Polymeric piezoelectric film element, and power storage device and load detection device using the same

Abstract

Provided is a polymer piezoelectric film element which generates electricity at a high degree of sensitivity in response to vibrations across a broad frequency band, including vibrations of a comparatively low frequency no higher than 10Hz such as, for example, those caused by the motion of humans or animals or faint contact stress, and also including vibrations of a high frequency equal to or higher than 10Hz such as those caused by automobiles, trains and other transport vehicles, building construction work, and factory equipment in the manufacturing industry, is also capable of using the same as power or as a sensor, can be made into a thin film and at a high yield can be used as a stably driving power supply device, a tactile sensor, or a vitals sensor for measuring bioelectric signals such as pulse waves, heart rates and respiration waves. The present invention pertains to: a polymer piezoelectric film element characterized in that an electrode sheet is formed on both surfaces of a polymer piezoelectric film, and by having a structure which has bumps and dips or a wave-shaped structure which has peaks and valleys in an axis perpendicular to said surfaces; and a power storage device which generates electricity by receiving external stress via the piezoelectric effect and changing the same to power, a sensor for detecting said stress, or a vitals sensor for measuring bioelectric signals.

Description

[Technical field]

[0001] The present invention relates to a polymer piezoelectric film element characterized in that electrode sheets are formed on both sides of a polymer piezoelectric film and that the surface has an uneven structure or a wavy structure with peaks and valleys along the vertical axis, as well as an electricity storage device and a load detection device that include the polymer piezoelectric film element. [Background technology]

[0002] According to the Agency for Natural Resources and Energy's comprehensive energy statistics, after World War II, Japan experienced high economic growth from the 1950s to the 1970s, and subsequent IT innovations led to a steady increase in domestic primary energy supply until the early 2000s, and after the Tohoku Pacific Ocean Earthquake in 2011, it stabilized at around 20,000 petajoules per year until 2019. In recent years, with society becoming increasingly electrified, the proportion of primary energy supplied as electricity has risen from 41% in 1990 to over 46% in 2018.

[0003] According to the Energy White Paper 2019, the breakdown of electricity generation for electricity supply in 2019 was 40% liquid natural gas (hereinafter referred to as LNG), 32% coal, 9% oil, 8% hydroelectric, 3% nuclear, and 8% renewable energy. A characteristic of the above-mentioned period since 2011 is that dependence on LNG and coal has increased due to the shutdown of some nuclear power plants. However, as set as a goal in the 2016 Paris Agreement, there is an urgent need to reduce greenhouse gas emissions, mainly carbon dioxide, in order to curb global warming, and there is a global demand to gradually move away from coal-fired power generation and switch to renewable energy. Note that renewable energy is defined in the Energy Supply Structure Enhancement Act as "solar power, wind power, and other non-fossil energy sources that are recognized as being able to be used permanently as energy sources and are specified by government ordinance," and solar power, wind power, geothermal power, solar heat, biomass, etc. are specified.

[0004] Looking globally, the United States, the second largest electricity supplier, is proportionally dependent on LNG, coal, and nuclear power, with renewable energy accounting for 10%. China, the world's largest electricity supplier, relies heavily on coal, with renewable energy accounting for 9%. In Europe, the dependency ratio varies from country to country, but it is noteworthy that Germany relies on renewable energy for 34%. The difference is that while the renewable energy of these major countries is mainly wind power, Japan has a high proportion of solar power.

[0005] The world is facing the challenge of reducing its dependence on power generation from fossil fuels such as LNG, coal, and oil and shifting to renewable energy. On the other hand, the autonomous driving of transportation, mainly automobiles, the further spread of computers and mobile terminals, the high-speed communication of large amounts of data, the acceleration of digital transformation, and the creation of new value through the Internet of Things (hereinafter referred to as IoT) are becoming more and more common, and more electronic devices are being used for these activities. And the electricity required to run these electronic devices will continue to increase for the time being. The society that will be created as a result is said to be a data-driven society, where diverse and huge amounts of data are accumulated in cyberspace and used for services provided to people. Against this background, more electronic devices are being used in daily life, but the electricity that runs them should not depend on the aforementioned fossil fuel-based power generation in the future.

[0006] In addition, we should not passively receive only the electricity generated by large-scale power plants, including some renewable energy sources such as hydroelectric, nuclear, and wind power. In other words, it would be desirable to have a device that can convert previously overlooked energy sources into electricity, independent of such power sources. Such a device would become a locally produced and locally consumed power source that drives electronic devices and sensors installed in all places, including mountainous areas, oceans, and polar regions where humans cannot easily reach. Primary batteries are an independent power source, but their usable time is limited, and they are not suitable for the future society, where stable operation is required without leaking important information, such as the aforementioned automatic driving, high-speed data communication, and IoT. Secondary batteries are also not suitable as a power source, because they need to be charged after power is consumed.

[0007] If we could find an energy source that was previously overlooked in a familiar, ordinary, semi-permanently existing physical phenomenon, and convert that physical phenomenon into voltage to generate electricity, we could drive electronic devices and sensors semi-permanently unless they were damaged mechanically. This would eliminate the need to replace or charge batteries, and would make it possible to continue collecting important information without leaking it in the new society mentioned above. Furthermore, since there is no need to set up a power grid to supply electricity generated by power plants, it is also effective for capital investment with limited funds. In addition, the ability to convert familiar physical phenomena into voltage is valuable in itself, and it can be used as a sensor to obtain signals to prevent accidents and disasters.

[0008] Examples of familiar physical phenomena that can be converted into electricity include light, stress, heat, and magnetic fields. When converting light into electricity, the photovoltaic effect of semiconductors, such as solar cells, is used. On the other hand, materials called ferroelectrics are used to convert stress and heat into electricity. The phenomenon of converting stress into electricity is called the piezoelectric effect, and the phenomenon of converting heat into electricity is called the pyroelectric effect, and both are manifested by ferroelectrics. However, a temperature change is required to obtain the pyroelectric effect, and it is difficult to generate electricity at a constant temperature. In addition, the phenomenon of converting a magnetic field into electricity is called the magnetoelectric effect, and research on materials that combine ferroelectricity and ferromagnetism has progressed in recent years, but the magnetic field on Earth is very small, so it is insufficient for practical use. For these reasons, expanding the use of the piezoelectric effect is important in obtaining electricity from energy sources that have been overlooked in the past. Stresses such as vibrations occur in various places, such as the movements of humans and animals, transportation such as automobiles and trains, construction work related to construction, and factory equipment in the manufacturing industry, so they can be converted into electricity by using such places. Furthermore, it is also possible to use them as sensors to detect the occurrence of stress. In the following, the use of this piezoelectric effect to generate electric charge and use it as electricity or a sensor will be referred to as "power generation."

[0009] Power generation technology using vibration has been studied for many years. Patent Document 1 shows that a vibration power generation device including a support base, a plurality of elastic bodies supporting the support base, and a plurality of power generation elements provided on the support base stably generates power in response to input vibration. In the device, the support base and the plurality of elastic bodies serve as a first resonator, and the plurality of power generation elements serve as a second resonator, and the difference in natural frequency between the first resonator and the second resonator is set to ±15% or less, thereby enabling stable power generation. However, the power generation element shown in Patent Document 1 is integrated with a piezoelectric element and a leaf spring whose one end freely swings, and the piezoelectric layer constituting the piezoelectric element uses an inorganic ferroelectric material that is hard and brittle and is selected from lead zirconate titanate (hereinafter referred to as PZT), aluminum nitride, lithium tantalate, lithium niobate, etc., so that the range of the stress that can be applied and the range of the displacement that can be induced are not wide.

