Structure

Abstract

Provided is a structure formed to have an electret part. This structure is formed to have a flexible member on the outside of the electret part. The electret part is a ceramic electret containing ceramic components and comprises a charge retention ceramic part and an inner electrode positioned inside the charge retention ceramic part, wherein the electret part has flexibility.

Description

Technical Field

[0001] The present disclosure relates to a structure exhibiting a flexoelectric effect.

Background Art

[0002] While the piezoelectric effect is an electric polarization phenomenon that occurs in proportion to the stress applied to a material, the flexoelectric effect is an electric polarization phenomenon that occurs in proportion to the spatial rate of change of the strain of a material, that is, the "strain gradient" (for example, Non-Patent Document 1). For example, since liquid crystals can easily exhibit large shape changes, it is known that electric polarization due to such a phenomenon appears remarkably. On the other hand, it is known that in ordinary solid materials, there are few deformation modes in which a large strain gradient appears, and the polarization due to the piezoelectric effect is generally larger.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Currently, there are few examples of practically using the flexoelectric effect in solid materials, and for example, those using polymer thin films are only known (for example, Patent Document 1).

[0006] The inventor of the present invention has found that there is still room for development regarding solid materials capable of exhibiting the flexoelectric effect.

[0007] The present invention has been made in view of the above problems. That is, the main object of the present invention is to provide a new structure capable of exhibiting the flexoelectric effect.

Means for Solving the Problems

[0008] The inventor of the present application has attempted to solve the above problems by dealing with them in a new direction rather than following the extension of the prior art. As a result, the inventor has arrived at the invention of a structure in which the above main object is achieved.

[0009] The structure according to the present disclosure includes an electret part, The structure has a flexible member outside the electret part, The electret part is a ceramic electret containing a ceramic component, and includes a charge-holding ceramic part and an internal electrode located inside the charge-holding ceramic part, The electret part has flexibility.

Effects of the Invention

[0010] The structure according to the present disclosure is a new structure capable of exhibiting the flexoelectric effect. Specifically, the structure of the present disclosure is a structure that exhibits the flexoelectric effect and has a ceramic electret, and is a new flexoelectric structure at least in that respect.

Brief Description of the Drawings

[0011]

Figure 1

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Figure 6

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Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Modes for Carrying Out the Invention

[0012] Hereinafter, the structure according to an embodiment of the present invention will be described in more detail. Although the description will be made with reference to the drawings as necessary, various elements in the drawings are merely shown schematically and exemplarily for the understanding of the present invention, and the appearance and / or dimensional ratios may be different from the actual ones.

[0013] The "cross-sectional view" directly or indirectly described in this specification is based on, for example, a virtual cross-section obtained by cutting the structure along the stacking direction of the layers constituting the structure. Similarly, the direction of "thickness" directly or indirectly described in this specification is based on, for example, the stacking direction of the layers constituting the structure.

[0014] The "vertical direction" and "horizontal direction" directly or indirectly used in this specification correspond to the vertical direction and horizontal direction in the drawing, respectively. Unless otherwise specified, the same reference numerals or symbols indicate the same members or parts or the same meaning content. In a preferred embodiment, where the stacking direction of the structure may correspond to the vertical direction, the vertically downward direction (i.e., the direction in which gravity acts) can be regarded as corresponding to the "downward direction" / "bottom surface side", and the opposite direction can be regarded as corresponding to the "upward direction" / "top surface side".

[0015] All kinds of numerical ranges mentioned in this specification are intended to include the numerical values of the lower limit and the upper limit themselves unless otherwise specified. The terms such as "about", "approximately" and "degree" mean that they may include variations or differences of several percent, for example, ± 10%.

[0016] ≪Findings and the like that are the basis of the present disclosure≫ A solid material, a solid material body or a solid article (hereinafter also collectively referred to as "solid material article") that can exhibit the flexoelectric effect is called a flexoelectret or a flexoelectret structure. FIG. 9 schematically shows how a "strain gradient" occurs in a conventional flexoelectret structure. When a force (F) is applied to a flexoelectric 100 having a shape such as a rod or a beam as shown in Fig. 9(A) and a bending moment acts, as shown in Fig. 9(B), strain changes along the thickness direction of the flexoelectric 100, for example, with a gradient (preferably a constant gradient) from compression to tension. Such a spatial strain change rate is referred to as a "strain gradient".

