unit 56, and a notification unit 57. Each functional configuration is implemented by the CPU 50A reading an execution program stored in the storage device 50D and executing it.

[0089] The detection unit 55 has the function of detecting the digital signals related to each piezoelectric substrate 12 output from the AD converter 42 via the communication I / F 50E. This allows detection of where the bedridden person's body is located within the detection area 27 of the bed 20. Furthermore, the detection unit 55 converts the detected data into digitized data, thereby determining the degree of pressure applied to each detection area 27.

[0090] The determination unit 56 has the function of determining the dynamic position of a bedridden person by comparing the output signals of adjacent piezoelectric substrates 12. For example, if the voltage output of one piezoelectric substrate 12 decreases while the voltage output of an adjacent piezoelectric substrate 12 increases, the determination unit 56 determines that the bedridden person has turned over. Alternatively, if the voltage output of all piezoelectric substrates 12 decreases, the determination unit 56 determines that the bedridden person has risen from the bed device 10. Furthermore, if the voltage outputs of the piezoelectric substrates 12 at either end of the bed width are greater, the determination unit 56 determines that the bedridden person is lying sideways.

[0091] The notification unit 57 has the function of notifying the caregiver of the determination result regarding turning over, getting up, or lateral deviation of the sleeping position made by the determination unit 56. For example, the notification unit 57 can transmit the determination result to the caregiver's mobile phone via the communication I / F 50E. Furthermore, for example, the notification unit 57 can output text information related to the determination result to the monitor 44 or audio information related to the determination result to the speaker 46 via the communication I / F 50E.

[0092] [Piezoelectric substrate]

[0093] The outline of the piezoelectric substrate used for detecting pressure in bed device 10 of the present embodiment will be described.

[0094] The piezoelectric substrate of this embodiment includes a long conductor and a long first piezoelectric body spirally wound in one direction with respect to the conductor.

[0095] As the first piezoelectric body, an organic piezoelectric material can be used. As the organic piezoelectric material, both low-molecular-weight materials and high-molecular-weight materials can be used. For example, the following can be cited: polyvinylidene fluoride or polyvinylidene fluoride copolymers; polyvinylidene cyanide or vinylidene cyanide copolymers; or odd-numbered nylons such as nylon 9 and nylon 11, aromatic nylons, alicyclic nylons; or helical chiral polymers such as polylactic acid; polyhydroxycarboxylic acids such as polyhydroxybutyrate; cellulose derivatives; polyurea; and the like.

[0096] As the first piezoelectric body, from the viewpoints of good piezoelectric properties, processability, and availability, a polymer organic piezoelectric material, particularly an optically active helical chiral polymer, is preferred.

[0097] The piezoelectric substrate of the present embodiment is a piezoelectric substrate in which:

[0098] The first piezoelectric body includes an optically active helical chiral polymer (A) (hereinafter also referred to as "helical chiral polymer (A)").

[0099] The longitudinal direction of the first piezoelectric body is substantially parallel to the main orientation direction of the helical chiral polymer (A) contained in the first piezoelectric body.

[0100] The orientation degree F of the first piezoelectric body determined by the following formula (a) based on X-ray diffraction measurement is within a range of 0.5 or more and less than 1.0.

[0101] Orientation F = (180° - α) / 180° (a)

[0102] Here, α represents the half-value width of the peak derived from the orientation, and the unit of α is degree.

[0103] Hereinafter, in the description of the piezoelectric substrate of this embodiment, the “elongated conductor” may be simply referred to as the “conductor”, and the “elongated first piezoelectric body” may be simply referred to as the “first piezoelectric body”.

[0104] Here, the orientation degree F of the first piezoelectric body is an indicator of the degree of orientation of the helical chiral polymer (A) contained in the first piezoelectric body, for example, the c-axis orientation degree measured using a wide-angle X-ray diffraction device (RINT2550 manufactured by Rigaku Corporation, with attached device: rotating sample stage, X-ray source: CuKα, output: 40kV, 370mA, detector: scintillation counter).

[0105] In addition, an example of a method for measuring the orientation degree F of the first piezoelectric body is shown in Examples to be described later.

[0106] The term "one direction" in the context of the piezoelectric substrate refers to the direction in which the first piezoelectric element is wound from the near side to the far side of the conductor when the piezoelectric substrate of this embodiment is viewed from one axial end of the conductor. Specifically, this refers to either the right direction (right-handed rotation, i.e., clockwise rotation) or the left direction (left-handed rotation, i.e., counterclockwise rotation).

[0107] The piezoelectric substrate of the present embodiment has the above-described structure, and thus has excellent piezoelectric sensitivity and excellent piezoelectric output stability.

[0108] In more detail, in the piezoelectric substrate of this embodiment, piezoelectricity is exhibited by making the first piezoelectric body contain a helical chiral polymer (A), making the length direction of the first piezoelectric body roughly parallel to the main orientation direction of the helical chiral polymer (A), and making the orientation degree F of the first piezoelectric body greater than 0.5 and less than 1.0.

[0109] In addition, the piezoelectric substrate of this embodiment has a structure in which the first piezoelectric body is spirally wound in one direction with respect to a conductor.

[0110] In the piezoelectric substrate of this embodiment, by arranging the first piezoelectric body in the above-mentioned manner, when tension (stress) is applied in the longitudinal direction of the piezoelectric substrate, a shear force is applied to the helical chiral polymer (A), and polarization of the helical chiral polymer (A) occurs in the radial direction of the piezoelectric substrate. When the first piezoelectric body wound into a spiral shape is regarded as a collection of microscopic regions that can be regarded as a plane relative to its longitudinal direction, when a shear force caused by tension (stress) is applied to the helical chiral polymer on the plane constituting the microscopic regions, the polarization direction of the helical chiral polymer (A) is different from the polarization direction of the helical chiral polymer (A) due to the piezoelectric stress constant d. 14 The directions of the generated electric fields are roughly the same.

[0111] Specifically, for example, in the case of polylactic acid, a homopolymer of L-lactic acid (PLLA) whose molecular structure includes a left-handed helical structure, when tension (stress) is applied to a structure in which a first piezoelectric element, whose length direction is approximately parallel to the main orientation direction of the PLLA, is wound in a left-handed helical shape around a conductor, an electric field (polarization) is generated in a radially parallel direction from the center toward the outside of a circle of a circular cross-section perpendicular to the tension. Conversely, when tension (stress) is applied to a structure in which a first piezoelectric element, whose length direction is approximately parallel to the main orientation direction of the PLLA, is wound in a right-handed helical shape around a conductor, an electric field (polarization) is generated in a radially parallel direction from the outside toward the center of a circle of a circular cross-section perpendicular to the tension.

[0112] Furthermore, for example, in the case of a homopolymer of D-lactic acid (PDLA) whose molecular structure includes a right-handed helical structure, when tension (stress) is applied to a structure in which a first piezoelectric element, with its length direction approximately parallel to the main orientation direction of PDLA, is wound in a left-handed helical pattern around a conductor, an electric field (polarization) is generated parallel to the radial direction, extending from the outside toward the center of a circle with a circular cross-section perpendicular to the tension. Conversely, when tension (stress) is applied to a structure in which a first piezoelectric element, with its length direction approximately parallel to the main orientation direction of PDLA, is wound in a right-handed helical pattern around a conductor, an electric field (polarization) is generated parallel to the radial direction, extending from the center toward the outside of a circle with a circular cross-section perpendicular to the tension.

[0113] It is therefore considered that when tension is applied in the longitudinal direction of the piezoelectric substrate, a potential difference proportional to the tension is generated in phase at each portion of the first piezoelectric body arranged in a spiral shape, thereby effectively detecting a voltage signal proportional to the tension.

[0114] Therefore, according to the piezoelectric substrate of this embodiment, a piezoelectric substrate having excellent piezoelectric sensitivity and excellent piezoelectric output stability can be obtained.

[0115] In particular, compared with the piezoelectric substrate using pyroelectric PVDF as the helical chiral polymer (A), the piezoelectric substrate using non-pyroelectric polylactic acid-based polymer as the helical chiral polymer (A) has further improved piezoelectric sensitivity stability and piezoelectric output stability (stability over time or stability relative to temperature changes).

[0116] Furthermore, regarding the piezoelectric element having piezoelectric fibers described in Japanese Patent Application Laid-Open No. 2008-146528, the winding direction of the piezoelectric fibers relative to the conductive fibers is not limited, and the origin and direction of the force constituting the shear force are different from those of the piezoelectric substrate of this embodiment. Therefore, it is believed that even if tension is applied to the piezoelectric element described in Japanese Patent Application Laid-Open No. 2008-146528, no polarization is generated in the radial direction of the piezoelectric element, that is, the piezoelectric stress constant d is not increased. 14 Furthermore, no polarization is generated in the direction of the generated electric field, so the piezoelectric sensitivity is insufficient.

[0117] Here, the fact that the longitudinal direction of the first piezoelectric element is substantially parallel to the main orientation direction of the helical chiral polymer (A) has the advantage that the first piezoelectric element is highly resistant to stretching in the longitudinal direction (i.e., has excellent tensile strength in the longitudinal direction). Therefore, even if the first piezoelectric element is wound into a spiral shape in one direction relative to the conductor, it is unlikely to break.

[0118] Furthermore, the longitudinal direction of the first piezoelectric body is roughly parallel to the main orientation direction of the helical chiral polymer (A), which is advantageous in terms of productivity when, for example, the stretched piezoelectric film is slit to obtain the first piezoelectric body (eg, slit tape).

[0119] In this specification, the term "substantially parallel" means that the angle formed by two line segments is greater than 0° and less than 30° (preferably greater than 0° and less than 22.5°, more preferably greater than 0° and less than 10°, further preferably greater than 0° and less than 5°, and especially preferably greater than 0° and less than 3°).

[0120] In this specification, the main orientation direction of the helical chiral polymer (A) refers to the main orientation direction of the helical chiral polymer (A). The main orientation direction of the helical chiral polymer (A) can be confirmed by measuring the orientation degree F of the first piezoelectric body.

[0121] When the first piezoelectric body is produced by melt-spinning a raw material and then stretching the melted material, the main orientation direction of the helical chiral polymer (A) in the produced first piezoelectric body is referred to as the main stretching direction. The main stretching direction refers to the stretching direction.

[0122] Similarly, when the first piezoelectric body is produced by stretching a film and slitting the stretched film, the main orientation direction of the helical chiral polymer (A) in the produced first piezoelectric body is referred to as the main stretching direction. Here, the so-called main stretching direction refers to the stretching direction in the case of uniaxial stretching and the stretching direction with a higher stretching ratio in the case of biaxial stretching.

[0123] Hereinafter, a first embodiment of the piezoelectric substrate according to the present disclosure will be described in detail.

[0124] [Piezoelectric Substrate of First Embodiment]

[0125] In the piezoelectric substrate of the first embodiment, it is preferable that the long conductor is an internal conductor, and the long first piezoelectric body is spirally wound in one direction along the outer peripheral surface of the internal conductor.

[0126] By using the internal conductor as the conductor, the first piezoelectric body can be easily arranged in a spiral shape in one direction while maintaining the spiral angle β with respect to the axial direction of the internal conductor.

[0127] Here, the "helix angle β" refers to the angle formed by the axial direction of the conductor and the direction in which the first piezoelectric body is arranged relative to the axial direction of the conductor (the longitudinal direction of the first piezoelectric body).

[0128] Therefore, for example, when tension is applied in the longitudinal direction of the piezoelectric substrate, the helical chiral polymer (A) is easily polarized in the radial direction of the piezoelectric substrate. As a result, a voltage signal (charge signal) proportional to the tension can be effectively detected as an electrical characteristic.

[0129] Furthermore, the piezoelectric substrate of the above structure has the same internal structure (internal conductor and dielectric) as a coaxial cable. Therefore, when the piezoelectric substrate is applied to a coaxial cable, for example, a structure with high electromagnetic shielding properties and strong resistance to noise can be formed.

[0130] The piezoelectric substrate of the first embodiment preferably further includes a second elongated piezoelectric body spirally wound in a direction different from the one direction.

[0131] Furthermore, it is preferred that the second piezoelectric body contains an optically active helical chiral polymer (A).

[0132] The longitudinal direction of the second piezoelectric body is substantially parallel to the main orientation direction of the helical chiral polymer (A) contained in the second piezoelectric body.

[0133] The orientation degree F of the second piezoelectric body determined by X-ray diffraction measurement and the above formula (a) is in the range of 0.5 or more and less than 1.0,

[0134] The chirality of the helical chiral polymer (A) contained in the first piezoelectric body is different from the chirality of the helical chiral polymer (A) contained in the second piezoelectric body.

[0135] Thus, for example, when tension is applied in the longitudinal direction of the piezoelectric substrate, polarization occurs in both the helical chiral polymer (A) contained in the first piezoelectric layer and the helical chiral polymer (A) contained in the second piezoelectric layer. The polarization direction is radial to the piezoelectric substrate.

[0136] As a result, a voltage signal (charge signal) proportional to tension can be detected more efficiently, thereby further improving the piezoelectric sensitivity and the stability of the piezoelectric output.

[0137] In particular, when the piezoelectric substrate of the first embodiment includes a first external conductor, and the piezoelectric body has a two-layer structure comprising a first piezoelectric body and a second piezoelectric body, the gaps between the first and second piezoelectric bodies and the internal conductor and first external conductor are small, allowing for close contact. This allows the electric field generated by tension to be efficiently transmitted to the electrodes. Therefore, this is a preferred embodiment for achieving a sensor with higher sensitivity.

[0138] The piezoelectric substrate of the first embodiment preferably further includes a first insulator wound in a spiral shape along the outer circumference of the inner conductor from the viewpoint of improving the piezoelectric sensitivity and the stability of the piezoelectric output.

[0139] The first insulator is arranged on the side opposite to the internal conductor when viewed from the first piezoelectric body.

[0140] For example, when the piezoelectric substrate of the first embodiment includes a first external conductor, repeated bending or bending with a small radius of curvature can easily create gaps in the wound first piezoelectric body, potentially causing an electrical short circuit between the internal conductor and the first external conductor. In this case, providing a first insulator allows for more reliable electrical shielding between the internal conductor and the first external conductor. Furthermore, high reliability can be ensured even in applications involving bending.

[0141] The piezoelectric substrate of the first embodiment preferably further includes a second elongated piezoelectric body wound in a direction different from the one direction.

[0142] The second piezoelectric body includes an optically active helical chiral polymer (A),

[0143] The longitudinal direction of the second piezoelectric body is substantially parallel to the main orientation direction of the helical chiral polymer (A) contained in the second piezoelectric body.