[0010] In addition, this vibration power generation device is made up of multiple springs, piezoelectric elements, and power generation elements in a complex configuration, and as a result, its thickness is on the order of centimeters, which means that it is bulky and cannot be installed casually when considering connecting it to the electronic devices and sensors used in daily life mentioned above.Furthermore, it has low productivity and problems with durability against vibration.

[0011] Patent Document 2 discloses a vibration power generation element that includes a cantilever equipped with a piezoelectric element and a weight located at a position away from the cantilever, and generates power when the weight collides with the cantilever when an external force is applied. As in Patent Document 1, the structure is such that only one end of the cantilever is fixed to the housing (hereinafter referred to as a cantilever structure), and the piezoelectric film is made of a hard and brittle perovskite oxide such as PZT, so that the range of stress that can be applied and the range of displacement that can be induced are not wide. Furthermore, the vibration power generation element fixed to a base made of silicon or stainless steel needs to be placed in a vacuum, which puts pressure on production costs, and although the initial performance of the power generation element can be guaranteed, there is a concern that the cantilever and the piezoelectric film may be damaged by an external force.

[0012] In the cantilever beam structure of Patent Documents 1 and 2, the piezoelectric element vibrates only at a specific resonant frequency, so the vibration conditions are limited. Therefore, in order to make it possible to apply it to vibrations in a wide frequency range, Patent Document 3 introduces a vibration power generation device with a doubly supported beam structure with both ends fixed. In order to make the device have a doubly supported beam structure, multiple piezoelectric bodies are placed on a metal elastic plate with slits, and the multiple metal elastic plates are connected by connecting members. The metal elastic plate is displaced by vibration, and the displacement is converted into voltage by the piezoelectric body in this power generation device, which is used inside and outside of a car as an in-vehicle application system. The power generation device of this invention also uses a nonlinear spring to convert vibration into electrical energy.

[0013] In Patent Documents 1 to 3, inorganic ferroelectrics are used as piezoelectric bodies, but since Kawai et al. discovered the ferroelectricity of polyvinylidene fluoride in 1969, research and development of polymeric materials that exhibit the piezoelectric effect has been progressing (Non-Patent Document 1). The motivation for development using polymeric materials is the attractive mechanical properties, such as the ability to create a unique balance between hardness and softness that can only be expressed in polymeric materials, toughness, and the ability to be made into thin films. Attempts to create new value by replacing the performance obtained by using inorganic materials with polymeric materials, not limited to the piezoelectric effect, have been made in various fields for many years, and are always an important perspective in material development. For example, in the automotive field, the proportion of steel materials was high in the past, but the increase in the proportion of polymeric materials such as polypropylene has realized weight reduction, creating the value of being able to travel long distances with less energy. In the healthcare field, eyeglass lenses, which were previously made of glass, have been replaced with a polymeric material called thiourethane, which is thin, lightweight, and has excellent impact resistance, allowing many people to wear eyeglasses easily without feeling their weight. Furthermore, in the recent electronics field, electrical wiring, which is made by surface treatments such as photoresist coating, etching, and plating, is being subjected to active research and development into print-oriented pastes and inks that incorporate fine particles of hard metals and flexible polymeric materials such as polyurethane and organic solvents in response to the recent demand for flexibility and freedom of design, and a new market is being created. Thus, polymeric materials have the potential to bring about innovation in all fields, and it can be understood that research and development into polymeric materials aimed at the piezoelectric effect was also started in response to such expectations.

[0014] In fact, inorganic ferroelectrics such as PZT exhibit excellent piezoelectric effects when made into single crystal or polycrystalline structures, but have the disadvantage that they are easily subject to restrictions on the conditions under which they can be used due to their brittle nature. On the other hand, polymeric materials that exhibit a piezoelectric effect (hereinafter referred to as polymeric piezoelectric materials) are characterized by having a crystalline structure, but also containing a certain proportion of amorphous structure. Since amorphous structures do not usually exhibit a piezoelectric effect, polymeric piezoelectric materials often have an inferior piezoelectric effect compared to inorganic ferroelectrics, but they have the advantage of being less susceptible to breakage due to their excellent flexibility and toughness. This advantage is realized by the mixture of crystalline and amorphous structures (Non-Patent Document 2).

[0015] One example of an invention that uses polymeric piezoelectric materials is a flexible piezoelectric sheet described in Patent Document 4, in which a polymeric piezoelectric layer such as polyamino acids, polysaccharides, polylactic acid, or polyvinylidene fluoride is sandwiched between two conductive cloth layers made of substrate fibers such as silk impregnated with conductive polymer materials such as poly(3,4-ethylenedioxythiophene) and poly(styrenesulfonic acid). This invention uses cloth containing a conductive polymer material as the electrode substrate, and is structured to have flexibility in combination with a polymeric piezoelectric material, but there are still issues regarding the safety of the conductive polymer material when it comes into contact with the human body.

[0016] Furthermore, as another example using polymeric piezoelectric materials, there is a laminated power generating body and its power generating device that obtains electricity from various marine energies such as tidal currents, tides, and waves, as described in Patent Document 5. The laminated power generating body has a piezoelectric film and electrodes formed on both sides of a base made of a flexible elastic material, and the flexible elastic material is made of silicone rubber, natural rubber, or synthetic rubber, and the piezoelectric film is made of polyvinylidene fluoride or polyvinylidene cyanide. However, it can only be applied to calm oceans, and it cannot be said that it can overcome the challenges of renewable energy. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] WO2020 / 230509 [Patent Document 2] WO2020 / 235208 [Patent Document 3] Patent Publication No. 2020-61938 [Patent Document 4] Patent Publication No. 2020-119995 [Patent Document 5] Patent Publication 2014-111911 [Non-patent literature]

[0018] [Non-Patent Document 1] H.Kawai;Jpn.J.Appl.Phys.,8,975(1969) [Non-Patent Document 2] Field Responsive Polymers,Chapter6,pp88-103 [Non-Patent Document 3] Kenji Uchino Ferroelectric Devices Morikita Publishing Co., Ltd. P.142 Summary of the Invention [Problem to be solved by the invention]

[0019] However, the power generating element shown in Patent Document 1 is an integrated leaf spring and piezoelectric element, and the piezoelectric layer that constitutes the piezoelectric element is made of an inorganic ferroelectric material selected from PZT, aluminum nitride, lithium tantalate, lithium niobate, etc., but the piezoelectric layer is hard and brittle, so the range of stress that can be applied and the range of displacement that can be induced are not wide.

[0020] In addition, the vibration power generation element of Patent Document 2 uses a perovskite oxide for the piezoelectric film, so the range of stress that can be applied and the range of displacement that can be induced are not wide, and the cantilever that receives the vibration with the piezoelectric film on it is often made of metals such as aluminum and zirconia, which cannot be said to have the tenacity, i.e., toughness, against displacement. Furthermore, since the weight is provided at a position separated from the cantilever, the thickness increases by the distance, so that when considering installation in existing equipment, the design would change, making it difficult to use.

[0021] Furthermore, the vibration power generation device of Patent Document 3 employs a double-supported beam structure, and although a stopper and a fixed lubricant layer such as Teflon electroless nickel are provided so as not to exceed the elastic limit of the piezoelectric body, the structure is complicated. Also, the piezoelectric body uses a material selected from aluminum nitride, scandium-containing aluminum nitride, magnesium- and niobium-containing aluminum nitride, potassium sodium niobate, etc., which are similar to the materials described in Patent Documents 1 and 2, and is subject to mechanical destruction in the same manner as the above.