[0017] Referring to the schematic diagram of Fig. 10, the case where a strain gradient occurs in a crystal structure such as a perovskite structure will be described. For example, when compression is applied to the upper ions (white) in the crystal structure shown in Fig. 10(A) from the left - right direction (or horizontal direction), and tension is applied to the lower ions (gray) from the left - right direction (or horizontal direction), the central ion (black circle) moves downward (Fig. 10(B)). As a result, such ions are electrically polarized so that, for example, in the case of positive ions, the lower part of the crystal structure is positively charged.

[0018] Thus, the flexoelectric effect is a phenomenon that does not depend on the polarization treatment of solid material products. However, it is considered that the magnitude of the polarization due to the flexoelectric effect becomes even larger when polarization treatment is performed.

[0019] Here, when a solid material product is subjected to stress, the electric polarization that can occur in the solid material product can be expressed by the following formula (I). [Formula I] TIFF0007704200000001.tif92170

[0020] The μ (flexoelectric coefficient) is a fourth - order tensor quantity and represents the proportionality constant between the strain gradient and the polarization amount.

[0021] For example, in the case of deformation by bending (bending mode) as shown in Fig. 9, since the strain can change symmetrically above and below the neutral plane, the polarization amount due to the piezoelectric effect can be canceled out as a whole. Therefore, formula (I) can be expressed by the following formula (II). [Formula II] TIFF0007704200000002.tif46170 [Formula III] TIFF0007704200000003.tif64170

[0022] Thus, the flexoelectric effect in solid material products, particularly the flexoelectric effect caused by bending, can be evaluated by the flexoelectric coefficient.

[0023] In the case of general polymers, the flexoelectric coefficient is 1.0×10 -8 C / m. For example, in the case of polyvinylidene fluoride (PVDF), which is known as a piezoelectric polymer, it is known to be 1.3×10 -8 C / m.

[0024] For example, as shown in FIG. 11, in the polymer flexoelectret 200 formed by sandwiching a thin film 201 of a charged polymer (e.g., polytetrafluoroethylene (PTFE)) that holds charges between two outer polymer (PTFE) thin films 202, the flexoelectric coefficient is about five times that of a normal polymer, specifically up to 5.3×10 -8 C / m, by pre-polarizing the two outer polymer thin films 202 with the charged polymer thin film 201 (e.g., Patent Document 1).

[0025] However, in the case of conventional flexoelectric materials, the problem was that the flexoelectric effect was smaller than the piezoelectric effect. In particular, the problem was that the flexoelectric coefficient was small compared to the piezoelectric constant. Further, in the case of conventional polymer electrets, since they are manufactured using a polymer as a raw material, they have poor durability such as weather resistance, and when they are brought into contact with or immersed in a liquid such as water and / or an organic solvent, there are problems such as charge disappearance and reduction of the electric effect. The present disclosure has a background of attempting to solve such problems. More specifically, at least one of the following matters: the flexoelectric coefficient, the flexoelectric effect, durability such as weather resistance, and the ability to maintain the flexoelectric effect for a longer time with less charge disappearance even when brought into contact with or immersed in a liquid such as water and / or an organic solvent. The present disclosure has been developed to provide a structure having more suitable flexoelectric performance.

[0026] The structure of the present disclosure has been obtained through the above-described development process. This will be described below.

[0027] For example, the flexoelectric coefficient in the bending mode is proportional to the thickness of the entire flexoelectric structure and the charge density of the electret part, as shown by the following formula (IV) (for example, Non-Patent Document 2). [Formula IV] TIFF0007704200000004.tif70170

[0028] From such findings, it was found that the higher the charge density of the electret part, the larger the flexoelectric coefficient. Therefore, the present inventors considered using a ceramic electret having a higher charge density than a polymer electret such as a charged polymer. Further, in order to develop a more desirable ceramic electret product for the bending mode, the present inventors considered improving the flexoelectric coefficient even in the bending mode.