[0144] The orientation degree F of the second piezoelectric body determined by X-ray diffraction measurement and the above formula (a) is in the range of 0.5 or more and less than 1.0,

[0145] The first piezoelectric body and the second piezoelectric body form a braided rope structure that alternates and crosses each other.

[0146] The chirality of the helical chiral polymer (A) contained in the first piezoelectric body is different from the chirality of the helical chiral polymer (A) contained in the second piezoelectric body.

[0147] Thus, for example, when tension is applied in the longitudinal direction of the piezoelectric substrate, polarization occurs in both the helical chiral polymer (A) contained in the first piezoelectric layer and the helical chiral polymer (A) contained in the second piezoelectric layer. The polarization direction is radial to the piezoelectric substrate.

[0148] This allows for more efficient detection of a voltage signal proportional to tension, resulting in further improvements in piezoelectric sensitivity and piezoelectric output stability.

[0149] In particular, when the piezoelectric substrate of the first embodiment includes a first external conductor and the piezoelectric body forms a braided rope structure comprising a first piezoelectric body and a second piezoelectric body, a suitable gap exists between the first and second piezoelectric bodies. Therefore, even when a force is applied that causes the piezoelectric substrate to bend and deform, the gap absorbs the deformation, making it easier for the piezoelectric substrate to bend and deform gently. Therefore, the piezoelectric substrate of the first embodiment can be suitably used as a structural component of, for example, a wearable product that extends along a three-dimensional plane.

[0150] The piezoelectric substrate of the first embodiment preferably further includes a first insulator wound along the outer circumference of the inner conductor from the viewpoint of improving the piezoelectric sensitivity and the stability of the piezoelectric output.

[0151] The first piezoelectric body and the first insulator form a braided rope structure that alternately crosses each other.

[0152] This makes it easier to maintain the first piezoelectric element wound in one direction relative to the internal conductor when the piezoelectric substrate is bent and deformed. From the perspective of easily applying tension to the first piezoelectric element, it is preferable that there is no gap between the first piezoelectric element and the first insulator in this type of braided rope structure.

[0153] In the piezoelectric substrate of the first embodiment, from the perspective of improving the piezoelectric sensitivity and the stability of the piezoelectric output, the first piezoelectric body is preferably wound at an angle of 15° to 75° (45°±30°) relative to the axial direction of the internal conductor, and more preferably wound at an angle of 35° to 55° (45°±10°).

[0154] In the piezoelectric substrate of the first embodiment, from the viewpoint of improving the piezoelectric sensitivity and the stability of the piezoelectric output, the first piezoelectric body has a fiber shape formed by a single bundle or multiple bundles, and the major axis diameter of the cross section of the first piezoelectric body is preferably 0.0001mm to 10mm, more preferably 0.001mm to 5mm, and even more preferably 0.002mm to 1mm.

[0155] Here, when the cross section of the first piezoelectric body (preferably, the fibrous piezoelectric body) is circular, the "long axis diameter of the cross section" corresponds to the "diameter".

[0156] When the cross section of the first piezoelectric body is irregularly shaped, the "long axis diameter of the cross section" refers to the longest width among the widths of the cross section.

[0157] When the first piezoelectric body is a piezoelectric body formed of a plurality of bundles, the “long axis diameter of the cross section” refers to the long axis diameter of the cross section of the piezoelectric body formed of the plurality of bundles.

[0158] In the piezoelectric substrate of this embodiment (e.g., the piezoelectric substrate of the first embodiment), the first piezoelectric body preferably has a long, flat plate shape from the perspective of improving piezoelectric sensitivity and piezoelectric output stability. The thickness of the first piezoelectric body is 0.001 mm to 0.2 mm, the width of the first piezoelectric body is 0.1 mm to 30 mm, and the ratio of the width of the first piezoelectric body to the thickness of the first piezoelectric body is 2 or greater.

[0159] The following describes in more detail the dimensions (thickness, width, ratio (width / thickness, length / width)) of the first piezoelectric body having a long flat plate shape (hereinafter also referred to as a "long flat plate piezoelectric body").

[0160] The thickness of the first piezoelectric body is preferably 0.001 mm to 0.2 mm.

[0161] By setting the thickness to 0.001 mm or more, the strength of the long flat-plate piezoelectric body can be ensured, and the long flat-plate piezoelectric body also has excellent manufacturability.

[0162] On the other hand, by setting the thickness to 0.2 mm or less, the degree of freedom of deformation (flexibility) of the elongated flat-plate piezoelectric body in the thickness direction is improved.

[0163] In addition, the width of the first piezoelectric body is preferably 0.1 mm to 30 mm.

[0164] By setting the width to 0.1 mm or more, the strength of the first piezoelectric body (long flat piezoelectric body) can be ensured. In addition, the long flat piezoelectric body has excellent manufacturability (for example, manufacturability in the slitting step described later).

[0165] On the other hand, by setting the width to 30 mm or less, the degree of freedom of deformation (flexibility) of the long flat-plate piezoelectric body is improved.

[0166] Furthermore, the ratio of the width of the first piezoelectric body to the thickness of the first piezoelectric body (hereinafter also referred to as "ratio [width / thickness]") is preferably 2 or greater.

[0167] By setting the ratio [width / thickness] to 2 or greater, the principal surface becomes clear, making it easier to form electrode layers (e.g., external conductors) with uniform orientation along the entire length of the first piezoelectric element (elongated flat-plate piezoelectric element). For example, it is easier to form an external conductor on at least one side of the principal surface. This results in excellent piezoelectric sensitivity and excellent piezoelectric sensitivity stability.

[0168] The width of the first piezoelectric body is more preferably 0.5 mm to 15 mm.

[0169] When the width is 0.5 mm or greater, the strength of the first piezoelectric body (long flat piezoelectric body) is further improved. In addition, the torsion of the long flat piezoelectric body can be further suppressed, thereby further improving the piezoelectric sensitivity and stability.

[0170] When the width is 15 mm or less, the degree of deformation freedom (flexibility) of the long flat-plate piezoelectric body is further improved.

[0171] The ratio of the length to the width of the first piezoelectric body (hereinafter also referred to as the ratio [length / width]) is preferably 10 or greater.

[0172] When the ratio [length / width] is greater than 10, the degree of deformation freedom (flexibility) of the first piezoelectric body (elongated flat-plate piezoelectric body) is further improved. Furthermore, in piezoelectric devices (piezoelectric fabrics, piezoelectric knitted fabrics, etc.) using elongated flat-plate piezoelectric bodies, piezoelectric properties can be imparted over a wider range.

[0173] In the piezoelectric substrate of this embodiment, when the first piezoelectric body has a long flat plate shape, a functional layer is preferably disposed on at least one principal surface side of the first piezoelectric body from the viewpoint of improving piezoelectric sensitivity and piezoelectric output stability.

[0174] The functional layer preferably includes at least one of an easy-adhesion layer, a hard coat layer, an antistatic layer, an anti-blocking layer, a protective layer, and an electrode layer.

[0175] Therefore, it is easier to apply to, for example, piezoelectric devices (piezoelectric fabrics, piezoelectric knitted fabrics, etc.), force sensors, actuators, and biological information acquisition devices.

[0176] The functional layer preferably includes an electrode layer.

[0177] Therefore, when the piezoelectric substrate is used as one of the components of a piezoelectric device (piezoelectric fabric, piezoelectric knitted fabric, etc.), a force sensor, an actuator, or a biological information acquisition device, the first external conductor and the conductor (preferably the internal conductor) can be connected more simply. Therefore, when tension is applied to the piezoelectric substrate of this embodiment, a voltage signal corresponding to the tension can be easily detected.

[0178] In the piezoelectric substrate of the present embodiment, it is preferable that at least one of the surface layers of the laminate including the first piezoelectric body and the functional layer is an electrode layer.

[0179] Therefore, when the piezoelectric substrate is used as one of the components of a piezoelectric device (piezoelectric fabric, piezoelectric knitted fabric, etc.), a force sensor, an actuator, or a biological information acquisition device, the first external conductor or conductor (preferably an internal conductor) can be connected to the laminate more simply. Therefore, when tension is applied to the piezoelectric substrate of this embodiment, a voltage signal corresponding to the tension can be easily detected.

[0180] The conductor of the piezoelectric substrate of this embodiment is preferably a tinsel wire.

[0181] The brocade thread has a structure consisting of rolled copper foil spirally wound around the fiber. By using copper with high electrical conductivity, the output impedance can be reduced. Therefore, when tension is applied to the piezoelectric substrate of this embodiment, a voltage signal corresponding to the tension is easily detected. As a result, the piezoelectric sensitivity and piezoelectric output stability are further improved.

[0182] The piezoelectric substrate of this embodiment preferably has an adhesive layer between the conductor and the first piezoelectric body.

[0183] As a result, the relative position of the conductor and the first piezoelectric body becomes less likely to deviate, making it easier to apply tension to the first piezoelectric body and shear stress to the helical chiral polymer (A) contained in the first piezoelectric body. Consequently, a voltage output proportional to the tension can be effectively detected from the conductor (preferably a signal line conductor). Furthermore, the presence of the adhesive layer further increases the absolute value of the generated charge per unit tensile force.

[0184] In the piezoelectric substrate of this embodiment, from the viewpoint of further improving piezoelectricity, the helical chiral polymer (A) contained in the first piezoelectric body is preferably a polylactic acid-based polymer having a main chain containing a repeating unit represented by the following formula (1).

[0185] [Chemical Formula 1]

[0186]

[0187] In the piezoelectric substrate of the present embodiment, from the viewpoint of further improving the piezoelectricity, the optical purity of the helical chiral polymer (A) contained in the first piezoelectric body is preferably 95.00% ee or higher.

[0188] In the piezoelectric substrate of the present embodiment, from the viewpoint of further improving the piezoelectricity, the helical chiral polymer (A) contained in the first piezoelectric body preferably contains the D-isomer or the L-isomer.

[0189] In the piezoelectric substrate of the present embodiment, from the viewpoint of further improving piezoelectricity, the content of the helical chiral polymer (A) contained in the first piezoelectric body is preferably 80% by mass or more relative to the total amount of the first piezoelectric body.

[0190] The piezoelectric substrate of this embodiment preferably further includes a first external conductor on the outer periphery.

[0191] Here, the "periphery" refers to the outer peripheral portion of the piezoelectric substrate.

[0192] This makes it possible to achieve electrostatic shielding and suppress voltage changes in the conductor (preferably, the internal conductor) due to the influence of external static electricity.

[0193] The piezoelectric substrate of the present embodiment preferably further includes a second insulator on the outer periphery of the first outer conductor.

[0194] By providing the piezoelectric substrate of this embodiment with a second insulator, it is possible to suppress the infiltration of liquids such as water and sweat, and the infiltration of dust from the outside. Therefore, the occurrence of leakage current between a conductor (preferably an internal conductor) and an external conductor caused by water, sweat, dust, etc. can be suppressed. As a result, when the piezoelectric substrate is used as one of the components of, for example, a piezoelectric device (piezoelectric fabric, piezoelectric knitted fabric, etc.), a force sensor, an actuator, or a biological information acquisition device, a stable output (robust against various environmental changes and less prone to fluctuations in sensitivity) can be achieved.

[0195] Hereinafter, a specific aspect A of the piezoelectric substrate according to the first embodiment will be described with reference to the drawings.

[0196] [Specific method A]

[0197] Figure 6A It is a side view showing a specific aspect A of the piezoelectric substrate according to the first embodiment. Figure 6B for Figure 6A XX' line cross-sectional view.

[0198] The piezoelectric substrate 12 of the specific embodiment A includes an elongated internal conductor 16A as a conductor, an elongated first piezoelectric body 18A, and an adhesive layer (not shown) disposed between the internal conductor 16A and the first piezoelectric body 18A.

[0199] like Figure 6A As shown, the first piezoelectric body 18A is spirally wound in one direction from one end to the other end at a spiral angle β1 along the outer peripheral surface of the internal conductor 16A without a gap.

[0200] The “helix angle β1” refers to an angle formed between the axial direction G1 of the internal conductor 16A and the arrangement direction of the first piezoelectric body 18A with respect to the axial direction of the internal conductor 16A.

[0201] In the specific embodiment A, the first piezoelectric body 18A is wound in a counterclockwise manner with respect to the internal conductor 16A. Specifically, from one end side ( Figure 6A When the piezoelectric substrate 12 is viewed (the right end side is shown in FIG), the first piezoelectric body 18A is wound in a counterclockwise manner from the front side to the back side of the internal conductor 16A.

[0202] in addition, Figure 6A In FIG, the main orientation direction of the helical chiral polymer (A) contained in the first piezoelectric body 18A is indicated by a double-headed arrow E1. That is, the main orientation direction of the helical chiral polymer (A) is substantially parallel to the arrangement direction of the first piezoelectric body 18A (the longitudinal direction of the first piezoelectric body 18A).

[0203] Furthermore, an adhesive layer (not shown) is disposed between the internal conductor 16A and the first piezoelectric body 18A. Thus, the piezoelectric substrate 12 of the specific embodiment A is configured such that the relative positions of the first piezoelectric body 18A and the internal conductor 16A do not shift even when tension is applied in the longitudinal direction of the piezoelectric substrate 12.

[0204] Hereinafter, the function of the piezoelectric substrate 12 in the specific embodiment A will be described.

[0205] For example, when tension is applied in the longitudinal direction of the piezoelectric substrate 12, a shear force is applied to the helical chiral polymer (A) contained in the first piezoelectric body 18A, and the helical chiral polymer (A) is polarized. The polarization of the helical chiral polymer (A) is considered to be as follows: Figure 6B The arrow in the middle shows that the polarization is generated in the radial direction of the piezoelectric substrate 12, and the polarization directions are generated in a phase-matched manner. As a result, a voltage signal proportional to the tension can be effectively detected.

[0206] Furthermore, in the piezoelectric substrate 12 of the specific embodiment A, since the adhesive layer is disposed between the internal conductor 16A and the first piezoelectric body 18A, tension is more easily applied to the first piezoelectric body 18A.

[0207] As described above, the piezoelectric substrate 12 according to the specific embodiment A has excellent piezoelectric sensitivity and excellent piezoelectric output stability.

[0208] Next, a specific embodiment B of the piezoelectric substrate according to the first embodiment will be described with reference to the drawings. In the following description, the same elements as those in the specific embodiment A are denoted by the same reference numerals, and duplicate descriptions will be omitted.

[0209] 〔Specific method B〕

[0210] Figure 7 It is a side view showing a specific aspect B of the piezoelectric substrate according to the first embodiment.

[0211] The piezoelectric substrate 12A of the specific embodiment B is different from the piezoelectric substrate 12 of the first embodiment in that it includes a second piezoelectric body 18B having an elongated shape.