[0022] In Patent Document 4, unlike the inorganic ferroelectric piezoelectric layers in Patent Documents 1 to 3, polymeric piezoelectric materials with flexibility such as polyamino acids, polysaccharides, polylactic acid, and polyvinylidene fluoride are used, and the electrode substrate is also designed to be flexible, making the piezoelectric sheet adaptable to various locations and shapes, including the human body. However, when using polymeric piezoelectric materials, the problem of having to handle output voltages lower than those of inorganic ferroelectrics is encountered. The voltage output in response to stress is expressed by the following formula (1), and the proportionality constant, the piezoelectric d constant, corresponds to the value of d33, which is specific to the material, when the piezoelectric material is placed horizontally and stress is applied from the vertical axis. For example, the d33 of the inorganic ferroelectric PZT is 289 pC / N, while the d33 of the polymeric ferroelectric PVDF is only 35 pC / N (Non-Patent Document 3).

[0023] In other words, since polymer ferroelectrics have a significantly lower output voltage than inorganic ferroelectrics, they can be used as sensors for limited applications, but are clearly insufficient for use as sensors that can detect vibrations of various frequencies and intensities, or for use as electricity storage devices that can use the resulting output voltage to drive other electronic devices.

[0024]

number

[0025] Unlike PVDF, which creates a crystal structure by uniaxial stretching and becomes a polymer ferroelectric by applying an electric field, polylactic acid is a polymer piezoelectric material that shows a piezoelectric effect only by creating a crystal structure by uniaxial stretching, but is not a ferroelectric. Due to the material properties, polylactic acid has a d33 of zero, and no output voltage due to normal stress can be obtained. In this case, an output voltage is generated by stretching the film and pulling it in a direction at 45° to the stretching direction. In addition, polymer ferroelectrics such as PVDF have a very low output voltage compared to inorganic ferroelectrics, and polymer piezoelectric materials such as polylactic acid, which generate a weak output voltage only by pulling in a limited direction, are difficult to use in practice, including the fact that the output voltage is low.

[0026] In other words, it is necessary to increase the output voltage to a level where polymer piezoelectric materials can partially replace inorganic ferroelectrics, and if this is achieved, when used as a sensor, it will lead to minimizing the effects of external noise, and when used as a power storage device, it will be possible to obtain large power generation from small stresses, making it possible to utilize energy that has been wasted up until now. In other words, technological development to increase the output voltage will help popularize devices that use polymer piezoelectric materials.

[0027] In Patent Document 5, a film of a polymeric piezoelectric material such as polyvinylidene fluoride or polyvinylidene cyanide is used to create a power generator that can respond to marine energy such as tidal currents, tides, and waves of various magnitudes, and is suitable for utilizing the vibration of fluids such as seawater, but when subjected to vibrations from solid objects on land such as the movements of humans and animals, transportation such as automobiles and trains, construction work, factory equipment in the manufacturing industry, etc., it is expected that a power generator in which rod-shaped power generators are arranged will easily break when subjected to stress, making it difficult to apply. In other words, a device design that will not break even when subjected to various vibrations on land is required.

[0028] As described above, generating electricity from vibrations, which are physical phenomena in our daily lives, such as vibrations generated by the movements of humans and animals, transportation such as automobiles and trains, construction-related work, factory equipment in the manufacturing industry, etc., using the piezoelectric effect is a clean form of locally produced electricity that does not use electricity generated at power plants, and the electricity supplied semi-permanently from there drives electronic devices and sensors without interruption, making it possible to realize a data-driven society, and is highly cost-effective in that it does not require battery replacement or charging or the construction of a new power grid. Furthermore, the piezoelectric effect can not only secure electricity, but can also function as a vibration detection sensor that reports the presence of stress, and can also collect information such as the presence and movement of humans, animals, and automobiles, and signs of noise and abnormal phenomena in the construction and manufacturing industries.

[0029] The present invention aims to provide a polymer piezoelectric film element that is highly sensitive to vibrations over a wide frequency band, including weak contact stress or relatively low-frequency vibrations of, for example, 10 Hz or less such as those caused by human or animal movements, and high-frequency vibrations of 10 Hz or more such as those caused by transportation such as automobiles and trains, construction-related work, and factory equipment in the manufacturing industry, and that can be used as a sensor that detects vibrations and loads and operates stably without being easily damaged, a vital sensor or tactile sensor that measures bioelectric signals such as pulse waves, heartbeats, and respiratory waves, or a power storage device that provides power to drive other electronic devices. [Means for solving the problem]

[0030] The present invention relates to a polymer piezoelectric film element having electrode sheets formed on both sides of a polymer piezoelectric film, the surface of which has an uneven structure or a wavy structure with peaks and valleys along the vertical axis, the polymer piezoelectric film element generating electricity through the piezoelectric effect when subjected to external stress, and the element relates to a sensor for detecting vibration or load, a vital sensor or tactile sensor for measuring bioelectric signals such as pulse waves, heartbeats, and respiratory waves, and an electricity storage device that generates power to drive other electronic devices. Effect of the Invention

[0031] According to the present invention, by using a polymer piezoelectric film having characteristics such as thinness, flexibility, and toughness, it can be easily buried in the ground such as a floor to generate electricity from the walking of humans or land animals or the running of automobiles, or it can be attached to trains, heavy machinery, and manufacturing equipment to generate electricity from stress such as vibrations of a wide frequency range generated by these. This makes it possible to provide a sensor that detects vibrations, a sensor that detects loads, a vital sensor or tactile sensor that measures bioelectric signals such as pulse waves, heartbeats, and respiratory waves, or an electricity storage device that generates power to drive other electronic devices. [Brief description of the drawings]

[0032] [Figure 1] This explains how electrode sheets are formed on both sides of a polymeric piezoelectric film to form a polymeric piezoelectric film element having an uneven structure or a wavy structure with peaks and valleys along the perpendicular axis of the surface. [Diagram 2] This describes a cross-sectional structure in which, by placing a wire on an electrode sheet, a concave-convex structure or a wavy structure with peaks and valleys is formed and maintained along the vertical axis of the surface. [Diagram 3] This describes a cross-sectional structure in which, by placing a wire between an electrode sheet and a polymeric piezoelectric film, a concave-convex structure or a wavy structure with peaks and valleys is formed and maintained on the perpendicular axis of the surface. [Figure 4] The present invention describes a cross-sectional structure in which a molded body having an uneven structure or a wavy structure with peaks and valleys is placed on an electrode sheet to form and maintain an uneven structure or a wavy structure with peaks and valleys. [Diagram 5] This describes an energy storage device circuit consisting of a polymer piezoelectric film element, a full-wave rectifier circuit consisting of four diode elements, a capacitor, and a DC-DC converter. [Figure 6] This describes the measurement of a pulse wave, as an example of a bioelectric signal, using a polymer piezoelectric film element. [Figure 7] This describes a circuit that uses a polymer piezoelectric film element to output a constant voltage according to the applied load. [Figure 8]This explains how the circuit in FIG. 7 outputs a constant voltage when static loads of 2.0 kg, 4.5 kg, 7.5 kg, and 11 kg are applied to the polymer piezoelectric film element for 10 seconds each in that order. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, an embodiment of the present invention will be described.

[0034] From here, the configuration of the polymer piezoelectric film element according to this embodiment will be described with reference to FIG. 1. The polymer piezoelectric film element according to this embodiment is made by forming an upper electrode sheet and a lower electrode sheet on both sides of a polymer piezoelectric film, and then forming an uneven structure or a wave structure with peaks and valleys on the vertical axis of the surface. Note that the upper electrode sheet and the lower electrode sheet do not mean top and bottom, but are merely classified in terms of description. This uneven structure or wave structure with peaks and valleys is characterized by having a raised convex or mountain and a depressed concave or valley with respect to the vertical axis of the polymer piezoelectric film on which the upper electrode sheet and the lower electrode sheet are formed, but the convex and concave, or the mountain and valley, do not mean top and bottom, but are simply classified in terms of description.

