WO2019044318A1

WO2019044318A1 - Vital sign detection device

Info

Publication number: WO2019044318A1
Application number: PCT/JP2018/028419
Authority: WO
Inventors: 高橋　渉; 厚輝清水; 忠優近藤; 陽加藤
Original assignee: 住友理工株式会社
Priority date: 2017-08-29
Filing date: 2018-07-30
Publication date: 2019-03-07
Also published as: JP6487507B2; JP2019037672A

Abstract

Provided is a vital sign detection device (1) comprising a piezoelectric sensor (10) positioned on bedding (40), said piezoelectric sensor (10) comprising: a piezoelectric layer (11) including an elastomer and piezoelectric particles; electrode layers (12a, 12b); and protective layers (13a, 13b) including elastomers. The piezoelectric sensor (10) is flexible, expandable, and contractible and is formed into a rectangular thin plate, the width thereof being between 5-100mm inclusive, the length thereof being 100-1000mm inclusive, the ratio of length to width (length/width) thereof being 2-200 inclusive, and the thickness thereof being 0.05-5mm inclusive. In the piezoelectric sensor (10), the area of a pressure-sensitive part (S) wherein the electrode layers (12a, 12b) overlap in the thickness direction via the piezoelectric layer (11) is 20% or more of the area of the piezoelectric sensor (10). On the basis of an output signal from the piezoelectric sensor (10), the vital sign detection device (1) detects the respiration and/or the heartbeat of a subject (P).

Description

Biological information detection device

The present invention relates to a biological information detection apparatus including a flexible and stretchable piezoelectric sensor for detecting at least one of a subject's respiration and heart rate.

For example, measurement of respiratory condition is useful for detection and treatment of apnea syndrome. Also, measurement of heart rate is useful for measuring sleep quality and detecting heart disease. As described above, for the purpose of health management, disease detection, and treatment, it has been performed to measure the respiratory state and heart rate of a subject.

For example, Patent Document 1 discloses a flexible piezoelectric element having a piezoelectric sheet in which a piezoelectric ceramic powder is mixed in a polymer matrix, and flexible electrodes disposed on both sides thereof, and the flexible sheet. An abnormality monitoring apparatus is disclosed, which comprises: human body information detecting means for detecting human body information such as respiration based on the output voltage of the piezoelectric element. Patent Document 2 includes a piezoelectric cable sensor installed in a bed, and extracts at least two of heartbeat information, body motion information and respiration information from output information of the piezoelectric cable sensor, and A biometric sensor is described that determines the condition.
Patent Document 3 describes a biological information measurement panel including a silicone rubber laying plate, and a piezoelectric film sensor that detects a strain of the laying plate that is generated along with the biological activity of a subject.

Japanese Patent Application Laid-Open No. 2002-16301 JP 2005-95307 A JP, 2014-124310, A International Publication No. 2017/010135

The piezoelectric sensor described in Patent Documents 1 to 3 is a piezoelectric layer in which a piezoelectric ceramic powder such as lead zirconate titanate (PZT) is mixed in a resin such as chlorinated polyethylene or chloroprene, or polyvinylidene fluoride (PVDF) It has a piezoelectric layer made of resin. For this reason, the piezoelectric sensor is flexible but has poor flexibility and stretchability. Therefore, when the piezoelectric sensor is disposed on the bedding and the subject lies on the bedding, it is easy to feel discomfort such as hardness or stiffness. Since the subject is aware of the piezoelectric sensor, there is a possibility that heart rate measurement can not be accurately performed or sleep is disturbed. In this case, the discomfort may be reduced if the piezoelectric sensor is placed under cushioned bedding such as a mattress. However, since the conventional piezoelectric sensor can not expand and contract following the movement of the subject or the bedding, if a mattress or the like intervenes between the subject and the piezoelectric sensor, weak vibrations such as respiration and heart beat are generated. It is difficult to detect.

In this respect, in the biological information measurement panel described in Patent Document 3, a silicone rubber laying plate is disposed under the subject, and the piezoelectric sensor is disposed so as not to overlap the subject. The strain of the floor plate caused by the biological activity of the subject is detected by the piezoelectric sensor. However, since the silicone rubber laying plate has visco-elasticity, the vibration caused by the biological activity of the subject is largely attenuated before being transmitted to the piezoelectric sensor. For this reason, it is difficult to accurately detect weak vibrations such as respiration and heart beats.

On the other hand, Patent Document 4 describes a flexible piezoelectric sensor having a piezoelectric layer containing an elastomer, an electrode layer, and a protective layer. However, in order to detect at least one of the subject's respiration and / or heart rate by placing on bedding, further study is required such as optimizing the shape and size of the piezoelectric sensor.

The present invention has been made in view of such circumstances, and it is difficult for a subject to feel discomfort even when placed in bedding, and a biological information detection apparatus capable of accurately detecting at least one of respiration and heartbeat. The challenge is to provide

In order to solve the above problems, the biological information detection apparatus of the present invention is disposed in bedding, and includes at least one of a piezoelectric layer including an elastomer and piezoelectric particles, an electrode layer disposed to sandwich the piezoelectric layer, and the electrode layer. And a protective layer containing an elastomer, wherein the width is 5 mm or more and 100 mm or less, the length is 100 mm or more and 1000 mm or less, and the ratio of length to width (length / width) is 2 or more and 200 or less, thickness Has a rectangular thin plate shape of 0.05 mm or more and 5 mm or less, and is provided with a piezoelectric sensor having expansion and contraction flexibility, and in the piezoelectric sensor, the area of the pressure sensitive portion where the electrode layer overlaps in the thickness direction via the piezoelectric layer is And 20% or more of the area of the piezoelectric sensor, and detecting at least one of the respiration and the heartbeat of the subject based on an output signal from the piezoelectric sensor.

The biological information detection apparatus of the present invention includes a piezoelectric layer including an elastomer and a protective layer, and includes a piezoelectric sensor having stretch flexibility. For this reason, even if the piezoelectric sensor is disposed on the bedding and the subject lies on top of it, the subject is unlikely to feel discomfort such as hardness or stiffness. The piezoelectric sensor can expand and contract following the movement of the subject and the bedding. For this reason, it is possible to accurately detect respiratory sounds derived from weak vibrations due to respiration and heart beat, respiration and heart beat. The piezoelectric sensor is in the form of a rectangular thin plate having a length (longitudinal length) which is twice or more the width (longitudinal length). And the area of the pressure sensitive portion occupying the area of the piezoelectric sensor is 20% or more. Since the piezoelectric sensor has an elongated shape and the area of the pressure sensing unit is large, the pressure sensitive unit is likely to overlap with a part of the body of the subject when the piezoelectric sensor is disposed on the bedding. Therefore, it is possible to detect weak vibrations due to respiration and heart beat without leaking. Piezoelectric sensors are compact compared to large area planar sensors, such as those placed on the entire surface of a mattress. Therefore, the texture of mattresses and sheets is not lost. Further, since the area overlapping with the body of the subject is small, the discomfort is further reduced. Furthermore, it is easy to carry, attach and remove.

