JPWO2015167013A1 - Sound wave / impact detector - Google Patents

Abstract

A sound wave / impact detection element having a porous resin body made of a resin having no dipole due to a molecule and a crystal structure, and an external force absorbing sheet.

Description

  The present invention relates to a sound wave / impact detection element.

Since sound waves, especially ultrasonic sensors, can be examined non-destructively and harmlessly, etc., they can be used for various inspections such as inspection of structural defects, diagnosis of human and animal diseases, sounding instruments and detectors. Applied to the field.
In addition, the impact detection sensor can be used to detect the activation of airbags in automobiles, monitor precision devices such as hard disks, test when developing protective materials, sensors for measuring the number of vehicles and vehicle classification, and hitting sensors for game equipment and sports equipment. Can be used.

  As an element for detecting sound waves, for example, Patent Document 1 discloses a damper material, an ultrasonic transmission / reception element that is a polymer piezoelectric element, a composite piezoelectric element, or a coated ceramic piezoelectric element fixed to the front surface thereof, and further on the front surface thereof. An ultrasonic probe constituted by a coated wear-resistant film is disclosed.

JP 2002-365270 A

However, conventional sensing elements that detect sound waves and impacts have problems in terms of durability, such as maintaining long-term characteristics, and there is room for further improvement.
The present invention has been made in view of such problems, and an object of the present invention is to provide a sound wave / impact detection element excellent in sound wave / impact detection ability and durability.

Under such circumstances, the present inventors have intensively studied to solve the above problems, and as a result, have obtained a porous resin body made of a resin having no dipole due to the molecule and crystal structure, and an external force absorbing sheet. According to the sound wave / impact detection element possessed, it has been found that the above object can be achieved, and the present invention has been completed.
The configuration of the present invention is as follows.

  [1] A sound wave / impact detection element having a porous resin body made of a resin having no dipole due to a molecule and a crystal structure, and an external force absorbing sheet.

  [2] The sound wave / impact detection element according to [1], wherein the porosity of the porous resin body is 60% or more.

  [3] The sound wave / impact detection element according to [1] or [2], wherein the resin is polytetrafluoroethylene.

[4] The sound wave / impact detection element according to any one of [1] to [3], wherein the porous resin body includes a non-woven fabric or a woven fabric formed from fibers made of resin.
[5] The sound wave / impact detection element according to [4], wherein an average fiber diameter of the fibers is 0.05 to 50 μm.

  [6] The sound wave / impact detection element according to any one of [1] to [5], wherein the porous resin body is subjected to polarization treatment.

[7] The sound wave / impact detection element according to any one of [1] to [6], wherein the external force absorption sheet has an external force absorption rate of 50% or more.
[8] The sound wave / impact detection element according to any one of [1] to [7], wherein a sound wave transmittance of the external force absorbing sheet is 20% or more.
[9] The sound wave / impact detection element according to any one of [1] to [8], wherein the loss elastic modulus of the external force absorbing sheet is 1 × 10 ³ to 1 × 10 ⁷ Pa.
[10] The sound wave / impact detection element according to any one of [1] to [9], wherein the thickness of the external force absorbing sheet is 0.05 to 10 mm.

  [11] The sound wave / impact detection element according to any one of [1] to [10], wherein the external force absorbing sheet is laminated on the porous resin body.

  According to the present invention, it is possible to provide a sound wave / impact detection element excellent in sound wave / impact detection ability and durability.

<< Sound wave / impact detector >>
The sound wave / impact detection element of the present invention is an element for detecting sound waves and / or shocks, and includes a porous resin body made of a resin having no dipole due to a molecule and a crystal structure, and an external force absorbing sheet. For this reason, the sound wave / impact detection element of the present invention is excellent in sound wave / impact detection ability and durability.
The sound wave / impact detection element of the present invention can be used for various inspections such as inspection of structural defects, diagnosis of human or animal diseases, determination of whether or not an impact of an object has exceeded an allowable level, a sounding instrument or a detector. It can be used in the field, and can be suitably used for applications where it is desired to detect sound waves and impacts in an environment where the temperature is higher than room temperature or in an environment where a high pressure is applied (eg, an environment where the pressure is 1 MPa or more). It should also be used suitably for air bag activation judgment of automobiles, monitoring of precision equipment such as hard disks, testing during the development of protective materials, sensors for measuring the number of vehicles and vehicle classification, impact sensors for game equipment and sports equipment, etc. Can do.

