TW201939775A - Piezoelectric sensor capable of smoothly following extension of measured body and precisely measuring movement of measured body - Google Patents

Abstract

The present invention provides a piezoelectric sensor, which is provided with flexibility on the surface direction and may smoothly follow the extension of a measured body to precisely measure the movement of the measured body and detect the movement of the measured body on the surface direction for the mounting surface of the piezoelectric sensor. The piezoelectric sensor of the present invention is characterized in having: a piezoelectric sheet containing porous synthetic resin sheet; a signal electrode layer which is laminated on one surface of the piezoelectric sheet and contains conductive particles and flexible adhesive resin; and, a grounding electrode layer, which is laminated on the other surface of the piezoelectric sheet and contains conductive particles and flexible adhesive resin.

Description

Piezoelectric Inductor

The invention relates to a piezoelectric inductor.

The piezoelectric sheet is a material that imparts a permanent charge to the inside by injecting a charge into an insulating polymer material.

Patent Document 1 discloses a piezoelectric inductor using a piezoelectric sheet. The piezoelectric inductor includes: a piezoelectric sheet; a first ground electrode that is integrated with the first area layer of the piezoelectric sheet and has a first notch; a signal electrode that is formed on the second area layer of the piezoelectric sheet It is integrated and has a third notch; and a second ground electrode, which is laminated and integrated on the signal electrode in a state of being electrically insulated from the signal electrode and has a second notch. Moreover, notch portions of the signal electrode, the first ground electrode, and the second ground electrode overlap each other in at least a part of the thickness direction of the piezoelectric sheet. A portion of the piezoelectric sheet exposed from a portion where the notch portions of the signal electrode, the first ground electrode, and the second ground electrode overlap each other in the thickness direction of the piezoelectric sheet is used as an exposed portion.

[Prior technical literature]

[Patent Literature]

[Patent Document 1] WO2010 / 101084

However, the piezoelectric body constituting the piezoelectric inductor of Patent Document 1 carries a signal signal. The insulating film of the electrode and the ground electrode is made of a resin film such as polyethylene terephthalate or polyethylene naphthalate.

Therefore, the piezoelectric sensor of Patent Document 1 has no stretchability in the face direction and no followability for extension. Therefore, it has a problem that it cannot be used for wearable applications that are used by being attached to the skin surface of a human body, for example.

The invention provides a piezo-electric inductive sensor, which has plane-direction elasticity, can smoothly follow the extension of the measured body to accurately measure the movement of the measured body, and can also detect the piezo-electrical measurement of the measured body. Movement in the face direction of the mounting surface of the device.

The piezoelectric inductor of the present invention is characterized by comprising: a piezoelectric sheet containing a porous synthetic resin sheet; and a signal electrode layer which is laminated on one surface of the above-mentioned piezoelectric sheet and includes conductive fine particles and a stretchable adhesive resin And a ground electrode layer, which is laminated on the other surface of the piezoelectric sheet and contains conductive fine particles and a stretchable adhesive resin.

The piezoelectric inductor of the present invention has the structure as described above, and therefore has elasticity in the plane direction. The piezoelectric inductive sensor of the present invention smoothly follows the target when the installation surface of the piezoelectric inductive sensor is moved in the plane direction when the moving surface of the object to be detected (hereinafter referred to as "the measured body") is expanded or contracted. The expansion and contraction of the measurement object maintains excellent adhesion to the measurement object, and it is possible to accurately measure the movement of the measurement object (stretch and contraction followability).

Furthermore, the piezoelectric inductor of the present invention can also detect a movement in a plane direction (stretchability) of the arrangement surface of the piezoelectric inductor of the object to be measured.

1‧‧‧piezo sheet

2‧‧‧Signal electrode layer

3‧‧‧ ground electrode layer

4, 5‧‧‧ stretchable synthetic resin sheet

6, 7‧‧‧ fixative

A‧‧‧Voltage Inductor

FIG. 1 is a cross-sectional view showing a piezo-inductor of the present invention.

Fig. 2 is a cross-sectional view showing another example of the piezoelectric inductor of the present invention.

Fig. 3 is a sectional view showing still another example of the piezoelectric inductor of the present invention.

An example of the piezoelectric inductor of the present invention will be described with reference to the drawings. As shown in FIG. 1, the piezoelectric sensor A includes a piezoelectric sheet 1 including a porous synthetic resin sheet. The synthetic resin constituting the porous synthetic resin sheet is not particularly limited, and examples thereof include polyolefin resins such as polyethylene resins and polypropylene resins, fluorine resins such as polyvinylidene fluoride, polylactic acid, and liquid crystal resins. It is preferable that the laminated sheet of a non-woven cloth made of polytetrafluoroethylene includes a polyolefin-based resin, and more preferably a polypropylene-based resin.

The synthetic resin is preferably excellent in insulation. As the synthetic resin, it is preferable that the volume resistivity value (hereinafter, simply referred to as “volume resistivity value”) after the application of a voltage of 500V for 1 minute in accordance with JIS K6911 is 1.0 × 10. ¹⁰ Q. m or more synthetic resin.

The above-mentioned volume resistivity value of the synthetic resin is that the piezoelectric sheet has more excellent piezoelectricity, and is preferably 1.0 × 10 ¹² Q. m or more, more preferably 1.0 × 10 ¹⁴ Q. m or more.