[0212] It should be noted that the chirality of the helical chiral polymer (A) contained in the first piezoelectric body 18A and the chirality of the helical chiral polymer (A) contained in the second piezoelectric body 18B are different from each other.

[0213] Similar to the specific embodiment A, the first piezoelectric body 18A is spirally wound in one direction from one end to the other end at a spiral angle β1 without any gap along the outer peripheral surface of the internal conductor 16A.

[0214] On the other hand, Figure 7As shown, the second piezoelectric body 18B is spirally wound along the outer peripheral surface of the first piezoelectric body 18A at a spiral angle β2 which is substantially the same as the spiral angle β1 and in a direction opposite to the winding direction of the first piezoelectric body 18A.

[0215] The so-called "helix angle β2" has the same meaning as the above-mentioned helix angle β1.

[0216] Here, the so-called "direction opposite to the winding direction of the first piezoelectric body 18A" in the specific embodiment B is a clockwise rotation. That is, from one end side of the axial direction G2 of the internal conductor 16A ( Figure 7 When the piezoelectric substrate 12A is viewed (the right end side is shown in FIG), the second piezoelectric body 18B is wound in a clockwise manner from the front side to the back side of the internal conductor 16A.

[0217] in addition, Figure 7 , the main orientation direction of the helical chiral polymer (A) contained in the second piezoelectric body 18B is indicated by a double-headed arrow E2. That is, the main orientation direction of the helical chiral polymer (A) contained in the second piezoelectric body 18B is approximately parallel to the configuration direction of the second piezoelectric body 18B (the length direction of the second piezoelectric body 18B).

[0218] Hereinafter, the function of the piezoelectric substrate 12A in the specific embodiment B will be described.

[0219] For example, when tension is applied in the longitudinal direction of the piezoelectric substrate 12A, shear stress is applied to both the helical chiral polymer (A) contained in the first piezoelectric layer 18A and the helical chiral polymer (A) contained in the second piezoelectric layer 18B, causing polarization. The polarization direction is radial to the piezoelectric substrate 12A. This allows for efficient detection of a voltage signal proportional to the tension.

[0220] As described above, the piezoelectric substrate 12A of the specific embodiment B further improves the piezoelectric sensitivity and the stability of the piezoelectric output.

[0221] In particular, when the piezoelectric substrate 12A of specific embodiment B includes an external conductor, the piezoelectric body comprises a first piezoelectric body and a second piezoelectric body, forming a two-layer structure. Consequently, the gaps between the first and second piezoelectric bodies and the internal and external conductors are small, allowing for close contact. This allows the electric field generated by tension to be efficiently transmitted to the electrodes. Therefore, this is a preferred embodiment for achieving a sensor with higher sensitivity.

[0222] Next, a specific embodiment C of the piezoelectric substrate according to the first embodiment will be described with reference to the drawings. In the following description, the same elements as in specific embodiments A and B are denoted by the same reference numerals, and duplicate descriptions will be omitted.

[0223] 〔Specific Method C〕

[0224] Figure 8 It is a side view showing a specific aspect C of the piezoelectric substrate according to the first embodiment.

[0225] The piezoelectric substrate 12B of the specific embodiment C differs from the piezoelectric substrate 12A of the specific embodiment B in that the first piezoelectric bodies 18A and the second piezoelectric bodies 18B alternately cross each other to form a braided rope structure.

[0226] It should be noted that the chirality of the helical chiral polymer (A) contained in the first piezoelectric body 18A and the chirality of the helical chiral polymer (A) contained in the second piezoelectric body 18B are different from each other.

[0227] like Figure 8 As shown, in the piezoelectric substrate 12B of specific embodiment C, the first piezoelectric body 18A is spirally wound in a left-handed manner at a spiral angle β1 relative to the axial direction G3 of the internal conductor 16A, and the second piezoelectric body 18B is spirally wound in a right-handed manner at a spiral angle β2, and the first piezoelectric body 18A and the second piezoelectric body are alternately crossed.

[0228] in addition, Figure 8 In the braided rope structure shown, the main orientation direction (double-headed arrow E1) of the helical chiral polymer (A) contained in the first piezoelectric body 18A is approximately parallel to the arrangement direction of the first piezoelectric body 18A. Similarly, the main orientation direction (double-headed arrow E2) of the helical chiral polymer (A) contained in the second piezoelectric body 18B is approximately parallel to the arrangement direction of the second piezoelectric body 18B.

[0229] Next, the function of the piezoelectric substrate 12B in the specific embodiment C will be described.

[0230] As in Specific Embodiment B, for example, when tension is applied in the longitudinal direction of the piezoelectric substrate 12B, polarization occurs in both the helical chiral polymer (A) contained in the first piezoelectric layer 18A and the helical chiral polymer (A) contained in the second piezoelectric layer 18B. The polarization direction is in the radial direction of the piezoelectric substrate 12B. This allows for efficient detection of a voltage signal proportional to the tension.

[0231] As described above, the piezoelectric substrate 12B of the specific embodiment C further improves the piezoelectric sensitivity and the stability of the piezoelectric output.

[0232] In particular, when the piezoelectric substrate 12B of embodiment C includes an external conductor, when tension is applied in the longitudinal direction of the piezoelectric substrate 12B, shear stress is applied to the left-handed first piezoelectric element and the right-handed second piezoelectric element forming the braided rope structure. This aligns their polarization directions, increasing the volume fraction (the volume fraction contributes to the piezoelectric performance of the insulator between the internal and external conductors (i.e., the first and second piezoelectric elements)), thereby further improving the piezoelectric performance. Therefore, the piezoelectric substrate 12B of embodiment C can be suitably used as a structural component along a three-dimensional plane, such as a wearable product.

[0233] Next, the conductor, the first piezoelectric body, and the like included in the piezoelectric substrate of this embodiment will be described.

[0234] <Conductor>

[0235] The piezoelectric substrate of this embodiment has a long conductor.

[0236] The conductor (eg, inner conductor) in this embodiment is preferably a signal line conductor.

[0237] The signal line conductor is a conductor for efficiently detecting an electrical signal from the first piezoelectric body or the second piezoelectric body. Specifically, it is a conductor for detecting a voltage signal (charge signal) corresponding to the applied tension when tension is applied to the piezoelectric substrate of this embodiment.

[0238] Conductors that are preferably good electrical conductors can include copper wire, aluminum wire, SUS wire, metal wire coated with an insulating film, carbon fiber, resin fiber integrated with carbon fiber, brocade wire, and organic conductive materials. Brocade wire refers to a wire formed by spirally wrapping copper foil around fibers. Brocade wire and carbon fiber are preferred conductors for improving piezoelectric sensitivity and piezoelectric output stability, as well as imparting high flexibility.

[0239] In particular, in applications requiring low electrical resistance and bendability and flexibility (for example, applications such as wearable sensors mounted inside clothing), brocade thread is preferably used.

[0240] In addition, carbon fibers are preferably used in applications where processing into woven fabrics, knitted fabrics, etc. that require very high bendability and flexibility (e.g., piezoelectric fabrics, piezoelectric knitted fabrics, piezoelectric sensors (woven piezoelectric sensors, knitted piezoelectric sensors)) is required.

[0241] Furthermore, when the piezoelectric substrate of this embodiment is used as a fiber and processed into a piezoelectric fabric or piezoelectric knitted fabric, flexibility and high flexibility are required. For such applications, a filamentous or fibrous signal conductor is preferred. Piezoelectric substrates with filamentous or fibrous signal conductors have high flexibility and are therefore suitable for processing on weaving and knitting machines.

[0242] <First Piezoelectric Body>

[0243] The piezoelectric substrate of this embodiment includes a first piezoelectric body having an elongated shape.

[0244] The first piezoelectric body is a piezoelectric body containing an optically active helical chiral polymer (A).

[0245] (Helical Chiral Polymer (A))

[0246] The first piezoelectric body in this embodiment includes an optically active helical chiral polymer (A).

[0247] Here, the "optically active helical chiral polymer" refers to a polymer having a helical molecular structure and exhibiting molecular optical activity.

[0248] Examples of the helical chiral polymer (A) include polypeptides, cellulose derivatives, polylactic acid-based polymers, polypropylene oxide, and poly(β-hydroxybutyric acid).

[0249] Examples of the polypeptide include poly(γ-benzyl glutarate) and poly(γ-methyl glutarate).

[0250] Examples of the cellulose derivatives include cellulose acetate and cyanoethyl cellulose.

[0251] From the perspective of improving the piezoelectricity of the first piezoelectric body, the optical purity of the helical chiral polymer (A) is preferably 95.00% ee or higher, more preferably 96.00% ee or higher, further preferably 99.00% ee or higher, and even more preferably 99.99% ee or higher. It is desirably 100.00% ee. It is believed that by adjusting the optical purity of the helical chiral polymer (A) to the above range, the stacking properties of the polymer crystals exhibiting piezoelectricity are improved, resulting in improved piezoelectricity.

[0252] Here, the optical purity of the helical chiral polymer (A) is a value calculated by the following formula.

[0253] Optical purity (%ee) = 100 × |L volume - D volume| / (L volume + D volume)

[0254] That is, the optical purity of the helical chiral polymer (A) is the following value:

[0255] The value obtained by dividing (dividing by) the "amount difference (absolute value) between the amount of the L-isomer of the helical chiral polymer (A) [mass %] and the amount of the D-isomer of the helical chiral polymer (A) [mass %]" by the "total amount of the L-isomer of the helical chiral polymer (A) [mass %] and the amount of the D-isomer of the helical chiral polymer (A) [mass %]" is obtained by multiplying (demultiplying) the obtained value by "100".

[0256] The amounts of the L-isomer (mass %) and the D-isomer (mass %) of the helical chiral polymer (A) are values ​​obtained by high performance liquid chromatography (HPLC). The details of the specific measurements will be described later.

[0257] The helical chiral polymer (A) is preferably a polymer having a main chain comprising a repeating unit represented by the following formula (1) from the viewpoint of improving optical purity and enhancing piezoelectricity.

[0258] [Chemical Formula 2]

[0259]

[0260] Examples of polymers having a repeating unit represented by the above formula (1) as a main chain include polylactic acid-based polymers.

[0261] Here, the polylactic acid-based polymer refers to "polylactic acid (a polymer comprising repeating units derived solely from monomers selected from L-lactic acid and D-lactic acid)", "a copolymer of L-lactic acid or D-lactic acid and a compound copolymerizable with the L-lactic acid or D-lactic acid", or a mixture of the two.

[0262] Among polylactic acid-based polymers, polylactic acid is preferred, and a homopolymer of L-lactic acid (PLLA, also referred to as "L-isomer") or a homopolymer of D-lactic acid (PDLA, also referred to as "D-isomer") is most preferred.

[0263] Polylactic acid is a polymer formed by polymerizing lactic acid through ester bonds and connecting them in long chains.

[0264] It is known that polylactic acid can be produced by the following methods: a lactide method via lactide; a direct polymerization method in which lactic acid is heated in a solvent under reduced pressure to polymerize while removing water; and the like.

[0265] Examples of the polylactic acid include homopolymers of L-lactic acid, homopolymers of D-lactic acid, block copolymers containing at least one polymer of L-lactic acid and D-lactic acid, and graft copolymers containing at least one polymer of L-lactic acid and D-lactic acid.

[0266] The glass transition temperature of polylactic acid varies depending on the molecular weight and the degree of crystallinity caused by stretching, but is approximately 50°C to 70°C.

[0267] Examples of the "compound copolymerizable with L-lactic acid or D-lactic acid" include hydroxycarboxylic acids such as glycolic acid, dimethylglycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxypropionic acid, 3-hydroxypropionic acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxyhexanoic acid, 3-hydroxyhexanoic acid, 4-hydroxyhexanoic acid, 5-hydroxyhexanoic acid, 6-hydroxyhexanoic acid, 6-hydroxymethylhexanoic acid, and mandelic acid; cyclic esters such as glycolide, β-methyl-δ-valerolactone, γ-valerolactone, and ε-caprolactone; oxalic acid, malonic acid , succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, terephthalic acid and other polycarboxylic acids and their anhydrides; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, butanediol, 1,4-hexanedimethanol and other polyols; polysaccharides such as cellulose; aminocarboxylic acids such as α-amino acids; and so on.

[0268] Examples of the "copolymer of L-lactic acid or D-lactic acid and a compound copolymerizable with the L-lactic acid or D-lactic acid" include block copolymers and graft copolymers having a polylactic acid sequence capable of forming a helical crystal.

[0269] Furthermore, the concentration of the structure derived from the copolymer component in the helical chiral polymer (A) is preferably 20 mol% or less.

[0270] For example, when the helical chiral polymer (A) is a polylactic acid-based polymer, the concentration of the structure derived from the copolymer component is preferably 20 mol% or less relative to the total molar number of the structure derived from lactic acid and the structure derived from a compound copolymerizable with lactic acid (copolymer component) in the polylactic acid-based polymer.

[0271] Polylactic acid-based polymers can be produced by, for example, the following methods: a method of obtaining them by direct dehydration condensation of lactic acid as described in Japanese Patent Application Laid-Open No. 59-096123 and Japanese Patent Application Laid-Open No. 7-033861; a method of ring-opening polymerization using lactide, a cyclic dimer of lactic acid, as described in U.S. Patents Nos. 2,668,182 and 4,057,357; and the like.

[0272] Furthermore, in order to achieve an optical purity of 95.00% ee or higher for the polylactic acid-based polymer obtained by each of the above-mentioned production methods, for example, when producing polylactic acid by the lactide method, it is preferred to polymerize lactide whose optical purity has been increased to 95.00% ee or higher by crystallization.

[0273] -Weight average molecular weight-

[0274] The weight average molecular weight (Mw) of the helical chiral polymer (A) is preferably 50,000 to 1,000,000.

[0275] The mechanical strength of the first piezoelectric body is improved by setting the Mw of the helical chiral polymer (A) to 50,000 or more. The Mw is preferably 100,000 or more, and more preferably 200,000 or more.

[0276] On the other hand, by setting the Mw of the helical chiral polymer (A) to 1,000,000 or less, the moldability when forming the first piezoelectric body by molding (eg, extrusion molding, melt spinning) is improved. The Mw is preferably 800,000 or less, more preferably 300,000 or less.

[0277] Furthermore, from the viewpoint of the strength of the first piezoelectric body, the molecular weight distribution (Mw / Mn) of the helical chiral polymer (A) is preferably 1.1 to 5, more preferably 1.2 to 4, and even more preferably 1.4 to 3.

[0278] The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the helical chiral polymer (A) are values ​​measured by gel permeation chromatography (GPC). Here, Mn is the number average molecular weight of the helical chiral polymer (A).