  The sound wave / impact detection element of the present invention is not particularly limited in its structure as long as it has the porous resin body and the external force absorbing sheet, but the external force absorbing sheet is laminated on the porous resin body. A laminate in which an external force absorbing sheet is laminated on a porous resin body is preferable.

As a laminate in which an external force absorbing sheet is laminated on the sheet-like porous resin body, a laminate in which an external force absorbing sheet is laminated on at least one surface of a piezoelectric element including the sheet-like porous resin body. If it is, it will not be restrict | limited especially, From the point of obtaining the sound wave and the impact detection element containing the porous resin body which hold | maintains a high piezoelectric rate, the front and back of the piezoelectric element containing a sheet-like porous resin body ( A laminate in which an external force absorbing sheet is laminated on two surfaces having the largest area), or a laminate in which an external force absorbing sheet is laminated on the entire surface of a piezoelectric element including a sheet-like porous resin body. preferable.
A sound wave / impact detecting element including a porous resin body that retains a high piezoelectric rate is obtained. From the viewpoint of ease of manufacturing, cost, etc., the front and back surfaces of the piezoelectric element including a sheet-like porous resin body are provided. A laminate in which an external force absorbing sheet is laminated is preferable. From the viewpoint of obtaining a sound wave / impact detection element including a porous resin body that retains a higher piezoelectric rate, the laminate includes a sheet-like porous resin body. A laminate in which an external force absorbing sheet is laminated on the entire surface of the piezoelectric element is preferable.

  In the sound wave / impact detection element of the present invention, there may be a conventionally known layer or the like other than the porous resin body and the external force absorbing sheet. For example, the laminate includes the porous resin body and the external force absorbing member. Conventionally used for sound wave detection elements and impact detection elements, between the sheet and the side of the porous resin body that is opposite to the side that contacts the external force absorption sheet, and that that is opposite to the side of the external force absorption sheet that contacts the porous resin body In addition, known layers such as an electrode layer, a surface smoothing layer, a protective layer, an insulating layer, and an adhesive layer may be present.

  In the laminated body, the external force absorbing sheet also serves to prevent the electric charge held in the porous resin body from being electrically connected to the external environment and attenuated. Can be obtained.

  The thickness of the laminate may be appropriately adjusted according to the application to be used, and is not particularly limited, but is, for example, 50 μm to 50 mm, preferably 100 μm to 10 mm.

<Porous resin body>
In the sound wave / impact detection element of the present invention, a porous resin body made of a resin having no dipole due to the molecule and crystal structure is used as a piezoelectric material, and converts sound waves / impact into electric power by converting the sound wave / impact into electric power. It plays the role of detecting impact.
The porous resin body has high charge responsiveness to minute external force, high sound wave / impact detection ability, and can retain electric charge even in a high temperature environment. It is possible to obtain a sound wave / impact detecting element that is excellent in resistance, large in flexibility, excellent in impact resistance and heat resistance, and lightweight. Furthermore, since the porous resin body can be easily formed into an arbitrary shape such as a thin film or a large area, a sound wave / impact detection element having an arbitrary shape can be manufactured according to a desired application. .

  The porous resin body is preferably a structure made of a resin capable of holding an electric charge, and more preferably a structure made of a resin having heat resistance.

  The resin having no dipole due to the molecule and crystal structure is not particularly limited as long as the molecule and crystal structure are not polar resins, but polyolefin resin (polyethylene, polypropylene, ethylene propylene resin, etc.), polyester resin Non-fluorinated resins such as resins (polyethylene terephthalate, etc.), polyurethane resins, polystyrene resins, silicone resins, etc., and polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA), tetrafluoro Examples thereof include fluorine resins such as ethylene-hexafluoropropylene copolymer (FEP).

Among these, from the viewpoints of heat resistance and weather resistance, a resin that has a high continuous usable temperature and does not have a glass transition point in the operating temperature range of the sound wave / impact detection element is preferable. The continuous useable temperature can be measured by a continuous use temperature test described in UL746B (UL standard), preferably 50 ° C or higher, more preferably 100 ° C or higher, and further preferably 200 ° C or higher. . Moreover, it is preferable that it is resin which shows water repellency from a moisture-resistant viewpoint.
As the resin having these characteristics, for example, polyolefin resin and fluorine resin are preferable, fluorine resin is more preferable, and PTFE is particularly preferable.