Examples of the polyethylene resin include an ethylene homopolymer or a copolymer of ethylene containing more than 50% by mass of an ethylene component and at least one α-olefin having 3 to 20 carbon atoms. Examples of the ethylene homopolymer include low-density polyethylene (LDPE) obtained by radical polymerization under high pressure, and high-density polyethylene (HDPE) produced by polymerization under intermediate and low pressure in the presence of a catalyst. Wait. By copolymerizing ethylene with an α-olefin, linear low-density polyethylene (LLDPE) can be obtained. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4 -Methyl-1-pentene, 1-octene, 1-nonene, 1-decene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-icosene, etc. An α-olefin having 4 to 10 carbon atoms is preferred. The content of the α-olefin in the linear low-density polyethylene is usually 1 to 15% by mass.

As a polypropylene-based resin, if it contains a propylene component exceeding 50 mass, it is not special Other limitations include, for example, a propylene homopolymer (homopolypropylene), a copolymer of propylene and at least one olefin having a carbon number of 20 or less other than propylene, and the like. The polypropylene resin may be used alone or in combination of two or more. The copolymer of propylene and at least one olefin having a carbon number of 20 or less other than propylene may be either a block copolymer or a random copolymer.

Examples of the α-olefin copolymerized with propylene include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1 -Nonene, 1-decene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-icosene, and the like.

The foaming ratio of the porous synthetic resin sheet is preferably 1.5 to 15 times, more preferably 2 to 10 times, even more preferably 2 to 8 times, and most preferably 3 to 7 times. If the foaming magnification of the porous synthetic resin sheet is 1.5 times or more, the stretchability in the planar direction of the piezoelectric sheet is excellent, and the follow-up stretchability and the stretchability detectability are improved, which is preferable. If the foaming ratio of the porous synthetic resin sheet is 15 times or less, the mechanical strength of the piezoelectric sensor will be improved or the bubble diameter will be reduced and the piezoelectricity of the piezoelectric sheet will be stabilized, and the telescopic followability and telescopic detection will be improved. Better. The expansion ratio of the porous synthetic resin sheet refers to a value obtained by dividing the density of the entire synthetic resin constituting the porous synthetic resin sheet by the density of the porous synthetic resin sheet.

The porosity of the porous synthetic resin sheet is preferably 30% or more, more preferably 45% or more, and even more preferably 60% or more. The porosity of the porous synthetic resin sheet is preferably 95% or less, more preferably 93% or less, and even more preferably 90% or less. If the porosity of the porous synthetic resin sheet is 30% or more, the stretchability in the plane direction of the piezoelectric sheet is excellent, and the stretch followability and stretch detection are improved, which is preferable. If the porosity of the porous synthetic resin sheet is less than 95%, the mechanical strength of the piezoelectric sensor will be increased or the bubble diameter will be reduced, and the piezoelectricity of the piezoelectric sheet will be stable, and the follow-up and detection of telescopicity will be improved. good. The porosity of the porous synthetic resin sheet refers to a value obtained by multiplying the total volume of pores in the porous synthetic resin sheet by the apparent volume of the porous synthetic resin sheet and multiplying by 100.

The thickness of the porous synthetic resin sheet is preferably 10 to 300 μm, and more preferably 30 to 200 μm. When the thickness of the porous synthetic resin sheet is 10 μm or more, the mechanical strength of the piezoelectric sheet is improved. Ruoda If the thickness of the porous synthetic resin sheet is 300 μm or less, the piezoelectricity of the piezoelectric sheet is stable, which is preferable.

The expansion ratio of the piezoelectric sheet 1 is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, and most preferably 1.8% or more. The expansion and contraction ratio of the piezoelectric sheet is preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, and most preferably 7% or less. If the expansion and contraction ratio of the piezoelectric sheet 1 is 0.5% or more, it is preferable that the expansion and contraction followability and the expansion and contraction detection properties are improved. If the expansion and contraction ratio of the piezoelectric sheet 1 is 30% or less, it is preferable that the piezoelectric sheet maintains stable piezoelectricity for a long period of time, and the expansion and contraction followability and the detection of the expansion and contraction are improved. The expansion ratio (%) of the piezoelectric sheet refers to a value measured based on the following points. First, a flat square test piece with a side of 5 cm was cut out from the piezoelectric sheet, and the test piece was stretched with a force of 10 N in the direction of any edge, and the length (cm) of the test piece in the elongation direction was measured. The expansion ratio (%) of the piezoelectric sheet refers to a value calculated based on the following formula.