[0279] An example of a method for measuring Mw and Mw / Mn of the helical chiral polymer (A) by GPC is shown below.

[0280] -GPC measurement equipment-

[0281] Waters GPC-100

[0282] -column-

[0283] Showa Denko Co., Ltd., Shodex LF-804

[0284] -Sample Preparation-

[0285] The first piezoelectric body is dissolved in a solvent (eg, chloroform) at 40° C. to prepare a sample solution having a concentration of 1 mg / ml.

[0286] -Measurement conditions-

[0287] 0.1 ml of the sample solution was introduced into the column under the conditions of solvent [chloroform], temperature 40°C and flow rate 1 ml / min.

[0288] The sample concentration in the sample solution after column separation was measured using a differential refractometer.

[0289] A universal calibration curve was prepared using polystyrene standard samples to calculate the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the helical chiral polymer (A).

[0290] As the polylactic acid-based polymer as an example of the helical chiral polymer (A), commercially available polylactic acid can be used.

[0291] Examples of commercially available products include PURASORB (PD, PL) manufactured by PURAC, LACEA (H-100, H-400) manufactured by Mitsui Chemicals, and Ingeo TM biopolymer, etc.

[0292] When a polylactic acid polymer is used as the helical chiral polymer (A), it is preferably produced by a lactide method or a direct polymerization method in order to make the weight average molecular weight (Mw) of the polylactic acid polymer 50,000 or more.

[0293] The first piezoelectric body in this embodiment may contain only one type of the helical chiral polymer (A), or may contain two or more types.

[0294] The content of the helical chiral polymer (A) in the first piezoelectric body of the present embodiment (the total content when two or more types are present) is preferably 80% by mass or more relative to the total amount of the first piezoelectric body.

[0295] <Stabilizer>

[0296] The first piezoelectric body preferably further contains a stabilizer (B) having a weight average molecular weight of 200 to 60,000 and having one or more functional groups selected from the group consisting of carbodiimide, epoxy, and isocyanate groups in one molecule. This can further improve the moist heat resistance.

[0297] As the stabilizer (B), the “stabilizer (B)” described in paragraphs 0039 to 0055 of International Publication No. 2013 / 054918 can be used.

[0298] Examples of the compound containing a carbodiimide group in one molecule (carbodiimide compound) that can be used as the stabilizer (B) include monocarbodiimide compounds, polycarbodiimide compounds, and cyclic carbodiimide compounds.

[0299] As the monocarbodiimide compound, dicyclohexylcarbodiimide, bis-2,6-diisopropylphenylcarbodiimide, and the like are preferred.

[0300] In addition, as the polycarbodiimide compound, compounds produced by various methods can be used. Compounds produced by existing polycarbodiimide production methods (for example, U.S. Patent No. 2,941,956, Japanese Patent Publication No. 47-33279, J. Org. Chem. 28, 2069-2075 (1963), Chemical Review 1981, Vol. 81, No. 4, pp. 619-621) can be used. Specifically, the carbodiimide compounds described in Japanese Patent No. 4,084,953 can also be used.

[0301] Examples of the polycarbodiimide compound include poly(4,4′-dicyclohexylmethanecarbodiimide), poly(N,N′-di-2,6-diisopropylphenylcarbodiimide), and poly(1,3,5-triisopropylphenylene-2,4-carbodiimide).

[0302] The cyclic carbodiimide compound can be synthesized according to the method described in JP-A-2011-256337 or the like.

[0303] As the carbodiimide compound, commercially available products can be used. Examples thereof include B2756 (trade name) manufactured by Tokyo Chemical Industry Co., Ltd., CARBODILITE LA-1 (trade name) manufactured by Nisshinbo Chemical Inc., and Stabaxol P, Stabaxol P400, and Stabaxol I (all trade names) manufactured by Rhein Chemie.

[0304] Examples of compounds containing an isocyanate group in one molecule (isocyanate compounds) that can be used as the stabilizer (B) include 3-(triethoxysilyl)propyl isocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, xylylenediisocyanate, hydrogenated xylylenediisocyanate, and isophorone diisocyanate.

[0305] Examples of compounds containing an epoxy group in one molecule (epoxy compounds) that can be used as the stabilizer (B) include phenyl glycidyl ether, diethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, phenol Novolac type epoxy resins, cresol Novolac type epoxy resins, and epoxidized polybutadiene.

[0306] As described above, the weight average molecular weight of the stabilizer (B) is 200 to 60,000, more preferably 200 to 30,000, and even more preferably 300 to 18,000.

[0307] When the molecular weight is within the above range, the stabilizer (B) can more easily migrate and the moist heat resistance improving effect can be more effectively exhibited.

[0308] The weight average molecular weight of the stabilizer (B) is particularly preferably 200 to 900. A weight average molecular weight of 200 to 900 is substantially the same as a number average molecular weight of 200 to 900. Furthermore, when the weight average molecular weight is 200 to 900, the molecular weight distribution may be 1.0. In this case, "weight average molecular weight of 200 to 900" may be simply referred to as "molecular weight of 200 to 900."

[0309] When the first piezoelectric body contains a stabilizer (B), the first piezoelectric body may contain only one type of stabilizer, or may contain two or more types of stabilizers.

[0310] When the first piezoelectric body contains a stabilizer (B), the content of the stabilizer (B) is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of the helical chiral polymer (A), more preferably 0.01 to 5 parts by mass, further preferably 0.1 to 3 parts by mass, and especially preferably 0.5 to 2 parts by mass.

[0311] When the content is 0.01 parts by mass or more, the moist heat resistance is further improved.

[0312] Moreover, when the said content is 10 mass parts or less, the fall of transparency can be suppressed further.

[0313] A preferred embodiment of the stabilizer (B) includes a stabilizer (B1) having a number average molecular weight of 200 to 900 and a stabilizer (B2) having a weight average molecular weight of 1,000 to 60,000, wherein the stabilizer (B1) has one or more functional groups selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group, and the stabilizer (B2) has two or more functional groups selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group in one molecule. It should be noted that the stabilizer (B1) having a number average molecular weight of 200 to 900 has a weight average molecular weight of approximately 200 to 900, and the number average molecular weight and weight average molecular weight of the stabilizer (B1) are approximately the same value.

[0314] When the stabilizer (B1) and the stabilizer (B2) are used in combination as the stabilizer, it is preferred to contain a larger amount of the stabilizer (B1) from the viewpoint of improving transparency.

[0315] Specifically, from the viewpoint of achieving both transparency and moist heat resistance, the amount of stabilizer (B2) is preferably in the range of 10 to 150 parts by mass, more preferably 50 to 100 parts by mass, relative to 100 parts by mass of stabilizer (B1).

[0316] Specific examples of the stabilizer (B) (stabilizers B-1 to B-3) are shown below.

[0317] [Chemical Formula 3]

[0318]

[0319] The compound names, commercially available products, etc. are shown below for the stabilizers B-1 to B-3.

[0320] Stabilizer B-1: The compound name is bis-2,6-diisopropylphenylcarbodiimide. The weight-average molecular weight (in this example, simply "molecular weight") is 363. Commercially available products include "Stabaxol I" manufactured by Rhein Chemie and "B2756" manufactured by Tokyo Chemical Industry Co., Ltd.

[0321] Stabilizer B-2: The compound name is poly(4,4′-dicyclohexylmethanecarbodiimide). Commercially available products include “CARBODILITE LA-1” manufactured by Nisshinbo Chemical Inc., which is a stabilizer having a weight-average molecular weight of approximately 2,000.

[0322] Stabilizer B-3... The compound name is poly(1,3,5-triisopropylphenylene-2,4-carbodiimide). Commercially available products include "Stabaxol P" manufactured by Rhein Chemie, which has a weight-average molecular weight of approximately 3,000. Another commercially available product is "Stabaxol P400" manufactured by Rhein Chemie, which has a weight-average molecular weight of 20,000.

[0323] <Other ingredients>

[0324] The first piezoelectric body may contain other components as needed.

[0325] Examples of other components include known resins such as polyvinylidene fluoride, polyethylene resin, and polystyrene resin; known inorganic fillers such as silica, hydroxyapatite, and montmorillonite; known crystal nucleating agents such as phthalocyanine; and stabilizers other than stabilizer (B).

[0326] Examples of the inorganic filler and the crystal nucleating agent include the components described in paragraphs 0057 to 0058 of International Publication No. 2013 / 054918.

[0327] (Orientation degree F)

[0328] As described above, the orientation degree F of the first piezoelectric body in this embodiment is 0.5 or more and less than 1.0, preferably 0.7 or more and less than 1.0, and more preferably 0.8 or more and less than 1.0.

[0329] When the orientation degree F of the first piezoelectric body is 0.5 or more, more molecular chains of the helical chiral polymer (A) (eg, polylactic acid molecular chains) are arranged in the stretching direction, resulting in an increased rate of oriented crystal formation and the ability to exhibit higher piezoelectricity.

[0330] When the orientation degree F of the first piezoelectric body is less than 1.0, the longitudinal tear strength is further improved.

[0331] (Crystallinity)

[0332] The crystallinity of the first piezoelectric body in this embodiment is a value measured by the above-mentioned X-ray diffraction measurement (wide-angle X-ray diffraction measurement).

[0333] The crystallinity of the first piezoelectric body in this embodiment is preferably 20% to 80%, more preferably 25% to 70%, and even more preferably 30% to 60%.

[0334] By setting the crystallinity to 20% or more, the piezoelectricity can be maintained at a high level. By setting the crystallinity to 80% or less, the transparency of the first piezoelectric body can be maintained at a high level.

[0335] By setting the crystallinity to 80% or less, for example, when the piezoelectric film used as the raw material of the first piezoelectric body is stretched to produce the first piezoelectric body, whitening and cracking are less likely to occur, thereby facilitating the production of the first piezoelectric body. Furthermore, by setting the crystallinity to 80% or less, for example, when the raw material of the first piezoelectric body (e.g., polylactic acid) is melt-spun and then stretched to produce the first piezoelectric body, a fiber with high bendability and flexibility is formed, facilitating the production of the first piezoelectric body.

[0336] (Transparency (internal haze))

[0337] The first piezoelectric body of this embodiment is not particularly required to have transparency, but may of course have transparency.

[0338] The transparency of the first piezoelectric body can be evaluated by measuring the internal haze. Here, the internal haze of the first piezoelectric body refers to the haze excluding the haze caused by the outer surface shape of the first piezoelectric body.

[0339] When transparency is required, the internal haze of the first piezoelectric body relative to visible light is preferably 5% or less. From the perspective of further improving transparency and longitudinal tear strength, it is more preferably 2.0% or less, and even more preferably 1.0% or less. The lower limit of the internal haze of the first piezoelectric body is not particularly limited, and an example of the lower limit is 0.01%.

[0340] The internal haze of the first piezoelectric body is a value measured at 25° C. using a haze meter [TC-HIII DPK manufactured by Tokyo Denshoku Co., Ltd.] for the first piezoelectric body having a thickness of 0.03 mm to 0.05 mm in accordance with JIS-K7105.

[0341] An example of a method for measuring the internal haze of the first piezoelectric body is described below.

[0342] First, a sample 1 was prepared in which only silicone oil (SHIN-ETSU SILICONE (trademark), model number: KF96-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.) was sandwiched between two glass plates, and the haze in the thickness direction of the sample 1 (hereinafter referred to as haze (H2)) was measured.

[0343] Next, a sample 2 was prepared in which a plurality of first piezoelectric bodies whose surfaces were uniformly coated with silicone oil were sandwiched side by side without a gap between the two glass plates. The haze in the thickness direction of the sample 2 (hereinafter referred to as haze (H3)) was measured.

[0344] Next, the difference between them is calculated according to the following formula to obtain the internal haze (H1) of the first piezoelectric body.

[0345] Internal haze (H1) = haze (H3) - haze (H2)

[0346] Here, the haze (H2) and the haze (H3) were each measured using the following apparatus under the following measurement conditions.

[0347] Measuring device: HAZE METER TC-HIIIDPK manufactured by Tokyo Denshoku Co., Ltd.

[0348] Sample size: width 30mm × length 30mm

[0349] Measurement conditions: According to JIS-K7105

[0350] Measurement temperature: room temperature (25°C)

[0351] (Shape and size of the first piezoelectric body)

[0352] The piezoelectric substrate of this embodiment includes a first piezoelectric body having an elongated shape.

[0353] The first elongated piezoelectric body is preferably a piezoelectric body having a fiber shape (filament shape) formed of a single bundle or a plurality of bundles, or a piezoelectric body having an elongated flat plate shape.

[0354] Hereinafter, a piezoelectric body having a fiber shape (hereinafter also referred to as a fiber-shaped piezoelectric body) and a piezoelectric body having a long flat plate shape (hereinafter also referred to as a long flat plate-shaped piezoelectric body) will be described in this order.

[0355] -Fiber-shaped piezoelectric body-

[0356] Examples of the fibrous piezoelectric body include monofilament yarn and multifilament yarn.

[0357] ·Monofilament yarn

[0358] The single yarn fineness of the monofilament yarn is preferably 3 dtex to 30 dtex, more preferably 5 dtex to 20 dtex.

[0359] If the single yarn fineness is less than 3 dtex, it is difficult to handle the yarn in the woven fabric preparation process and weaving process. On the other hand, if the single yarn fineness is greater than 30 dtex, it is easy for the yarns to fuse.

[0360] Regarding monofilament yarn, it is preferable to obtain it by direct spinning and stretching in consideration of cost.

[0361] ·Multifilament yarn

[0362] The total fineness of the multifilament yarn is preferably 30 dtex to 600 dtex, more preferably 100 dtex to 400 dtex.

[0363] The multifilament yarn may be a single-step yarn such as a spun yarn or a two-step yarn obtained by stretching UDY (unstretched yarn) or POY (highly oriented unstretched yarn).

[0364] As commercially available products of polylactic acid-based monofilament yarn and polylactic acid-based multifilament yarn, ECODEAR manufactured by Toray can be used. (R) TERRAMAC manufactured by PLA and Unitika Ltd. (R) , KURARAY CO., LTD. PLASTARCH (R) .

[0365] The method for producing the fibrous piezoelectric body is not particularly limited, and the fibrous piezoelectric body can be produced by a known method.

[0366] For example, a filament yarn (monofilament yarn, multifilament yarn) serving as the first piezoelectric body can be obtained by melt-spinning a raw material (e.g., polylactic acid) and then stretching it (melt spinning and stretching method). It should be noted that after spinning, the ambient temperature near the yarn is preferably maintained within a certain temperature range until it is cooled and solidified.

