Power generation plant

Abstract

A power generation device (1) is provided with: a power generation section (10) having an electret (2) having a first electrification surface (21) and a second electrification surface (22), a first electrode (31) formed on the first electrification surface (21), and a second electrode (32) formed on the second electrification surface (22); and at least one of an electricity storage section (41) and an output section (42) electrically connected to the power generation section (10). The electret (2) is an electret formed by subjecting an electret material containing an inorganic dielectric having a band gap energy of 4 eV or more to polarization treatment. At least one of the first electrode (31) and the second electrode (32) is disposed on at least one of the corresponding first electrification surface (21) and the second electrification surface (22) in a state in which it becomes a part of a current collecting surface (20) exposed.

Description

[0001] Cross-reference of related applications

[0002] This application is based on Japanese Patent Application No. 2020-032538, filed on February 28, 2020, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to power generation equipment that uses electrets. Background Technology

[0004] As an energy harvesting technology that converts energy present in the environment into electricity, the practical application of environmental power generation devices that generate electricity using electrostatic induction of electrets has been studied. As the constituent materials of electrets, organic polymer materials such as fluoropolymers are generally used; for example, materials using chain-like fluorinated resins and polymers with fluorinated aliphatic ring structures in their main chains are known to be used.

[0005] As an environmental power generation element utilizing electrets, a vibration power generation element has been proposed. This element vibrates a movable electrode opposite to the electret on a fixed electrode, causing a change in the amount of charge induced by the movable electrode, which is then extracted as electricity. Furthermore, various applications of such vibration power generation elements have been studied in various fields. For example, Patent Document 1 discloses the application of an electrostatic induction type conversion element to sensors and actuators. This electrostatic induction type conversion element is constructed as follows: a fluoropolymer film is formed on the opposing surfaces of a pair of substrates to create an electret; one of the substrates is used as a fixed substrate, allowing it to move relative to the other substrate, which is a movable substrate. The electrostatic induction type conversion element is arranged such that electrets and conductors are mixed on the opposing surfaces, and their area ratio is specified.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 4871642 Summary of the Invention

[0009] For such a vibration-generating element, electricity can be generated by the relative movement of a movable electrode opposite the electret due to vibration as external energy, causing a change in the capacitance between the electret and the movable electrode. In other words, when using a vibration-generating element as a power generation device, even when connected to loads such as sensors or actuators, power generation cannot occur unless kinetic energy such as vibration is input from the outside, limiting the applicable environment for the power generation device. Alternatively, to efficiently utilize environmental vibrations, careful consideration must be given to the configuration of the electret and conductor, as in Patent Document 1, which can easily complicate the electrode structure and the support structure of the movable electrode.

[0010] The purpose of this invention is to provide a power generation device that uses electrets and can generate electricity even in an environment where no kinetic energy such as vibration is input from the outside.

[0011] One aspect of the present invention relates to a power generation device comprising:

[0012] The power generation section includes an electret having a first charged surface and a second charged surface with different polarities, a first electrode formed on the first charged surface, and a second electrode formed on the second charged surface; and

[0013] At least one of the energy storage unit and the output unit that is electrically connected to the aforementioned power generation unit.

[0014] The aforementioned electret is an electret material containing an inorganic dielectric with a band gap energy of 4 eV or higher, which is electretized through polarization treatment.

[0015] At least one of the first electrode and the second electrode is configured to be exposed on the corresponding first charged surface and the second charged surface, so as to be part of the collector surface.

[0016] In the power generation device configured as described above, the inorganic dielectric constituting the electret has a high band gap energy of 4 eV or more, which can increase the insulation breakdown voltage during polarization treatment. Therefore, for example, by applying a high voltage under heating conditions, a high surface potential can be obtained. Furthermore, it has been determined that by forming electrodes on the two charged surfaces of the electret, for example, by configuring one electrode with a portion of the charged surface exposed and connecting it to the energy storage section or the output section, electricity can be extracted.

[0017] The reason is not yet clear, but it is speculated that due to the high surface potential of the electret, floating charges are fixed to the exposed collecting surface. On the other hand, due to the time-varying residual polarization of the inorganic dielectric constituting the electret, charge movement can be achieved. Thus, power generation can be performed even when there is no external energy input. Since no movable part is needed in the power generation section, a simpler configuration can be made.

[0018] As described above, a power generation device can be provided that uses electrets and can generate electricity even in environments where no kinetic energy such as vibration is input from the outside. Attached Figure Description

[0019] The above-mentioned objects, other objects, features, and advantages of the present invention will become more apparent from the accompanying drawings and from the following detailed description. The drawings are as follows:

[0020] Figure 1 This is a schematic diagram showing the overall general structure of the power generation equipment in Embodiment 1.

[0021] Figure 2 This is a schematic diagram showing an example of the arrangement of the first electrode formed on the first charged surface of the electret constituting the power generation unit in Embodiment 1.

[0022] Figure 3 This is a schematic diagram used to explain the operation of the power generation unit and the configuration example of the transfer switch unit in Embodiment 1.

[0023] Figure 4 This is a schematic diagram used to explain the power generation mechanism of the power generation device in Embodiment 1.

[0024] Figure 5 This is a schematic diagram used to illustrate the polarization method of the electret in Embodiment 1.

[0025] Figure 6 This is a schematic diagram used to illustrate the method for measuring the surface potential in Experimental Example 1.

[0026] Figure 7 This is a graph showing the time-varying surface potential after repeated measurements in Experimental Example 1.

[0027] Figure 8 This is a schematic diagram used to illustrate the method for measuring the amount of induced charge in Experimental Example 1.

[0028] Figure 9 This is a graph showing the time-varying amount of induced charge in Experimental Example 1.

[0029] Figure 10 This is a graph showing the relationship between the Ca substitution amount and the surface potential of the LAO-based composite oxide used as an electret material in Experimental Example 2.

[0030] Figure 11 This is a schematic diagram showing an example of the shape of the plurality of electrode portions formed on the electret as the first electrode in Embodiment 2.

[0031] Figure 12 This is a schematic diagram illustrating an example of an assembly of multiple electrode portions formed on an electret as the first electrode in Embodiment 2.

[0032] Figure 13 This is a schematic diagram and graph showing the relationship between the electrode spacing and surface potential of the multiple electrode portions formed on the electret in Experimental Example 3. Detailed Implementation

[0033] (Implementation Method 1)

[0034] The following description refers to Embodiment 1, which relates to the power generation equipment.

[0035] like Figure 1 As shown, the power generation device 1 of this method includes: a power generation section 10 using an electret 2, and at least one of an energy storage section 41 and an output section 42 electrically connected to the power generation section 10. The energy storage section 41 and the output section 42 constitute a power supply section 4, and the power generated by the power generation section 10 can be supplied to the outside through the power supply section 4.

[0036] In the power generation section 10, the electret 2 has a first charged surface 21 and a second charged surface 22 charged with different polarities. A first electrode 31 is formed on the first charged surface 21, and a second electrode 32 is formed on the second charged surface 22.