[0035] Here, the uneven structure or the wavy structure with peaks and valleys according to this embodiment refers to unevenness or peaks and valleys that have a height difference and a width. Focusing on one concave or convex, or one peak or valley, the shape of the outermost surface of the polymeric piezoelectric film element is measured by a method such as a stylus surface shape measurement or a laser microscope, and the height difference is defined as the height from the flat part of the outermost surface (hereinafter referred to as the flat part) to the top of the rise, or the depth to the lowest point of the depression. The length of the rise or the length of the depression from the flat part to the flat part across one concave or convex, or one peak or valley, is defined as the width.

[0036] In the present invention, for example, the height difference is preferably 80 μm or more, more preferably 200 μm or more. If the height difference is less than 80 μm, the sensitivity or output voltage is low, and the effect of the uneven structure or the wavy structure with peaks and valleys may be difficult to achieve. Furthermore, the width of the unevenness or peaks and valleys is preferably 0.1 mm or more, more preferably 1 mm or more. If the width is less than 0.1 mm, the effect of the uneven structure or the wavy structure with peaks and valleys may be difficult to achieve. Furthermore, the upper limit of the height difference or width is not particularly limited, as it is determined depending on the size, design, and usage method of the element.

[0037] Furthermore, as long as this uneven structure or a wavy structure with peaks and valleys can be formed and the polymeric piezoelectric film can be held so as not to return to the original horizontal state of FIG. 1 over time, the method of forming the structure is not particularly limited. For example, as shown in FIG. 2, a method of placing a wire on the lower electrode sheet or / and the upper electrode sheet and holding it by pressing and fixing it with a pressure-sensitive film, as shown in FIG. 3, a method of placing a wire between the electrode sheet and the polymeric piezoelectric film and pressing and fixing it with a pressure-sensitive film, as shown in FIG. 4, a method of placing a molded body such as an embossed molded body having an uneven structure or a wavy structure with peaks and valleys on the electrode sheet and pressing and fixing it with a pressure-sensitive film, a method of scattering granular objects such as beads on the electrode sheet or / and the polymeric piezoelectric film and pressing and fixing it, etc. In FIG. 2 and FIG. 3, four wires are placed on one electrode sheet, or two wires are placed on each of the electrode sheets, but in this embodiment, the wires can be placed on one or both electrode sheets, and the number is not limited, and one or more wires are placed. Furthermore, two or more wires may be placed parallel to each other or cross each other in a plane. The method is not limited to wires, and wire or thread-like fiber may be used. Methods for forming and maintaining an uneven structure or a corrugated structure with peaks and valleys include, but are not limited to, a method of manually applying pressure while applying pressure, a method of using a laminator, a method of using a vacuum packaging device, and the like. When placing a wire, not only a structure in which one or more wires are placed linearly, but also a structure in which the wire is formed into a closed ring such as a circle, a triangle, a square, a pentagon, or a hexagon, or a network structure with such ring gaps may be placed.

[0038] The wire is preferably made of a material having a circular cross-sectional diameter of 0.10 mm to 1.0 mm and a Young's modulus of 1 GPa or more. If the cross-sectional diameter is less than 0.10 mm, it is not possible to form a concave-convex structure with sufficient height difference and width, or a wavy structure with peaks and valleys, to generate electricity in the polymeric piezoelectric film element. It has been found that if the cross-sectional diameter exceeds 1.0 mm, the rigidity of the polymeric piezoelectric film element described below becomes significant, resulting in a decrease in electromotive force and problems with practicality. The cross-sectional shape of the wire is not particularly limited, but in the case of acute angles such as a triangle or a square, there is a risk of cracking the electrode sheet or polymeric piezoelectric film during the above-mentioned pressure-bonding and fixing, so that in addition to a circle, it is preferable that the shape is a pentagon, hexagon, or ellipse. Furthermore, the material of the wire is not particularly limited, but since it is necessary to transfer the shape of the wire to the polymer piezoelectric film, the lower electrode sheet, and the upper electrode sheet to form an uneven structure or a wavy structure with peaks and valleys, it is preferable that the core is made of a metal such as iron, copper, aluminum, magnesium, titanium, zinc, chromium, etc., or an alloy thereof, plastic, or ceramic, which has a Young's modulus of 1 GPa or more. In the case of a wire made of a material with a Young's modulus of less than 1 GPa, the stress of the crimping and fixing is used to deform the wire itself, and an uneven structure with sufficient height difference and width to generate electricity, or a wavy structure with peaks and valleys is not formed.

[0039] The wire may be protected from metal corrosion and scratches by applying resin, paint, coating, etc. to the inside and / or outside of the wire. The wire may also be in the form of a granular object instead of a wire. The granular object preferably has an outer diameter of 0.10 mm or more and 1.0 mm or less, and is made of a material with a Young's modulus of 1 GPa or more.

[0040] The polymeric piezoelectric film according to this embodiment is prepared in the form of a film. Any polymeric compound can be used for the polymeric piezoelectric film as long as it outputs a voltage when subjected to stress. For example, there are polymeric compounds such as polyvinylidene fluoride (hereinafter referred to as PVDF), vinylidene fluoride-trifluoroethylene copolymer (hereinafter referred to as P(VDF-TrFE)), poly-L-lactic acid (hereinafter referred to as PLLA), poly-D-lactic acid (hereinafter referred to as PDLA), poly-γ-methyl-L-glutamate, poly-γ-benzyl-L-glutamate, polypropylene oxide, nylon 11, polyvinyl chloride, and polyurea. From the viewpoint of availability, it is preferable to select from PVDF, P(VDF-TrFE) and PLLA. Note that PVDF creates a β-type crystal structure when it is made into a film by uniaxial stretching, and when both sides of the PVDF film are brought into contact with electrodes and an electric field is applied, it becomes a ferroelectric substance by polarization treatment, and has a piezoelectric effect. On the other hand, P(VDF-TrFE) may be polarized by applying an electric field to a film that has been uniaxially stretched to a β-type crystal structure, as with PVDF, or may be coated on a suitable substrate with a varnish prepared by dissolving P(VDF-TrFE) powder in a polar organic solvent such as methyl ethyl ketone, N-methyl-2-pyrrolidone, dimethylacetamide, N,N-dimethylformamide, triethyl phosphate, or cyclopentanone, and then heated to a temperature at which the polarization of P(VDF-TrFE) disappears, i.e., above the Curie temperature, while simultaneously removing the organic solvent by heating, and cooled below the crystallization temperature to form a β-type crystal structure, which is then polarized by applying an electric field to make it a ferroelectric, thereby obtaining a piezoelectric effect. When a film is formed by coating a varnish, the polymeric piezoelectric film of P(VDF-TrFE) is peeled off from the substrate to which the varnish has been applied and used.

[0041] The piezoelectric d constant d33 of the PVDF film produced by the above process is 35 pC / N when stress is applied from the vertical axis. In the case of a P(VDF-TrFE) film, the piezoelectric d constant depends on the molar ratio of the copolymerization monomer trifluoroethylene (hereinafter referred to as TrFE). For example, when the molar ratio is 20%, d33 is 27 pC / N, when the molar ratio is 30%, d33 is 22 pC / N, and when the molar ratio is 45%, d33 is 20 pC / N. Unlike PVDF and P(VDF-TrFE), PLLA and PDLA exhibit the piezoelectric effect due to the orientation and crystallization of molecular chains caused by uniaxial stretching, so they are not polarized by applying an electric field to become ferroelectric. In the case of a PLLA film, the piezoelectric effect of d33 is not exhibited by stress applied from the vertical axis, but the piezoelectric effect is exhibited by pulling the film toward the horizontal axis at an angle of 45° to the uniaxial stretching direction. In this case, the piezoelectric d constant d14 is 6.5 pC / N. Thus, in order to realize the piezoelectric effect, it is necessary to understand the characteristics of each polymer compound and perform appropriate processing. The thickness of the polymer piezoelectric film is preferably 5 μm to 100 μm, more preferably 40 μm to 100 μm. This thickness range forms an uneven structure with sufficient height difference and width to generate electricity, or a wavy structure with peaks and valleys.