It is a layout of a living body information detecting device which is one embodiment of the present invention. It is a top view of the piezoelectric sensor in the biometric information detection apparatus. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 5 is a graph showing a respiration waveform measured by the piezoelectric sensor of Example 1. It is a graph which shows the cardiac-beats waveform measured with the same piezoelectric sensor.

One embodiment of a living body information detection apparatus of the present invention will be described using the drawings. FIG. 1 shows a layout of the biological information detection apparatus of this embodiment. FIG. 2 shows a top view of the piezoelectric sensor in the biological information detection apparatus. FIG. 3 shows a III-III cross-sectional view of FIG. In FIG. 1, the biological information detection apparatus is shown in a transparent manner. In FIG. 2, the electrode layer and the piezoelectric layer are shown in transmission.

As shown in FIGS. 1 to 3, the biological information detection apparatus 1 includes a piezoelectric sensor 10, wires 20a and 20b, and a control circuit unit 30. In the present embodiment, the shoulder width direction of the subject P is defined as the left-right direction, and the height direction is defined as the front-rear direction in a state where the subject P is lying on his / her back on the mattress. The width of the piezoelectric sensor 10 is the length in the front-rear direction, and the length is the length in the left-right direction. The piezoelectric sensor 10 is fixed to the back of a cover 40 that covers the bed mattress. The mattress cover of the bed is included in the concept of "bedding" in the present invention. The piezoelectric sensor 10 extends in a band shape in the left-right direction. A portion of the piezoelectric sensor 10 is disposed below the chest of the subject P. The piezoelectric sensor 10 has a rectangular thin plate shape with a width of 25 mm, a length of 550 mm, and a thickness of 0.45 mm. The ratio of length to width (length / width) is 22. The piezoelectric sensor 10 has flexibility in expansion and contraction, and includes the piezoelectric layer 11, a pair of electrode layers 12a and 12b, and a pair of protective layers 13a and 13b.

The piezoelectric layer 11 contains a carboxyl group-modified hydrogenated nitrile rubber (XH-NBR) and barium titanate particles. The content of barium titanate particles is 48% by volume when the volume of XH-NBR is 100%. The piezoelectric layer 11 has a rectangular thin film shape with a width of 20 mm, a length of 550 mm, and a thickness of 0.06 mm (60 μm). The piezoelectric layer 11 is subjected to polarization treatment, and the barium titanate particles are polarized in the thickness direction (vertical direction) of the piezoelectric layer 11. The breaking elongation of the piezoelectric layer 11 is 120%.

The electrode layer 12a contains acrylic rubber and conductive carbon black. The electrode layer 12a has a rectangular thin film shape with a width of 15 mm, a length of 550 mm, and a thickness of 0.015 mm (15 μm). The electrode layer 12 a is disposed on the top surface of the piezoelectric layer 11. The wiring 20a is connected to the left end of the electrode layer 12a. The material, shape, and size of the electrode layer 12 b are the same as those of the electrode layer 12 a. The electrode layer 12 b is disposed on the lower surface of the piezoelectric layer 11. The wiring 20b is connected to the left end of the electrode layer 12b.

The protective layer 13a is made of a thermoplastic polyester elastomer, and has a rectangular thin film shape with a width of 25 mm, a length of 550 mm, and a thickness T of 0.18 mm (180 μm). The protective layer 13a is disposed on the upper surface of the electrode layer 12a. The material, shape, and size of the protective layer 13 b are the same as those of the protective layer 13 a. The protective layer 13 b is disposed on the lower surface of the electrode layer 12 b. The breaking elongation of the protective layers 13a and 13b is 480%.

The piezoelectric layer 11, the electrode layers 12a and 12b, and the protective layers 13a and 13b have the same length but different widths. As shown by dotted hatching in FIG. 2, as viewed from above, a pressure sensitive portion S (a portion where the electrode layers 12a and 12b overlap the piezoelectric layer 11 in the thickness direction) is formed at the center in the width direction of the piezoelectric sensor 10. It is done. The area of the pressure sensing unit S is 60% of the area of the piezoelectric sensor 10.

The elastic modulus of the piezoelectric sensor 10 is 46 MPa. The piezoelectric sensor 10 can extend 10% or more in the left-right direction. When the piezoelectric sensor 10 is stretched by 10% in the left-right direction, the tensile load is 23.3 N, and the sensitivity coefficient in the left-right direction is 220 pC / N. Moreover, the ratio of the tensile load of Formula (I) mentioned later (The tensile load of a piezoelectric layer / (the tensile load of an electrode layer + the tensile load of a protective layer)) is 0.5.

The electrode layer 12a and the control circuit unit 30 are electrically connected by the wiring 20a. The electrode layer 12 b and the control circuit unit 30 are electrically connected by the wiring 20 b. When a load is applied to the piezoelectric sensor 10 due to the respiration and heartbeat of the subject P, an electric charge is generated in the piezoelectric layer 11. The generated charge (output signal) is detected by the control circuit unit 30 as a change in voltage or current. Based on this, the subject's respiration and heart beat are detected.

In the present embodiment, the base materials of the piezoelectric layer 11 and the electrode layers 12a and 12b constituting the piezoelectric sensor 10 are all elastomers. The protective layers 13a and 13b are also made of an elastomer. For this reason, the piezoelectric sensor 10 has flexibility in extension and contraction. Therefore, even if the piezoelectric sensor 10 is disposed on the mattress and the subject P lies on the mattress, the subject P is unlikely to feel discomfort such as hardness or stiffness. The piezoelectric sensor 10 can expand and contract following the movement of the subject P and the mattress, so that weak vibrations due to breathing and heartbeat can be detected with high accuracy. The piezoelectric sensor 10 has a band shape, and the pressure sensing unit S overlaps the body of the subject P. For this reason, it is possible to detect weak vibrations due to breathing and heartbeat without leaking. The piezoelectric sensor 10 is smaller than a large area planar sensor disposed on the entire surface of the mattress. Thus, the texture of the cover 40 is not impaired. Further, since the area overlapping with the body of the subject P is small, the discomfort is further reduced. Since the piezoelectric sensor 10 is small, it is easy to carry, attach and remove.

Heretofore, an embodiment of the living body information detection apparatus of the present invention has been described. The biological information detection apparatus of the present invention is not limited to the above embodiment, and can be implemented in various forms with modifications, improvements, etc. which can be made by those skilled in the art without departing from the scope of the present invention. Can.

<Piezoelectric layer>
The piezoelectric layer comprises an elastomer and piezoelectric particles. As the elastomer, one or more types selected from crosslinked rubber and thermoplastic elastomer may be used. As a flexible elastomer having a relatively small elastic modulus, urethane rubber, silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber, natural rubber, isoprene rubber, ethylene-propylene-diene rubber (EPDM) And ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-acrylic acid ester copolymer, butyl rubber, styrene-butadiene rubber, fluororubber, epichlorohydrin rubber and the like. Alternatively, an elastomer modified by introducing a functional group may be used. As the modified elastomer, for example, a hydrogenated nitrile rubber having one or more selected from a carboxyl group, a hydroxyl group and an amino group is preferable.