Stretch rate (%) = 100 × [Length of test piece in the direction of elongation (cm) -5] / 5

The 5% elongation resistance rate of the piezoelectric sheet 1 is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less. If the resistance value change rate at 5% elongation is 10% or less, the piezoelectric sensor also maintains excellent piezoelectricity in a state where the piezoelectric sensor is extended in the plane direction. The change rate of the resistance value of the piezoelectric sheet at 5% elongation is the change rate between the initial resistance value between 2 points and the resistance value at 5% elongation, which is the resistance value (Ω) at 5% elongation divided by The value obtained from the initial resistance value (Ω) (resistance value (Ω) at 5% elongation / initial resistance value (Ω)). The rate of change in resistance at 5% elongation of a piezoelectric sheet refers to a value measured according to the following points. The piezoelectric piece was cut out into a flat square shape with a side of 6 cm to prepare a test piece. An electrode is mounted on each of the centers of the opposite sides of the upper surface of the test piece, and the resistance value of the piezoelectric sheet between the electrodes is measured. The obtained resistance value is set as the initial resistance value. Then, the test piece was extended by only 3 mm in a direction parallel to any side of the upper surface. An electrode was mounted on each of the centers orthogonal to the elongation direction of the test piece and facing each other, and the resistance value of the piezoelectric piece between the electrodes was measured. The obtained resistance value was set to a resistance value at 5% elongation. Then, divide "resistance value (Ω) at 5% elongation" by The value obtained by the "initial resistance value (Ω)" is set to the "resistance value change rate at 5% elongation". The resistance value of the piezoelectric sheet can be measured using, for example, a measurement device commercially available under the trade name "LCR Meter IM3523" from HIOKI.

The piezoelectric synthetic sheet 1 is configured by charging a porous synthetic resin sheet. The method for charging the porous synthetic resin sheet is not particularly limited, and examples thereof include a method of applying a DC electric field to the porous synthetic resin sheet.

The method for applying a direct-current electric field to the porous synthetic resin sheet is not particularly limited, and examples thereof include the following methods (1) and (2).

(1) Hold a porous synthetic resin sheet with a pair of flat electrodes, connect the flat electrode in contact with the surface to be charged to a high-voltage DC power supply, and ground the other flat electrode to apply the porous synthetic resin sheet. A method of injecting an electric charge into a synthetic resin by direct current or pulse-like high voltage to charge a porous synthetic resin sheet.

(2) On the first surface of the porous synthetic resin sheet, a grounded flat electrode is superimposed in a tight state, and on the second surface side of the porous synthetic resin sheet, a high-voltage power source with a direct current is arranged at a certain interval. Ground electrode or needle electrode. Then, the corona discharge is generated by concentrating the electric field near the front end of the needle electrode or near the surface of the wire electrode to ionize air molecules, and the generated air ions are repelled by the polarity of the needle electrode or wire electrode, so that Method for charging a porous synthetic resin sheet.

The absolute value of the DC processing voltage when a DC electric field is applied to the porous synthetic resin sheet is preferably 5 to 40 kV, and more preferably 10 to 30 kV. By adjusting the DC processing voltage to the above range, the obtained piezoelectric sheet also maintains excellent piezoelectricity when it is stretched.

The signal electrode layer 2 is laminated on one side (the first side) of the piezoelectric sheet 1 and the ground electrode layer 3 is laminated on the other side (the second side) of the piezoelectric sheet 1 to form a piezoelectric sensor.器 A。 Device A. Furthermore, by measuring the potential of the signal electrode using the ground electrode as a reference electrode, the potential generated by the piezoelectric sheet of the piezoelectric sensor can be measured. In addition, one surface (first surface) of the piezoelectric sheet 1 refers to a surface of the piezoelectric sheet 1. Face with the largest area. The other surface (second surface) of the piezoelectric sheet 1 refers to a surface on the opposite side to one surface (first surface) of the piezoelectric sheet 1.

Specifically, on one side of the piezoelectric sheet 1, a signal electrode layer 2 containing conductive fine particles and a stretchable adhesive resin is laminated. The signal electrode layer 2 is formed by dispersing conductive fine particles in a stretchable adhesive resin. Therefore, it exhibits excellent stretchability and can smoothly follow the arrangement surface of a piezo-electric sensor on the object to be measured. Movement in the direction of the face. This makes it possible to accurately detect the movement of the object to be measured (the telescopic followability) by using the piezoelectric sensor, and also to accurately detect the surface on which the piezoelectric sensor is arranged on the object to be measured. Directional movement (telescopic detection). In addition, the number of the signal electrode layers 2 laminated on one surface of the piezoelectric sheet 1 may be one or a plurality of patterned ones.

Similarly, on the other side of the piezoelectric sheet 1, a ground electrode layer 3 containing conductive fine particles and a stretchable adhesive resin is also laminated. The ground electrode layer 3 is formed by dispersing conductive fine particles in a stretchable adhesive resin. Therefore, the ground electrode layer 3 exhibits excellent stretchability, and can smoothly follow the arrangement surface of the piezoelectric sensor on the object to be measured. Movement in the direction of the face. This makes it possible to accurately detect the movement of the object to be measured (the telescopic followability) by using the piezoelectric sensor, and also to accurately detect the surface on which the piezoelectric sensor is arranged on the object to be measured. Directional movement (telescopic detection). In addition, the number of the ground electrode layers 2 laminated on one surface of the piezoelectric sheet 1 may be one or a plurality of patterned ones.

The conductive fine particles constituting the signal electrode layer 2 and the ground electrode layer 3 are not particularly limited as long as they can impart conductivity to the signal electrode layer 2 and the ground electrode layer 3. Examples include silver fine particles, aluminum fine particles, copper fine particles, and nickel. Metal particles such as fine particles and palladium particles; carbon-based conductive particles such as carbon black, graphite, carbon nanotubes, carbon fibers, and metal-coated carbon black; ceramic-based conductive particles such as tungsten carbide, titanium nitride, zirconium nitride, and titanium carbide ; Conductive potassium titanate whiskers and the like, preferably metal fine particles, more preferably silver fine particles. The conductive fine particles may be used alone or in combination of two or more. Moreover, news The conductive particles included in the electrode layer 2 and the conductive particles included in the ground electrode layer 3 may be the same or different.