[0042] The lower electrode sheet and the upper electrode sheet according to the present embodiment are not particularly limited, but preferably have a Young's modulus of 1 MPa or more and a thickness of 100 nm or more and 100 μm or less. Examples of materials having a Young's modulus of 1 MPa or more include metals such as aluminum, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, silver, indium, tin, tungsten, platinum, and gold, oxides and alloys of these metals, conductive carbon compounds such as graphene and carbon nanotubes, and organic polymer conductive compounds such as polythiophene, polyethylenedioxythiophene / polystyrenesulfonic acid, polyaniline, polypyrrole, polyacetylene, polyparaphenylene, and polyparaphenylenevinylene. The method for forming the polymer piezoelectric film is also not particularly limited, and may be a method of bonding via a conductive adhesive layer, a vacuum deposition method or a sputtering method, soft blanket gravure offset printing using a paste or ink of such a conductive material, inkjet printing, a dispenser, screen printing, gravure offset printing, flexographic printing, letterpress reverse printing, spin coating, spray coating, blade coating, dip coating, cast coating, roll coating, bar coating, die coating, or other printing method, followed by baking to form an electrode sheet, or the like.

[0043] However, in the process of forming the lower electrode sheet and the upper electrode sheet, attention must be paid to the heat resistance of the polymer piezoelectric film. For PVDF and P(VDF-TrFE), if they are heated above their Curie temperature, the polarization disappears, and they no longer become ferroelectric, losing their piezoelectric effect, so the electrode sheet must be formed at a temperature below the Curie temperature. The Curie temperature is about 170°C for PVDF. For P(VDF-TrFE), the Curie temperature differs depending on the molar ratio of TrFE, so the electrode sheet must be formed at a temperature below the Curie temperature of the copolymer with the molar ratio used. For example, when the molar ratio of TrFE is 20%, the Curie temperature is 130-140°C, when the molar ratio is 30%, the Curie temperature is 95-105°C, and when the molar ratio is 45%, the Curie temperature is 57-62°C. Be sure to understand the Curie temperatures of the PVDF and P(VDF-TrFE) you are using, and handle them below that temperature. Since the piezoelectric effect of PLLA starts to decrease at or above the glass transition temperature of 66° C., it is preferable to form the electrodes at temperatures below 65° C. In addition, it is preferable to keep not only the heating temperature but also the heating time as short as possible.

[0044] In addition, when the Young's modulus of the lower electrode sheet and the upper electrode sheet is less than 1 MPa, the stress when transferring the shape of the wire to the polymer piezoelectric film to form an uneven structure or a wavy structure with peaks and valleys is alleviated by the electrode sheet, and a problem occurs in that an uneven structure with sufficient height difference and width to generate electricity, or a wavy structure with peaks and valleys cannot be formed. In addition, if the thickness of the electrode sheet is 100 nm or less, a break may occur near the wire during the transfer, causing a loss of conductivity, and if it is 100 μm or more, the electrode sheet is too hard and the wire shape cannot be transferred to the polymer piezoelectric film, making it difficult to apply a stress sufficient to form an uneven structure with sufficient height difference and width to generate electricity, or a wavy structure with peaks and valleys. In addition, the lower electrode sheet and the upper electrode sheet may use the same material and forming method, or different materials and forming methods.

[0045] The polymer piezoelectric film element produced by the above method outputs a voltage in response to stress applied from the vertical axis shown in Figure 1. In the present invention, we have attempted to clarify the effect on the output voltage of uneven structures or wave structures with peaks and valleys created by various wire arrangement designs. The relationship between stress and output voltage is expressed by the following formula (2).

[0046]

number

[0047] In the present invention, wires of various cross-sectional diameters and materials, the number of wires, the spacing between the wires, and the arrangement were changed, and stress was applied to the polymer piezoelectric film element from the vertical axis, and the output voltage was measured. From this measurement, a in formula (2) was calculated. In the present invention, it is defined as a force proportional constant. When the output proportional constant specific to a concave-convex structure or a corrugated structure with peaks and valleys is large, the output voltage becomes high, and therefore the polymer piezoelectric film element has high capabilities. The details of the experiment will be described in the Examples and Comparative Examples below, but in the polymer piezoelectric film element using PVDF, as shown in Figures 2, 3, and 4, the concave-convex structure of PVDF made by placing a wire or a molded body, or the corrugated structure with peaks and valleys, resulted in a high output proportional constant that was not expressed by PVDF in the horizontal film state shown in Figure 1, and a high output voltage was obtained. Furthermore, in the horizontal film state shown in Figure 1, in PLLA, which generates almost no electricity in response to stress from the vertical axis, the concave-convex structure made by placing a wire or a molded body, or the corrugated structure with peaks and valleys, shows a large output proportional constant, and a high output voltage is obtained. From this, the concave-convex structure made by the wire or the corrugated structure with peaks and valleys can amplify the electromotive force, piezoelectric sensitivity, etc. of the polymer piezoelectric film.

[0048] That is, by creating a concave-convex structure or a corrugated structure with peaks and valleys in a polymer piezoelectric film, not limited to PVDF or PLLA, the stress applied from the vertical axis is concentrated on the convex or crest, and / or the concave or valley, thereby increasing the amount of charge generated in three axial directions. The present invention has revealed that the increased generated charge is dispersed in three directions including the horizontal axis in FIG. 1, thereby significantly improving the level of electromotive force and piezoelectric sensitivity, thereby amplifying the piezoelectric effect. Note that an electrode sheet and a wire or molded body may be placed on one polymer piezoelectric film, but the amplification effect of the piezoelectric effect can also be obtained by sandwiching two or more polymer piezoelectric films between conductive double-sided adhesive sheets or the like and laminating them, and then placing a wire or molded body on them.

[0049] Furthermore, the present invention is an electricity storage device characterized in that the power generated by applying stress to the polymer piezoelectric film element of the present embodiment is stored in a capacitor or capacitor. To explain in detail, the voltage output by applying stress from a vertical axis to the polymer piezoelectric film element with enhanced electromotive force of the present invention is stored as an electric charge in an electronic component such as a capacitor such as an electric double layer capacitor or a supercapacitor, and it has been found that electricity can be stored using a polymer piezoelectric film that has previously been difficult to store electricity due to its low electromotive force. Since the voltage output by the polymer piezoelectric film element is a sine wave voltage having both positive and negative polarities, the negative polarity voltage is inverted to a positive polarity and rectified to a positive polarity voltage to be recovered as electricity. As a method of rectification, for example, half-wave rectification using one diode element or full-wave rectification using four diode elements is used, but full-wave rectification is preferably used in terms of efficiency. As shown in FIG. 5, the rectified voltage is recovered in a capacitor or the like in a circuit. Furthermore, the voltage stored in the capacitor can be boosted as a DC voltage by connecting it to a DC-DC converter (DCDC converter) and used as power to drive other electronic devices.