  In particular, when PTFE is used as the resin, it is possible to obtain a sound wave / impact detection element having a good balance between heat resistance, sound wave / impact detection ability and durability. Since the performance and structure can be maintained even under the environment, it can be suitably used as a sound wave / impact detection element for inspection of high-temperature members such as for underground excavation and oil plant piping.

The porous resin body may contain a conventionally known additive in addition to the resin as long as the effects of the present invention are not impaired.
For example, as the porous resin body, from the viewpoint that a high piezoelectric constant can be maintained for a long period of time, matrix resin and charge-induced hollow particles (particles in which a conductive substance is attached to at least a part of the surface of the hollow particles) The structure containing these may be sufficient.

The porous resin body has a porosity calculated by the following formula of preferably 60% or more, more preferably 80 to 99%. A porous resin body having a porosity in the above range is preferable because of its high charge retention amount.
Porosity = (true resin density−apparent density) × 100 / true resin density Note that the apparent density uses a value calculated using the weight of the porous resin body and the apparent volume.

The shape of the porous resin body may be appropriately selected according to the application to be used, but is preferably a sheet from the viewpoint of ease of production, sound wave / impact detection properties, and the like.
When the porous resin body is in the form of a sheet, the thickness is not particularly limited, but is, for example, 10 μm to 1 mm, and preferably 50 μm to 500 μm.

  The porous resin body can be obtained by various conventionally known methods. For example, a method of forming pores using the phase change of the solution containing the resin (phase separation method), a method of mixing and dispersing additives for pore formation in the resin and removing them after molding (extraction) Method), molding the resin, and then chemically cutting the bond of a part of the molded body, or conversely performing a binding reaction (chemical treatment method), stretching the resin, A method of forming micropores in the microfibril structure part, a method of mixing and dispersing additives and forming pores during stretching (stretching method), and a method of forming pores by irradiating neutron beams, lasers, etc. ( Irradiation etching method), a method of forming a porous body by fusing resin fine pieces by heating or the like (fusion method), a method of forming pores using a foaming agent (foaming method), Method to form pores by combining (composite method), dry spinning, wet spinning, dry Wherein spinning, melt spinning, to form a fiber (fiber) from the resin by electrospinning like, a method of forming a woven or nonwoven fabric using the fiber and the like.

  The porous resin body is preferably a structure including a nonwoven fabric or a woven fabric formed from fibers made of resin from the viewpoint that durability and deformation performance can be maintained over a long period of time. The structure may include the non-woven fabric or woven fabric, or may be a structure made of only the non-woven fabric or woven fabric, or a laminate in which a conventionally known layer is laminated on the surface of the non-woven fabric or woven fabric. Also good.

  The average fiber diameter of the fiber is preferably 0.05 to 50 μm, more preferably 0.1 to 20 μm, and still more preferably 0.5 μm to 5 μm. A porous resin body containing fibers having an average fiber diameter in the above range can form a sufficient space for holding electric charges by increasing the fiber surface area, and even if it is made into a thin film, the fiber distribution uniformity is increased. It is preferable in that it can be used.

  The average fiber diameter can be adjusted by appropriately selecting the conditions for forming the fiber.For example, when the fiber is formed by electrospinning, the humidity is reduced during electrospinning, and the nozzle diameter is adjusted. There is a tendency that the average fiber diameter of the obtained fiber can be reduced by decreasing the voltage, increasing the applied voltage, or increasing the voltage density.

  The average fiber diameter was determined by observing the fiber (group) to be measured with a scanning electron microscope (SEM) (magnification: 10000 times), and randomly selecting 20 fibers from the obtained SEM image. The fiber diameter (major diameter) of each fiber is measured, and is an average value calculated based on the measurement result.