[0037] The electret 2 is an electret material containing an inorganic dielectric with a band gap energy of 4 eV or higher, which is electretized through polarization treatment. At least one of the first electrode 31 and the second electrode 32 formed on the electret 2 is arranged in a state where it is exposed on at least one of the corresponding first charged surface 21 and the second charged surface 22, so as to become part of the current collector surface 20.

[0038] At this time, a current collecting surface 20 is formed on the electret 2, and a storage unit 41 or an output unit 42 is connected between the first electrode 31 and the second electrode 32 that are in contact with the current collecting surface 20. Thus, the charge accumulated in the current collecting surface 20 can be taken out and stored in the storage unit 41, or output to the outside through the output unit 42.

[0039] The following is a detailed description of a specific example of the electret 2 used in the power generation equipment 1.

[0040] The specific configuration examples of the power generation section 10 and power generation equipment 1 using electret 2 will be described in detail later.

[0041] The electret material constituting electret 2 of this embodiment comprises an inorganic dielectric material with a band gap energy of 4 eV or higher as the main component. Here, "main component" can refer to an electret material composed solely of inorganic dielectric material, or it can refer to the addition of other components during the process of manufacturing the inorganic dielectric material into an electret material. Furthermore, it is also possible that other components are added during the process of manufacturing electret 2 from the electret material, within the range where the desired electret properties can be obtained.

[0042] Electret 2 is formed by polarizing such an electret material, thus electretizing it. In other words, "electretization" refers to the process of exhibiting a surface potential through polarization treatment, thereby creating a charged material. Here, the electret material is formed, for example, into a plate shape of a specified thickness, and electretized with the thickness direction as the polarization direction X, thereby obtaining electret 2 which maintains a positive or negative charge on the surface and provides an electrostatic field to the surroundings.

[0043] Here, will Figure 1 The vertical direction is designated as the polarization direction X of the electret 2. Hereinafter, one surface along polarization direction X will be referred to as the upper surface, and the other as the lower surface. In this case, the upper surface of the electret 2 becomes the first charged surface 21, and the lower surface becomes the second charged surface 22, both charged with different polarities. Furthermore, the electret 2 has a configuration where a portion of the first charged surface 21 on the upper surface is exposed to the atmosphere; this exposed surface is designated as the collector surface 20. The second charged surface 22 on the lower surface is not configured to have an exposed surface, but a portion may also be exposed.

[0044] As an inorganic dielectric material that can be used as an electret material, inorganic compounds with an apatite structure containing phosphate ions and hydroxide ions are used, for example. Apatite refers to inorganic compounds with the compositional formula M 10 The term (ZO4)6(X)2 is a general term for compounds, where ZO4 and X in the formula correspond to phosphate ions and hydroxide ions, respectively. Typically, these compounds often have a hexagonal crystal system with space group P63 / m and non-stoichiometric compositions. Inorganic compounds with an apatite structure containing phosphate and hydroxide ions refer to those with the formula M... 10 The compound represented by (PO4)6(OH)2, as a metallic element M, can be represented by divalent alkaline earth metals such as Ca.

[0045] By using such an inorganic compound, an electret 2 with a high surface potential can be obtained, enabling a high charge trapping capacity. Preferably, hydroxyapatite (HA) is used as the inorganic compound having an apatite structure containing phosphate ions and hydroxide ions. Hydroxyapatite is a compound with the following composition (Ca) under stoichiometric conditions. 10 (PO4)6(OH)2) has a crystal structure in which the unit cell is classified as hexagonal and the space group is P63 / m.

[0046] Preferably, in the inorganic compound that becomes an inorganic dielectric material, the content of hydroxide ions in the apatite structure is less than the stoichiometric ratio. Hydroxyapatite is produced by sintering raw material powder containing hydroxide ions and phosphate ions, for example, at a temperature exceeding 1250°C and less than 1500°C, to obtain a hexagonal hydroxyapatite crystal structure, during which the content of hydroxide ions is less than the stoichiometric ratio. This is because when hydroxyapatite is heated, dehydration occurs from the hydroxyl groups, resulting in the formation of hydroxyapatite oxide (OHA), leading to crystal defects.

[0047] Alternatively, as an inorganic dielectric, an oxide material can be used that comprises a composite oxide containing two different metallic elements A and B, and represented by the formula ABO3, as its basic composition. The composite oxide preferably uses a composite oxide with an amorphous structure or a perovskite crystal structure, and may have a composition where the oxygen content is lower than the basic composition due to defects formed in the structure (formula ABO3). x (x≤3). Preferably, if the composition has less oxygen than the stoichiometry of the basic composition, defects are easily introduced and the surface potential is easily increased.

[0048] In electret 2, the presence of defects is considered important for the surface potential. If amorphous (non-crystalline) composite oxides or perovskite composite oxide crystals are used in the band gap material, defects are easily introduced. Thus, electret 2 with a high surface potential can be obtained, enabling high charge trapping.

[0049] For example, amorphous composite oxides are more prone to forming defects caused by unbonded dangling bonds compared to perovskite oxide crystals of the same composition. Furthermore, perovskite oxide crystals can introduce defects through elemental substitution, as described later. Moreover, when using amorphous composite oxides, they can be formed at lower temperatures than oxide crystals, thus suppressing thermal damage to wiring and the like during device fabrication.

[0050] A perovskite-structured composite oxide refers to a composite oxide with a perovskite-type crystal structure represented by the formula ABO3, typically possessing a cubic crystal system. Metal element A is located at each vertex of the cubic crystal, metal element B is located at the center of the cubic crystal, and oxygen atoms O are coordinated octahedrally with respect to metal elements A and B. In perovskite structures, non-stoichiometric compositions are also common due to the lack of oxygen atoms. In such cases, the composition can be represented by ABO3. x (x < 3) indicates that the oxygen content is less than the stoichiometric ratio, thus causing crystal defects. Preferably, a configuration with a lower oxygen content than the stoichiometric ratio contributes to an increase in surface potential.

[0051] As a specific example, a composite oxide represented by the formula ABO3 can be configured such that the metal element A (A site) is a rare earth element R selected from La, Y, Pr, Sm, and Nd, and the metal element B (B site) is Al. The perovskite-structured composite oxide (RAlO3; rare earth aluminate) formed by combining trivalent rare earth element R with trivalent Al has a relatively high band gap energy of 4 eV or more and a relatively low relative permittivity (e.g., below 100), thus enabling the achievement of a high surface potential. Furthermore, it can be fabricated using relatively inexpensive materials, which is advantageous in terms of manufacturing cost.

[0052] In the perovskite structure, there are no particular restrictions as long as the combination of metal element A occupying site A and metal element B occupying site B satisfies the formula ABO3. In this case, for example, in addition to the combination of trivalent metal element A and trivalent metal element B, it can also be a combination of monovalent and pentavalent, or divalent and tetravalent.