[0050] Furthermore, it was found that the polymeric piezoelectric film element of this embodiment can detect pulse waves by lightly applying it to the wrist and neck with a soft touch, for example, by reducing the electrode sheet size to 15 mm x 15 mm. As shown in Figure 6, it was found that the pulse wave detected by the polymeric piezoelectric film element of this embodiment has the same shape and frequency as the pulse wave waveform obtained by attaching a commercially available photoelectric volumetric pulse wave meter to the fingertips of the hand. It is small, lightweight, and can be used as a low-cost pulse wave detection element.

[0051] In addition, the load detection device is characterized in that a constant voltage is output from an operational amplifier when a load is applied to the polymer piezoelectric film element of this embodiment. It has been found that when a load is applied to the polymer piezoelectric film element from a vertical axis and the element is connected to an electronic circuit that outputs a constant voltage according to the load value, a voltage value proportional to the load value can be output, making the element a load detection device. The electronic circuit is not particularly limited, but for example, as shown in FIG. 7, a method can be used in which the voltage output by the polymer piezoelectric film element is temporarily collected in a capacitor, and the voltage of the capacitor is detected by a voltage follower using an operational amplifier. EXAMPLES

[0052] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0053] [Example 1] A copper foil electrode sheet having a size of 82.5 mm x 82.5 mm, in which a copper foil with a Young's modulus of 110 GPa and a conductive adhesive layer are laminated, and a conductive adhesive layer of DAITAC (registered trademark) E20CU (manufactured by DIC Corporation) was attached to both sides of a polymeric piezoelectric film of polyvinylidene fluoride having a thickness of 80 μm and a size of 82.5 mm x 82.5 mm so as to be in contact with the polymeric piezoelectric film. On one side of this electrode sheet, a copper wire having a cross-sectional diameter of 0.5 mm and a Young's modulus of 110 GPa was placed with a length of 82.5 mm and a length of 82.5 mm, so as to be parallel to the 82.5 mm side of the copper foil electrode sheet, and the end was fixed with tape. This was fixed from above and below with a pressure-bonding film using a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and a polymeric piezoelectric film element having an uneven structure or a wavy structure with peaks and valleys on the vertical axis of the surface was produced. When the shape of the pressure-bonding film surface was measured using a stylus-type surface shape measuring device DektakXT (manufactured by Bruker), the height difference was 200 μm and the width was 4.0 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa using a pressure probe, a voltage of 14 to 29 mV was output. As a result, the output proportionality constant was 0.93 mV / Pa on average. In the element produced from the KF Piezo Film (registered trademark) of Comparative Example 1 described later, the output proportionality constant was 0.036 mV / Pa on average, and in comparison, the output voltage increased by an average of 26 times in the uneven structure or the wavy structure with peaks and valleys of this example.

[0054] [Example 2] Copper foil electrode sheets were attached to both sides of the polymeric piezoelectric film in the same manner as in Example 1. On each of these copper foil electrode sheets, one copper wire with a cross-sectional diameter of 0.5 mm and a Young's modulus of 110 GPa was placed with a length of 82.5 mm so as to be parallel to one of the 82.5 mm sides of the copper foil electrode sheet, and the distance between the two wires was 5 mm, and the ends were fixed with tape. This was fixed by pressure bonding from above and below with a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and a polymeric piezoelectric film element having an uneven structure on the vertical axis of the surface or a wavy structure with peaks and valleys was produced. When the shape of the pressure-bonded film surface was measured in the same manner as in Example 1, the height difference was 200 μm and the width was 4.0 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa with a pressure probe, a voltage of 84 to 138 mV was output. As a result, the output proportionality constant was 5.3 mV / Pa on average. Since the output proportionality constant of the element made from the KF Piezoelectric Film (registered trademark) of Comparative Example 1 described later was 0.036 mV / Pa on average, the output voltage increased by an average of 147 times due to the uneven structure or the waveform structure with peaks and valleys of this example.

[0055] [Example 3] The polymeric piezoelectric film of Example 1 was replaced with a polymeric piezoelectric film of poly-L-lactic acid, 50 μm thick and 82.5 mm × 82.5 mm, μ-Flex (registered trademark) (manufactured by Mitsui Chemicals, Inc.), to produce a polymeric piezoelectric film element having an uneven structure on the vertical axis or a wave structure with peaks and valleys. When the shape of the pressure-bonded film surface was measured in the same manner as in Example 1, the height difference was 290 μm and the width was 4.0 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa with a pressure probe, a voltage of 3.1 to 14 mV was output. As a result, the output proportionality constant was 0.33 mV / Pa on average. Since the output proportionality constant is 0 mV / Pa in μ-Flex (registered trademark) of Comparative Example 2 described later, the output to vertical stress in the polymeric piezoelectric film element of poly-L-lactic acid was observed for the first time.

[0056] [Example 4] The polymeric piezoelectric film of Example 2 was replaced with a polymeric piezoelectric film of poly-L-lactic acid, 50 μm thick and 82.5 mm × 82.5 mm, MuFlex (registered trademark) (manufactured by Mitsui Chemicals, Inc.), to produce a polymeric piezoelectric film element having an uneven structure on the vertical axis or a wave structure with peaks and valleys. When the shape of the pressure-bonded film surface was measured in the same manner as in Example 1, the height difference was 290 μm and the width was 4.0 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa with a pressure probe, a voltage of 4.7 to 13 mV was output. As a result, the output proportionality constant was 0.37 mV / Pa on average.

[0057] [Example 5] A polymeric piezoelectric film element was produced by replacing the wire described in Example 4 with a copper wire having a cross-sectional diameter of 0.26 mm and a Young's modulus of 110 GPa. The shape of the surface of the pressure-bonded film was measured in the same manner as in Example 1, and the height difference was 136 μm and the width was 3.5 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa with a pressure probe, a voltage of 4.4 to 16 mV was output. As a result, the output proportionality constant was 0.41 mV / Pa on average.

[0058] [Example 6] A polymeric piezoelectric film element was produced by replacing the wire described in Example 4 with a copper wire having a cross-sectional diameter of 1.0 mm and a Young's modulus of 110 GPa. The shape of the surface of the pressure-bonded film was measured in the same manner as in Example 1, and the height difference was 446 μm and the width was 4.5 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa with a pressure probe, a voltage of 3.1 to 20 mV was output. As a result, the output proportionality constant was 0.36 mV / Pa on average.

[0059] [Example 7] A copper foil electrode sheet having a size of 82.5 mm x 82.5 mm, in which a copper foil with a Young's modulus of 110 GPa and a conductive adhesive layer were laminated, and a conductive adhesive layer of DAITAC (registered trademark) E20CU (manufactured by DIC Corporation) was attached to both sides of the polymer piezoelectric film of poly-L-lactic acid in Example 3. A copper foil electrode sheet having a size of 82.5 mm x 82.5 mm, in which a copper foil with a Young's modulus of 110 GPa and a conductive adhesive layer were laminated, and a conductive adhesive layer of DAITAC (registered trademark) E20CU (manufactured by DIC Corporation) was attached so as to be in contact with the polymer piezoelectric film. A copper wire having a cross-sectional diameter of 0.5 mm was formed into a circular ring shape with an inner diameter of 15 mm on one side of the electrode sheet. This was fixed by pressure bonding from above and below with a pressure bonding film using a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and a polymer piezoelectric film element having an uneven structure or a wavy structure with peaks and valleys on the vertical axis of the surface was produced. When the shape of the pressure bonding film surface was measured in the same manner as in Example 3, the height difference was 290 μm and the width was 4.0 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress of 13 to 34 Pa was applied from the vertical axis with a pressure probe, a voltage of 2.7 to 12 mV was output. As a result, the output proportionality constant was 0.24 mV / Pa on average.