The fiber diameter variation coefficient calculated by the following formula of the fiber is preferably 0.7 or less, more preferably 0.01 to 0.5. When the fiber diameter variation coefficient is within the above range, the fiber has a uniform fiber diameter, and the nonwoven fabric obtained using the fiber has a higher porosity. Since it is obtained, it is preferable.
Fiber diameter variation coefficient = standard deviation / average fiber diameter (“standard deviation” is the standard deviation of the fiber diameters of the 20 fibers)

  The fiber length of the fiber is preferably 0.1 to 1000 mm, more preferably 0.5 to 100 mm, and still more preferably 1 to 50 mm.

The method for forming the fiber is not particularly limited, but the fiber obtained by the electrospinning method has a small fiber diameter, and the nonwoven fabric obtained by using the fiber has a high hollow ratio and a high specific surface area. From the viewpoint of obtaining a porous resin body having piezoelectric characteristics, the electrospinning method is preferable.
A porous resin body can be produced by accumulating the obtained fibers into a nonwoven fabric or weaving them into a woven fabric and molding them.

[Electrospinning method]
When forming a fiber made of a resin using the electrospinning method, for example, a spinning solution containing the resin and, if necessary, a solvent is used.

  The ratio of the resin contained in the spinning solution is, for example, 5 to 100% by weight, preferably 5 to 80% by weight, and more preferably 10 to 70% by weight.

  The solvent is not particularly limited as long as it can dissolve or disperse the resin. For example, water, dimethylacetamide, dimethylformamide, tetrahydrofuran, methylpyrrolidone, xylene, acetone, chloroform, ethylbenzene, cyclohexane, benzene, sulfolane. , Methanol, ethanol, phenol, pyridine, propylene carbonate, acetonitrile, trichloroethane, hexafluoroisopropanol, and diethyl ether. These solvents may be used alone or in combination of two or more.

  The solvent is contained in the spinning solution in an amount of, for example, 0 to 90% by weight, preferably 10 to 90% by weight, and more preferably 25 to 80% by weight.

  In addition to the resin and the solvent, the spinning solution may further contain additives such as a surfactant, a dispersant, a charge adjusting agent, functional particles, an adhesive, a viscosity adjusting agent, and a fiber forming agent. When the spinning solution contains a resin having low solubility in a solvent and the solvent (for example, when the resin is PTFE and the solvent is water), fiber formation is further performed from the viewpoint of forming the resin into a fiber shape during spinning. It is preferable that an agent is included.

  The fiber forming agent is preferably a polymer having high solubility in a solvent, such as polyethylene oxide, polyethylene glycol, dextran, alginic acid, chitosan, starch, polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, Examples thereof include cellulose and polyvinyl alcohol.

  The amount used when the fiber forming agent is used depends on the viscosity of the solvent and the solubility of the resin in the solvent, but is, for example, 0.1 to 15% by weight, preferably 1 to 10% by weight in the spinning solution. .

  The spinning solution can be produced by mixing the resin and, if necessary, a solvent and an additive by a conventionally known method.

Preferable examples of the spinning solution include the following spinning solution (1).
Spinning liquid (1): 30 to 70% by weight, preferably 35 to 60% by weight of PTFE, 0.1 to 10% by weight, preferably 1 to 7% by weight, and a total of 100% by weight. Spinning solution containing solvent

  The applied voltage when performing electrospinning is preferably 1 to 100 kV, more preferably 5 to 50 kV, and still more preferably 10 to 40 kV.

  The tip diameter (outer diameter) of the spinning nozzle used for electrospinning is preferably 0.1 to 2.0 mm, more preferably 0.2 to 1.6 mm.

  More specifically, for example, when the spinning solution (1) is used, the applied voltage is preferably 10 to 50 kV, more preferably 10 to 40 kV, and the tip diameter (outer diameter) of the spinning nozzle is used. ) Is preferably 0.3 to 1.6 mm.

As a method for producing the fiber, a method for producing a fiber made of PTFE by an electrospinning method will be specifically described. As a method for producing the PTFE fiber, a conventionally known production method can be employed, and examples thereof include the following methods described in JP-T-2012-515850.
Providing a spinning solution comprising PTFE, a fiber forming agent and a solvent and having a viscosity of at least 50,000 cP;
Spinning the spinning solution from a nozzle and forming a fiber by electrostatic traction;
Collecting the fibers on a collector (eg, a take-up spool) to form a precursor;
Calcining the precursor to remove the solvent and the fiber former to form PTFE fibers.