The electromotive field (V / m) generated when a load is applied to the piezoelectric layer is the piezoelectric strain constant (C / N) of the piezoelectric layer, the dielectric constant (F / m), and the applied load (N / m ² ) It is shown by following Formula (a).
EMF = piezoelectric distortion constant / dielectric constant × load (a)
From the viewpoint of increasing the electromotive field, it is desirable that the dielectric constant of the piezoelectric layer be small. In this case, it is desirable to use an elastomer having a relatively small dielectric constant. For example, urethane rubber, silicone rubber, NBR, H-NBR, XH-NBR, etc. are suitable as an elastomer having a relative dielectric constant of 15 or less (measurement frequency: 100 Hz).

Piezoelectric particles are particles of a compound having piezoelectricity. As a compound having piezoelectricity, a ferroelectric having a perovskite crystal structure is known, and, for example, barium titanate, strontium titanate, potassium niobate, sodium niobate, lithium niobate, potassium sodium niobate And potassium sodium niobate, lead zirconate titanate (PZT), barium strontium titanate (BST), bismuth lanthanum titanate (BLT), bismuth strontium tantalate (SBT), and the like. As the piezoelectric particles, one or two or more of them may be used.

The particle diameter of the piezoelectric particles is not particularly limited. For example, when plural types of piezoelectric particle powders having different average particle diameters are used, it is possible to mix large diameter piezoelectric particles and small diameter piezoelectric particles in the elastomer. In this case, small diameter piezoelectric particles enter between large diameter piezoelectric particles, and pressure is easily transmitted to the piezoelectric particles. As a result, the piezoelectric strain constant of the piezoelectric layer can be increased, and the electromotive voltage can be increased.

The piezoelectric particles may be single particles or an aggregate of a plurality of particles. In the case of including an aggregate of a plurality of piezoelectric particles, it becomes easy to balance the flexibility and the piezoelectricity. For example, if a large amount of piezoelectric particles is added to the elastomer, although the piezoelectricity is improved, the volume fraction of the elastomer is reduced, so the flexibility is reduced. On the other hand, when the compounding amount of the piezoelectric particles is small, the volume ratio of the elastomer becomes large and the flexibility is improved, but the piezoelectricity is reduced. According to the study of the present inventor, it is confirmed that, by increasing the flexibility of the piezoelectric layer, specifically, the breaking elongation, the change in electromotive voltage is reduced even if the expansion and contraction are repeated, that is, the expansion and contraction durability is improved. ing. For this reason, it is desirable to reduce the compounding amount of the piezoelectric particles as much as possible to secure desired piezoelectricity.

As an assembly in which a plurality of piezoelectric particles are aggregated, an aggregate in which individual particles are aggregated by electrostatic force or the like, a conjugate in which individual particles are chemically bonded, and the like can be mentioned. The latter combination is preferable from the viewpoint that individual particles are not easily separated and a linked structure of piezoelectric particles is easily formed. Although the manufacturing method of a coupling body is not specifically limited, For example, after baking the powder which consists of single particle | grains, it can grind | pulverize and manufacture. The difference between aggregates and conjugates can be analyzed as follows. First, the piezoelectric layer is heated to remove the elastomeric component. Next, the remaining piezoelectric particles are dispersed in a good solvent and subjected to ultrasonic treatment. As a result, if it is separated into individual particles, it is judged as an aggregate, and if it is not separated, it is a binder. Here, the good solvent refers to a polar solvent which hardly precipitates when the piezoelectric particles are dispersed. Specifically, any solvent may be used as long as it has an SP value (solubility parameter) of 8 or more and 13 or less and can dissolve the elastomer. For example, 2-methoxyethanol is mentioned.

An aggregate of a plurality of piezoelectric particles can be defined as particles having a diameter larger than twice the average particle diameter of individual piezoelectric particles. Here, as the diameter (d2) of the aggregate, the median diameter measured by the laser diffraction / scattering type particle diameter distribution measuring apparatus is adopted. As the average particle diameter (d1) of the piezoelectric particles, a scanning electron microscope (SEM) photograph of the aggregate is taken, and the average value of the maximum diameters of 100 or more piezoelectric particles arbitrarily selected without deviation is adopted. Do. And, those which satisfy 2d1 <d2 are an aggregate.

The elastomer and the piezoelectric particles may be chemically bonded, for example, by surface treatment of the piezoelectric particles. As a method of surface treatment of the piezoelectric particles, a method in which a surface treatment agent having a functional group capable of reacting with the elastomer polymer is reacted in advance with the piezoelectric particles, and the piezoelectric particles are mixed with the elastomer polymer. Examples thereof include a method of dissolving in acid, alkali or subcritical water to form a hydroxyl group, and then mixing with an elastomer polymer having a functional group capable of reacting with the hydroxyl group. When the piezoelectric particles are chemically bonded to the elastomer, the piezoelectric particles are less likely to be misaligned even if expansion and contraction are repeated. In addition, since the piezoelectric particles are less likely to be separated from the elastomer, fluctuations in physical properties and output from initial values are reduced. This stabilizes the output and improves the sag resistance of the piezoelectric layer. In addition, since the breaking elongation of the piezoelectric layer becomes large, it is possible to suppress the deterioration of the piezoelectric performance due to the local breakage or the like at the time of elongation. As a result, high piezoelectric performance can be maintained even in the expanded state.

The content of the piezoelectric particles may be determined in consideration of the piezoelectric layer, and hence the flexibility of the piezoelectric sensor and the piezoelectric performance of the piezoelectric layer. When the content of the piezoelectric particles is increased, the piezoelectric performance of the piezoelectric layer is improved but the flexibility is reduced. Therefore, it is desirable to adjust the content of the piezoelectric particles so that the desired flexibility can be realized in the combination of the elastomer and the piezoelectric particles used. For example, the content of the piezoelectric particles may be 30% by volume or more and 50% by volume or less based on 100% by volume of the elastomer.

The piezoelectric layer may contain, in addition to the elastomer and the piezoelectric particles, reinforcing particles having a dielectric constant smaller than that of the piezoelectric particles. The relative permittivity of the reinforcing particles is desirably, for example, 100 or less, and preferably 30 or less, on the condition that the relative permittivity of the reinforcing particles is smaller than that of the piezoelectric particles.