[0367] Furthermore, the filament yarn serving as the first piezoelectric body can also be obtained by, for example, further splitting the filament yarn obtained by the above-mentioned melt spinning and stretching method.

[0368] Cross-sectional shape

[0369] As the cross-sectional shape of the fibrous piezoelectric body, various cross-sectional shapes such as circular, elliptical, rectangular, cocoon-shaped, ribbon-shaped, four-leaf-shaped, star-shaped, and irregular-shaped can be applied in the cross-section in the direction perpendicular to the longitudinal direction of the fibrous piezoelectric body.

[0370] -Elongated flat piezoelectric body-

[0371] Examples of the long flat-plate piezoelectric body include a long flat-plate piezoelectric body (for example, a slit tape) obtained by slitting a piezoelectric film produced by a known method or a commercially available piezoelectric film.

[0372] By using a long flat-plate piezoelectric body as the first piezoelectric body, it can be in close contact with the conductor in a planar manner, and thus the charge generated by the piezoelectric effect can be efficiently detected in the form of a voltage signal.

[0373] The long flat-plate piezoelectric body (first piezoelectric body) in this embodiment preferably has a functional layer disposed on at least one principal surface side of the first piezoelectric body.

[0374] The functional layer may have a single-layer structure or a structure including two or more layers.

[0375] For example, when functional layers are arranged on the two main surface sides of a long flat piezoelectric body, the functional layer arranged on one main surface (for convenience, also referred to as the "surface") and the functional layer arranged on the other surface (for convenience, also referred to as the "back") can each independently be a single-layer structure or a structure comprising two or more layers.

[0376] As the functional layer, various functional layers can be mentioned.

[0377] Examples of the functional layer include an adhesive layer, a hard coat layer, a refractive index adjusting layer, an antireflection layer, an antiglare layer, a slip layer, an antiblocking layer, a protective layer, an adhesive layer, an antistatic layer, a heat dissipation layer, an ultraviolet absorbing layer, an anti-Newton ring layer, a light scattering layer, a polarizing layer, a gas barrier layer, a color tone adjusting layer, and an electrode layer.

[0378] The functional layer may be a layer including two or more of these layers.

[0379] Furthermore, the functional layer may be a layer having two or more of these functions.

[0380] When functional layers are provided on both main surfaces of the long flat piezoelectric body, the functional layer arranged on the front side and the functional layer arranged on the back side may be the same functional layer or different functional layers.

[0381] The functional layer also has the effect of compensating for defects such as mold marks or prints on the surface of the elongated planar piezoelectric body, thereby improving the appearance. In this case, the smaller the refractive index difference between the elongated planar piezoelectric body and the functional layer, the less reflection occurs at the interface between the elongated planar piezoelectric body and the functional layer, further improving the appearance.

[0382] The functional layer preferably includes at least one of an easy-adhesion layer, a hard coat layer, an antistatic layer, an anti-adhesion layer, a protective layer, and an electrode layer. This makes it more suitable for applications such as piezoelectric devices (piezoelectric fabrics, piezoelectric knitted fabrics, etc.), force sensors, actuators, and biological information acquisition devices.

[0383] More preferably, the functional layer includes an electrode layer.

[0384] The electrode layer may be provided in contact with the long flat-plate piezoelectric body, or may be provided via a functional layer other than the electrode layer.

[0385] A particularly preferred embodiment of the elongated flat-plate piezoelectric body (first piezoelectric body) of this embodiment includes functional layers on both principal surfaces of the elongated flat-plate piezoelectric body, and the functional layers on both surfaces include electrode layers.

[0386] In the elongated flat-plate piezoelectric body (first piezoelectric body) of this embodiment, it is preferred that at least one of the surface layers of the laminate comprising the first piezoelectric body and the functional layer be an electrode layer. That is, in the elongated flat-plate piezoelectric body (first piezoelectric body) of this embodiment, it is preferred that at least one of the surface layer on the front side and the surface layer on the back side be an electrode layer (in other words, the electrode layer be exposed).

[0387] Therefore, when a long flat-plate piezoelectric body is used as one of the components of a piezoelectric device (piezoelectric fabric, piezoelectric knitted fabric, etc.), a force sensor, an actuator, or a biological information acquisition device, the conductor (preferably an internal conductor) or the first external conductor can be connected to the laminate more simply, thereby improving the productivity of the piezoelectric device (piezoelectric fabric, piezoelectric knitted fabric, etc.), the force sensor, the actuator, and the biological information acquisition device.

[0388] The material for the functional layer is not particularly limited, and examples thereof include inorganic materials such as metals and metal oxides; organic materials such as resins; and composite compositions comprising resins and fine particles. For example, the resin may be a cured product obtained by curing with heat or active energy radiation. In other words, a curable resin may also be used.

[0389] Examples of the curable resin include at least one material (curable resin) selected from the group consisting of acrylic compounds, methacrylic compounds, vinyl compounds, allyl compounds, urethane compounds, epoxy compounds, epoxide compounds, glycidyl compounds, oxetane compounds, melamine compounds, cellulose compounds, ester compounds, silane compounds, organosilicon compounds, siloxane compounds, silica-acryl hybrid compounds, and silica-epoxy hybrid compounds.

[0390] Among these, acrylic compounds, epoxy compounds, and silane compounds are more preferred.

[0391] Examples of the metal include at least one selected from Al, Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, In, Sn, W, Ag, Au, Pd, Pt, Sb, Ta, and Zr, or alloys thereof.

[0392] Examples of the metal oxide include titanium oxide, zirconium oxide, zinc oxide, niobium oxide, antimony oxide, tin oxide, indium oxide, cerium oxide, aluminum oxide, silicon oxide, magnesium oxide, yttrium oxide, ytterbium oxide, tantalum oxide, and at least one of composite oxides thereof.

[0393] Examples of the fine particles include fine particles of the metal oxides described above, and fine particles of resins such as fluorine-based resins, silicone-based resins, styrene-based resins, and acrylic resins. Furthermore, hollow fine particles having pores inside these fine particles are also exemplified.

[0394] From the perspective of transparency, the average primary particle size of the microparticles is preferably from 1 nm to 500 nm, more preferably from 5 nm to 300 nm, and even more preferably from 10 nm to 200 nm. By setting the average primary particle size to 500 nm or less, scattering of visible light can be suppressed, while by setting the average primary particle size to 1 nm or more, secondary aggregation of the microparticles can be suppressed, which is preferable from the perspective of maintaining transparency.

[0395] The thickness of the functional layer is not particularly limited, but is preferably in the range of 0.01 μm to 10 μm.

[0396] The upper limit of the thickness is more preferably 6 μm or less, and further preferably 3 μm or less. The lower limit is more preferably 0.01 μm or more, and further preferably 0.02 μm or more.

[0397] When the functional layer is a multilayer film comprising multiple functional layers, the above thickness represents the thickness of the multilayer film as a whole. Furthermore, the functional layers may be located on both sides of the elongated planar piezoelectric body. Furthermore, the refractive indices of the functional layers may be different.

[0398] The method for producing the long flat-plate piezoelectric body is not particularly limited, and the long flat-plate piezoelectric body can be produced by a known method.

[0399] In addition, for example, as a method of manufacturing the first piezoelectric body from a piezoelectric film, a raw material (such as polylactic acid) can be formed into a film to obtain an unstretched film, the unstretched film can be stretched and crystallized, and the obtained piezoelectric film can be cut to obtain it.

[0400] Here, "cutting" means cutting the piezoelectric film into long strips.

[0401] It should be noted that either of the above-mentioned stretching and crystallization can be performed first. Alternatively, a method can be used in which the unstretched film is subjected to pre-crystallization, stretching, and crystallization (annealing) in sequence. Stretching can be uniaxial stretching or biaxial stretching. In the case of biaxial stretching, it is preferred to increase the stretch ratio in one direction (the main stretching direction).

[0402] Regarding the method for producing the piezoelectric film, known documents such as Japanese Patent No. 4934235, International Publication No. 2010 / 104196, International Publication No. 2013 / 054918, and International Publication No. 2013 / 089148 can be appropriately referred to.

[0403] <Second Piezoelectric Body>

[0404] The piezoelectric substrate according to the first embodiment may include a second piezoelectric body having an elongated shape.

[0405] The second piezoelectric body preferably has the same characteristics as those of the first piezoelectric body.

[0406] That is, it is preferred that the second piezoelectric body contains an optically active helical chiral polymer (A),

[0407] The longitudinal direction of the second piezoelectric body is substantially parallel to the main orientation direction of the helical chiral polymer (A) contained in the second piezoelectric body.

[0408] The orientation degree F of the second piezoelectric body determined by the above formula (a) based on X-ray diffraction measurement is in the range of 0.5 or more and less than 1.0.

[0409] The second piezoelectric body preferably has the same characteristics as those of the first piezoelectric body in terms of characteristics other than those described above.

[0410] Among them, from the perspective of further exerting the effects of the present disclosure, the winding directions of the first piezoelectric body and the second piezoelectric body, and the chirality of the helical chiral polymer (A) contained in the first piezoelectric body and the second piezoelectric body can be appropriately selected according to the morphology of the piezoelectric substrate.

[0411] An example of a preferred combination of the winding directions of the first piezoelectric body and the second piezoelectric body, and the chirality of the helical chiral polymer (A) contained in the first piezoelectric body and the second piezoelectric body is as described in the above specific embodiment.

[0412] In addition, the second piezoelectric body may have characteristics different from those of the first piezoelectric body.

[0413] <First Insulator>

[0414] The piezoelectric substrate according to the first embodiment may further include a first insulator.

[0415] The first insulator is preferably wound in a spiral shape along the outer peripheral surface of the inner conductor.

[0416] In this case, the first insulator may be arranged on the side opposite to the internal conductor when viewed from the first piezoelectric body, or may be arranged between the internal conductor and the first piezoelectric body.

[0417] In addition, the winding direction of the first insulator may be the same as or different from the winding direction of the first piezoelectric body.

[0418] In particular, when the piezoelectric substrate of the first embodiment has a first external conductor, the piezoelectric substrate of the first embodiment further has a first insulator, thereby having the advantage of easily suppressing electrical short circuits between the internal conductor and the external conductor when the piezoelectric substrate is bent and deformed.

[0419] The first insulator is not particularly limited, and examples thereof include vinyl chloride resin, polyethylene resin, polypropylene resin, ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoropropyl vinyl ether copolymer (PFA), fluorinated rubber, polyester resin, polyimide resin, polyamide resin, polyethylene terephthalate resin (PET), rubber (including elastomer), etc.

[0420] From the viewpoint of winding the conductor, the first insulator preferably has an elongated shape.

[0421] <Second Insulator>

[0422] In the piezoelectric substrate of this embodiment, when the first outer conductor is provided on the outer periphery, a second insulator may be further provided on the outer periphery of the first outer conductor.

[0423] Thus, when functioning as a piezoelectric sensor, the internal conductor serving as the signal line can be electrostatically shielded, and voltage changes in the conductor (preferably the internal conductor) due to the influence of external static electricity can be suppressed.

[0424] The second insulator is not particularly limited, and for example, the materials exemplified as the first insulator can be used.

[0425] The shape of the second insulator is not particularly limited, as long as it can cover at least a portion of the first outer conductor.

[0426] (1st outer conductor)

[0427] The piezoelectric substrate of this embodiment preferably further includes a first external conductor on the outer periphery.

[0428] When functioning as a piezoelectric sensor, the first external conductor of this embodiment is preferably a ground conductor.

[0429] The ground conductor refers to a conductor that forms a pair with a conductor (preferably a signal line conductor) when detecting a signal.

[0430] The material of the ground conductor is not particularly limited, but the following materials can be mainly used depending on the cross-sectional shape.

[0431] For example, as a material of the ground conductor having a rectangular cross section, a copper foil tape obtained by rolling a copper wire having a circular cross section into a flat plate shape, an Al foil tape, or the like can be used.

[0432] For example, as a material of a grounding conductor having a circular cross section, copper wire, aluminum wire, SUS wire, metal wire covered with an insulating film, carbon fiber, resin fiber obtained by integrating carbon fiber, and brocade wire obtained by spirally winding copper foil around fiber can be used.

[0433] As the material of the ground conductor, a material obtained by coating an organic conductive material with an insulating material can be used.

[0434] In order to prevent a short circuit with the signal line conductor, the ground conductor is preferably arranged so as to cover the conductor (preferably the signal line conductor) and the first piezoelectric body.

[0435] As a method of covering the signal line conductor, the following methods can be selected: a method of winding copper foil or the like into a spiral shape for covering; a method of forming a tubular braided rope of copper wire or the like and wrapping the signal line conductor therein; and the like.

[0436] It should be noted that the method of covering the signal line conductor is not limited to these methods. By covering the signal line conductor, electrostatic shielding can be achieved, and voltage changes of the signal line conductor caused by the influence of external static electricity can be prevented.

[0437] Furthermore, one of the preferred configurations is to arrange the ground conductor so as to wrap the minimum basic structural unit of the piezoelectric substrate of this embodiment (ie, the conductor and the first piezoelectric body) in a cylindrical shape.

[0438] The cross-sectional shape of the ground conductor can be various, such as circular, elliptical, rectangular, or irregular. A rectangular cross-sectional shape, in particular, allows for close planar contact with the conductor (preferably a signal line conductor), the first piezoelectric element, and, if necessary, the first insulator and the second piezoelectric element. Therefore, the charge generated by the piezoelectric effect can be effectively detected as a voltage signal.

[0439] <Adhesive Forming Adhesive Layer>

[0440] The piezoelectric substrate of this embodiment preferably has an adhesive layer between the conductor and the first piezoelectric body.

[0441] The adhesive forming the adhesive layer is used to mechanically integrate the conductor and the first piezoelectric body, or, when the piezoelectric substrate has an external conductor, to maintain the distance between electrodes (between the conductor and the external conductor).

[0442] By providing an adhesive layer between the conductor and the first piezoelectric body, when tension is applied to the piezoelectric substrate of this embodiment, the relative positions of the conductor and the first piezoelectric body are less likely to deviate, making it easier to apply tension to the first piezoelectric body. Consequently, a voltage output proportional to the tension can be effectively detected from the conductor (preferably a signal line conductor). As a result, the piezoelectric sensitivity and the stability of the piezoelectric output are further improved. Furthermore, the presence of the adhesive layer further increases the absolute value of the charge generated per unit tensile force.

[0443] On the other hand, a piezoelectric base material without an adhesive layer between the conductor and the first piezoelectric body retains its softness even after being processed into piezoelectric fibers, etc., and therefore provides a good wearing feel when made into a wearable sensor, etc.

[0444] As materials of the adhesive forming the adhesive layer, the following materials can be used.