[0053] Regarding the composition ABO3, it can be a part of the metal element A at site A or a part of the metal element B at site B, or both of these can be replaced by dopants composed of different metal elements. In this case, when the dopant element is a metal element with a lower valence than metal elements A and B, defects caused by oxygen vacancies are easily generated in the structure. For example, when metal element A is a trivalent rare earth element R, a divalent alkaline earth metal element (including Mg) is preferred; when metal element B is trivalent Al, one or more elements selected from divalent alkaline earth metal elements (including Mg) and Zn are preferred.

[0054] There are no particular restrictions on the combination of metal elements A and B; the dopant element only needs to be a metal element with a lower valence than the metal elements A and B being replaced. Because of the substitution by a lower-valence dopant element, crystal defects caused by oxygen deficiency are generated in the perovskite structure to maintain electroneutrality, which helps to increase the surface potential. At this point, there is a correlation between the amount of dopant substitution and the amount of defects. Therefore, by controlling the amount of dopant introduced, the amount of defects affecting the surface potential can be controlled, resulting in stable surface potential characteristics.

[0055] Specifically, a representative example of rare-earth aluminates is lanthanum aluminate (LaAlO3), which can be described as having a composition obtained by replacing a portion of La with an alkaline earth metal element (e.g., Ca). In this case, it can be derived from the formula (La,Ca)AlO3. 3-δ In the formula, δ represents the oxygen defect amount. The oxygen defect amount varies depending on the substitution amount of the dopant element, the atmosphere, etc. When the substitution ratio of the dopant element is set as x (atomic %), if the oxygen defect is caused by substitution, the composition formula becomes La. (1-x) Ca x AlO 3-x / 2 .

[0056] The substitution ratio of the dopant element replacing metal element A can be appropriately set, for example, in the range of 0.5 atomic% to 20 atomic%. Similarly, the substitution ratio of the dopant element replacing metal element B is preferably set, for example, in the range of 0.5 atomic% to 20 atomic%. When the substitution ratio is set to 0.5 atomic% or more, an increase in surface potential can be obtained compared to the case where no dopant element is introduced. Preferably, when the substitution ratio is set to 1 atomic% or more, the surface potential is significantly increased. However, when the substitution ratio approaches 20 atomic%, a tendency is observed for the effect of the introduction of the dopant element to decrease. The reason for this is not necessarily clear, but it is speculated that it plays a role in the direction of decreasing surface potential due to a greater increase in relative permittivity. Therefore, the substitution ratio should be appropriately set in a manner that yields the desired characteristics, within a range where the substitution ratio does not exceed 20 atomic%.

[0057] In this method, the electret 2 is obtained by polarizing the aforementioned inorganic dielectric material, such as a material obtained by forming an inorganic compound with an apatite structure into a sintered body of a predetermined shape (hereinafter referred to as an inorganic compound sintered body), or a material obtained by forming a perovskite structure composite oxide into a sintered body of a predetermined shape (hereinafter referred to as a composite oxide sintered body). The inorganic compound sintered body or the composite oxide sintered body that becomes the electret 2 can have any external shape (e.g., a rectangular plate or a disk shape).

[0058] Furthermore, the electret 2 can be fabricated into a film containing such an inorganic dielectric material (hereinafter referred to as an inorganic dielectric film). For example, if the inorganic dielectric material is an inorganic compound, it becomes an inorganic compound film; if it is a composite oxide, it becomes a composite oxide film. Such an inorganic dielectric film can be formed on a substrate by depositing the inorganic dielectric material on a substrate using any film-forming method such as sputtering, and in the form of a thin film with a desired thickness. As the substrate, in addition to conductive substrates such as conductive Si substrates, insulating substrates can also be used.

[0059] Furthermore, the electret 2 can be fabricated into a composite film by dispersing inorganic dielectric particles in a base film. These inorganic dielectric particles are obtained by preparing such inorganic dielectric materials into particle form. In this case, a material composed of inorganic dielectric particles and a base material can be used, for example, by any method such as printing, to form a composite film of desired thickness on a substrate. As the base material for the base film, any material with excellent heat resistance and voltage resistance can be used. In addition to organic materials such as polyimide, any material capable of liquid film formation can also be used.

[0060] Therefore, the shape of the electret 2 is not particularly limited. In addition, when the electret 2 is formed on the substrate, it can also be configured such that other layers such as a conductive film are stacked between the electret 2 and the substrate. Alternatively, the electret 2 formed on the substrate can be used in the state after being peeled off from the substrate after polarization treatment.

[0061] The polarization treatment method for electret formation is not particularly limited, and is performed by forming electrodes on both surfaces of an electret material of a predetermined shape and applying a voltage. The polarization treatment conditions are preferably, for example, applying a DC voltage at a temperature of 100°C or higher and an electric field strength of 1 kV / mm or higher. In power generation applications, to achieve efficient power generation, a surface potential of 100V or higher is required; the desired surface potential can be achieved through polarization treatment with an electric field strength of 1 kV / mm or higher. Furthermore, by performing polarization treatment at a temperature higher than room temperature, stable electret performance can be achieved even in applications where the operating environment is high-temperature.

[0062] exist Figure 1 In this process, the power generation unit 10 is formed by forming a pair of electrodes on the two surfaces of the electret 2 thus obtained. The two surfaces of the electret 2, which are polarized in the X direction, are charged with different polarities. The upper surface is designated as the first charged surface 21 (e.g., negative polarity), and the lower surface is designated as the second charged surface 22 (e.g., positive polarity). The first electrode 31 and the second electrode 32 are respectively disposed thereon.

[0063] Furthermore, the polarities of the first charged surface 21 and the second charged surface 22 are examples of different charged states.

[0064] In the power generation unit 10, the first electrode 31 disposed on the first charged surface 21 is formed by an assembly of multiple electrode portions 30, which are electrically connected to each other. In areas where the multiple electrode portions 30 are not disposed, the first charged surface 21 is exposed to the atmosphere, and this exposed surface functions as a collector surface 20. On the collector surface 20 of the first charged surface 21, charges corresponding to the internal polarization state of the electret 2 (e.g., negative polarity) are stored, exhibiting a surface potential (e.g., negative polarity), while a portion of these charges move via adjacent first electrodes 31, enabling current collection.

[0065] like Figure 2 As shown, the plurality of electrode portions 30 that form the first electrode 31 can, for example, be configured as a plurality of parallel strip electrodes 30a and an annular electrode 30b surrounding the outer side of the strip electrodes 30a. Figure 2In the example shown in the left figure, the electret 2 has a rectangular shape, corresponding to the first charged surface 21 of the same shape, and the annular electrode 30b is formed as a rectangular ring of a predetermined width along the periphery of the first charged surface 21. The strip electrodes 30a are arranged, for example, between two opposing sides of the annular electrode 30b, and are formed with a predetermined width and a predetermined interval.