In the structure in which the piezoelectric particles having a large relative dielectric constant are connected, the external force is easily transmitted to the piezoelectric particles, and therefore, the improvement of the piezoelectric strain constant of the formula (a) can be expected. However, when the piezoelectric particles having a large relative dielectric constant are connected, the dielectric constant of the entire piezoelectric layer is increased. On the other hand, when both the piezoelectric particles and the reinforcing particles are contained in the piezoelectric layer, the connection between the piezoelectric particles having large relative dielectric constants is divided by the presence of the reinforcing particles having a smaller relative dielectric constant. Thereby, the rise in the dielectric constant of the entire piezoelectric layer can be suppressed. On the other hand, since the connection structure of the particles is maintained by the reinforcing particles and the piezoelectric particles, the piezoelectric strain constant can be maintained. That is, when reinforcing particles are contained in the piezoelectric layer, the dielectric constant of the entire piezoelectric layer can be made smaller than in the case where only piezoelectric particles are contained while maintaining the piezoelectric strain constant. Therefore, a large electromotive field can be obtained by the above-mentioned equation (a).

As the reinforcing particles, particles having a large electric resistance are desirable. When the electrical resistance of the reinforcing particles is large, the dielectric breakdown strength of the piezoelectric layer is increased. Thereby, in polarization processing of the piezoelectric layer described later, a high electric field can be applied to shorten the processing time. In addition, productivity can be improved because the number of piezoelectric sensors broken during the polarization process can be reduced.

Also, it is desirable that the reinforcing particles be chemically bonded to the elastomer. In this case, a network of reinforcing particles is formed in the elastomer, so that ionized impurity ions such as a crosslinking agent, an additive, and moisture in the air are less likely to move, and the electrical resistance of the piezoelectric layer is increased. Chemical bonding between the reinforcing particles and the elastomer can be realized, for example, by surface-treating the reinforcing particles. As a method of surface treatment, there is a method in which a surface treatment agent having a functional group capable of reacting with the elastomeric polymer is reacted in advance with the reinforcing particles, and the reinforcing particles are mixed with the elastomeric polymer. Alternatively, it may be dissolved in subcritical water to form a hydroxyl group, and then mixed with an elastomeric polymer having a functional group capable of reacting with the hydroxyl group. When the reinforcing particles are chemically bonded to the elastomer, the reinforcing particles are less likely to be displaced even after repeated expansion and contraction. In addition, since the reinforcing particles are less likely to be separated from the elastomer, the fluctuation of the physical properties and the output from the initial value is reduced. This stabilizes the output and improves the sag resistance of the piezoelectric layer. In addition, since the breaking elongation of the piezoelectric layer becomes large, it is possible to suppress the deterioration of the piezoelectric performance due to the local breakage or the like at the time of elongation. As a result, high piezoelectric performance can be maintained even in the expanded state.

The type of reinforcing particles is not particularly limited. For example, particles of oxides such as titanium dioxide, silica, barium titanate, rubber, resin, etc. can be used. However, when relatively soft particles such as rubber particles are included, the applied load may be attenuated by the resin particles and may not be transmitted to the piezoelectric particles. From the viewpoint of facilitating the transfer of force to the piezoelectric particles to increase the piezoelectric strain constant of the piezoelectric layer in the above-mentioned formula (a) and increasing the electromotive field, the reinforcing particles have a modulus of elasticity higher than that of the base material elastomer. It is better to use larger particles. For example, metal oxide particles such as titanium dioxide are preferable because they have a small relative dielectric constant and a large effect of improving the dielectric breakdown resistance. As a method of producing metal oxide particles, a sol-gel method is preferable because particles having a low crystallinity and a small relative dielectric constant can be obtained.

The piezoelectric layer is manufactured by curing a composition obtained by adding a powder of piezoelectric particles, a crosslinking agent and the like to an elastomeric polymer under predetermined conditions. Thereafter, the piezoelectric layer is subjected to polarization treatment. That is, a voltage is applied to the piezoelectric layer to align the polarization direction of the piezoelectric particles in a predetermined direction.

The inventors of the present invention have found that in a thin film piezoelectric sensor, the smaller the cross-sectional area perpendicular to the tensile direction of the piezoelectric layer, the greater the sensitivity to the applied load. Therefore, it is desirable that the piezoelectric layer be thin. For example, the thickness of the piezoelectric layer is preferably 200 μm or less, and more preferably 100 μm or less. On the other hand, if it is too thin, dielectric breakdown is likely to occur at the time of polarization treatment. Therefore, the thickness of the piezoelectric layer is preferably 10 μm or more, and more preferably 20 μm or more.

<Electrode layer>
The electrode layer is preferably deformable following the piezoelectric layer. The flexible electrode layer can be formed of, for example, a conductive material in which a conductive material is blended with a binder, conductive fibers, or the like. As the binder, it is desirable to use one or more selected from an elastomer, that is, a crosslinked rubber and a thermoplastic elastomer. Examples of the elastomer having a relatively small elastic modulus and being flexible and having good adhesion to the piezoelectric layer include acrylic rubber, silicone rubber, urethane rubber, urea rubber, fluororubber, H-NBR and the like. Further, an elastomer modified by introducing a functional group may be used, such as an epoxy group modified acrylic rubber, a carboxyl group modified hydrogenated nitrile rubber and the like.

The type of conductive material is not particularly limited. For example, metal particles made of silver, gold, copper, nickel, rhodium, palladium, chromium, titanium, platinum, iron, and alloys thereof, metal oxide particles made of zinc oxide, titanium oxide, etc., titanium carbonate, etc. It may be suitably selected from conductive carbon materials such as metal carbide particles, metal nanowires made of silver, gold, copper, platinum, nickel and the like, carbon black, carbon nanotubes, graphite, thin layer graphite, graphene and the like. Also, metal-coated particles such as silver-coated copper particles may be used. As the conductive material, one of these may be used alone, or two or more of these may be mixed and used. The electrode layer may contain, as other components, a crosslinking agent, a crosslinking accelerator, a dispersing agent, a reinforcing material, a plasticizer, an antiaging agent, a coloring agent, and the like.

For example, when using an elastomer as a binder, a conductive material, if necessary, an additive is added to a polymer solution in which the polymer of the elastomer component is dissolved in a solvent, and the conductive paint is prepared by stirring and mixing. Can. The electrode may be formed by directly applying the prepared conductive paint on one surface of the piezoelectric layer. Alternatively, a conductive paint may be applied to the release film to form an electrode, and the formed electrode may be transferred to one surface of the piezoelectric layer.

<Protective layer>
The protective layer is laminated to at least one of the electrode layers and comprises an elastomer. For example, the protective layer may be disposed on one or both of the lamination direction outer sides of the laminate of the piezoelectric layer and the electrode layer. Further, in the case where a plurality of units in which a piezoelectric layer is interposed between a pair of electrode layers are stacked, a protective layer may be disposed between the electrode layers adjacent in the stacking direction. By arranging the protective layer, the insulation of the piezoelectric sensor can be secured, and the destruction of the piezoelectric sensor due to the mechanical stress from the outside can be suppressed. Further, the strain of the piezoelectric layer can be increased by the extension of the protective layer, and the sensitivity of the sensor can be improved.