[Production method of non-woven fabric or woven fabric]
In order to form a nonwoven fabric using the fiber, the step of forming the fiber and the step of collecting the obtained fibers into a sheet to form the nonwoven fabric may be performed separately or simultaneously. (In other words, a nonwoven fabric may be formed by collecting fibers while collecting fibers). Specifically, for example, a step of forming a fiber by using an electrospinning method and a step of collecting the obtained fibers into a sheet to form a nonwoven fabric may be simultaneously performed, or a step of forming a fiber. After performing, you may perform the process of accumulating the fiber obtained by the wet method in a sheet form, and forming a nonwoven fabric.

  Examples of a method for forming a nonwoven fabric by the wet method include a method of forming (paper making) a sheet by depositing (accumulating) the fibers on a mesh using an aqueous dispersion containing the fibers. .

  The amount of fiber used in this wet method is preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, based on the total amount of the aqueous dispersion. If the fiber is used within this range, water can be efficiently used in the process of depositing the fiber, and the dispersion state of the fiber is improved, so that a uniform wet nonwoven fabric can be obtained.

  In order to improve the dispersion state, the aqueous dispersion is added with a dispersant or an oil agent composed of a cationic, anionic, or nonionic surfactant, or an antifoaming agent that suppresses the generation of bubbles. May be.

The woven fabric formed from the fiber can be manufactured by a method including a step of forming a fiber and a step of weaving the obtained fiber into a sheet to form a woven fabric.
As a method of weaving the fiber into a sheet, a conventionally known weaving method can be used, and methods such as a water jet room, an air jet room, and a rapier room can be used.

Basis weight of the nonwoven fabric and woven fabric, preferably 100 g / m ² or less, more preferably 0.1 to 50 g / m ^2, more preferably from 0.1 to 20 g / m ^2.
The thickness of the nonwoven fabric and the woven fabric is usually 10 μm to 1 mm, preferably 50 μm to 500 μm.
The basis weight and thickness tend to increase by increasing the spinning time or increasing the number of spinning nozzles.

  The non-woven fabric and woven fabric are obtained by accumulating or weaving the fibers in a sheet shape. Such non-woven fabric and woven fabric are composed of a single layer, or composed of two or more layers having different materials and fiber diameters. Any of these may be used.

[Polarization treatment]
The porous resin body is preferably subjected to polarization treatment.
As the method for the polarization treatment, a conventionally known method can be used, and is not particularly limited, and examples thereof include voltage application processing such as DC voltage application processing and AC voltage application processing, and corona discharge processing.

For example, the corona discharge treatment can be performed using a commercially available device composed of a high voltage power source and electrodes.
The discharge conditions may be appropriately selected according to the porous resin body to be used. As preferable conditions, the voltage of the high voltage power source is −0.1 to −100 kV, more preferably −1 to −20 kV, and the current is set to 0.1. 1 to 100 mA, more preferably 1 to 80 mA, the interelectrode distance is 0.1 to 100 cm, more preferably 1 to 10 cm, and the applied voltage is 0.01 to 10.0 MV / m, more preferably 0.5 to 2. A condition of 0 MV / m is mentioned.

The polarization treatment may be performed on a porous resin body alone, but as a sound wave / impact detection element of the present invention, a laminate of a porous resin body and an external force absorbing sheet or the above-described conventionally known layer is used. For example, it is preferable to perform a polarization treatment after forming the stacked body, for example, after stacking an insulating layer.
This is because the layer laminated on the porous resin body serves to prevent the electric charge held in the porous resin body from being attenuated by being electrically connected to the external environment. It is considered that an impact detection element can be obtained, and a new interface that can hold electric charge between the porous resin body and the layer laminated on the porous resin body tends to be formed. This is because it is considered that the piezoelectricity of the porous resin body in the sound wave / impact detection element is improved.

<External force absorbing sheet>
The external force absorbing sheet (also referred to as “stress absorbing sheet”) absorbs the external force applied to the porous resin body, and the porous resin body is completely compressed by the external force (the porosity becomes 0%). Any sheet that can prevent this is not particularly limited.
The external force means a force applied to the element from the outside of the sound wave / impact detection element of the present invention, such as pressure or impact.