[0066] On the first charged surface 21, the collector surface 20 is formed by a plurality of exposed strip-shaped surfaces surrounded by strip electrodes 30a and annular electrodes 30b. In this way, if a plurality of collector surfaces 20 are formed on the first charged surface 21 and are connected to the strip electrodes 30a or annular electrodes 30b at their respective peripheries, the movable charge accumulated on the collector surface 20 can be easily removed via the adjacent strip electrodes 30a or annular electrodes 30b.

[0067] Or, such as Figure 2 As shown in the right figure, in the case of a disk-shaped electret 2, strip electrodes 30c extending along the periphery of a first charged surface 21 of the same shape and connecting multiple strip electrodes 30a to each other can be configured. Alternatively, annular electrodes 30b (not shown) surrounding the outer side of the multiple strip electrodes 30a can be formed as an annulus with a predetermined width along the periphery of the first charged surface 21. The multiple strip electrodes 30a are formed parallel to each other with a predetermined width, for example, with the strip electrode 30c as one end side, or with a predetermined interval between them on the inner side of the annular electrode 30b.

[0068] In this configuration, the second electrode 32 is formed, for example, on the entire surface of the second charged surface 22. The area where the second electrode 32 is disposed is not necessarily limited, and it may also be a configuration in which a portion of the second charged surface 22 is exposed. The first electrode 31 and the second electrode 32 are metallic electrodes, for example, made of electrode materials containing precious metals such as gold (Au) or platinum (Pt) or precious metal alloys.

[0069] At this time, as Figure 3 As shown in the figure above, the energy storage unit 41 and the output unit 42, which can serve as the power supply unit 4, are electrically connected between the first electrode 31 and the second electrode 32 of the power generation unit 10 to extract the generated charge. The energy storage unit 41 and the output unit 42 are connected in parallel between the first wiring L1 connected to the first electrode 31 and the second wiring L2 connected to the second electrode 32. By inserting a switching unit 5 into the first wiring L1, for example, the connection between the power generation unit 10 and one of the energy storage unit 41 and the output unit 42 can be switched.

[0070] The energy storage unit 41 stores the electricity generated by the power generation unit 10, and can be configured using energy storage elements C such as capacitors. The output unit 42 has an output terminal 42a that connects to an external load (load resistor R), and can supply the electricity generated by the power generation unit 10 to the outside through the output terminal 42a. The output unit 42 can supply the electricity generated by the power generation unit 10 directly to the outside, or it can supply the stored electricity of the energy storage unit 41 to the outside.

[0071] like Figure 3 As shown in the figure below, the changeover switch unit 5 can also be a combination of multiple on / off switches 51 to 53. For example, it may include an on / off switch 51 for opening and closing the first wiring L1; an on / off switch 52 for opening and closing the branch line of the branch wiring L11 that connects the first wiring L1 to the energy storage unit 41 or the output unit 42, which is connected to one end of the energy storage unit 41 (here, the positive terminal side); and an on / off switch 53 for opening and closing the branch line connected to one end of the output unit 42 (here, the positive terminal side). The other end of the energy storage unit 41 and the output unit 42 (here, the negative terminal side) is connected to the second wiring L2 via the branch wiring L2.

[0072] The changeover switch unit 5 can control the switching of on / off switches 51 to 53 respectively via a changeover control unit (not shown). For example, when on / off switch 51 is closed and the generator unit 10 is connected to the power supply unit 4, the generator unit 10 can be connected to the energy storage unit 41 or the output unit 42 by closing on / off switch 52 or on / off switch 53, supplying generated power to one of them. Conversely, when on / off switch 51 is open and the connection between the generator unit 10 and the power supply unit 4 is disconnected, the stored power in the energy storage unit 41 can be supplied to the output unit 42 by closing both on / off switches 52 and 53.

[0073] Furthermore, the configuration of the changeover switch 5 can be arbitrarily changed. It can be a configuration without the on / off switch 51, or it can be a configuration that only has a changeover switch to switch the connection position between the power generation unit 10 and the energy storage unit 41 or the connection position between the power generation unit 10 and the output unit 42.

[0074] At this time, by switching the switch unit 5, the state is such that the energy storage unit 41 or the output unit 42 is connected between the first electrode 31 and the second electrode 32, thereby the charge (e.g., negative charge) accumulated on the collector surface 20 can move to the energy storage unit 41 or the output unit 42.

[0075] The generator mechanism of the generator unit 10 configured in this way has not necessarily been determined, but it can be considered, for example, as described below, with reference to Figure 4 Please provide an explanation.

[0076] like Figure 4As shown in the left figure, the electret 2 after polarization treatment is in the following state: In the inorganic dielectric that becomes the electret material, multiple electric dipoles D existing inside are neatly arranged in the polarization direction X, generating residual polarization P. Consequently, charged molecules, ions, etc. (floating charges) from the atmosphere are adsorbed corresponding to the polarization direction X of the electret 2. For example, as shown in the figure, when the first charged surface 21 on the upper surface is the positive electrode side, the opposite polarity negative charges N exist in a way that eliminates the residual polarization P. These negative charges N are usually bound by the first charged surface 21 and cannot move freely.

[0077] In contrast, it was confirmed that in the inorganic dielectric material that serves as an electret material in this manner, as in the experimental example described later, electrodes are placed on both surfaces of the electret 2, thereby enabling charge extraction. The reason for this is not necessarily clear, but it is speculated that due to the adsorption of ions in the atmosphere, the magnitude of the residual polarization P changes over time, resulting in the generation of a mobile negative charge N.

[0078] For example, such as Figure 4 As shown in the right figure, the charge required to eliminate the changed residual polarization P' (P > P') changes, resulting in an excess of charge on the first charged surface 21 (collector surface 20). In this case, a portion of the remaining negative charge N can be captured by electrodes or the like, enabling it to function as a power generation unit 10.

[0079] (Experimental Example 1)

[0080] The electret 2 constituting the power generation section 10 of Embodiment 1 was manufactured using the following method.

[0081] As the inorganic dielectric material constituting electret 2, an inorganic compound with an apatite structure, namely hydroxyapatite oxide (hereinafter referred to as OHA; band gap energy: 5.3 eV), was used as Experimental Example 1 to prepare an experimental sample of electret 2 obtained by polarizing the sintered body of OHA.

[0082] <Powder Preparation>

[0083] First, as a raw material for the OHA sintered body, the following hydroxyapatite (hereinafter referred to as HA) powder is prepared and weighed to a specified sample size. Relative to this HA powder, the following polyvinyl alcohol (hereinafter referred to as PVA) is weighed at 3.2% by mass.

[0084] • Apatite (HAP) monoclinic Ca for biomaterials research 10 (PO4)6(OH)2; Manufactured by Fujifilm and Koei Tecmo Chemical Co., Ltd.

[0085] • Polyvinyl alcohol degree of polymerization 1500; manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd.

[0086] Next, add an appropriate amount of pure water to the petri dish and heat it on a stirrer while dissolving the weighed PVA. Then, add the pre-weighed HA to the PVA solution in the petri dish and mix. Cover the petri dish with plastic wrap and place it in a desiccator heated to above 100°C for at least one day.