The average particle diameter of the conductive fine particles contained in the signal electrode layer 2 is preferably 0.01 to 50 μm, more preferably 0.1 to 30 μm, and even more preferably 0.5 to 25 μm. The average particle diameter of the conductive fine particles contained in the ground electrode layer 3 is preferably 0.01 to 50 μm, more preferably 0.1 to 30 μm, and even more preferably 0.5 to 25 μm. When the average particle diameter of the conductive fine particles is within the above-mentioned range, the signal electrode layer 2 and the ground electrode layer 3 can maintain the stretchability and be provided with conductivity to the signal electrode layer 2 and the ground electrode layer 3.

The average particle diameter of the conductive fine particles can be measured based on the following points. The signal electrode layer 2 and the ground electrode layer 3 are cut in the thickness direction, and an arbitrary part of the cut surface is photographed with an electron microscope to obtain a magnified photograph with a magnification of 1000 times. The diameter of any 100 conductive fine particles among the conductive fine particles appearing on the enlarged photograph was measured. The diameter of the conductive fine particles refers to the diameter of a true circle with the smallest diameter that can surround the conductive fine particles appearing on the enlarged photograph. The arithmetic mean value of the diameters of the conductive fine particles is defined as the average particle diameter of the conductive fine particles.

The content of the conductive fine particles contained in the signal electrode layer 2 is preferably 40 to 90 parts by mass, more preferably 60 to 85 parts by mass, and even more preferably 60 to 80 parts by mass relative to 100 parts by mass of the adhesive resin. The content of the conductive fine particles contained in the ground electrode layer 3 is preferably 40 to 90 parts by mass, more preferably 60 to 85 parts by mass, and even more preferably 60 to 80 parts by mass relative to 100 parts by mass of the adhesive resin. If the content of the conductive particles contained in the signal electrode layer 2 and the ground electrode layer 3 is within the above range, it is possible to maintain the elasticity of the signal electrode layer 2 and the ground electrode layer 3 and impart the signal electrode layer 2 and the ground electrode layer 3 Conductivity.

As long as the bonding resin constituting the signal electrode layer 2 and the ground electrode layer 3 can provide the signal electrode layer 2 and the ground electrode layer 3 with the expansion and contraction following the piezoelectric sheet in the plane direction, and can be expanded and contracted without causing damage such as cracks, etc. Sex.

Examples of the binder resin include modified polysiloxane and acrylic modified polymer. Materials, styrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and polyamide-based thermoplastics Elastomers, thermoplastic elastomers such as 1,2-polybutadiene-based thermoplastic elastomers, polychloroprene (CR), EPDM, polyisoprene rubber (IR), polybutadiene rubber (BR), Rubber materials such as styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene copolymer rubber, butyl rubber, etc. The adhesive resin may be used alone or in combination of two or more.

The method for laminating and integrating the signal electrode layer 2 and the ground electrode layer 3 on the surface of the piezoelectric sheet 1 is not particularly limited, and examples thereof include the following methods (1) and (2).

(1) A conductive coating made by dispersing or dissolving conductive fine particles and a binder resin in a solvent is applied to the surface of a piezoelectric sheet, and then the solvent of the conductive coating is removed to thereby make the signal electrode layer 2 or A method for integrating the ground electrode layer 3 with the surface area layer of the piezoelectric sheet 1.

(2) A conductive paint obtained by dispersing conductive fine particles in a hardening resin is coated on the surface of a piezoelectric sheet, and then the hardening resin is hardened by heating or free radiation to make a bonding resin, thereby making a signal A method for integrating the electrode layer 2 or the ground electrode layer 3 on the surface area layer of the piezoelectric sheet 1.

Examples of the free radiation include electron beams, ultraviolet rays, alpha rays, beta rays, and gamma rays.

The stretch ratio of the signal electrode layer 2 is preferably 0.5%, more preferably 3% or more, particularly preferably 5% or more, and most preferably 7% or more. The expansion ratio of the signal electrode layer 2 is preferably 23% or less, more preferably 15% or less, even more preferably 13% or less, and most preferably 11% or less. If the expansion ratio of the signal electrode layer 2 is 0.5% or more, the expansion followability and the expansion detection are improved, which is better. If the expansion ratio of the signal electrode layer 2 is 23% or less, the piezoelectricity accuracy of the piezo sensor is improved, and the expansion followability and expansion detection are improved, which is better. The expansion ratio (%) of the signal electrode layer 2 is a value measured based on the following points. First, cut out a 5 cm flat square test piece from the signal electrode layer 2 and place the test piece in the direction of any edge. The force was 10 N, and the length (cm) of the test piece in the elongation direction was measured. The expansion ratio (%) of the signal electrode 2 is a value calculated based on the following formula. The stretch ratio of the signal electrode layer 2 can be measured using, for example, a tensile machine commercially available from Orientec.