The external force absorption rate of the external force absorbing sheet is preferably 50% or more, more preferably 80 to 100%.
Since the sound absorption rate is within the above range, it is possible to prevent the porous resin body from being completely compressed by the external force (the porosity becomes 0%). In addition, a sensing element having excellent durability can be obtained.
When the external force absorption rate of the external force absorbing sheet is 100%, the detection element of the present invention is a sound wave detection element. Further, when the external force absorption rate of the external force absorbing sheet is less than 100%, the detecting element of the present invention is an element that detects the presence of an impact (external force) that cannot be absorbed by the external force absorbing sheet, and the external force absorbing sheet It is an element which detects the sound wave which permeate | transmits. Therefore, for example, by measuring the external force absorption rate of the external force absorbing sheet to be used in advance, it is determined whether or not the external force absorbing sheet can absorb the target (allowable level) impact (external force) or more. Can do.
Specifically, the external force absorption rate is the impact (X: voltage value) when an external force absorbing sheet is not used when a load cell is used and an iron ball having a height of 500 mm to 30 g above the load cell is freely dropped. ) And the impact (Y: voltage value) when the external force absorbing sheet is arranged on the load cell, [[XY] × 100 / X] can be calculated.

The sound transmittance of the external force absorbing sheet is preferably 20% or more, and more preferably 50% or more.
When the sound wave transmittance is in the above range, even when the sound wave / impact detection element is a laminated body in which an external force absorbing sheet is laminated on a porous resin body, sound waves are hardly absorbed by the external force absorbing sheet portion, and the porous body is porous. Since most of the sound waves can be detected by the resin body portion, it is preferable as a high-performance sound wave / impact detection element.
The sound wave transmittance can be measured according to JIS A 1405-1.

The loss elastic modulus of the external force absorbing sheet is not particularly limited, but is preferably 1 × 10 ³ to 1 × 10 ⁷ Pa, more preferably 1 × 10 ⁴ to 1 × 10 ⁶ Pa.
By using an external force absorbing sheet having a loss elastic modulus in the above range, a highly sensitive sound wave / impact detection element can be obtained.
Specifically, the loss elastic modulus can be measured based on JIS K 7244.

The volume resistivity of the external force absorbing sheet is 1 × 10 ¹³ Ω · cm or more, preferably 1 × 10 ¹⁴ Ω · cm or more. If it exists in this range, it is preferable at the point of the long-term charge retention improvement of a porous resin body.
The volume resistivity is measured based on the double ring electrode method using an external force absorbing sheet to be measured.

  The thickness of the external force absorbing sheet is not particularly limited, and is preferably such that the external force absorption rate, the sound wave transmittance, and the loss elastic modulus are in the above ranges, preferably 0.05 to 10 mm, and more preferably. Is 0.1 to 5 mm.

  The external force absorbing sheet is not particularly limited, and is preferably a sheet made of a material having an external force absorption rate, a sound wave transmittance, and a loss elastic modulus within the above ranges, and has excellent adhesion to the porous resin body. From the point of view, a sheet made of an organic polymer is preferable, and a sheet made of a heat resistant organic polymer is more preferable from the viewpoint of obtaining a sound wave / impact detecting element excellent in heat resistance. From the viewpoint of external force absorption characteristics, the external force absorption sheet is preferably a porous sheet or a gel sheet.

  Examples of such an organic polymer include a thermosetting polymer and a thermoplastic polymer. Thermosetting polymers include polyimide, epoxy resin, thermosetting rubber (eg, vinylidene fluoride rubber, silicone rubber), polyurethane, phenolic resin, imide resin (eg, polyimide, polyamideimide, bismaleimide), silicone Examples thereof include resins. Thermoplastic polymers include acrylic resin, methacrylic resin, polypropylene, polyamide, vinyl chloride resin, silicone resin, fluororesin (eg PTFE, PCTFE, ETFE, PVdF, PFA, FEP), nylon, polystyrene, high density polyethylene, Examples thereof include low density polyethylene, polyphenylene sulfide, polyethylene oxide, polysulfone, and vinylidene chloride. From the viewpoint of external force absorption characteristics, it is preferable to use a material having a high elastic modulus as the organic polymer, for example, it is preferable to use a thermosetting rubber.