For example, when a force is applied in the stacking direction of the piezoelectric sensor (when the piezoelectric sensor is compressed), a shear force acts on the piezoelectric layer by the protective layer extending in the surface direction. As a result, in addition to the pressing force in the stacking direction, a tensile force in the surface direction is applied to the piezoelectric layer, and distortion of the piezoelectric layer is increased. As a result, the amount of charge generated in the piezoelectric layer is increased, and the sensitivity of the sensor is improved. The sensitivity improvement effect by the protective layer is more remarkable as the elastic modulus in the tensile direction of the protective layer is smaller.

As the elastomer of the protective layer, at least one selected from crosslinked rubber and thermoplastic elastomer may be used. Examples of the elastomer having a relatively small elastic modulus and flexibility and good adhesion to the electrode layer include natural rubber, isoprene rubber, butyl rubber, acrylic rubber, silicone rubber, urethane rubber, urea rubber, fluororubber, NBR and the like. In particular, from the viewpoint of measuring human biological information, silicone rubber and urethane rubber having good affinity with the living body are desirable, and it is desirable not to contain substances extracted with time, such as plasticizers.

In order to reduce the change in sensitivity of the sensor after repeated use, it is desirable that the protective layer be excellent in sag resistance. In addition, since the protective layer plays a role of protecting the piezoelectric sensor from external mechanical stress, it is desirable that the protective layer be excellent in wear durability and tear durability. In addition, in order to prevent the protective layer from being broken at the time of elongation and the piezoelectric sensor from being broken, it is desirable that the breaking elongation of the protective layer be larger than the breaking elongation of the piezoelectric layer. In the present specification, the breaking elongation adopts the value of elongation at break measured by the tensile test specified in JIS K6251: 2010. The tensile test is conducted using a dumbbell-shaped No. 5 test piece at a tensile speed of 100 mm / min.

The Poisson's ratio of the elastomer is approximately 0.5. For this reason, in the protective layer made of an elastomer, the force applied in the thickness direction acts as the force in the surface direction as it is. Therefore, as the thickness of the protective layer is larger, the strain increase effect of the piezoelectric layer is larger, and the sensitivity improvement effect of the sensor is larger. On the other hand, when the thickness of the protective layer is increased, the piezoelectric sensor is thickened, and the subject is likely to feel discomfort. Therefore, the thickness per one protective layer may be, for example, 5 μm or more and 1000 μm or less. The thickness of the protective layer in the present specification is the thickness of a portion of one layer of the protective layer to be laminated to the electrode layer, as indicated by a symbol T in FIG.

<Piezoelectric sensor>
Piezoelectric sensors are placed on the bedding. Beddings are not particularly limited, but include bed mattresses, mattresses, their covers and sheets. For example, it may be disposed on a mattress or the like, or may be disposed only between the mattress or the like and the cover, but it is also possible to sew them, fasten them with a surface fastener or snap button, or adhere them with an adhesive. Good. From the viewpoint of accurately detecting weak vibrations caused by respiration and heart rate, the piezoelectric sensor is configured so that the pressure sensing unit overlaps with a part of the subject's body when the subject is lying on the bedding. It is desirable to be placed in

The piezoelectric sensor has a rectangular thin plate shape. The piezoelectric sensor has a width of 5 mm to 100 mm, a length of 100 mm to 1000 mm, a ratio of length to width (length / width) of 2 to 200, and a thickness of 0.05 mm to 5 mm. is there. If the width is small, the sensitivity is low and it becomes difficult to detect weak vibrations. The preferred width is 10 mm or more. On the other hand, if the width is large, the sensitivity is high, but the subject may easily feel discomfort or there is a possibility that the breathability may be deteriorated and sweat may be easily scratched. The preferred width is 50 mm or less. The longer the length, in other words, the larger the ratio to the width, the easier it is for the subject's body to overlap, making it easier to detect weak vibrations due to breathing and heart beats. The preferred length is 300 mm or more. On the other hand, the preferred length is 800 mm or less from the viewpoint of easy installation in bedding. If the thickness is large, the subject is likely to feel discomfort. The preferred thickness is 2 mm or less.

When the elastic modulus of the piezoelectric sensor is large, the subject is likely to feel discomfort such as hardness or stiffness, which leads to disturbing sleep and discomfort. On the other hand, when the elastic modulus is small, it becomes difficult to handle, and the extension displacement with respect to the load becomes large and the durability is lowered. Therefore, the elastic modulus of the piezoelectric sensor is desirably 10 MPa or more and 100 MPa or less. In the present specification, the elastic modulus is a value calculated from a stress-elongation curve obtained by a tensile test defined in JIS K7127: 1999. The tensile test shall be conducted at a tensile speed of 100 mm / min using a test piece of test piece type 2.

Piezoelectric sensors have stretch flexibility. For example, if the tensile strain of the piezoelectric sensor is 10% or less, it can be said that it has stretch flexibility. In the present specification, tensile strain is a value measured as follows, and is an indicator of whether or not it has stretch flexibility. First, the length L ₀ of the initial state (unloaded state before extension) of the piezoelectric sensor is measured. Next, the piezoelectric sensor is stretched by 20% in the longitudinal direction (length is 1.2 L ₀ ), and held for 10 seconds at a temperature of 10 to 30 ° C. as it is. Then, back to the initial state, measuring the length L ₁ of the piezoelectric sensor. And the elongation rate with respect to the initial state calculated by following Formula (b) is defined as tensile strain.
Tensile strain (%) = (L ₁ -L ₀ ) / L ₀ × 100 (b)
The piezoelectric sensor extends 10% or more in the longitudinal direction. The term “10% elongation in the longitudinal direction” means that the length in the longitudinal direction is 1.1 times the length in the unloaded state. For example, it is desirable that the tensile load when the piezoelectric sensor is elongated by 10% in the longitudinal direction is 100 N or less. When the tensile load exceeds 100 N, the subject is likely to feel discomfort such as hardness or stiffness, which leads to disturbing sleep and discomfort. The preferred tensile load is 75N or less. The tensile load at 10% elongation is subjected to the tensile test specified in JIS K 7127: 1999 as in the case of the elastic modulus (test piece: test piece type 2, tensile speed: 100 mm / min), 10% elongation The load at the time of

The piezoelectric sensor is used in a stretched state by the load of the subject. For this reason, it is desirable that it has a sensor capability that can detect respiration and heart rate even in an extended state, and the sensitivity coefficient of the sensor is large. From such a point of view, it is desirable that the sensitivity coefficient in the longitudinal direction when the piezoelectric sensor is elongated by 10% in the longitudinal direction is 50 pC / N or more. The sensitivity factor in the longitudinal direction refers to the amount of charge (C / m ² ) per unit area generated when a tensile load in the longitudinal direction is applied to the piezoelectric sensor (N / m ² ) It is the divided value.

From the viewpoint of securing the durability of the piezoelectric sensor, it is desirable that the piezoelectric sensor satisfy the following equation (I).
0.1 ≦ tension load of piezoelectric layer / (tension load of electrode layer + tension load of protective layer) ≦ 2 (I)
The tensile load of each layer may be calculated by multiplying the elastic modulus of each layer obtained by the above-described tensile test defined in JIS K 7127: 1999 by the thickness and the width in the non-load state of each layer. The thickness of the electrode layer is the sum of the thicknesses of the two electrode layers sandwiching the piezoelectric layer. If two protective layers are arranged, the thickness of the protective layer is the sum of the thicknesses of the two protective layers. In the case where the elastic modulus and the thickness are different between the two electrode layers, the elastic modulus × thickness × width is calculated for each layer, and the sum thereof is used. The same applies to the protective layer.