Stretch rate (%) = 100 × [Length of test piece in the direction of elongation (cm) -5] / 5

The expansion ratio of the ground electrode layer 3 is preferably 0.5%, more preferably 3% or more, particularly preferably 5% or more, and most preferably 7% or more. The stretch ratio of the ground electrode layer 3 is preferably 23% or less, more preferably 15% or less, even more preferably 13% or less, and most preferably 11% or less. If the expansion ratio of the ground electrode layer 3 is 0.5% or more, it is preferable that the expansion followability and the expansion detection are improved. If the expansion ratio of the ground electrode layer 3 is 23% or less, the piezoelectricity accuracy of the piezo sensor is improved, and the followability and detection of the expansion and contraction are improved, which is better. The expansion ratio (%) of the ground electrode layer 3 is a value measured based on the following points. First, a flat square test piece with a side of 5 cm was cut out from the ground electrode layer 3, and the test piece was stretched with a force of 10 N in the direction of any edge, and the length (cm) of the test piece in the elongation direction was measured. The expansion ratio (%) of the ground electrode 3 is a value calculated based on the following formula. The stretch ratio of the ground electrode layer 3 can be measured using, for example, a tensile machine commercially available from Orientec.

Stretch rate (%) = 100 × [Length of test piece in the direction of elongation (cm) -5] / 5

In the above, the case where the signal electrode layer 2 and the ground electrode layer 3 are directly laminated and integrated on the surface of the piezoelectric sheet 1 has been described. Another aspect of the piezo-inductor A is shown in FIG. 2 and FIG. 3. The signal electrode layer 2 and the ground electrode layer 3 may be carried on the surfaces of the stretchable synthetic resin sheets 4 and 5 (integrated layers), and the stretchable synthetic resin sheets 4 and 5 may be used as the signal electrode layer 2 Or, the method in which the formation surface of the ground electrode layer 3 faces the piezoelectric sheet 1 is integrated on the surface of the piezoelectric sheet 1 via a fixative as necessary to form a piezoelectric inductor A.

If the stretchable synthetic resin sheets 4 and 5 can be used without causing damage such as cracks, etc. In this case, the expansion and contraction following the expansion and contraction in the plane direction of the piezoelectric sheet 1 is not particularly limited. Examples of the synthetic resin constituting the stretchable synthetic resin sheets 4 and 5 include styrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and polyester-based thermoplastics. Thermoplastic elastomers such as elastomers, polyamide-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, 1,2-polybutadiene-based thermoplastic elastomers, polychloroprene (CR), EPDM, polyisoprene Diene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene copolymer rubber, butadiene Rubber materials such as base rubber. The adhesive resin may be used alone or in combination of two or more.

The stretch ratio of the stretchable synthetic resin sheets 4 and 5 is preferably 0.5% or more, more preferably 3% or more, particularly preferably 5% or more, and most preferably 7% or more. The stretch ratio of the stretchable synthetic resin sheets 4 and 5 is preferably 28% or less, more preferably 20% or less, particularly preferably 18% or less, and most preferably 16% or less. When the stretch ratio of the stretchable synthetic resin sheets 4 and 5 is 0.5% or more, the stretch followability and stretch detection are improved, which is preferable. If the stretch ratio of the stretchable synthetic resin sheets 4 and 5 is 28% or less, the piezoelectricity accuracy of the piezo sensor is improved, which is preferable. The stretch ratio (%) of the stretchable synthetic resin sheets 4 and 5 is a value measured based on the following points. First, cut out a flat square test piece with a side of 5 cm from the stretchable synthetic resin sheets 4 and 5, and stretch the test piece at a direction of any edge with a force of 10 N, and measure the length of the test piece in the elongation direction at the time of extension. (cm). The stretch ratio (%) of the stretchable synthetic resin sheets 4 and 5 means a value calculated based on the following formula. The stretch ratio of the stretchable synthetic resin sheets 4 and 5 can be measured using, for example, a tensile machine commercially available from Orientec.

Stretch rate (%) = 100 × [Length of test piece in the direction of elongation (cm) -5] / 5

The method for supporting the signal electrode layer 2 or the ground electrode layer 3 on the surfaces of the stretchable synthetic resin sheets 4 and 5 is not particularly limited, and examples thereof include the methods shown in (1) and (2) below.

(1) A conductive paint obtained by dispersing or dissolving conductive fine particles and a binder resin in a solvent is applied to the surface of a stretchable synthetic resin sheet, and then the solvent of the conductive paint is removed to thereby make the signal electrode layer. 2 or a method in which the ground electrode layer 3 is integrated with the surface area layers of the stretchable synthetic resin sheets 4 and 5.

(2) A conductive paint obtained by dispersing conductive fine particles in a curable resin is applied to the surfaces of the stretchable synthetic resin sheets 4 and 5, and the curable resin is hardened by heating or free radiation to form a bond. A method of integrating a signal electrode layer 2 or a ground electrode layer 3 with a surface area layer of a stretchable synthetic resin sheet 4 or 5 using a resin.

The piezoelectric sheet and the stretchable synthetic resin sheet may be subjected to a known surface treatment to improve the adhesion of the conductive paint. Examples of the surface treatment method include corona treatment, primer treatment, and sandblasting.

The method of integrating the stretchable synthetic resin sheets 4 and 5 carrying the signal electrode layer 2 or the ground electrode layer 3 with the surface area layer of the piezoelectric sheet 1 is not particularly limited, and examples thereof include the following (1) and ( 2).