[0445] Epoxy adhesives, polyurethane adhesives, vinyl acetate resin emulsion adhesives, (EVA) emulsion adhesives, acrylic resin emulsion adhesives, styrene-butadiene rubber latex adhesives, silicone resin adhesives, α-olefin (isobutylene-maleic anhydride resin) adhesives, vinyl chloride resin solvent adhesives, rubber adhesives, elastic adhesives, chloroprene rubber solvent adhesives, nitrile rubber solvent adhesives, cyanoacrylate adhesives, etc. can be used.

[0446] -Elastic modulus-

[0447] The elastic modulus of the adhesive in this embodiment after bonding is preferably approximately equal to or higher than the elastic modulus of the first piezoelectric element. If a material with an elastic modulus lower than that of the first piezoelectric element is used, the strain (piezoelectric strain) caused by the tension applied to the piezoelectric substrate in this embodiment is mitigated in the adhesive, reducing the efficiency of strain transmission to the first piezoelectric element. Consequently, when the piezoelectric substrate in this embodiment is used in a sensor, for example, the sensitivity of the sensor is likely to decrease.

[0448] -thickness-

[0449] The thickness of the adhesive at the joint in this embodiment is preferably as thin as possible, as long as no gaps are created between the bonded components and the bond strength is not reduced. By reducing the thickness of the joint, the strain caused by the tension applied to the piezoelectric substrate is less likely to be relieved in the adhesive, effectively reducing the strain applied to the first piezoelectric element. Consequently, when the piezoelectric substrate of this embodiment is used in, for example, a sensor, the sensitivity of the sensor is improved.

[0450] -Adhesive application method-

[0451] The method for applying the adhesive is not particularly limited, but the following two methods can be mainly used.

[0452] Method of joining by applying adhesive after processing

[0453] For example, the following method can be cited: after completing the configuration of the conductor (preferably the signal line conductor) and the first piezoelectric body, and processing and configuring the signal line conductor and the ground conductor, an adhesive is configured at the interface between the conductor and the first piezoelectric body for bonding by using methods such as dip coating and impregnation.

[0454] Furthermore, in addition to bonding the conductor and the first piezoelectric body by the above-described method, each member included in the piezoelectric substrate of this embodiment may be bonded to each other as needed.

[0455] Method of preparing uncured adhesive before processing and joining after processing

[0456] For example, the following method can be cited: using a gravure coater, a dip coater, etc., a photocurable adhesive, a thermosetting adhesive, a thermoplastic adhesive, etc. is pre-coated on the surface of the first piezoelectric body and dried. After completing the arrangement of the conductor and the first piezoelectric body, the adhesive is cured by ultraviolet irradiation and heating, thereby bonding the interface between the conductor and the first piezoelectric body.

[0457] Furthermore, in addition to bonding the conductor and the first piezoelectric body by the above-described method, each member included in the piezoelectric substrate of this embodiment may be bonded to each other as needed.

[0458] The above method has the following characteristics: after the adhesive is applied and dried, processing can be performed using a dry process, making processing easy; and since a uniform coating thickness can be easily formed, variations in sensor sensitivity, etc. are small.

[0459] <Method for Manufacturing Piezoelectric Substrate>

[0460] The method for manufacturing the piezoelectric substrate of this embodiment is not particularly limited, and can be manufactured, for example, by preparing a first piezoelectric body and spirally winding the first piezoelectric body in one direction around a separately prepared conductor (preferably a signal line conductor).

[0461] The first piezoelectric body can be manufactured using a known method or can be purchased commercially.

[0462] Furthermore, when the piezoelectric substrate of the present embodiment includes a second piezoelectric body and a first insulator as necessary, the piezoelectric substrate can be manufactured by winding the first piezoelectric body in a spiral shape.

[0463] The winding directions of the first and second piezoelectric bodies and the chirality of the helical chiral polymer (A) contained in the first and second piezoelectric bodies are preferably appropriately selected according to the form of the piezoelectric substrate as described above.

[0464] Furthermore, when the piezoelectric substrate of this embodiment includes a first external conductor (for example, a ground conductor), the piezoelectric substrate can be manufactured by disposing the first external conductor using the above-mentioned method or a known method.

[0465] Note that, for example, the above-mentioned method can be used to bond the conductor and the first piezoelectric body, and as needed, the various components included in the piezoelectric substrate of this embodiment, via an adhesive.

[0466] In the piezoelectric substrate of this embodiment, when a tensile force is applied, a shear strain proportional to the tensile force is applied to the helical chirality (A), and is detected from the conductor as a voltage signal (charge signal).

[0467] <Function>

[0468] The effects of bed device 10 according to this embodiment are as follows.

[0469] like Figure 2 As shown, in this embodiment, the sensor unit 32 is installed on the bed board 24 so that the arrangement direction of each region 34 is oriented in the bed width direction, which is a predetermined direction. Therefore, if a person is lying on the mattress 26, pressure is applied from the person's body in the radial direction of the piezoelectric substrate 12 in the sensor unit 32 for each region 34. As a result, each piezoelectric substrate 12 outputs a voltage corresponding to the pressure. In the AD converter 42, which receives the voltage output from each piezoelectric substrate 12, the voltage output, which is an analog signal, is converted into a digital signal and output to the processing PC 50. The detection unit 55 in the processing PC 50 then detects the digital signal, thereby detecting whether the person is on the mattress 26 and in which detection region 27 (region 34) the person is lying. For example, if the voltage output V of a certain piezoelectric substrate 12 exceeds the threshold value Vt, it can be detected that the person is lying in the region 34 where the piezoelectric substrate 12 is located, that is, the detection region 27 on the mattress 26.

[0470] Furthermore, the bed device 10 of this embodiment can be configured as a human body detection system capable of detecting when a bedridden person turns over by providing a determination unit 56 in the processing PC 50 of the human body detection device 30. In the bed device 10 as a human body detection system, regions 34 are provided on the reference surface 33 along the bed width, which serves as a predetermined direction. A piezoelectric substrate 12 is disposed in each region 34. Furthermore, the determination unit 56 compares the voltage outputs of adjacent piezoelectric substrates 12 in the bed width direction, thereby determining the movement of the bedridden person on the mattress 26 (or reference surface 33). In practice, the detection unit 55 of the processing PC 50 records the moment when the voltage output V from each piezoelectric substrate 12 exceeds a threshold value Vt. The determination unit 56 can determine whether the bedridden person has turned over and in which direction based on the order in which the piezoelectric substrates 12 exceed the threshold value Vt.

[0471] As described above, according to this embodiment, not only the presence or absence of a lying person can be detected, but also the position of the bed surface of the bed 20 can be detected. Furthermore, by using the processing PC 50 to monitor the positional deviation of the bed occupant on the bed surface and notifying the bed occupant and a caregiver, it is possible to prevent falls from the bed 20.

[0472] The sensor unit 32 of this embodiment includes a linear piezoelectric substrate 12. Therefore, there are no restrictions on the configuration within region 34. For example, by arranging the piezoelectric substrate 12 in a wavy or spiral pattern along the reference plane 33 within region 34, the direction and sensitivity of pressure detection can be varied. Furthermore, in this embodiment, region 34 is divided into four sections along the width of the bed, but this is not limiting. More than four sections can be provided, or additional sections can be added along the length of the bed. This can improve the resolution of body detection for bedridden individuals.

[0473] In addition, the piezoelectric substrate 12 is characterized by having a first piezoelectric body 18A in the form of an elongated strip that is spirally wound in one direction relative to the internal conductor 16A. The pressure input to the first piezoelectric body 18A is detected based on the potential difference between the internal conductor 16A and the first piezoelectric body 18A. According to the bed device 10 of this embodiment, by using a piezoelectric body as a sensor for detecting pressure, it is no longer necessary to supply power to the sensor. Therefore, compared to a load sensor that uses a strain gauge as a sensor for detecting pressure, for example, no power is consumed in the standby state. In other words, it can be driven by a simple circuit and is therefore suitable for miniaturization. In addition, the polylactic acid used in the piezoelectric body is cheaper than the load sensor, so the manufacturing cost of the sensor part can be suppressed.

[0474] <Notes>

[0475] The human body detection device 30 of this embodiment can be assembled onto an existing bed 20 to form a bed device 10, or it can be installed on a carpet, floor, or tatami mat. The human body detection device 30 installed on a carpet, floor, or tatami mat can also achieve the same functions and effects as the bed device 10 described above. The human body detection device 30 of this embodiment can be combined with existing bedding, allowing users to use existing bedding as is and preventing a worsening of sleep quality.

[0476] In the bed device 10 of this embodiment, the piezoelectric substrate 12 is covered with an insulating member 38, but the present invention is not limited thereto. The piezoelectric substrate 12 can also be directly arranged between the mattress 26 and the cushioning material 37. The cushioning material 37 is subjected to a compressive load from the human body on the bed 20 and is strained, thereby applying tension to the piezoelectric substrate 12. Therefore, if the amount of strain of the cushioning material 37 relative to a certain load is large, the sensitivity of the piezoelectric substrate 12 can be improved. In other words, in order to make the piezoelectric substrate 12 sensitive, the cushioning material 37 is preferably a soft material with a low elastic modulus, a low rubber hardness, and a low density. As a specific material, it is preferred to use a foamed low elastic modulus resin material. As the foamed resin material, materials such as soft polyurethane foam, hard polyurethane foam, polystyrene foam, polyethylene foam, polypropylene foam, EVA cross-linked foam, PET resin foam, phenolic foam, silicone foam, polyvinyl chloride foam, urea foam, acrylic foam, polyimide foam, and EPDM foam can be used. On the other hand, if the elastic modulus, rubber hardness, or density of the material constituting the cushioning material 37 is too low, the strain caused by a large compressive load will cause the cavitation in the cushioning material 37 to collapse, making it difficult to generate strain, and thus making it difficult to achieve high-sensitivity sensing. To avoid reaching this compressive deformation region where strain is difficult to generate, the thickness of the cushioning material 37 should be appropriately optimized according to the applied load.

[0477] Furthermore, as the expansion ratio of the foamed plastic increases, the variation in density and rubber hardness increases, leading to greater variation in the sensor sensitivity of the piezoelectric substrate 12. Furthermore, materials such as natural rubber experience significant changes in rubber hardness over time, leading to greater variation in sensor sensitivity. EPDM foam, for example, is preferred, as it exhibits minimal changes over time.

[0478] Furthermore, when the cushioning material 37 is used in the bed 20, flame retardancy is often required. The cushioning material 37 is preferably made of a foamed plastic compounded with various flame retardant additives for flame retardancy, or a resin inherently flame retardant such as polyvinyl chloride foam or polyimide foam.

[0479] Alternatively, the cushioning material 37 may be disposed directly between the mattress 26 and the support plate 36 without providing the cushioning material 37 .

[0480] In the bed device of each embodiment, the support plate 36 is not necessarily required, and the cushioning material 37 may be provided on the bed board 24. In this case, the piezoelectric substrate 12 may be directly disposed between the mattress 26 and the cushioning material 37, or directly between the mattress 26 and the bed board 24.

[0481] The insulating member 38 serving as the covering member in this embodiment is, but is not limited to, an adhesive tape or an adhesive film. Examples of the insulating member 38 include a laminate, a heat shrink tube, and a covering made of an insulating material (e.g., a PET or fluorine tape wrapped around a piezoelectric wire).

[0482] It should be noted that the processing involved in the detection unit 55, the determination unit 56, and the notification unit 57 that the CPU 50A reads the software (program) and executes in the above embodiment can also be performed by various processors other than the CPU. As examples of the processor in this case, there can be exemplified: a PLD (Programmable Logic Device) such as an FPGA (Field-Programmable Gate Array) whose circuit configuration can be changed after manufacturing; and a dedicated circuit such as an ASIC (Application Specific Integrated Circuit) that is a processor having a circuit configuration specifically designed to perform specific processing; and the like. In addition, various processing can be performed using one of the various processors mentioned above, or by a combination of two or more processors of the same or different types (for example, multiple FPGAs, and a combination of a CPU and an FPGA, etc.). In addition, more specifically, the hardware structure of the various processors mentioned above is a circuit that combines circuit elements such as semiconductor elements.

[0483] In addition, the above embodiment describes a method in which the execution program is pre-stored (installed) in the storage device 50D, but the present invention is not limited to this. Each program can also be provided in the form of being recorded on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory. In addition, the program can also be downloaded from an external device via a network.

[0484] <Second embodiment>

[0485] based on Figure 9 , a bed device 10A according to a second embodiment will be described.

[0486] The bed device 10A of the second embodiment is different from the first embodiment in the arrangement of the piezoelectric substrate 12. Figure 9 In the figure, only the arrangement of the piezoelectric substrate 12 relative to the mattress 26 is shown, and the frame 22, the bed board 24, the support plate 36, the cushioning material 37 and the insulating member 38 are omitted (hereinafter, Figures 10 to 12Hereinafter, differences from the first embodiment will be described.

[0487] In the mattress 26 of this embodiment, as in the first embodiment, the detection region 27 is divided into four parts in the bed width direction. On the other hand, in each detection region 27, the piezoelectric substrate 12 is arranged along the bed length direction.

[0488] When the piezoelectric substrate 12 is arranged along the bed width direction, as in the first embodiment, the pressure detection accuracy in the bed width direction is less likely to vary within each detection region 27. In contrast, when the piezoelectric substrate 12 is arranged along the bed length direction, as in the second embodiment, a pressure detection range can be ensured in the bed length direction within each detection region 27. Therefore, even when there are differences in height between bed users lying on the mattress 26, the pressure detection accuracy in the bed length direction is less likely to vary.

[0489] In addition, in this embodiment, the same functions and effects as those of the above-mentioned first embodiment are achieved.

[0490] <Third embodiment>

[0491] based on Figure 10 , a bed device 10B according to a third embodiment will be described.

[0492] The bed device 10B of the third embodiment differs from the first and second embodiments in the arrangement of the piezoelectric substrate 12. The differences from the first and second embodiments will be described below.

[0493] In the mattress 26 of this embodiment, as in the first embodiment, the detection region 27 is divided into four sections in the bed width direction. In each detection region 27, the piezoelectric substrate 12 is arranged in a wave shape extending along the bed length direction, with amplitude in the bed width direction.

[0494] In the bed device 10B of this embodiment, the pressure detection range is broad across both the bed's longitudinal and width directions within each detection region 27. Therefore, according to this embodiment, the pressure detection accuracy in each detection region 27 is less likely to vary in both the bed's longitudinal and width directions.

[0495] In addition, in this embodiment, the same functions and effects as those of the above-mentioned first embodiment are achieved.

[0496] <Fourth embodiment>

[0497] based on Figure 11 , a bed device 10C according to a fourth embodiment will be described.