[0060] [Comparative Example 1] A copper foil electrode sheet having a size of 82.5 mm x 82.5 mm, in which a copper foil with a Young's modulus of 110 GPa and a conductive adhesive layer are laminated, and a conductive adhesive layer of DAITAC (registered trademark) E20CU (manufactured by DIC Corporation) was attached to both sides of a polyvinylidene fluoride polymer piezoelectric film having a thickness of 80 μm and a size of 82.5 mm x 82.5 mm, so that it is in contact with the polymer piezoelectric film. The device was fixed by pressure bonding from above and below with a pressure bonding film using a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and as in Example 1, this element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa using a pressure probe, and a voltage of 0.50 to 1.2 mV was output. As a result, the output proportionality constant was 0.036 mV / Pa on average.

[0061] [Comparative Example 2] Using a 50μm thick, 82.5mm x 82.5mm polymeric piezoelectric film of poly-L-lactic acid, MuFlex (registered trademark) (Mitsui Chemicals, Inc.), an electrode sheet was attached in the same manner as in Comparative Example 1, and the device was fixed from above and below with pressure films using a desktop roll laminator H355A3 (Acco Brands Japan, Inc.). As in Example 1, this element was placed on a horizontal vibration table and a stress in the range of 13 to 34 Pa was applied from the vertical axis with a pressure probe, but no voltage was generated. The output proportionality constant was 0mV / Pa.

[0062] [Example 8] A copper foil electrode sheet having a size of 82.5 mm x 82.5 mm, in which a copper foil with a Young's modulus of 110 GPa and a conductive adhesive layer are laminated, and a conductive adhesive layer of DAITAC (registered trademark) E20CU (manufactured by DIC Corporation) was attached to one side of a polymeric piezoelectric film of polyvinylidene fluoride having a thickness of 80 μm and a size of 82.5 mm x 82.5 mm so as to be in contact with the polymeric piezoelectric film. Two sheets were produced. Of these, one sheet was attached with a conductive nonwoven double-sided adhesive tape 9720S (manufactured by 3M Japan Co., Ltd.) of the same size as the electrode to the electrode side and the reverse side of the KF piezo film. Furthermore, the electrode side and reverse side of the remaining KF piezo film with an electrode on one side were attached to one side of the conductive nonwoven double-sided adhesive tape. On each surface of the copper foil electrode sheet on which the KF piezo film was laminated via the conductive tape, a copper wire with a cross-sectional diameter of 0.5 mm and a Young's modulus of 110 GPa was placed with a length of 82.5 mm, parallel to the sides of the copper foil electrode sheet, and parallel to each other with a distance of 5 mm between the two wires, and the wire ends were fixed with tape. This was fixed by pressure bonding from above and below with a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and a polymeric piezoelectric film element having an uneven structure or a wavy structure with peaks and valleys on the vertical axis of the surface was produced. When the shape of the pressure bonded film surface was measured in the same manner as in Example 1, the height difference was 240 μm and the width was 3.5 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa with a pressure probe, a voltage of 12 to 42 mV was output. As a result, the output proportionality constant was 0.93mV / Pa on average.

[0063] [Comparative Example 3] An element was prepared by laminating a KF piezo film via conductive tape in the same manner as in Example 8, and similarly, it was fixed from above and below with pressure-bonding films using a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and when a stress in the range of 13 to 34 Pa was applied from the vertical axis in the same manner as in Example 8, a voltage of 0.8 to 3.8 mV was output. As a result, the output proportionality constant was 0.10 mV / Pa on average.

[0064] [Example 9] A copper foil electrode sheet having a size of 38 mm x 38 mm, in which copper foil with a Young's modulus of 110 GPa and a conductive adhesive layer are laminated, and a conductive adhesive layer of DAITAC (registered trademark) E20CU (manufactured by DIC Corporation) was attached to both sides of a 38 mm x 38 mm thick, 38 mm x 38 mm polyvinylidene fluoride polymer piezoelectric film. A copper wire having a cross-sectional diameter of 0.5 mm and a Young's modulus of 110 GPa was placed on each side of the copper foil electrode sheet, with a length of 38 mm, so that it was parallel to the 38 mm side of the copper foil electrode sheet and so that the two wires crossed each other at right angles in the same plane, and the ends were fixed with tape. This was fixed from above and below with a pressure-bonding film using a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and a polymeric piezoelectric film element having an uneven structure or a wavy structure with peaks and valleys on the vertical axis of the surface was produced. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress in the range of 19 to 90 Pa was applied from the vertical axis with a pressure probe, a voltage of 26 to 161 mV was output. As a result, the output proportionality constant was 1.5 mV / Pa on average. The output voltage increased by an average of 42 times compared to the output proportionality constant of the element produced from the KF Piezo Film (registered trademark) in Comparative Example 4 described later, which was 0.036 mV / Pa on average.

[0065] [Example 10] On each side of the same polymeric piezoelectric film as in Example 9, a copper wire with a cross-sectional diameter of 0.5 mm and a Young's modulus of 110 GPa was placed at a length of 38 mm so that the two wires crossed each other perpendicularly in the plane, and the ends were fixed with tape. Furthermore, a copper foil electrode sheet with a size of 38 mm x 38 mm, in which a copper foil with a Young's modulus of 110 GPa and a conductive adhesive layer were laminated, and a conductive adhesive layer of DAITAC (registered trademark) E20CU (manufactured by DIC Corporation) was attached to both sides of the polymeric piezoelectric film so as to contact the polymeric piezoelectric film and cover the wire. This was fixed by pressure bonding from above and below with a pressure bonding film using a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and a polymeric piezoelectric film element having an uneven structure or a wave structure with peaks and valleys on the vertical axis of the surface was produced. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress in the range of 19 to 90 Pa was applied from the vertical axis with a pressure probe, a voltage of 75 to 748 mV was output. As a result, the output proportionality constant was 5.3 mV / Pa on average. As described in Comparative Example 4 below, the output proportionality constant of the horizontal KF Piezo Film (registered trademark) was 0.036 mV / Pa on average, so the output voltage increased by an average of 147 times due to the uneven structure or the wavy structure with peaks and valleys of this example.

[0066] [Example 11] Instead of the poly-L-lactic acid polymeric piezoelectric film and the copper foil electrode sheet of MuFlex (registered trademark) (manufactured by Mitsui Chemicals, Inc.) of Example 7, a water / alcohol solution of polyethylenedioxythiophene / polystyrenesulfonic acid (manufactured by Heraeus) was applied and the water / alcohol was evaporated by heating to form a double-sided electrode, and a polymeric piezoelectric film element having an uneven structure on the vertical axis or a wave structure with peaks and valleys was produced in the same manner as in Example 7. When the shape of the pressure-bonded film surface was measured in the same manner as in Example 7, the height difference was 260 μm and the width was 4.5 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis in the range of 13 to 34 Pa with a pressure probe, a voltage of 8.4 to 21 mV was output. As a result, the output proportionality constant was 0.65 mV / Pa on average.

[0067] [Example 12] As in Example 1, copper foil electrode sheets were attached to both sides of the polymeric piezoelectric film. On one side of this electrode sheet, a PET molded body with convex lines of 2 mm width, 80 mm length, and 0.4 mm height difference formed in a grid pattern at 3 mm intervals was placed so that the convex surface was in contact with the electrode sheet as shown in FIG. 4, and the convex surface was fixed with a pressure-bonded film from above and below using a desktop roll laminator H355A3 (manufactured by ACCO Brands Japan Co., Ltd.), and a polymeric piezoelectric film element having an uneven structure or a wave structure with peaks and valleys on the vertical axis of the surface was produced. When the shape of the pressure-bonded film surface was measured as in Example 1, the height difference was 84 μm and the width was 4.0 mm. When this polymeric piezoelectric film element was placed on a horizontal vibration table and a stress was applied from the vertical axis of the PET molded body in the range of 13 to 34 Pa with a pressure probe, a voltage of 25 to 29 mV was output. As a result, the output proportionality constant was 1.2 mV / Pa on average. As in Comparative Example 1 described above, the output proportionality constant for the horizontal KF piezo film (registered trademark) was 0.036 mV / Pa on average, so the output voltage increased by an average of 33 times in the uneven structure of this embodiment or the waveform structure with peaks and valleys.