[0087] <Powder Classification and Molding>

[0088] The dried sample was transferred from the petri dish to a mortar and pestle and pulverized using a mortar and pestle. Next, approximately 0.3 g of the powder, graded to 30 μm–38 μm, was measured and shaped into 13 mm φ discs using a uniaxial pressure molding machine. Initially, a pressure of 30 MPa was applied for 2 minutes; subsequently, pressures were applied sequentially at 60 MPa for 2 minutes, then at 90 MPa for 2 minutes, and finally at 120 MPa for 3 minutes, resulting in a molded body containing a HA·PVA mixed powder.

[0089] Furthermore, in the case of further preparing large disc-shaped samples, approximately 0.55 g of powder graded to 30 μm–38 μm was measured each time and shaped into a disc shape with a 18 mm φ using a uniaxial pressure molding machine. In this case, pressure was initially applied at 60 MPa for 2 minutes, followed by 120 MPa for 2 minutes, then further at 180 MPa for 2 minutes, and finally at 240 MPa for 3 minutes, to obtain a molded body containing HA·PVA mixed powder.

[0090] <Preparation of OHA Sintered Samples>

[0091] The resulting molded body was placed on an alumina sintering boat lined with a platinum screen, and sintered in a tubular furnace at 1400°C for 2 hours under atmospheric conditions. This produced a disc-shaped OHA sintered sample.

[0092] <Polarization Treatment>

[0093] use Figure 5 The polarization treatment apparatus shown was used to polarize the OHA sintered sample thus obtained. Figure 5In the OHA sintered sample 11, a pair of gold electrodes 2a and 2b are pre-sintered on the upper and lower surfaces 11a and 11b in the thickness direction (polarization direction X) (the gold electrode 2b on the lower surface is not shown in the diagram). The OHA sintered sample 11 is clamped between two alumina rods 13, each wound with platinum wire 12, so that a voltage can be applied between the pair of gold electrodes 2a and 2b. The two alumina rods 13 are longer than the diameter of the OHA sintered sample 11 and are fixed by binding their ends with fluoropolymer (polytetrafluoroethylene) wire 14 in the length direction (orthogonal to the polarization direction X). Next, it is wound around a polarization apparatus, and the entire assembly is coated with silicone oil 15 to prevent insulation damage from air.

[0094] The polarization apparatus was placed in a box furnace and allowed to stabilize at 200°C. Next, while maintaining the temperature at 200°C, a DC electric field of 8.0 kV / mm was applied between a pair of gold electrodes 2a and 2b of the OHA sintered sample 11 for 1 hour to perform polarization treatment. After a specified time, the sample was allowed to cool naturally to below 40°C while the DC electric field was continuously applied.

[0095] <Construction of electret bodies>

[0096] After polarization treatment, a pair of gold electrodes 2a and 2b on both surfaces of the OHA sintered sample 11 were removed using a grinding wheel. Next, the OHA sintered body 11 was ultrasonically cleaned for 10 minutes each with ethanol and pure water. It was then further placed in a dryer at 100°C for at least 3 hours to obtain the electret 2.

[0097] <Surface Potential Measurement>

[0098] like Figure 6 As shown in the figure above, the electret 2 of Experimental Example 1 obtained as described above was placed on a grounded platform 16, and its surface potential was measured. A surface potentiometer (MODEL341-B: manufactured by Trek Japan Co., Ltd.) was used for the measurement. The measuring probe 17 was positioned opposite the electret 2 to measure the surface potential in a non-contact manner, and the value was read after 5400 seconds. The results are as follows: a high surface potential exceeding 3900V (absolute value) was obtained.

[0099] [Experimental Example 1: Surface Potential of OHA Electret: -3947V]

[0100] <Repeated Measurement of Surface Potential>

[0101] Furthermore, according to Figure 6 The surface potential was measured repeatedly in the order indicated by the arrows. First, as... Figure 6 As shown in the figure below, the measuring probe 17 is moved away from the position opposite the electret 2. Next, as... Figure 6 As shown in the middle figure, the grounded metal electrode plate 18 is short-circuited by contacting the surface of the electret 2. Then, the measuring probe 17 is aligned again using the above method, and the surface potential is measured. This operation is repeated. The time change of the surface potential is shown in the figure. Figure 7 .

[0102] like Figure 7 As shown, although the surface charge of electret 2 is removed by short-circuiting, and the surface potential is temporarily undetectable, the surface charge rises again afterward. Furthermore, by repeatedly short-circuiting and opening the circuit, the rise in surface charge occurs repeatedly. Although the surface charge decreases in the order of the second and third times compared to the first time, it stabilizes over time. This indicates that because the short circuit is broken, the surface of electret 2 becomes capable of being charged again, and the surface charge repeatedly recovers.

[0103] <Measurement of Induced Charge>

[0104] like Figure 8 The diagram schematically illustrates a power-generating section 10 on which a first electrode 31 and a second electrode 32 are formed on the first charged surface 21 and the second charged surface 22 of the electret 2, respectively, and connected to a known coulomb counter. The first electrode 31 has an electrode pattern in which multiple electrode sections 30 sandwich a strip-shaped current-collecting surface 20 adjacent to each other. For the electrode pattern that becomes the first electrode 31, a metal mask patterned with a linewidth of 100 μm and a spacing of 100 μm is provided on the first charged surface 21 of the electret 2, and a film with a thickness of about 300 nm is formed by sputtering a gold (Au) target.

[0105] The generator 10 is placed on a grounded metal platform, and the copper electrode plate and the coulomb counter probe are simultaneously in contact with the first charged surface 21 of the electret 2 to measure the induced charge. The time change of the induced charge is shown in... Figure 9 .

[0106] like Figure 9 As shown, by using the electret 2 of Experimental Example 1, the amount of induced charge increases over time, and the charge is continuously stored in the coulomb capacitor over time.

[0107] (Comparative Example 1)

[0108] For comparison, the surface potential and induced charge of electret films formed on substrates using the following fluoropolymer-based organic polymer materials as electret materials were similarly measured and evaluated.

[0109] CYTOP (registered trademark) CTL-809M manufactured by AGC Co., Ltd.

[0110] <Fabrication of Electret Membranes>

[0111] The fluoropolymer electret material described above was spin-coated onto a copper substrate at 500 rpm for 30 seconds. Then, a heat treatment was performed at 200°C for 1 hour, thereby producing the fluoropolymer electret film that is Comparative Example 1.

[0112] <Polarization Treatment>

[0113] The polarization treatment of the obtained fluoropolymer electret film used a corona discharge device. The electret film was placed on a stage heated to 120°C, and a DC voltage of -6.44kV was applied for 1 minute for corona discharge treatment to achieve polarization.

[0114] <Surface Potential Measurement>

[0115] The surface potential of the fluoropolymer electret film obtained as described above was measured in the same manner as in Test Example 1. The results are as follows: the surface potential of the fluoropolymer electret film was 300 V (absolute value), which was significantly lower than that of Sample 1.