The external force absorbing sheet can be formed by a conventionally known method. Examples of such a method include a method of forming a sheet by applying and drying a polymer liquid containing an organic polymer and a solvent on at least one surface of the porous resin body, and a porous resin body on the polymer liquid. The method of forming a sheet | seat by immersing and drying is mentioned.
The sound wave / impact detection element of the present invention may be manufactured by forming an external force absorbing sheet in advance by a conventionally known method and laminating the sheet on a porous resin body by a conventionally known method.

  Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by these.

[Example 1]
A sheet-like non-woven fabric (thickness 0.06 mm, empty) formed from PTFE fiber, which is a porous resin body, by accumulating PTFE fibers in a sheet shape by the electrospinning method described in JP-T-2012-515850. A porosity of 95%, an average fiber diameter of 900 nm) was obtained, and a PFA sheet (thickness: 0.025 mm, manufactured by Daikin Industries, Ltd., NEOFLON PFA) as an insulating layer was layered on the upper and lower surfaces of the nonwoven fabric, and 300 ° C. for 60 minutes. A laminated sheet having an insulating layer formed on the front and back surfaces of the porous resin body was produced by thermocompression bonding. After this laminated sheet was polarized by -15 kV corona discharge irradiation, electrodes were formed on both surfaces (on the insulating layer) of the obtained laminated sheet by vapor deposition, and lead wires were drawn out to produce an organic piezoelectric element.
A porous PTFE sheet (thickness 1 mm) having a porosity of 50% is laminated as an external force absorbing sheet on both surfaces (on the electrodes) of this organic piezoelectric element via an adhesive tape (FPR-12, manufactured by Sumitomo 3M Limited). Thus, a sound wave / impact detector was produced.

  When a 100 g iron ball was dropped from 50 cm above the element in a state where a static pressure of 100 MPa was applied to the upper surface of the produced sound wave / impact detection element, a voltage was generated, and the generated voltage was detected. That is, the impact could be detected by the produced sound wave / impact detector.

  Further, when a 50-db sound wave was irradiated toward the created sound wave / impact detection element, a voltage was generated, and the generated voltage was detected. That is, sound waves could be detected by the produced sound wave / impact detection element.

[Example 2]
A sound wave / impact detection element was produced in the same manner as in Example 1 except that a gel-like sheet (manufactured by Taika Co., Ltd., Alpha Gel) was used as the external force absorbing sheet instead of the porous PTFE sheet.
When a 100 g iron ball was dropped from 50 cm above the element in a state where a static pressure of 100 MPa was applied to the upper surface of the produced sound wave / impact detection element, a voltage was generated, and the generated voltage was detected. That is, the impact could be detected by the produced sound wave / impact detector.

[Comparative Example 1]
A device was produced in the same manner as in Example 1 except that the external force absorbing sheet was not provided.
When a 100 g iron ball was dropped from 50 cm above the element in a state where a static pressure of 100 MPa was applied to the upper surface of the manufactured element, no voltage could be detected. That is, the manufactured element could not detect the impact.

Claims (11)

  A sound wave / impact detection element comprising a porous resin body made of a resin having no dipole due to a molecule and a crystal structure, and an external force absorbing sheet.   The sound wave / impact detection element according to claim 1, wherein the porosity of the porous resin body is 60% or more.   The sound wave / impact detection element according to claim 1, wherein the resin is polytetrafluoroethylene.   The sound wave / impact detection element according to any one of claims 1 to 3, wherein the porous resin body includes a nonwoven fabric or a woven fabric formed from a fiber made of resin.   The sound wave / impact detection element according to claim 4 whose average fiber diameter of said fiber is 0.05-50 micrometers.   The sound wave / impact detection element according to claim 1, wherein the porous resin body is subjected to polarization treatment.   The sound wave / impact detection element according to claim 1, wherein an external force absorption rate of the external force absorbing sheet is 50% or more.   The sound wave / impact detection element according to claim 1, wherein a sound wave transmittance of the external force absorbing sheet is 20% or more. The sound wave / impact detection element according to any one of claims 1 to 8, wherein a loss elastic modulus of the external force absorbing sheet is 1 x 10 ³ to 1 x 10 ⁷ Pa.   The sound wave / impact detection element according to claim 1, wherein the external force absorbing sheet has a thickness of 0.05 to 10 mm.   The sound wave / impact detection element according to claim 1, wherein the external force absorbing sheet is laminated on the porous resin body.