When the ratio of the tensile load in the formula (I) is less than 0.1, when stress is applied to the piezoelectric sensor, the stress applied to the piezoelectric layer becomes relatively small, and the sensor sensitivity becomes low. On the other hand, when the tensile load ratio in the formula (I) exceeds 2, the stress applied to the piezoelectric layer becomes relatively large when the stress is applied to the piezoelectric sensor, so an excessive load is applied to the piezoelectric layer. , Durability may be reduced. Since the piezoelectric layer contains piezoelectric particles, the expansion rate varies within the layer, and a locally weak portion is likely to occur. For this reason, the breaking elongation of the piezoelectric layer is relatively small. That is, the piezoelectric layer is likely to be locally broken at the time of expansion. Here, when the ratio of the tensile load exceeds 2, the displacement of the piezoelectric layer which is easily broken at the time of elongation becomes rate-limiting. For this reason, there exists a possibility that durability may fall. On the other hand, when the ratio of the tensile load in Formula (I) is 0.1 or more and 2 or less, a balance between sensor sensitivity and durability can be maintained. Since the protective layer does not contain piezoelectric particles, local fracture is unlikely to occur and the breaking elongation is relatively large. By achieving uniform extension by the protective layer, the durability is enhanced. Moreover, since stress is easily transmitted to the piezoelectric layer, the sensor sensitivity is increased.

In the piezoelectric sensor, the pair of electrode layers are spaced apart in the polarization direction of the piezoelectric particles in the piezoelectric layer. The electrode layer may be formed on the entire surface of the piezoelectric layer, or may be formed on only a part of the surface. The portion where the electrode layer overlaps in the thickness direction via the piezoelectric layer is a pressure sensitive portion. The area of the pressure sensitive portion is 20% or more of the area of the piezoelectric sensor. It is preferable that the area of the pressure sensitive portion be 50% or more, and further 60% or more from the viewpoint that the pressure sensitive portion easily overlaps with a part of the body of the subject and detects weak vibrations due to respiration and heart beat without leaking. It is.

The piezoelectric sensor may be manufactured by bonding a piezoelectric layer, an electrode layer, and a protective layer by pressure bonding, fusion bonding, or an adhesive. For example, when a thermoplastic elastomer is used for the protective layer, the protective layer can be fused to the electrode layer and the piezoelectric layer by heating and softening. In addition, an adhesive layer may be provided between the protective layer and the electrode layer. It is desirable to use a thermoplastic elastomer that softens at a lower temperature than the protective layer as the adhesive layer. In this case, fusion at a lower temperature is possible, and the manufacturing cost can be reduced.

<Biometric information detector>
The biological information detection apparatus of the present invention may be configured to include a control device for processing an output signal from the piezoelectric sensor, in addition to the piezoelectric sensor. For example, as in the above embodiment, when the control circuit unit is provided as the control device, the control circuit unit receives the power supply and the charge (output signal) generated by the piezoelectric sensor, and the operation unit that processes it. A storage unit that temporarily stores data processed by the unit may be included. In addition, a charge amplifier, a recorder, or the like may be used as the control device.

Next, the present invention will be more specifically described by way of examples.

<Manufacturing of piezoelectric layer>
[Piezoelectric layer 1]
First, 100 parts by mass of a carboxyl group-modified hydrogenated nitrile rubber polymer ("Terban (registered trademark) XT 8889" manufactured by LANXESS CO., LTD.) As an elastomer was dissolved in acetylacetone to prepare a polymer solution. Next, 512 parts by mass of a powder of barium titanate particles as piezoelectric particles ("BTD-UP" manufactured by Nippon Chemical Industrial Co., Ltd.) was added to the prepared polymer solution and kneaded. Subsequently, the kneaded material was repeatedly passed through a triple roll five times to obtain a slurry. Then, 5 parts by mass of tetrakis (2-ethylhexyloxy) titanium as a crosslinking agent was added to the obtained slurry, and the mixture was kneaded with an air stirrer, and then the slurry was applied onto a substrate by a bar coating method. This was heated at 150 ° C. for 1 hour to produce a piezoelectric layer 1 having a thickness of 0.06 mm (60 μm). The content of piezoelectric particles in the piezoelectric layer 1 is 48% by volume based on 100% by volume of the elastomer. The breaking elongation of the piezoelectric layer 1 is 120%.

[Piezoelectric layer 2, 3]
Piezoelectric layers 2 and 3 were manufactured in the same manner as the piezoelectric layer 1 except that the compounding amount of the piezoelectric particles to the elastomer was 840 parts by mass in the piezoelectric layer 2 and 200 parts by mass in the piezoelectric layer 3. When the elastomer is 100% by volume, the content of piezoelectric particles in the piezoelectric layer 2 is 58% by volume, and the content of piezoelectric particles in the piezoelectric layer 3 is 26.5% by volume. The breaking elongation of the piezoelectric layer 2 is 8%, and the breaking elongation of the piezoelectric layer 3 is 420%.

[Piezoelectric layer 4]
A film "KF piezo 40 μm" made of polyvinylidene fluoride (PVDF) resin manufactured by Kureha Co., Ltd. was used. The breaking elongation of the piezoelectric layer 4 is 70%.

<Production of electrode layer>
[Electrode layer 1]
First, 100 parts by mass of an epoxy group-containing acrylic rubber polymer (Nippon Zeon Co., Ltd. “Nipol (registered trademark) AR51”) as an elastomer was dissolved in methyl ethyl ketone to prepare a polymer solution. Next, 10 parts by mass of conductive carbon black ("Ketchen black EC600JD" manufactured by Lion Corporation) was added to the prepared polymer solution, and dispersed by a bead mill to prepare a conductive paint. Subsequently, the conductive paint was applied by a bar coating method onto a film made of release-treated polyethylene terephthalate (PET). This was heated at 150 ° C. for 1 hour to produce an electrode layer 1 with a thickness of 0.015 mm (15 μm).