[0116] [Comparative Example 1: Surface potential of fluoropolymer electret film: -300V]

[0117] The results of Test Example 1 and Comparative Example 1 are shown in Table 1. Furthermore, the surface potentials in Table 1 are absolute values; unless otherwise specified, absolute values ​​will be used in the following description.

[0118] Table 1

[0119]

[0120] <Measurement of Induced Charge>

[0121] For the obtained electret film, a patterned electrode was formed in the same manner as in Experimental Example 1, and the amount of induced charge was measured. On the surface of the fluororesin electret film, a patterned electrode formed from a gold electrode film (approximately 300 nm thick) was sputtered in the same manner as in Experimental Example 1. The fluororesin electret film with the electrode pattern was placed on a grounded metal stage, and the probe of a coulometer was brought into contact with the electrode surface of the fluororesin electret film, thereby measuring the amount of induced charge. Figure 9 In this example, the time variation of the induced charge is shown together with the results of Experimental Example 1 as Comparative Example 1.

[0122] Here, Figure 9The results show the time-varying change in induced charge after correction based on the surface potential of Comparative Example 1 at the start of measurement. In Comparative Example 1, which used a fluoropolymer electret film, almost no change in induced charge over time was observed, indicating that it could not function as a power generator in the state of the fluoropolymer electret film. In contrast, as described above, it can be seen that the power generator 10 using the electret 2 of Test Example 1 has a higher induced charge than Comparative Example 1, and further increases over time, thus enabling it to be effectively used as a power generation device 1.

[0123] (Experimental Example 2)

[0124] The electret 2 constituting the power generation section 10 of Embodiment 1 was manufactured using the following method.

[0125] As the inorganic dielectric material constituting electret 2, an LAO-based composite oxide was used, which is composed of lanthanum aluminate (LaAlO3) with a perovskite structure in which a portion of the La atoms are replaced by doping elements. Here, the doping element is set to Ca, so that it becomes (LaAlO3) 0.995 Ca 0.005 AlO 3-δ The raw materials were prepared by means of the composition, and the resulting composite oxide sintered body was polarized to produce electret 2 of Experimental Example 2.

[0126] Furthermore, for LAO-based inorganic dielectric materials, lanthanum aluminate (LaAlO3), a representative composition, has a band gap energy of 5.6 eV. Even when Ca is used as a dopant to replace part of Al, it still has an almost equal band gap energy.

[0127] <Powder Preparation>

[0128] First, as raw materials for LAO-based composite oxide sintered bodies, nitrate reagents as shown below were prepared and weighed with Ca substitution amount of 0.5 atomic%. 20 ml of ultrapure water was added to a beaker containing each reagent to obtain a solution in which each reagent was dissolved.

[0129] ·La(NO3)3·6H2O(3N)6.03g Fujifilm Wako Pure Chemical Co., Ltd.

[0130] Al(NO3)3·9H2O(2N) 5.25g, manufactured by Fujifilm and Wako Pure Chemical Industries Co., Ltd.

[0131] Ca(NO3)2·4H2O(3N) 16.5mg Fujifilm Wako Pure Chemical Industries Co., Ltd.

[0132] The solutions of each reagent were transferred to plastic beakers and mixed using a stirrer. Stirring was performed by placing a stir bar in the plastic beaker and rotating the stir bar at 500 rpm. The pH of the beaker containing the mixed solution was adjusted to 10.5 by adding small amounts of 12M NaOH aqueous solution dropwise while measuring the pH with a pH meter. The precipitate was then recovered by filtration and washed with approximately 100 ml of ethanol and ultrapure water.

[0133] In addition, the NaOH and ethanol used in the NaOH aqueous solution were prepared using the following reagents.

[0134] • Premium grade NaOH (granular) manufactured by Kanto Chemical Co., Ltd.

[0135] Ethanol (99.5%) manufactured by Kanto Chemical Co., Ltd.

[0136] Next, the filter paper containing the cleaned sample was placed in a dryer at 120°C and dried for at least 12 hours. The dried sample was then placed in an agate mortar and pulverized for further classification (<100μm).

[0137] <Fabrication of Molded / Sintered Bodies>

[0138] The powder obtained through classification was placed in an alumina boat and pre-fired. As a pre-fired condition, the temperature was raised to 1000℃ at a heating rate of 2.5℃ / min and held at 1000℃ for 6 hours, and then the temperature was lowered to room temperature at a cooling rate of 2.5℃ / min.

[0139] The pre-fired sample was added to an agate mortar and pulverized, and further graded (<100μm) to prepare a molding powder. Approximately 0.65g of the molding powder was placed in a φ13mm molding device and pressurized at 250MPa for 3 minutes to form a disc-shaped molded body.

[0140] The shaped body was sintered above the sintering temperature to obtain an LAO sintered sample formed from a LAO-based composite oxide sintered body. As sintering conditions, the temperature was increased to 1650℃ at a heating rate of 2.5℃ / min, held at 1650℃ for 2 hours, and then decreased to room temperature at a cooling rate of 2.5℃ / min. The diameter of the obtained sintered sample was approximately φ11mm. The thickness was adjusted to 1mm by grinding.

[0141] Furthermore, elemental analysis of the obtained LAO sintered samples was performed using ICP-N (Inductively Coupled Phosphorus) spectrophotometry, confirming the desired composition (La). 0.995 Ca 0.005 AlO 3-δThe sintered body was obtained. Specifically, the LAO sintered sample was pulverized in a mortar and dissolved in a solvent. The resulting solution was used as the analytical sample, and the constituent elements of the sintered body were identified based on the emission lines of ICP (inductively coupled plasma). The results are shown below. Almost equivalent analytical results (0.51 atomic%) were obtained relative to the Ca substitution ratio (injected Ca substitution amount) of 0.5 atomic% during raw material preparation.

[0142] (Injected Ca substitution amount 0.5 atomic%)

[0143] ICP analysis result: 0.51 atoms

[0144] Furthermore, the analysis of LAO sintered samples is not limited to ICP-based spectroscopy; any method such as XPS (X-ray photoelectron spectroscopy) or XRF (X-ray fluorescence spectrometry) can also be used. By introducing dopant elements as described above, the substitution amount can be easily controlled, and quantitative evaluation can also be easily performed.

[0145] <Polarization treatment and surface potential measurement>

[0146] The LAO sintered sample thus obtained was subjected to polarization treatment in the same manner as in Example 1 to prepare electret 2. The surface potential of electret 2 was measured in the same way. The results are recorded in Table 1.

[0147] As shown in Table 1, in Experiment 2 where Ca replaced a portion of the La in LaAlO3, the surface potential was 438 V (absolute value). By applying a DC electric field of 8.0 kV / mm, a high surface potential of over 400 V was obtained.