[0029] As a result of various intensive studies including such circumstances, finally, the structure of the present disclosure as described below was developed. The structure has a flexible member on the outside of the electret portion, and the electret portion is a ceramic electret containing a ceramic component, and includes a charge-holding ceramic portion and an internal electrode located inside the charge-holding ceramic portion, and the electret portion has flexibility. Such a structure of the present disclosure can be a structure having improved flexoelectric performance in at least one aspect such as a flexoelectric coefficient, a flexoelectric effect, durability such as weather resistance, and the fact that charges are difficult to disappear even when in contact with or immersed in a liquid such as water and / or an organic solvent and the flexoelectric effect can be maintained for a longer time (note that the effects described in such a specification are merely examples and are not limited, and there may be additional effects).

[0030] ≪Structure of the Present Disclosure≫ The present disclosure relates to a structure having improved flexoelectric performance (hereinafter, may also be referred to as a "flexoelectric article" or a "flexoelectric structure").

[0031] In the present disclosure, "flexoelectric performance", particularly "improved flexoelectric performance" mainly means exhibiting a larger flexoelectric coefficient and a larger flexoelectric effect. As flexoelectric performance, it may further have performance such as durability such as weather resistance, and the fact that charges are difficult to disappear even when in contact with or immersed in a liquid such as water and / or an organic solvent and the flexoelectric effect can be maintained for a longer time.

[0032] The structure of the present disclosure is a structure capable of exhibiting a flexoelectric effect. Therefore, the structure of the present disclosure can also be referred to as a "flexoelectric body", a "flexoelectric article" or a "flexoelectric structure".

[0033] In the present disclosure, the "flexoelectric effect" means an electric polarization phenomenon that can occur in proportion to the spatial rate of change of strain in a structure, that is, the "strain gradient" (see FIG. 9). The flexoelectric effect is a phenomenon that can occur in a dielectric, but it is an electric polarization phenomenon that is completely different from the piezoelectric effect that can occur in proportion to stress.

[0034] For example, when a solid material product is subjected to stress, the electric polarization that can occur in such a solid material product can be expressed by the following formula (I) as described above. [Formula I] TIFF0007704200000005.tif90170

[0035] In the present disclosure, the "flexoelectric coefficient" (μ) is a fourth-order tensor quantity and means the proportionality constant between the strain gradient and the polarization amount.

[0036] In the bending mode as shown in FIG. 9, since the strain changes symmetrically above and below the neutral plane, the polarization amount due to the piezoelectric effect can be canceled out as a whole (σ (stress) = 0). Therefore, Formula (I) can be expressed by the following formula (II). [Formula II] TIFF0007704200000006.tif48170 [Formula III] TIFF0007704200000007.tif63170

[0037] In this way, in the bending mode, since the polarization amount due to the piezoelectric effect can be canceled out as a whole, the larger the value of the "flexoelectric coefficient" (μ), the larger the value of the electric polarization (P). In other words, the larger the flexoelectric coefficient, the greater the flexoelectric effect.

[0038] In the present disclosure, the "bending mode" means a system in which strain can occur in a structure when the structure is bent, in other words, a system in which a bending moment can act on the structure.

[0039] However, the flexoelectric effect in the present disclosure is not necessarily limited to the flexoelectric effect in the bending mode.

[0040] The "flexoelectric coefficient" of the flexoelectret structure of the present disclosure is, for example, greater than approximately 1.0×10 -8 C / m, preferably greater than 1.3×10 -8 C / m, more preferably greater than 5.0×10 -8 C / m, and even more preferably greater than 5.3×10 -8 C / m. When the flexoelectric coefficient is within such a range, a greater flexoelectric effect can be achieved. The upper limit value of such a flexoelectric coefficient is not particularly limited, and may be, for example, about 50×10 -8 C / m, about 40×10 -8 C / m, about 30×10 -8 C / m, about 20×10 -8 C / m, or about 10×10 -8 C / m.