(1) When the signal electrode layer 2 or the ground electrode layer 3 has adhesiveness or adhesiveness, the signal electrode layer 2 or the ground electrode layer 3 has the adhesiveness, and the carrier is supported on the surface of the piezoelectric sheet 1 A method for laminating and integrating the stretchable synthetic resin sheets 4 and 5 of the signal electrode layer 2 or the ground electrode layer 3 (see FIG. 2).

(2) A method of integrating the stretchable synthetic resin sheets 4, 5 carrying the signal electrode layer 2 or the ground electrode layer 3 on the surface area layer of the piezoelectric sheet 1 via a stretchable fixing agent 6, 7 (refer to the figure) 3).

In addition, the fixing agents 6, 7 are composed of a reaction system, a solvent system, a water system, and a hot-melt adhesive or an adhesive. From the viewpoint of maintaining the sensitivity of the piezoelectric sheet 1, the dielectric constant is preferably smaller than Low fixative. Examples of the fixing agents 6 and 7 include an adhesive such as an acrylic adhesive, a double-sided adhesive tape, and the like.

In a state where the stretchable synthetic resin sheets 4 and 5 carrying the signal electrode layer 2 or the ground electrode layer 3 are integrated with the surface area layer of the piezoelectric sheet 1 via the fixing agent, the expansion ratio of the fixing agent is preferably 0.5% or more, more preferably 3% or more, particularly preferably 5% or more, and most preferably 7% or more. The stretch ratio of the fixing agent is preferably 70% or less, more preferably 65% or less, and even more preferably 60% or less. If the expansion ratio of the fixing agent is 0.5% or more, the expansion followability and the expansion detection property are improved, which is preferable. Moreover, since the fixing agent has stretchability, peeling of the stretchable synthetic resin sheets 4 and 5 and the piezoelectric sheet 1 can be effectively prevented. If the expansion and contraction ratio of the fixing agent is 70% or less, it is preferable that the piezoelectric sensor maintain excellent piezoelectricity over time. The expansion ratio (%) of the fixing agent is a value measured based on the following points. First, a flat square test piece having a side of 5 cm was cut out from the fixing agent, and the test piece was stretched with a force of 10 N in the direction of any edge. The expansion ratio (%) of the fixing agent is a value calculated based on the following formula. The stretch ratio of the fixing agent can be measured using, for example, a tensile machine commercially available from Orientec.

Stretch rate (%) = 100 × [Length of test piece in the direction of elongation (cm) -5] / 5

When the piezoelectric inductor A configured as described above includes the piezoelectric sheet 1, the signal electrode layer 2, the ground electrode layer 3, and the stretchable synthetic resin sheets 4, 5 and the fixing agent 6, 7 constituting the piezoelectric sheet 1, The stretchable synthetic resin sheets 4 and 5 and the fixing agents 6 and 7 expand and contract freely in the plane direction of the piezoelectric sheet 1. Therefore, the piezoelectric sensor A attached to the measured object in a tight state smoothly expands and contracts following the movement in the plane direction of the arrangement surface of the piezoelectric sensor of the measured object, and maintains a good close contact with the quilted device. The state of the surface of the measurement object can accurately detect the movement of the measurement object. In this way, the piezoelectric sensor A can smoothly follow the movement in the direction of the surface of the object to be detected (the object to be measured) on which the piezoelectric sensor is disposed (the surface on which the piezoelectric sensor is disposed). Therefore, it is possible to smoothly follow the skin of a human body, etc., which perform fine movements. In addition, the piezo-inductor A is suitable for being applied to the skin of the human body or being worn by the human body, that is, a so-called wearable application, and can accurately detect a biological signal such as a pulse or a breathing signal. Examples of the measurement object include transportation equipment such as a human body, a concrete structure, a bridge, and a vehicle.

Furthermore, the piezoelectric sensor A smoothly follows the movement in the plane direction of the arrangement surface of the piezoelectric sensor on the object to be expanded and contracted. However, the thickness of the piezoelectric sheet 1 changes during the expansion and contraction. As a result of the change in thickness, a charge is exhibited. By detecting this electric charge, it is possible to detect the movement in the plane direction of the arrangement surface of the piezoelectric inductor on the object to be measured with high accuracy.

For example, the wall surface of a concrete structure such as a building is degraded over time due to exposure to sunlight or wind and rain, and cracks such as cracks are generated. If cracks occur, the wall surface of the concrete structure moves in the plane direction. Therefore, if the piezo-electric sensor A is adhered to the wall surface of the concrete structure in a tight state in advance, the piezo-electric sensor A can accurately detect the movement of the wall surface with cracks, and can quickly detect the concrete structure. The resulting cracks and other damages can be dealt with smoothly afterwards.

The overall expansion ratio of the piezo-inductor A is preferably 0.5% or more, more preferably 0.7% or more, more preferably 0.8% or more, and even more preferably 0.9% or more. The overall expansion ratio of the piezo-inductor A is preferably 15% or less, more preferably 13% or less, even more preferably 11% or less, and most preferably 4% or less. If the overall expansion ratio of the piezo-inductor A is 0.5% or more, the telescopic followability and the telescopic detection performance are improved, which is better. If the expansion ratio of the entire piezoelectric inductor A is 15% or less, it is preferable that the piezoelectric inductor maintains excellent piezoelectricity over time. The expansion ratio (%) of the entire piezoelectric inductor A refers to a value measured based on the following points. First, a flat square test piece with a side of 5 cm was cut out from the self-pressure inductor A, and the test piece was stretched with a force of 10 N in the direction of any edge, and the length of the test piece in the elongation direction (cm) was measured. ). The expansion ratio (%) of the piezoelectric sensor A is a value calculated based on the following formula. The expansion and contraction ratio of the piezoelectric sensor A can be measured using, for example, a tensile machine commercially available from Orientec.