[0068] [Example 13] The two electrode sheets of the polymer piezoelectric film element of Example 2 were connected to a full-wave rectifier circuit consisting of four diode elements as shown in Fig. 5, and further connected to a Zener diode for protecting the rectifier circuit and a 10 μF capacitor for storing the voltage output by the polymer piezoelectric film element. The polymer piezoelectric film element was placed on a horizontal stand and continuously pressed by hand from the vertical axis. When the voltage of the capacitor was measured with an oscilloscope, a voltage of 4.0 V was stored.

[0069] [Example 14] Seven wires of Example 2 were placed on each copper foil electrode sheet, and a polymeric piezoelectric film element was produced in the same manner as in Example 2. This polymeric piezoelectric film element was connected to a circuit similar to that of Example 13, and a 10 μF capacitor was connected to a DC-DC converter LTC3108 (manufactured by Analog Devices) shown in Figure 5. The polymeric piezoelectric film element was placed on a horizontal stand and continuously pressed by hand from the vertical axis, while the voltage of the capacitor was measured with an oscilloscope. After 4.0 V was stored in the capacitor, a boosted DC voltage of 2.4 V was output from the output terminal of the LTC3108.

[0070] [Example 15] Twelve of the wires of Example 4 were placed on each side of the copper foil electrode sheet, and a polymer piezoelectric film element was produced in the same manner as in Example 4. This polymer piezoelectric film element was connected to a circuit similar to that of Example 13, and the voltage of the capacitor was measured with an oscilloscope while continuously applying pressure by hand from the vertical axis of the polymer piezoelectric film element. A voltage of 0.4 V was stored.

[0071] [Comparative Example 4] When the electrode sheet of Comparative Example 1 was changed to a size of 38 mm x 38 mm and a stress was applied from the vertical axis in the range of 19 to 90 Pa, a voltage of 0.7 to 3.3 mV was output. As a result, the output proportionality constant was an average of 0.036 mV / Pa.

[0072] [Example 16] The length of the wire was 15 mm, the size of the electrode sheet was 15 mm x 15 mm, and a polymeric piezoelectric film element was produced in the same manner as in Example 2. Two electrode sheets were connected to a coaxial cable using a conductive adhesive, and the coaxial cable was connected to an oscilloscope. As a reference, a photoelectric volumetric pulse wave meter was attached to the fingertip to optically measure the pulse wave, while the polymeric piezoelectric film element was lightly applied to the pulse generation site of the wrist and neck, and a clear pulse wave was detected as shown in Figure 6. The waveform and frequency of the reference photoelectric volumetric pulse wave and the pulse wave using the polymeric piezoelectric film element were consistent.

[0073] [Comparative Example 5] When an element having an electrode sheet size of 15 mm x 15 mm and fabricated in the same manner as in Comparative Example 1 was applied to pulse generation areas on the wrist and neck in the same manner as in Example 16, no pulse waves were detected.

[0074] [Example 17] As shown in FIG. 7, the polymeric piezoelectric film element of Example 15 was connected to a voltage follower consisting of a 10 kΩ resistor, a 10 nF capacitor, and an operational amplifier, and the output voltage of the voltage follower was measured when static loads of 2.0 kg, 4.5 kg, 7.5 kg, and 11 kg were applied to the polymeric piezoelectric film element in this order. Furthermore, the output voltage of the voltage follower was measured when the loads were removed in this order of 11 kg, 7.5 kg, 4.5 kg, and 2.0 kg. As a result, as shown in FIG. 8, an output voltage of 150 mV was generated at 2.0 kg, 280 mV at 4.5 kg, 400 mV at 7.5 kg, and 550 mV at 11 kg was generated, and a constant voltage corresponding to the load was output. The output voltage was the same when the applied load was increased and when it was removed.

[0075] [Comparative Example 6] The element of Comparative Example 2 was connected to the same circuit as in Example 17, and static loads of 2.0 kg, 4.5 kg, 7.5 kg, and 11 kg were applied to the element in this order, but no output voltage was generated from the voltage follower.

[0076] This application claims priority from Japanese Patent Application No. 2021-076711 filed on April 28, 2021. The contents of the specification, claims and drawings of the above application are incorporated by reference into this application. [Industrial Applicability]

[0077] The polymeric piezoelectric film element of the present invention, which is characterized by having an uneven structure or a wavy structure with peaks and valleys on the vertical axis of the surface of the polymeric piezoelectric film, can be made into a sheet-like, light and flexible power generating device and a sensor for detecting stress or minute electromotive force, and can provide a device that can be easily installed without affecting the physical shape of the place where stress is generated. It can be used for sensors for welfare and medical applications, wearable device applications, transistor applications for smartphones, tablet terminals, computers, displays, etc., sensors or control parts for medical, nursing beds, crime prevention, childcare, automatic driving of automobiles, pet robots, drones, etc., and electronic parts applications for organic electroluminescence, liquid crystal displays, lighting, automobiles, robots, electronic glasses, music players, etc.

Claims

1. The piezoelectric film has electrode sheets formed on both sides thereof, and the polymeric piezoelectric film has an uneven structure or a wavy structure with peaks and valleys on a vertical axis of the surface thereof; A polymeric piezoelectric film element having the above structure, characterized in that the wires are placed on one or both of the electrode sheets and are pressure-bonded and fixed with a pressure-bonding film.

2. 2. The polymeric piezoelectric film element according to claim 1, wherein the polymeric piezoelectric film is a uniaxially stretched film of polyvinylidene fluoride containing a structural unit represented by the following general formula (1), which is subjected to a polarization treatment: 【Chemistry 1】

3. The polymeric piezoelectric film element according to claim 1, characterized in that the polymeric piezoelectric film is a uniaxially stretched film of a copolymer of vinylidene fluoride and trifluoroethylene, which contains a structural unit represented by the following general formula (2), and is subjected to a polarization treatment: 【Chemistry 2】

4. 2. The polymeric piezoelectric film element according to claim 1, wherein the polymeric piezoelectric film is a uniaxially stretched film of poly-L-lactic acid containing a constitutional unit represented by the following general formula (3): 【Chemistry 3】

5. 5. The polymer piezoelectric film element according to claim 1, wherein the electrode sheet has a Young's modulus of 1 MPa or more and a thickness of 100 nm or more and 100 μm or less.

6. A polymer piezoelectric film element described in any one of claims 1 to 5, characterized in that one or more of the wires are placed in a straight line.

7. A polymer piezoelectric film element described in any one of claims 1 to 5, characterized in that one or more of the wires are arranged in a loop.

8. A polymer piezoelectric film element described in any one of claims 1 to 7, characterized in that the wire is made of a material having a cross-sectional diameter of 0.10 mm or more and 1.0 mm or less and a Young's modulus of 1 GPa or more.

9. 13. An electricity storage device, comprising: a capacitor configured to store electric power generated by applying stress to the polymeric piezoelectric film element according to claim 1.

10. 2. A load detection device, comprising: an operational amplifier that outputs a constant voltage when a load is applied to the polymeric piezoelectric film element according to claim 1.

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