[0041] In the present disclosure, the shape of the flexoelectret structure is not particularly limited. The flexoelectret structure may have any shape, such as a plate-like or sheet-like shape (including strip-like), a rod-like shape, or a fibrous shape (including fiber), and therefore, its cross-sectional shape is not particularly limited. The cross-sectional shape of the flexoelectret structure may have any geometric shape, such as a rectangle and / or a circle.

[0042] In the present disclosure, the flexo-electret structure may have a shape and configuration that can be bent by an external force. In other words, the flexo-electret structure may have flexibility. It is preferable that the flexo-electret structure as a whole has flexibility.

[0043] In the present disclosure, the "flexibility" of the flexo-electret structure generally means that the structure (as well as components of the structure such as ceramic electrets and flexible members) bends or deforms under an external force, preferably meaning that the structure bends without cracking and / or chipping. Narrowly, "flexibility" means that, for example, as shown in FIG. 9, when the structure is bent, the structure bends at an arbitrary radius of curvature, that is, the ceramic electret and flexible member, which are components thereof, bend at an arbitrary radius of curvature (preferably without cracking and / or chipping).

[0044] When the flexoelectret structure receives an external force and bends as shown in, for example, FIG. 9(B) (preferably, when the structure bends without cracks and / or chips), the structure (preferably its electret part) may have a radius of curvature of approximately 5000 mm or less, for example, a radius of curvature of 4000 mm or less, 3000 mm or less, 2000 mm or less, 1500 mm or less, 1300 mm or less, 1200 mm or less, or 1100 mm or less, and preferably has a radius of curvature of 1000 mm or less. That is, in a preferred embodiment, when the structure of the present disclosure receives an external force and the electret part is displaced, the electret part has a radius of curvature of 1000 mm or less in a cross-sectional view. When the radius of curvature is within such a range, it is easier to exhibit greater flexibility, and as a result, a greater flexoelectric effect can be brought about. The lower limit value of the above-mentioned radius of curvature is not particularly limited, but may be, for example, about 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, or 950 mm. Note that the above-mentioned radius of curvature may be based on the contour (especially the main surface contour) of the structure or its electret part in a cross-sectional view or a side view of the structure obtained as an image such as an optical microscope photograph or an electron microscope photograph (for example, typically a cross-sectional view as shown in FIG. 9(B)), and may be based on the contour portion with the largest bending in the contour.

[0045] In the present disclosure, the "thickness" of the flexoelectret structure is not particularly limited. Preferably, the structure has a thickness that contributes to the bending of the structure and contributes to the above-mentioned flexibility, particularly the above-mentioned radius of curvature.

[0046] The overall thickness of the flexoelectret structure may be approximately 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less, for example, 10 mm or less. Further, the overall thickness of the flexoelectret structure may be 5 mm or less, for example, 3 mm or less, 2.2 mm or less, or 2 mm or less (the lower limit value of such a value may be, for example, about 0.5 mm or 1 mm). When the thickness of the structure is within such a range, it is easier to bring about a greater flexoelectric effect.

[0047] (First Embodiment) FIG. 1 shows a flexoelectric structure of the present disclosure as a first embodiment. The structure shown in FIG. 1 is for explaining the concept of the flexoelectric structure of the present disclosure, and the illustrated content is merely schematically and exemplarily shown for the understanding of the present invention.

[0048] The structure (10) shown in FIG. 1 (hereinafter sometimes referred to as "the structure of the present disclosure") is a structure having an electret part (1). The structure (10) has a flexible member (2) outside the electret part (1). Preferably, the structure (10) has flexible members (2) on the outsides corresponding to both sides of the electret part (1). It can also be said that the structure (10) has the electret part (1) inside the flexible member (2). Such an electret part (1) is a ceramic electret containing a ceramic component, and includes a charge-holding ceramic part (3) and an internal electrode (4) located inside or on the inner side of the charge-holding ceramic part (3), and the electret part (1) has flexibility. That is, the electret part (1) provided as a ceramic electret containing a ceramic component includes the internal electrode (4) and the charge-holding ceramic part (3) outside thereof, and has flexibility as a whole.