[0498] The bed device 10C of the fourth embodiment is different from the first embodiment in the number of divisions of the detection area 27 in the mattress 26. The differences from the first embodiment will be described below.

[0499] In the mattress 26 of this embodiment, the detection region 27, which serves as the pressure measurement range, is divided into four sections in the bed width direction and five sections in the bed length direction, for a total of 20 sections. In each detection region 27, the piezoelectric substrate 12 is arranged along the bed width direction.

[0500] In the bed device 10C of this embodiment, multiple piezoelectric substrates 12 are also arranged along the length of the bed, thereby increasing the pressure detection range. Furthermore, according to this embodiment, the number of piezoelectric substrates 12 per unit area is increased, thereby improving the resolution when detecting the body of a bedridden person.

[0501] It should be noted that when the piezoelectric substrates 12 are arranged as in this embodiment, the sensor units 32 of the first embodiment can be arranged side by side in the longitudinal direction of the bed, or 20 piezoelectric substrates 12 can be arranged on a support plate 36 of approximately the same size as the mattress 26.

[0502] In addition, in this embodiment, the same functions and effects as those of the above-mentioned first embodiment are achieved.

[0503] <Fifth embodiment>

[0504] based on Figure 12 , a bed device 10D according to a fifth embodiment will be described.

[0505] The bed device 10D of the fifth embodiment is different from the fourth embodiment in the arrangement of the piezoelectric substrate 12. The differences from the first and fourth embodiments will be described below.

[0506] As in the fourth embodiment, the mattress 26 of this embodiment is divided into four sections in the width direction and five sections in the length direction, for a total of 20 sections. Meanwhile, in each detection area 27, the piezoelectric substrate 12 is arranged in a spiral shape.

[0507] According to the bed device 10D of this embodiment, similar to the fourth embodiment, the resolution when detecting the body of a bedridden person can be improved. Furthermore, in this embodiment, the piezoelectric substrate 12 is arranged within a wide range of each detection area 27, so that the detection accuracy of the pressure in the bed length direction and the bed width direction is less likely to vary.

[0508] In addition, in this embodiment, the same functions and effects as those of the above-mentioned first embodiment are achieved.

[0509] <Sixth embodiment>

[0510] based on Figure 15A and Figure 15B , a bed device 10 according to a sixth embodiment will be described.

[0511] The bed device 10 of the sixth embodiment has the same configuration as the bed device 10 of the first embodiment, but differs in that a piezoelectric substrate 12C is used instead of the piezoelectric substrate 12. The differences from the first embodiment will be described below.

[0512] Figure 15A It is a side view showing an example of a piezoelectric substrate according to the sixth embodiment.

[0513] like Figure 15A As shown, in the piezoelectric substrate 12C according to the sixth embodiment, an outer conductor 19 is arranged on the outer periphery thereof, wound in a spiral shape in one direction. Specifically, the piezoelectric substrate 12C includes, in order from the inner side, an elongated inner conductor 16A, a functional layer 15, an elongated first piezoelectric body 18A, and an outer conductor 19.

[0514] The functional layer 15 is provided on the outer peripheral surface of the internal conductor 16A and is located between the internal conductor 16A and the first piezoelectric body 18A. It should be noted that the functional layer 15 is a layer provided as needed.

[0515] Hereinafter, the effects of the piezoelectric substrate 12C according to the sixth embodiment will be described.

[0516] Figure 15B Show Figure 15A For example, when tension is applied in the longitudinal direction of the piezoelectric substrate 12C, a shear force is applied to the helical chiral polymer (A) contained in the first piezoelectric body 18A, and the helical chiral polymer (A) is polarized. It is believed that the polarization of the helical chiral polymer (A) is as follows: Figure 15B The arrow in the middle indicates that the polarization is generated in the radial direction of the piezoelectric substrate 12C, and the polarization directions are generated in a phase-matched manner. This allows for efficient detection of a voltage signal proportional to the tension.

[0517] In particular, in the piezoelectric substrate 12C according to the sixth embodiment, the first piezoelectric body 18A is spirally wound in one direction without a gap along the outer circumference of the internal conductor 16A, so that the internal conductor 16A is not visible. Therefore, the adhesion between the internal conductor 16A and the first piezoelectric body 18A is improved, and a gap is less likely to form between the internal conductor 16A and the external conductor 19.

[0518] Here, if Figure 15BAs shown in FIG. 1 , the cross section of the piezoelectric substrate 12C according to the sixth embodiment, which is perpendicular to the central axis, is formed into an elliptical shape, not a circular shape. Since the cross section perpendicular to the central axis is elliptical, even when tension is applied in a high-temperature environment exceeding the glass transition temperature of the resin contained in the piezoelectric component, the resin can be prevented from curling up, and a decrease in piezoelectric sensitivity can be easily suppressed. Figure 15B As shown, the cross section of the piezoelectric substrate 12C perpendicular to the central axis is elliptical.

[0519] The elliptical shape is formed so that the dimension ratio (long diameter / short diameter) is, for example, in the range of 1.05 to 10.00. The elliptical shape is formed so that the aspect ratio is, for example, in the range of 0.04 to 0.9.

[0520] It should be noted that, in this embodiment, the cross section of the piezoelectric substrate 12C perpendicular to the central axis is not limited to an elliptical shape, and any shape other than a circular shape may be sufficient.

[0521] The piezoelectric substrate 12C according to the sixth embodiment is not limited to the above-described structure. For example, in the piezoelectric substrate 12C, an adhesive layer (not shown) may be provided between the internal conductor 16A and the first piezoelectric body 18A as a functional layer. This prevents the relative position of the first piezoelectric body 18A and the internal conductor 16A from shifting even when tension is applied in the longitudinal direction of the piezoelectric substrate 12C, making it easier to apply tension to the first piezoelectric body 18A.

[0522] In the piezoelectric substrate 12C according to the sixth embodiment, as described above, the functional layer 15 is provided between the internal conductor 16A and the first piezoelectric body 18A. The functional layer 15 may be provided at other positions as appropriate.

[0523] In the piezoelectric substrate 12C according to the sixth embodiment, an external conductor 19 is disposed on the outer circumference of the piezoelectric substrate 12C, wound in a spiral shape in one direction. The arrangement of the external conductor 19 is not limited thereto; it may be disposed on at least a portion of the outer circumference of the first piezoelectric body 18A. The winding direction of the external conductor 19 is also not particularly limited.

[0524] Conventionally, piezoelectric substrates have been used as piezoelectric components made of resins (such as polylactic acid). These substrates experience reduced piezoelectric sensitivity in high-temperature environments exceeding the glass transition temperature of the resin used in the piezoelectric component. Furthermore, after use in high-temperature environments exceeding the glass transition temperature, the piezoelectric sensitivity decreases relative to the initial value when the substrate returns to room temperature.

[0525] The reduction in piezoelectric sensitivity is thought to occur as follows. The resin (e.g., polylactic acid) is coated on the fibers in a spiral pattern. When tension is applied in a high-temperature environment exceeding the glass transition temperature of the resin contained in the piezoelectric component, it is believed that the elastic deformation range is exceeded, causing the resin to coil tightly. Therefore, it is speculated that piezoelectric sensitivity decreases when used in an environment exceeding the glass transition temperature of the resin contained in the piezoelectric component.

[0526] On the other hand, because the cross-section perpendicular to the central axis of the piezoelectric substrate 12C of this embodiment is non-circular, even when tension is applied in a high-temperature environment exceeding the glass transition temperature of the resin, the resin is prevented from curling up. Consequently, it is believed that a decrease in piezoelectric sensitivity can be suppressed.

[0527] Therefore, the piezoelectric substrate 12C of this embodiment and the bed device 10 using the piezoelectric substrate 12C have excellent piezoelectric sensitivity. In particular, when the piezoelectric substrate 12C is used in the bed device 10, even when the bed device 10 is exposed to a high temperature environment due to a rise in room temperature in the summer, a decrease in piezoelectric sensitivity can be suppressed.

[0528] As for non-circular shapes, from the perspective of suppressing the tightness of the resin and suppressing the reduction of piezoelectric sensitivity, there are no particular limitations as long as the shape is not circular. Examples of non-circular shapes include elliptical shapes, rectangular shapes, and irregular shapes other than elliptical and rectangular shapes. The irregular shape can be triangular or a polygon with a pentagon or larger shape. In addition, it can be a cocoon ball shape, a rhombus shape, or a trapezoidal shape. Among these, the elliptical shape is preferred.

[0529] In addition, with respect to the piezoelectric substrate 12C of this embodiment, from the perspective of suppressing a decrease in piezoelectric sensitivity, the dimension ratio of the major diameter to the minor diameter (major diameter / minor diameter) (hereinafter also referred to as "dimension ratio (major diameter / minor diameter)") in a cross section perpendicular to the central axis is preferably 1.05 to 10.00 (major diameter / minor diameter = 1.05 / 1 to 10.00 / 1). The dimension ratio (major diameter / minor diameter) is more preferably 1.05 to 5.00, and even more preferably 1.05 to 2.00. The dimension ratio (major diameter / minor diameter) represents the ratio of the shortest length passing through the center of the cross-sectional shape in a cross section perpendicular to the central axis to the length of the major diameter perpendicular to the major diameter.

[0530] The aspect ratio of the non-circular cross section may be 0.4 to 0.9, 0.4 to 0.8, or 0.4 to 0.5. The aspect ratio can be calculated using the following formula.

[0531] (Formula) Aspect Ratio = (Major Radius - Minor Radius) / Major Radius

[0532] (Supplementary Implementation Methods)

[0533] In the bed device of each embodiment, the piezoelectric substrate 12 (or piezoelectric substrates 12A to 12C) can also be used as a biological information acquisition device. Specifically, the piezoelectric substrate 12 of this embodiment can be made into a biological information acquisition device that can detect heart rhythm, pulse, cough, sneeze and snoring. For example, by extracting the vibration component corresponding to the heart rhythm from the voltage signal output from the piezoelectric substrate 12, it is possible to detect the heart rhythm or pulse. In addition, for example, by removing the low-frequency component corresponding to turning over from the voltage signal output from the piezoelectric substrate 12, or performing frequency analysis on the voltage signal, or pre-setting a threshold, it is possible to detect coughing and snoring.

[0534] The embodiments can be used in combination with each other as appropriate, and can be implemented in various forms within the scope not departing from the gist of the present disclosure.

[0535] For example, the piezoelectric substrate 12 of the third embodiment may be combined with the twenty detection regions 27 of the fourth embodiment, and a corrugated piezoelectric substrate 12 may be arranged in each of the twenty detection regions 27. Furthermore, for example, in the fifth embodiment, instead of arranging piezoelectric substrates 12 in all detection regions 27, piezoelectric substrates 12 may be arranged every other piezoelectric substrate 12 in both the bed length direction and the bed width direction.

[0536] Furthermore, for example, the piezoelectric substrate 12C of the sixth embodiment may be applied to the bed devices of the second to fifth embodiments.

[0537] Human body detection device 30 of the embodiment can be applied to the following devices other than bed device 10. For example, applicable devices include a body pressure distribution measuring device and a foot pressure distribution measuring system.

[0538] Example

[0539] Hereinafter, the present disclosure will be described in more detail with reference to Examples. However, the present disclosure is not limited to the following Examples as long as the gist of the present disclosure is not exceeded.

[0540] (1) Embodiments Related to Bed Devices

[0541] <Manufacturing of Bed Device>

[0542] like Figure 1 As shown, the bed device 10 of the first embodiment includes a single-sized bed 20 composed of a frame 22, a bed board 24, and a mattress 26. In the bed 20 of the first embodiment, a sensor unit 32 is disposed between the bed board 24 and the mattress 26.

[0543] The mattress 26 of Example 1 is made of polyurethane and has a width W of 970 mm, a length L of 2000 mm, and a thickness da of 40 mm. Furthermore, according to JIS K 6400-2 (Soft Foam Materials - Physical Properties - Part 2: Methods for Determining Hardness and Compression Stress-Strain Characteristics), Section 6.4, "Method A (Determination of the Force After 40% Constant Compression for 30 Seconds)," the hardness of the mattress 26 is 150 N.

[0544] As for the piezoelectric substrate 12, a micro-slit tape with a thickness of 50 μm and a width of 0.6 mm is made from the piezoelectric film (PLA film) manufactured in the above manner. Next, the micro-slit tape is wound in the S-winding (counterclockwise) direction at a 45° angle relative to the longitudinal direction of the brocade thread (model: u24) manufactured by Meisei Industry Co., Ltd. Furthermore, on the outside, a rolled copper foil with a width of 0.3 mm and a thickness of 30 μm as an external conductor is tightly wound in the Z-winding direction so that the micro-slit tape does not expose from the outside, thereby forming the piezoelectric substrate 12. Furthermore, the piezoelectric substrate 12 has a range from one end to 200 mm as the pressure measurement range, and an insulating component 38 is coated above and below the measurement range. The insulating component 38 is a polyimide adhesive tape with a total thickness of 60 μm, consisting of a polyimide film with a thickness of 25 μm and an adhesive layer with a thickness of 35 μm.

[0545] A sheet obtained by extrusion foaming polypropylene at a size of approximately 3 times was used as the support plate 36. The cushioning material 37 was a sponge sheet made of SBR (styrene butadiene rubber) with a width of 100 mm and a thickness of 5 mm.

[0546] As described above, the piezoelectric substrate 12 covered with the insulating member 38 is further bonded to the upper surface of the cushioning material 37 attached to the upper surface of the support plate 36 in each region 34, thereby forming the sensor unit 32. The sensor unit 32 of Example 1 is installed on the bed board 24 so as to straddle the bed board 24. In other words, it is installed in the center of the bed in the longitudinal direction.

[0547] The other end portion of each piezoelectric substrate 12 serves as a connection electrode portion, and the internal conductor 16A and the first piezoelectric body 18A in the connection electrode portion are electrically connected to the AD converter 42 .

[0548] <Confirmation of detection status>

[0549] The subject, who is a bedridden person, lies on the mattress 26 of the bed device 10. The subject turns over in the order of part A, part D, part A, part D, and part B from the center of the bed width direction (the boundary between parts B and C). At this time, the voltage output V of the piezoelectric substrate 12 of each detection area 27 is shown in FIG. Figure 13 .like Figure 13As shown, for each piezoelectric substrate 12, the pressure applied by the mattress 26 itself presents a reference voltage of 2.6 V, and the voltage in the detection area 27 where the subject lies is higher than 2.6 V. Furthermore, the position where the subject lies corresponds to the detection area 27 corresponding to the piezoelectric substrate 12 with the highest voltage value.