[0148] (Comparative Examples 2-3)

[0149] For comparison, an electret of Comparative Example 2 was prepared by polarizing a commercially available LaAlO3 (100) single-crystal substrate (manufactured by Crystal Base Co., Ltd.) using the same method as in Experimental Example 1, as a LaAlO3 sintered body with unsubstituted La. Additionally, a sintered body of barium titanate (BaTiO3) with a band gap energy of 3.5 eV, which is a perovskite-structured composite oxide, was prepared and polarized using the same method as in Experimental Example 1, thus producing an electret of Comparative Example 3.

[0150] For the electrets of Comparative Examples 2 and 3, the surface potential was measured in the same manner as in Experimental Example 1. The results are recorded in Table 1.

[0151] As shown in Table 1, in Comparative Example 2, which was formed from a single crystal of LaAlO3 and was not substituted by doping elements, the surface potential was 20V (absolute value), a significant decrease. Furthermore, in Comparative Example 3, which used BaTiO3 with a bandgap energy of less than 4eV, the surface potential was 4V, a further decrease.

[0152] (Experimental Examples 3-6)

[0153] An electret 2 formed from a sintered LAO-based composite oxide was fabricated using the same method as in Example 2. This LAO-based composite oxide sintered body was formed by... (1-x) Ca x AlO 3-δ The composition is obtained by changing the substitution ratio (x) of La based on the dopant element (Ca) as described below.

[0154] • Experimental Example 3 (La) 0.99 Ca 0.01 AlO 3-δ

[0155] • Experimental Example 4 (La) 0.95 Ca 0.05 AlO 3-δ

[0156] • Experimental Example 5 (La) 0.9 Ca 0.1 AlO 3-δ

[0157] • Experimental Example 6 (La) 0.8 Ca 0.2 AlO 3-δ

[0158] As shown in Table 2, using raw materials prepared by varying the substitution ratio (x) of La based on the dopant element (Ca) within the range of 1 atomic% to 20 atomic% to achieve the desired composition, shaped bodies were formed, sintered, and the resulting sintered samples were polarized to produce electret 2.

[0159] For the electrets 2 obtained in Experimental Examples 3 to 6, the surface potential was measured in the same manner as in Experimental Example 1, and the results are recorded in Table 2. Additionally, the relative permittivity of the composite oxide sintered body is also shown in Table 2.

[0160] Table 2

[0161]

[0162] As can be clearly seen from Table 2, in Experiments 3–6, the surface potential increased compared to Experiment 2, resulting in high surface potentials exceeding 1000V, ranging from 1400V (Experiment 6) to 3688V (Experiment 4). This is presumably because, relative to the perovskite structure of LaAlO3, substitution with lower valence dopants generates oxygen defects corresponding to the amount of substitution, contributing to the high surface potential.

[0163] Figure 10 Based on Comparative Example 2 and Experimental Examples 2-6, which showed the relationship between Ca substitution amount and surface potential, a high surface potential was observed under the condition of Ca substitution amount above 0.5 atomic%. As the Ca substitution amount increased to 1 atomic% to 5 atomic%, the surface potential increased significantly further. High surface potentials were also obtained in the range of Ca substitution amount exceeding 5 atomic%, but a tendency was observed that the higher the Ca substitution amount, the lower the surface potential.

[0164] On the other hand, as shown in Table 2, a tendency was observed that the higher the Ca substitution amount, the higher the relative permittivity of the composite oxide sinter. This is presumably because the amount of oxygen defects increases accordingly with the substitution ratio based on the dopant element, thereby increasing the surface potential. On the other hand, the increase in relative permittivity makes charge leakage easier to occur, thus suppressing the effect of increasing the surface potential.

[0165] Based on these results, the substitution ratio of the dopant element is preferably set to the range of 0.5 atomic% to 20 atomic% relative to the metal element A or B entering the perovskite structure at site A or site B.

[0166] As described above, by using an inorganic dielectric material formed from a composite oxide sintered body, it is possible to form an electret 2 with excellent thermal stability, controllable crystal defect quantity, and stable properties in the operating environment.

[0167] (Implementation Method 2)

[0168] Embodiment 2 related to the power generation device 1 will be described with reference to the accompanying drawings. The basic structure of this embodiment is the same as that of Embodiment 1 described above, and it is a variation of the electrode shape of the power generation unit 10. Hereinafter, the description will focus on the differences.

[0169] Furthermore, unless otherwise specified, any symbols used in Embodiment 2 that are the same as those used in the above embodiments represent the same constituent elements as those in the above embodiments.

[0170] In the above-described embodiment 1, as described above... Figure 2As shown, a first electrode 31 is formed on the first charged surface 21 of an electret 2 in the shape of a disk or rectangle, consisting of multiple strip electrodes 30a, 30c and annular electrodes 30b. However, these electrode shapes are just one example and can be different. For example, as... Figure 11 As shown, multiple electrode sections 30 can be interconnected and do not need to be in a shape surrounded by annular electrode 30b.

[0171] Specifically, such as Figure 11 As shown in (A), at one end of the plurality of parallel strip electrodes 30a, a strip electrode 30c orthogonal to the plurality of strip electrodes 30a can be formed along one side of the first charged surface 21. Alternatively, as shown in (B), a lattice-shaped electrode 30d can be used instead of the strip electrodes 30a, and as shown in (C), the strip electrodes 30a do not need to have a constant width. In this case, the strip electrodes 30a can, for example, become arc-shaped electrodes 30e, with part of their two side edges protruding outwards in an arc shape.

[0172] In addition, it can be like Figure 11 As shown in (D), the electrode can be a combination of rhomboid electrodes 30f interconnected at their vertices; or as shown in (E), it can be a combination of multiple concentric annular electrodes 30b; or as shown in (F), it can be a shape with multiple circular perforations 30h provided closer to the inner side than the outline of the circular electrode 30g. In any shape, the exposed surface of the current collecting surface 20 is formed by the multiple electrode portions 30 or the perforations 30h. In addition, the strip electrode 30c is formed on the periphery of the first charged surface 21 and led outward in a manner in which multiple electrode portions 30 are interconnected.

[0173] Thus, the shape of each electrode portion 30, or the shape of the electrode assembly formed by combining these shapes, can be arbitrarily set. Of course, it can also be set to... Figure 11 Shapes other than those shown in the diagram.

[0174] like Figure 12 As shown, multiple electrode portions 30 can be interconnected using wire bonding instead of forming annular electrodes 30b, strip electrodes 30c, etc., on the first charged surface 21. In this case, as... Figure 12 As shown in (A), multiple leads W are respectively connected to multiple strip electrodes 30a (refer to...). Figure 11 (A) in the middle. Additionally, in Figure 12 In (B) of the text, Figure 11 In (B), a portion of the lattice electrode 30d shown serves as a collector surface 20, and multiple rectangular electrodes 30i are arranged around the collector surface 20 and connected by multiple leads W.

[0175] In addition, such as Figure 12 As shown in (C) to (E), multiple circular electrodes 30g, rhomboid electrodes 30f, and annular electrodes 30b can be interconnected via multiple leads W. Figure 12 In the case of the circular electrode 30g shown in (F), a lead wire W is connected to extend it to the outside.