Stretch rate (%) = 100 × [Length of test piece in the direction of elongation (cm) -5] / 5

[Example]

Next, examples of the present invention will be described, but the present invention is not limited to the following implementations. Examples are limited.

(Examples 1 to 5)

100 parts by mass of a propylene-ethylene random copolymer (trade name "NOVATEC EG8B" manufactured by Japan Polypropylene Corporation, content of ethylene unit: 5 mass%), 3.3 parts by mass of trimethylolpropane trimethacrylate, and azo 2 parts by mass of dimethylamine and a phenolic antioxidant were supplied to an extruder and melt-kneaded. The T-die head mounted on the front end of the extruder is extruded in a sheet shape to produce a foamable resin sheet with a thickness of 180 μm. The foamable resin sheet was cut into a flat square shape with a side of 30 cm. Azoformamide was supplied to the extruder in an amount shown in Table 1.

Both sides of the obtained foamable resin sheet were irradiated with an electron beam under conditions of an acceleration voltage of 300 kV and an intensity of 25 kGy to crosslink the propylene-ethylene random copolymer constituting the foamable resin sheet. The foamable resin sheet is heated to 250 ° C. to expand the foamable resin sheet to obtain a foamed sheet. The surface temperature of the obtained foamed sheet was heated to 140 ° C and uniaxially extended. The expansion ratio, thickness, and porosity of the foamed sheet are shown in Table 1.

On the first surface of the foamed sheet, a grounded flat electrode is superimposed in a tight state, and on the second surface side of the foamed sheet, needle-shaped electrodes electrically connected to a direct-current high-voltage power supply are arranged at specific intervals. By concentrating the electric field near the surface of the needle electrode, a corona discharge is generated under the conditions of a voltage of -20kV, a discharge distance of 10 μm, and a voltage application time of 1 minute, and the air molecules are ionized. The polarity repels the generated air ions, applies a DC electric field to the foamed sheet, and injects a charge, thereby charging the entire foamed sheet. Then, the charged foamed sheet was kept in a state of being wrapped with grounded aluminum foil for 3 hours to obtain a piezoelectric sheet. The piezoelectric constant d33 of the piezoelectric sheet is shown in Table 1.

As the stretchable synthetic resin sheet, a 50-m-thick polyurethane-based thermoplastic elastomer sheet (Tough Grace manufactured by Takeda Industries, Ltd.) and a 25-m-thick polyurethane-based thermoplastic elastomer sheet are used. (Tough Grace manufactured by Takeda Sangyo Co., Ltd.) Two pieces each. Select a polyurethane thermoplastic elastomer with the thickness shown in Table 1. sheet. A conductive paint (a trade name "SX-ECA48" manufactured by Cemedine Corporation) containing silver fine particles (average particle diameter: 2 μm) and an acrylic modified polymer as a curable resin was prepared. After one surface of each of the two polyurethane-based thermoplastic elastomer sheets is coated with a conductive coating material, the conductive coating material is heated at 100 ° C. for 3 hours to harden the curable resin to make a binding resin, and uniformly form the silver fine particles. The electrode layer formed by dispersing in the binder resin is integrated with one area layer of a polyurethane-based thermoplastic elastomer sheet. The thickness of the electrode layer is shown in Table 1. The adhesive resin is elastic. The electrode layer contains 65 parts by mass of silver fine particles per 100 parts by mass of the adhesive resin.

A double-sided adhesive tape (trade name "WT # 5402" manufactured by Sekisui Chemical Industry Co., Ltd. with a thickness of 25 µm) was prepared as a fixing agent. A double-sided adhesive tape as a fixing agent is attached to both sides of the piezoelectric sheet. On each of the two faces of the piezoelectric sheet, a polyurethane-based thermoplastic elastomer sheet was integrated with a fixing agent so that the electrode layer became the piezoelectric sheet side, thereby obtaining a piezoelectric sheet. Fixatives are stretchable. The electrode layer carried on one surface of the polyurethane-based thermoplastic elastomer sheet in which one area layer of the piezoelectric sheet 1 is integrated is set as a signal electrode layer. The electrode layer carried on one surface of the polyurethane-based thermoplastic elastomer sheet integrated with the other area layer of the piezoelectric sheet 1 is set as a ground electrode layer. The polyurethane-based thermoplastic elastomer sheet, the signal electrode layer, and the ground electrode layer have a flat square shape with a side of 6 cm on one side of the same size as the piezoelectric sheet. Connect the wires to each of the signal electrode layer and the ground electrode layer.

(Comparative example 1)

An electrode layer composed of an aluminum box having a thickness of 10 μm was laminated on both sides of two polyurethane-based thermoplastic elastomer sheets through a double-sided adhesive tape to integrate them, except that the same points as in Example 1 were obtained. Get a piezo-inductor. Furthermore, the electrode layer made of aluminum foil is not stretchable.