[Electrode layer 2]
First, three kinds of monomers of ethyl acrylate (EA), acrylonitrile (AN) and allyl glycidyl ether (AGE) were suspension-polymerized to produce a glycidyl ether group-modified acrylic rubber polymer as an elastomer. The blend ratio of the monomers was 96% by mass of EA, 2% by mass of AN, and 2% by mass of AGE. Next, 68 parts by mass of a glycidyl ether group-modified acrylic rubber polymer is dissolved in butyl cellosolve acetate, and in this polymer solution, 35 parts by mass of a conductive material, 25 parts by mass of a dispersing agent, 6 parts by mass of a crosslinking agent, and crosslinking acceleration A liquid composition was prepared by adding 1 part by mass of the agent. Subsequently, the liquid composition was ground using a wet jet mill (“Nanoveita (registered trademark)” manufactured by Yoshida Kikko Co., Ltd.). The grinding process was performed a total of six times by pass operation (6 pass process). The first pass was performed with a straight type nozzle (nozzle diameter 170 μm) and a processing pressure of 90 MPa, and the second and subsequent passes were performed with a cross type nozzle (nozzle diameter 170 μm) and a processing pressure of 130 MPa. The liquid composition after the pulverization treatment was applied by a bar coating method on a release-treated PET film. This was heated at 150 ° C. for 2 hours to produce an electrode layer 2 with a thickness of 0.015 mm (15 μm). The detail of the used raw material is as follows.
Conductive material: Thin-layer graphite, "iGurafen-α" manufactured by ITEC Corporation.
Dispersing agent: High molecular weight polyester acid amidoamine salt, Kusumoto Chemicals Co., Ltd. "Disparon (registered trademark) DA7301".
Crosslinking agent: amino group-terminated butadiene-acrylonitrile copolymer, CVC Thermoset Specialties Ltd. "ATBN 1300 x 16".
Crosslinking accelerator: Zinc complex, KING INDUSTRIES, INC "XK-614".

[Electrode layer 3]
A conductive silver paste ("DW250-H-5" manufactured by Toyobo Co., Ltd.) was applied by a bar coating method on a release-treated PET film. This was heated at 150 ° C. for 1 hour to produce an electrode layer 3 with a thickness of 0.015 mm (15 μm).

[Electrode layer 4]
A conductive cloth having a thickness of 0.015 mm (15 μm) (“Sui-10-511M” manufactured by Salen Co., Ltd.) was used as the electrode layer 4.

<Production of Protective Layer>
[Protective layer 1]
A thermoplastic polyester elastomer ("Hytrel (registered trademark) 3046" manufactured by Toray DuPont Co., Ltd.) was molded into a sheet to produce a protective layer 1 having a thickness of 0.18 mm (180 μm). The breaking elongation of the protective layer 1 is 520%.

[Protective layer 2]
A polyester film having a thickness of 0.1 mm (100 μm) (“Diafoil (registered trademark)” manufactured by Mitsubishi Chemical Corporation) was used as protective layer 2. The breaking elongation of the protective layer 2 is 80%.

<Manufacture of Piezoelectric Sensor>
Various piezoelectric sensors were manufactured as follows by appropriately combining the manufactured piezoelectric layer, the electrode layer, and the protective layer. First, electrode layers were respectively disposed on two surfaces (upper and lower surfaces) in the thickness direction of the piezoelectric layer, and the piezoelectric layer and the electrode layer were pressure-bonded using a laminator ("LPD 3223" manufactured by Fuji Plastic Co., Ltd.). Next, the protective layer was laminated on both the upper and lower electrode layers, and the surface of the protective layer was ironed to soften the protective layer, thereby fusing the protective layer to the piezoelectric layer and the electrode layer. A DC power supply is connected to the electrode layer of the obtained protective layer / electrode layer / piezoelectric layer / electrode layer / protective layer, and a polarization process is performed by applying an electric field of 20 V / μm to the piezoelectric layer for 5 minutes. The Thus, a rectangular thin plate piezoelectric sensor having a width of 25 mm and a length of 550 mm was manufactured (see FIG. 2 and FIG. 3 mentioned above). At this time, the width of the piezoelectric layer is 20 mm, the width of the electrode layer is 15 mm, the width of the protective layer is 25 mm, and the length of each layer is all 550 mm. The thickness of the piezoelectric sensor is the sum of the thicknesses of the layers (piezoelectric layer + electrode layer × 2 + protective layer × 2). The area of the pressure sensitive portion is 60% of the area of the piezoelectric sensor.

In addition, various types of piezoelectric sensors having dimensions different from the basic shape can be obtained by changing at least one of the length, width, and thickness of each layer based on the piezoelectric sensor in which the piezoelectric layer 1, the electrode layer 1, and the protective layer 1 are stacked. Manufactured. In one piezoelectric sensor, the lengths of the piezoelectric layer, the electrode layer, and the protective layer are the same. That is, the length of each layer directly becomes the length of the piezoelectric sensor.

Tables 1 and 2 show the dimensions, configuration, and physical properties of the manufactured piezoelectric sensor. In the configuration, only dimensions different from the basic shape are shown in parentheses (the unit is mm and the length may be different, but it is omitted because it is the same as the length of the piezoelectric sensor). The measurement method of the sensitivity coefficient at 10% elongation among physical properties is as follows.

[Sensitivity factor at 10% extension]
The piezoelectric sensor was installed in a fatigue endurance tester ("MMT-101N" manufactured by Shimadzu Corporation) in a state where the piezoelectric sensor was elongated by 10% in the longitudinal direction, and loads in the tensile direction of 0.5N, 1N, and 1. in the longitudinal direction. 5N and 2N sin waves (frequency 1 Hz) were sequentially added. The amount of charge generated at that time was measured using a charge amplifier (“NEXUS Charge Amplifier type 2692” manufactured by Brüel & Keer Co., Ltd.) and an oscilloscope (Yokogawa Electric Corporation “DLM 2022”). Then, the amount of generated charge measured for each load was divided by the applied stress, and the average value was calculated to obtain the sensitivity coefficient of the piezoelectric sensor at 10% elongation.

As shown in Table 1, in the piezoelectric sensor of Example 3 using the piezoelectric layer 3 in which the compounding amount of the piezoelectric particles is small, and in the piezoelectric sensor of Example 4 in which the thickness of the piezoelectric layer is thin, the sensitivity at 10% elongation The coefficient has become smaller.

As shown in Table 2, the piezoelectric sensor of Comparative Example 1 using the piezoelectric layer 4 made of PVDF did not have stretch flexibility, and the elastic modulus became large. Similarly, the piezoelectric sensor of Comparative Example 11 using the protective layer 2 made of a polyester film also did not have stretch flexibility, and the elastic modulus became large. Further, the piezoelectric sensor of Comparative Example 10 using the electrode layer 4 made of a conductive cloth has a large tensile strain but does not have stretch flexibility, although the elastic modulus is not large.

<Evaluation method>
The manufactured piezoelectric sensor was used to measure the subject's respiration and heart rate, and at the same time, it was examined whether the subject felt discomfort. Moreover, the expansion-contraction durability of a piezoelectric sensor and the ease of installation were evaluated. The evaluation method of the piezoelectric sensor is as follows.