[0550] It should be noted that when the subject turns over, the voltage output of the corresponding piezoelectric substrate 12 in the detection area 27 immediately after the subject leaves is lower than the reference voltage of 2.6 V. This is because the pressure exerted by the mattress 26 itself decreases as the mattress 26, which has been compressed and deformed by the human body, returns to its original shape.

[0551] Here, the threshold Vt is set to 2.9V. Figure 14 Shown Figure 13 The moment the threshold is exceeded. It should be noted that the AD converter 42 of Example 1 is set to output 1V when the voltage output of each piezoelectric substrate 12 exceeds 2.9V. In this figure, the order of the detection areas 27 corresponding to the piezoelectric substrate 12 outputting 1V is: Part B, Part A, Part B, Part C, Part D, Part C, Part B, Part A, Part B, Part C, Part D, Part C, Part B. This matches the order of the detection areas 27 when the subject turns over.

[0552] As described above, according to the first embodiment, the position of the subject lying on the mattress 26 on the bed surface can be detected, and turning over can also be detected.

[0553] (2) Examples Related to Different Cross-Sectional Shapes of Piezoelectric Substrates

[0554] Next, the influence of the temperature due to the difference in cross-sectional shape of the piezoelectric substrate used in the bed device was evaluated.

[0555] <Fabrication of Piezoelectric Body>

[0556] To 100 parts by mass of polylactic acid (product name: Ingeo™ biopolymer, trademark: 4032D) manufactured by NatureWorks LLC, which is a helical chiral polymer, 1.0 part by mass of a stabilizer [a mixture of Stabaxol P400 (10 parts by mass) manufactured by Rhein Chemie, Stabaxol I (70 parts by mass) manufactured by Rhein Chemie, and CARBODILITE LA-1 (20 parts by mass) manufactured by Nisshinbo Chemical Inc.] was added and dry-blended to prepare a raw material.

[0557] The prepared raw material was placed in the hopper of an extruder, heated to 210°C, extruded from a T-die, and placed in contact with a casting roll at 50°C for 0.3 minutes to produce a pre-crystallized sheet with a thickness of 150 μm (pre-crystallization step). The crystallinity of the pre-crystallized sheet was measured and found to be 6%.

[0558] The obtained pre-crystallized sheet was heated to 70° C. and stretched in a roll-to-roll manner at a stretching speed of 10 m / min, and uniaxially stretched to 3.5 times in the MD direction (stretching step). The obtained film had a thickness of 49.2 μm.

[0559] Next, the uniaxially stretched film was brought into contact with a roll heated to 145° C. for 15 seconds in a roll-to-roll manner for annealing, and then rapidly cooled to produce a piezoelectric film (annealing step).

[0560] Next, the piezoelectric film was slit using a slitting machine, with the slitting direction roughly parallel to the stretching direction of the piezoelectric film. This resulted in a strip-shaped piezoelectric body (slit strip) with a width of 0.39 mm and a thickness of 50 μm. The cross-sectional shape of the resulting piezoelectric body was rectangular.

[0561] The obtained piezoelectric body had a glass transition temperature of 68.8°C.

[0562] -Measurement of physical properties of piezoelectric body-

[0563] The following physical properties of the obtained ribbon-shaped piezoelectric body were measured. The results are shown in Table 1.

[0564] The measurement was carried out in the following manner: using a wide-angle X-ray diffraction apparatus (RINT2550 manufactured by Rigaku Corporation, with attached device: rotating sample stage, X-ray source: CuKα, output: 40 kV 370 mA, detector: scintillation counter), the sample (piezoelectric body) was fixed on a support table, and the azimuthal angle distribution intensity of the crystal plane peak [(110) plane / (200) plane] was measured.

[0565] The orientation degree F (C-axis orientation degree) of the polylactic acid was calculated from the crystallinity and the peak half-value width (α) in the obtained azimuthal distribution curve (X-ray interferogram) using the following formula for evaluation. The results showed that the crystallinity was 45% and the orientation degree F was 0.97.

[0566] Orientation degree (F) = (180°-α) / 180°

[0567] (α is the half-peak width of the peak derived from orientation)

[0568] [Table 1]

[0569]

[0570] <Relative Dielectric Constant of Piezoelectric Material>

[0571] The measurement was performed in accordance with JIS C2151 (2006) using a dielectric constant measuring device (precision LCR meter HP4284A manufactured by Agilent Technologies, Inc.) at a measurement frequency of 1 kHz, a test environment of 22° C., and 60% RH. The relative dielectric constant εS of the piezoelectric body (slit tape) was 2.75.

[0572] [Example 2]

[0573] <Fabrication of Piezoelectric Substrate>

[0574] A piezoelectric substrate having a copper foil tape as an external conductor (ground conductor) was prepared by the method described below.

[0575] First, as an inner conductor (signal line conductor), a brocade wire U24-01-00 (wire outer diameter: 0.3 mm, length: 250 mm) manufactured by Meisei Industry Co., Ltd. was prepared.

[0576] As for the brocade thread used, the center line is made of meta-aramid fiber (40s double twisted), and two pieces of rolled copper foil (width 0.3mm × thickness 0.02mm) are used. They are wrapped in a spiral shape into a double layer, 22 times per 10mm, in a left-handed manner, so that the center line is not exposed.

[0577] By riveting, crimp terminals are provided at both ends of the prepared brocade wire as electrical and mechanical connection parts.

[0578] Next, the strip piezoelectric body (slit strip) with a width of 0.6 mm and a thickness of 49.2 μm obtained as described above is wound around the brocade thread in a left-handed manner in a spiral shape with no gaps (the brocade thread is not exposed and cannot be observed) in a direction of 45° relative to the long axis direction of the brocade thread (spiral angle 45°), thereby wrapping the brocade thread.

[0579] It should be noted that the so-called "left-handed" refers to the direction from one end ( Figure 6A When viewed from the right end side, the strip piezoelectric body is wound in a counterclockwise manner from the near side to the far side of the signal line conductor.

[0580] Next, in order to mechanically integrate the brocade thread and the strip piezoelectric body, ARON ALPHA (cyanoacrylate adhesive) 911P2 manufactured by Toagosei Co., Ltd. was dropped as an adhesive to impregnate the portion where the strip piezoelectric body was wound, thereby forming a functional layer.

[0581] Next, a copper foil tape with adhesive slit into a width of 0.6 mm was prepared as an external conductor and wrapped around the piezoelectric strip in the same manner as above without exposing the piezoelectric strip.

[0582] Next, after wrapping the external electrodes, a hot press (Imoto Manufacturing Co., Ltd., Model: IMC-1945-A) was used to hot press the axial 50 mm at a temperature of 80°C and a pressure of 14 MPa for 20 minutes. The shape of the cross section perpendicular to the central axis becomes Figure 15B As a result of hot pressing, a piezoelectric substrate with a major diameter of 0.497 mm, a minor diameter of 0.312 mm (minor diameter / major diameter ratio = 1 / 1.59) and an aspect ratio of 0.372 was obtained. The aspect ratio was calculated using the following formula.

[0583] (Formula) Aspect Ratio = (Major Radius - Minor Radius) / Major Radius

[0584] The piezoelectric substrate of Example 2 was obtained in the above manner.

[0585] It should be noted that brocade thread is equivalent to Figure 15A The inner conductor 16A in the strip piezoelectric body is equivalent to Figure 15A The first piezoelectric body 18A in the adhesive is not Figure 15A The ground conductor is not shown in the figure, but it is arranged between the internal conductor 16A and the first piezoelectric body 18A. Figure 15A Middle picture.

[0586] [Example 3]

[0587] A piezoelectric substrate of Example 3 was obtained in the same manner as in Example 2 except that an adhesive for integrating the brocade wire and the strip-shaped piezoelectric body was not applied and hot pressing was not performed.

[0588] <Temperature Characteristics Evaluation>

[0589] The amount of charge generated when a tensile force was applied to the piezoelectric substrates of Examples 2 and 3 (generated charge amount) was measured, and the generated charge amount per unit tensile force (hereinafter referred to as "sensitivity") was calculated based on the generated charge amount. At this time, the sensitivity was calculated at multiple locations at temperatures between 25°C and 80°C, and this was repeated three times to obtain temperature characteristics. The calculation results of Example 2 are shown in FIG. Figure 16A The calculation results of Example 3 are shown in Figure 16B .

[0590] like Figure 16AAs shown, for the piezoelectric substrate of Example 2, in the first cycle, the sensitivity changes little from 25°C to 50°C, the sensitivity increases from the initial value from 50°C to 70°C (reaching a maximum at 60°C), and the sensitivity decreases from 70°C to 80°C. Since the glass transition temperature of the polylactic acid constituting the piezoelectric substrate of this example is around 60°C, the sensitivity decreases with increasing temperature in the temperature range above 60°C. Furthermore, in the second cycle, the sensitivity of the piezoelectric substrate of Example 2 changes little from 25°C to 60°C, and the sensitivity decreases from 60°C to 80°C. Furthermore, in the third cycle, the piezoelectric substrate of Example 2 exhibits substantially the same temperature characteristics as in the second cycle.

[0591] As described above, the piezoelectric substrate of Example 2 shows that its temperature characteristics stabilize by repeating the cycle from 25°C to 80°C. This is believed to be because the sensitivity at 25°C returns to its initial value after measurement at 80°C after the second cycle. This demonstrates that the piezoelectric substrate of Example 2 exhibits excellent sensitivity.

[0592] It should be noted that Example 2 shows different temperature characteristics only in the first cycle from those in the second cycle onwards. This is probably because the gap generated by the pressurization during molding is elongated due to the tensile force in the first cycle, but does not elongate after the second cycle, so the temperature characteristics are stable.

[0593] like Figure 16B As shown, for the piezoelectric substrate of Example 3, the sensitivity change was small from 25°C to 60°C in the first cycle, but decreased from 60°C to 80°C. Furthermore, by repeating the second and third cycles, the sensitivity at 25°C to 60°C decreased overall.

[0594] The unstable temperature characteristics of the piezoelectric substrate of Example 3 are thought to be caused by the fact that the width of the piezoelectric strip became wider and the wire diameter became thinner after measurement at 80° C. In other words, the winding state of the piezoelectric strip changed depending on the ambient temperature.

[0595] In Examples 2 and 3, the width of the piezoelectric strip was observed under a microscope before and after the temperature characteristics evaluation. The results confirmed that the width of the piezoelectric strip narrowed by approximately 0.026% in the piezoelectric substrate of Example 2. Therefore, even after the piezoelectric substrate of Example 2 was measured at 80°C, no change in the tightness of the piezoelectric strip was observed.

[0596] On the other hand, the width of the piezoelectric strip of Example 3 was found to be approximately 15% wider and the wire diameter was found to be thinner. Therefore, it was found that the winding state of the piezoelectric strip of Example 3 changed significantly after the piezoelectric substrate of Example 3 was measured at 80°C.

[0597] The entire disclosure of Japanese Patent Application No. 2018-175421 filed on September 19, 2018 is incorporated herein by reference.

[0598] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each document, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

[0599] Description of Reference Numerals

[0600] 10, 10A, 10B, 10C, 10D Bed device (human body detection system)

[0601] 12 Piezoelectric substrate (biological information acquisition device)

[0602] 16A inner conductor (conductor)

[0603] 18A 1st piezoelectric body (piezoelectric body)

[0604] 24 bed board (board)

[0605] 26 Mattress (pressure part)

[0606] 30 Human body detection device

[0607] 33 datum plane

[0608] 34 areas

[0609] 37 Cushioning material (base)

[0610] 38 Insulating parts (covering parts)

[0611] 55 Testing Department

[0612] 56 Judgment Department

Claims

1. A human body detection device, comprising: A linear piezoelectric substrate is provided in each of a plurality of regions of the plate that intersect the direction of pressure applied from the human body so as to be axially arranged along the plate and detects pressure applied in the radial direction; Memory; a processor connected to the memory; a pressurizing portion that contacts the piezoelectric substrate and is disposed along the plate and is pressurized by contact with the human body; and a plurality of buffer materials, the buffer materials being in contact with the piezoelectric substrate for each of the piezoelectric substrates and being provided on the side opposite to the pressurizing portion across the piezoelectric substrate; wherein the processor is capable of detecting respective output signals of the piezoelectric substrates, The human body detection device is constructed as follows: the area of ​​each of the plurality of cushioning materials is smaller than the area of ​​each of the plurality of regions, the plurality of cushioning materials are arranged separately from each other, the cushioning materials are subjected to a compressive load from a pressurizing portion and are strained, thereby applying tension to the piezoelectric substrate.

2. The human body detection device according to claim 1, wherein: The piezoelectric substrate has: A long conductor; and A piezoelectric body in the form of a long strip that is spirally wound in one direction relative to the conductor, The pressure input to the piezoelectric body is detected based on the potential difference between the conductor and the piezoelectric body.

3. The human body detection device according to claim 2, wherein: The piezoelectric body uses an organic piezoelectric material.

4. The human body detection device according to claim 3, wherein: The piezoelectric body is a helical chiral polymer (A) having optical activity.

5. The human body detection device according to claim 4, wherein: The helical chiral polymer (A) is polylactic acid.

6. The human body detection device according to any one of claims 2 to 5, wherein: The piezoelectric substrate has a covering member around the piezoelectric body.

7. The human body detection device according to any one of claims 1 to 6, comprising: The base portion is adjacent to the piezoelectric substrate and is disposed on the opposite side of the pressurizing portion.

8. The human body detection device according to claim 7, wherein: The thickness of the pressurized portion is within a range of 0.005 to 200 mm, and the hardness of the pressurized portion is within a range of 50 to 200 N when measured according to the A method specified in JIS K6400-2.

9. The human body detection device according to claim 7 or 8, wherein: The pressurizing portion, the piezoelectric substrate, and the base portion are arranged along a pressurizing direction of the pressurizing portion.

10. The human body detection device according to any one of claims 7 to 9, wherein: The base is made of foamed plastic.

11. The human body detection device according to any one of claims 1 to 10, wherein: The piezoelectric substrate is a biological information acquisition device.

12. The human body detection device according to any one of claims 1 to 11, wherein: The cross-section of the piezoelectric substrate perpendicular to the axial direction is a non-circular cross-section.

13. The human body detection device according to claim 12, wherein: In the piezoelectric substrate, in a cross section perpendicular to the axial direction, a ratio of a major axis to a minor axis is 1.05 to 10.

00.

14. A bed device comprising the human body detection device according to any one of claims 1 to 13.

15. A human body detection system, comprising: The human body detection device according to any one of claims 1 to 13; The area of ​​the plate arranged along a specified direction; and The piezoelectric substrates disposed in the respective regions, The processor compares output signals of the piezoelectric substrates adjacent to each other in the predetermined direction to determine movement of the human body on the plate.

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