(Comparative example 2)

A piezoelectric inductor was obtained according to the same points as in Example 1 except that an electrode layer composed of aluminum was formed on each of two surfaces of two polyurethane-based thermoplastic elastomer sheets by sputtering. Furthermore, the electrode layer made of aluminum is not stretchable.

(Comparative example 3)

Except that a polyethylene terephthalate sheet having a thickness of 50 μm was used instead of the polyurethane-based thermoplastic elastomer sheet, a piezoelectric inductor was obtained according to the same points as in Example 1. Furthermore, the polyethylene terephthalate sheet is not stretchable.

With respect to the obtained piezoelectric sheet, the resistance value change rate at 5% elongation was measured according to the above-mentioned points, and the results are shown in Table 1.

The telescopic followability and telescopic detection of the obtained piezoelectric sheet were measured according to the following points, and the results are shown in Table 1.

The expansion and contraction of the obtained piezoelectric inductor was measured, and the results are shown in Table 1. The expansion and contraction ratios of the piezoelectric sheet, the fixing agent, the signal electrode layer, the ground electrode layer, and the stretchable synthetic resin sheet constituting the piezoelectric inductor were measured according to the above points, and the results are shown in Table 1. Furthermore, in Comparative Example 2, the electrode layer composed of aluminum cannot be separated, and the expansion and contraction of the signal electrode layer and the ground electrode layer cannot be measured.

(Telescopic followability)

Prepare a flat square rubber sheet that is stretchable and has a size one circle larger than that of a piezo sensor. The piezoelectric sensor was adhered to one side of the rubber sheet in a tight state through a double-sided adhesive tape having elasticity to produce a test body. Adjust so that the end edge of the piezo sensor and the end edge of the rubber sheet are parallel to each other.

Using an exciter, under the conditions of a load F of 1N, a dynamic load of ± 0.5N, a frequency of 30Hz, and an extrusion area of 1 cm ² , a compression force is applied to the piezoelectric inductor, and the voltage generated at this time is measured. The voltage system reads peak to peak. The voltage was read through an amplifier (manufactured by MSI) using an oscilloscope (manufactured by TEXIO Technologies).

The voltage of the piezoelectric sheet immediately after the piezoelectric inductor was attached to the rubber sheet was measured and set as the initial voltage.

Keep the rubber sheet stretched at only 1% or 5% of elongation along any end edge. In the present invention, the elongation is a value calculated by the following calculation formula.

Elongation (%) = 100 × size of the rubber sheet in the elongation direction after elongation / size of the rubber sheet in the elongation direction before elongation

In the elongation state, the voltage of the piezoelectric sheet was measured based on the same points as described above, and was set as the elongation voltage.

The piezoelectric inductor of Comparative Example 2 was disconnected when the aluminum layer was stretched, and the piezoelectric inductors of Comparative Examples 1 and 3 were peeled from the surface of the piezoelectric sheet when the signal electrode layer and the ground electrode layer were peeled off. Therefore, the elongation voltage cannot be measured.

(Stretch detection)

A test body was produced based on the same points as in the measurement of the telescopic followability. A tensile machine (manufactured by Orientec) was used to stretch the rubber sheet along any end edge only at an elongation of 1% or 5%, and the voltage generated during the elongation was measured. The voltage system measures the peak to peak of the elongation.

The piezoelectric inductor of Comparative Example 2 was disconnected when the aluminum layer was stretched, and the piezoelectric inductors of Comparative Examples 1 and 3 were peeled from the surface of the piezoelectric sheet when the signal electrode layer and the ground electrode layer were peeled off. Therefore, the voltage generated during elongation cannot be measured.

[Industrial availability]

The piezoelectric inductive sensor of the present invention has stretchability in the plane direction. Therefore, when the arrangement surface of the piezoelectric inductive sensor on the object to be expanded or contracted in the plane direction, it can smoothly follow the object It expands and contracts and maintains excellent adhesion to the object to be measured, so that the movement of the object can be accurately measured. Furthermore, the piezoelectric inductor of the present invention can also detect the movement in the plane direction of the arrangement surface of the piezoelectric inductor on the object to be measured.

Therefore, the piezoelectric inductor of the present invention can be suitably used for wearable applications. The piezoelectric inductive sensor of the present invention can be used for measuring the movement of a measurement object such as a transportation machine such as a vehicle, a human body, a concrete structure, a bridge, and the like.

Claims (4)

A piezoelectric inductor includes: a piezoelectric sheet containing a porous synthetic resin sheet; a signal electrode layer which is laminated on one side of the piezoelectric sheet and includes conductive fine particles and a stretchable adhesive resin; and a ground The electrode layer is laminated on the other surface of the piezoelectric sheet and includes conductive fine particles and a stretchable adhesive resin. For example, the piezo-electric inductive sensor according to item 1 of the patent application scope, wherein the signal electrode layer and / or the ground electrode layer are carried on a stretchable synthetic resin sheet. For example, the piezoelectric sensor according to the second patent application range, wherein the stretchable synthetic resin sheet contains a thermoplastic elastomer sheet or a rubber sheet. For example, the piezo-electric inductive sensor according to any one of claims 1 to 3, wherein the piezo-electric inductive device has an overall expansion ratio of 0.5% or more.