[Measurement of respiration and heart rate]
First, place a mattress pad (“Smart 025” manufactured by Airweave, approximately 1000 mm wide, approximately 1950 mm long, approximately 35 mm thick) on a mattress (“Coil Killer” manufactured by Gen of Tance Co., Ltd.) The piezoelectric sensor was placed on top of it. The piezoelectric sensor was disposed such that its long side and the short side of the mattress pad (the side extending in the shoulder width direction of the subject) were parallel. Then, with the subject lying on his / her back on the mattress pad, the pressure sensitive portion of the piezoelectric sensor was positioned under the subject's heart. Next, the subject lay supine on the mattress pad and began to measure respiration and heart rate. The devices for processing the output signal from the piezoelectric sensor include a charge amplifier ("NEXUS Charge Amplifier type 2692" manufactured by Brüel &Ke; r) and a data logger (recorder) ("NR-HA08" manufactured by Keyence Corporation). Using. The measurement was performed for 30 minutes each time, for a total of 5 times. And it is evaluated as good (it shows by * mark in the same table when it can not measure even when it can not measure even when it can not measure in the case (Table 3 and Table 4 which are mentioned later by 印 mark) which can be measured all five times. did. In the present embodiment, a biological information detection apparatus is configured by the piezoelectric sensor, the charge amplifier, and the data logger.

[Evaluation of discomfort]
When measuring the respiration and heart rate, when the subject lies on the mattress pad lying on his / her back, there is no sense of incongruity (indicated by a 印 in the same table) and a slight sense of incongruity. It was evaluated that there was a sense of incongruity (indicated by Δ in the table) and a degree of incongruity as indicated by a × in the table.

[Evaluation of stretch durability]
A piezoelectric sensor is installed in a fatigue endurance tester (same as above), and a sine wave (frequency: 1 Hz) with a tensile displacement of 10% is applied 200,000 times in the longitudinal direction, and the charge generated at that time is as charge amplifier (same as above) ) Was used. Stretch durability is good (shown by a circle in the table) if the amount of generated charge after 200,000 times is 60% or more with respect to the amount of initial generated charge, and stretch durability is poor if it is less than 60% In the same table, it was evaluated as x).

[Ease of installation]
The case where the piezoelectric sensor can be easily arranged to fit on the mattress pad can be shown (indicated by 印 in the same table), and the case where it can not be arranged as such can not be indicated (indicated by the × symbol in the same table) It was evaluated.

<Evaluation result>
Tables 3 and 4 show the evaluation results together with the configuration of the manufactured piezoelectric sensor. Moreover, the measurement result of the respiration measured by the piezoelectric sensor of Example 1 is shown in FIG. FIG. 5 shows the measurement results of the heart rate measured by the same piezoelectric sensor.

As shown in Table 3, according to the piezoelectric sensor of the example, it was possible to measure the respiration and the heartbeat without the subject feeling a sense of incongruity. Moreover, each piezoelectric sensor of the example was excellent also in terms of expansion and contraction durability and ease of installation. As shown in FIGS. 4 and 5, according to the piezoelectric sensor of the embodiment, it was possible to measure respiration and heart rate with high accuracy. The electrode layer 3 of the piezoelectric sensor of Example 10 is made of conductive silver paste. For this reason, the modulus of elasticity and the tensile load at 10% elongation become large as compared with the piezoelectric sensors of the other examples, and some discomfort is generated. The piezoelectric layer 2 of the piezoelectric sensor of Example 11 contains a larger amount of piezoelectric particles than the piezoelectric layers 1 and 3. For this reason, as with the piezoelectric sensor of Example 10, the elastic modulus and the tensile load at 10% elongation become large, and some discomfort is generated.

On the other hand, as shown in Table 4, in the piezoelectric sensors of Comparative Examples 2 to 9 in which the size and the area of the pressure sensitive portion are different from the piezoelectric sensor of the example, respiration and heartbeat can not be measured, or the subject feels uncomfortable There was a problem such as feeling. The piezoelectric sensor of Comparative Example 1 having the piezoelectric layer 4 made of PVDF, the piezoelectric sensor of Comparative Example 10 having the electrode layer 4 made of conductive cloth, and the piezoelectric sensor of Comparative Example 11 having the protective layer 2 made of polyester film Both have poor flexibility. Therefore, when using these piezoelectric sensors, the subject felt discomfort such as hardness and stiffness. In the piezoelectric sensor of Comparative Example 11, the breaking elongation of the piezoelectric layer 1 is larger than the breaking elongation of the protective layer 2. Therefore, the protective layer 2 may be broken at the time of elongation, and the displacement of the piezoelectric layer 1 which is likely to be locally broken may be limited and the durability may be reduced.

The biological information detection apparatus of the present invention can measure respiratory conditions and heart rate with high accuracy without stress, and therefore is useful in the field of medical care, care, health management, training and the like.

1: living body information detection device, 10: piezoelectric sensor, 11: piezoelectric layer, 12a, 12b: electrode layer, 13a, 13b: protective layer, 20a, 20b: wiring, 30: control circuit unit, 40: cover, P: covered Examiner, S: Pressure-sensitive part.

Claims

Placed in the bedding,
A piezoelectric layer containing an elastomer and piezoelectric particles, an electrode layer disposed sandwiching the piezoelectric layer, and a protective layer laminated on at least one of the electrode layers and containing an elastomer, and having a width of 5 mm or more and 100 mm or less , A rectangular thin plate with a length to width ratio of 100 mm to 1000 mm, a length to width ratio (length / width) of 2 to 200, and a thickness of 0.05 mm to 5 mm, and a piezoelectric sensor having stretch flexibility Equipped with
In the piezoelectric sensor, the area of the pressure sensitive portion in which the electrode layer overlaps in the thickness direction via the piezoelectric layer is 20% or more of the area of the piezoelectric sensor,
A biological information detection apparatus for detecting at least one of a subject's respiration and heart rate based on an output signal from the piezoelectric sensor.
The biological information detection apparatus according to claim 1, wherein the pressure sensitive unit is disposed so as to overlap with a part of the body of the subject in a state where the subject is lying on the bedding.
The elastic modulus of the piezoelectric sensor is 10 MPa or more and 100 MPa or less,
The biological information detection apparatus according to claim 1, wherein the piezoelectric sensor extends 10% or more in the longitudinal direction.
The piezoelectric sensor according to any one of claims 1 to 3, wherein a tensile load is 100 N or less when it is elongated by 10% in the longitudinal direction, and a sensitivity coefficient in the longitudinal direction is 50 pC / N or more when it is elongated by 10%. The biological information detection apparatus according to claim 1.
The biological information detection apparatus according to any one of claims 1 to 4, wherein the piezoelectric sensor satisfies the following formula (I).
0.1 ≦ tension load of piezoelectric layer / (tension load of electrode layer + tension load of protective layer) ≦ 2 (I)
The biological information detection apparatus according to any one of claims 1 to 5, wherein the breaking elongation of the protective layer is larger than the breaking elongation of the piezoelectric layer.
The biological information detection apparatus according to any one of claims 1 to 6, wherein the elastomer of the piezoelectric layer is a hydrogenated nitrile rubber having one or more selected from a carboxyl group, a hydroxyl group, and an amino group.
The biological information detection apparatus according to any one of claims 1 to 7, wherein a content of the piezoelectric particles in the piezoelectric layer is 30% by volume or more and 50% by volume or less based on 100% by volume of the elastomer.