[0176] In this case, in the power generation section 10, to efficiently extract charge, it is preferable that at least a portion of the electrode spacing between adjacent electrode sections 30 in the first electrode 31 is 8 mm or less. In other words, it is preferable that at least a portion of the width of the current collecting surface 20 formed between the multiple electrode sections 30 is 8 mm or less. Preferably, the wider the area where the electrode spacing is 8 mm or less, the better. For example, in the main region including the central portion of the first charged surface, the electrode shape and arrangement can be set such that the electrode spacing of the first electrode 31 is about 8 mm or less. The smaller the electrode spacing is than 8 mm, the narrower the width of the current collecting surface 20 formed between the electrodes, and the easier it is for the charge accumulated in the current collecting surface 20 to be captured by adjacent electrode sections 30.

[0177] (Experimental Example 3)

[0178] like Figure 13 As shown, multiple electrode portions 30, which serve as the first electrode 31, are formed on the first charged surface 21 of a disk-shaped electret 2, which is formed in the same manner as in Test Example 1. Multiple test samples are prepared by changing the electrode spacing. The multiple electrode portions 30 are approximately semi-circular in shape and are arranged in a parallel manner with opposing straight lines. The shortest distance between them, i.e., the electrode spacing d, is changed to 0.1 mm (100 μm), 1 mm, 2 mm, 4 mm, 6 mm, and 8 mm, thereby preparing each sample (sample 1 to sample 6) as test samples.

[0179] For these test samples, OHA sintered samples were prepared in the same manner as in Test Example 1, and polarization treatment was performed by applying a DC electric field of 8.0 kV / mm at 200°C for 1 hour to produce electret 2. For electret 2, after the gold electrode used for polarization treatment was removed by grinding, sputtering under masking was performed in the same manner as in Test Example 1, and a gold electrode film forming multiple electrode portions 30 was patterned with an electrode spacing d of 0.1 mm (100 μm) to 8 mm.

[0180] For the test samples thus obtained, the surface potential was measured in the same manner as in Test Example 1, and the surface charge state was evaluated. In this case, the electric field of the electret 2 was locally electrostatically shielded by grounding the multiple electrode portions 30. The surface potential measurement results of each test sample are shown in Table 3 and... Figure 13 .

[0181] Table 3

[0182] Sample 1 8 3670 Sample 2 6 2930 Sample 3 4 1813 Sample 4 2 1163 Sample 5 1 400 Sample 6 0.1 105

[0183] As shown in Table 3, the surface potentials of these samples 1 to 6 are all lower than those of Test Example 1 (surface potential: 3947V). Additionally, as... Figure 13 As shown, in sample 1 with an electrode spacing d of 8 mm, the surface potential is relatively high at 3670 V. Following the order of sample 2 (d = 6 mm), sample 3 (d = 4 mm), sample 4 (d = 2 mm), and sample 5 (d = 1 mm), the smaller the electrode spacing d, the lower the surface potential. In sample 6 (d = 0.1 mm), the surface potential is 105 V. This is presumably because, relative to the electret 2 of test example 1, by placing the first electrode 31 on the first charged surface 21, the charge on the surface of the collector surface 20 moves via the first electrode 31, resulting in a decrease in surface potential.

[0184] Based on this result, it is believed that if the first electrode 31 formed on the first charged surface 21 having the collecting surface 20 has an electrode spacing d of 8 mm or less for the plurality of electrode portions 30, it can achieve the function of capturing charge. Furthermore, it is believed that the smaller the electrode spacing d, the easier it is for the charge on the collecting surface 20 to move to adjacent electrode portions 30, resulting in a lower surface potential. Therefore, it is preferable to make the area of ​​8 mm or less wider, as this is beneficial for power generation in the power generation section 10. Therefore, it is preferable that the electrode spacing of the plurality of electrode portions 30 is formed such that at least a portion is 8 mm or less, and preferably almost entirely is about 8 mm or less.

[0185] As described above, by using an inorganic dielectric material with a band gap energy of 4 eV or more as an electret material and polarizing it, an electrode is arranged on at least one surface of the resulting electret 2 in such a way that a current collecting surface 20 is partially exposed, thereby obtaining a power generation device 1 that can generate electricity even in an environment where no external energy is input.

[0186] This invention is not limited to the embodiments described above, and can be applied to various embodiments without departing from its spirit. For example, the power generation device 1 may be configured such that the power supply unit 4 connected to the power generation unit 10 includes a load connected to the output unit 42, and the output unit 42 may be configured without a load and consist of an output terminal unit 42a for external output. Alternatively, the power supply unit 4 may consist only of an energy storage unit 41 or an output unit 42.

Claims

1. A power generation device (1), comprising: The power generation unit (10) has an electret (2) having a first charged surface (21) and a second charged surface (22) charged with different polarities, a first electrode (31) formed on the first charged surface, and a second electrode (32) formed on the second charged surface; and The power supply unit (4) includes at least one of an energy storage unit (41) and an output unit (42) electrically connected between the first electrode and the second electrode of the power generation unit. The electret is an electret material containing an inorganic dielectric with a band gap energy of 4 eV or higher, which is electretized through polarization treatment. One surface along the polarization direction is designated as the first charged surface, and the other surface is designated as the second charged surface. At least one of the first electrode and the second electrode is configured to be in contact with the corresponding first charged surface and at least one of the second charged surfaces, such that a portion of the collector surface (20) for storing charge is exposed.

2. The power generation equipment according to claim 1, wherein, The inorganic dielectric is an inorganic compound having an apatite structure containing phosphate ions and hydroxide ions.

3. The power generation equipment according to claim 1, wherein, The inorganic dielectric is a composite oxide with an amorphous structure or a perovskite structure, consisting of two different metal elements A and B and represented by the formula ABO3 as its basic component.

4. The power generation equipment according to claim 3, wherein, The metal element A in the composite oxide is a rare earth element R selected from La, Y, Pr, Sm and Nd, and the metal element B is Al.

5. The power generation equipment according to claim 4, wherein, The composite oxide has a composition in which at least a portion of the metal elements A and B is replaced by doping elements composed of different metal elements. The doping element replacing metal element A is an alkaline earth metal element, and the doping element replacing metal element B is one or more elements selected from alkaline earth metal elements and Zn.

6. The power generation equipment according to any one of claims 1 to 5, wherein, At least one of the first electrode and the second electrode is formed by an assembly of a plurality of electrode portions (30) adjacent to the current collecting surface. The plurality of electrode portions are electrically connected to each other, and on at least one of the corresponding first charged surface and second charged surface, the area where the plurality of electrode portions are not disposed is exposed to the atmosphere to form the current collecting surface.

7. The power generation equipment according to claim 6, wherein, The electrode portion has an electrode shape selected from one of the following: strip electrode, ring electrode, grid electrode, arc electrode, circular electrode, and rectangular electrode. At least a portion of the electrode spacing (d) of the plurality of adjacent electrode portions sandwiching the current collector surface is 8 mm or less.

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