[0049] In the structure (10) of the present disclosure, flexible members (2) are provided outside (preferably on both sides) of the flexible electret part (1). That is, two types of members exhibiting flexibility are provided so as to overlap or laminate each other. Since the electret part (1) provided as a ceramic electret has flexibility, and the flexible member (2) provided on its main surface also has flexibility, the structure of the present disclosure can exhibit flexibility. Therefore, the structure (10) of the present disclosure can be suitably bent as a whole, and preferably can be bent so that a bending moment is suitably generated. When the structure is bent as shown in FIG. 9 for example, a bending moment is suitably generated, resulting in a flexoelectric effect.

[0050] The structure (10) is characterized in that the electret part (1) is a ceramic electret containing a ceramic component, and the electret part (1) includes a charge-holding ceramic part (3) and an internal electrode (4) positioned inside thereof.

[0051] As will be described in detail below, the ceramic electret can exhibit technical effects different from those of the polymer electret. Specifically, the ceramic electret can have a higher charge density in the charge-holding ceramic part (3) and a higher flexoelectric coefficient compared with the conventional polymer electret. Therefore, in the structure of the present disclosure, a greater flexoelectric effect can be brought about (see the following formula (IV)). Compared with the conventional polymer electret, a greater voltage can be generated or electrified at the same displacement amount.

[0052] Also, within the range where the structure (10) has flexibility, by increasing the overall thickness of the flexoelectric structure, particularly the thickness of the flexible member, a greater flexoelectric effect can be brought about and a greater voltage can be generated (see the following formula (IV)). That is, the flexoelectric effect can be made more prominent due to the thickness of the flexible member. In this regard, as will be described later, the flexible member (2) may have a thickness greater than the respective thicknesses of the internal electrode (4) and the charge-holding ceramic part (3).

[0053] These effects can be understood from the fact that, as shown in the following formula (IV), for example, the flexoelectric coefficient in the bending mode can be proportional to the "thickness" of the entire flexoelectric structure and the "charge density" of the electret part. [Formula IV] TIFF0007704200000008.tif75170

[0054] Furthermore, in the structure of the present disclosure, by using a ceramic electret, the durability such as weather resistance can be improved compared to conventional polymer electrets, and preferably such durability is improved more significantly. Also, by using a ceramic electret, even when in contact with or immersed in a liquid such as water and / or an organic solvent, the charge is less likely to disappear and it becomes easier to maintain the flexoelectric effect for a longer time. Therefore, the structure of the present disclosure can be preferably used even in a more severe environment, particularly in the outdoors or in a higher temperature environment.

[0055] The electret part (1) included in the structure (10) can be regarded as a dielectric as described in detail below. Therefore, without being bound by a specific theory, when electric polarization occurs in the electret part (1), electric polarization is also preferably easily induced in the flexible member (2) positioned outside thereof, making it easier to exhibit a larger flexoelectric effect and enabling the generation of a larger voltage.

[0056] The radius of curvature of the structure (10) in the bending mode is, for example, 1500 mm or less, 1300 mm or less, 1200 mm or less, or 1100 mm or less, and preferably 1000 mm or less. That is, although the structure of the present disclosure is a laminate including a ceramic element, it can exhibit suitable flexibility and a more suitable flexoelectric effect can be brought about. The overall thickness of the structure (10) may be 0.1 mm or more and 10 mm or less, or 0.1 mm or more and 5 mm or less, etc.

[0057] In the structure (10), there are no particular restrictions on the ratio of the thicknesses of the charge-holding ceramic part (3) and the internal electrode (4) that can be included in the electret part (1), and the thickness of the flexible member (2). In a certain preferred embodiment, the structure has a thickness relationship of flexible member (2) > internal electrode (4) > charge-holding ceramic part (3). That is, the thickness of the flexible member (2) may be greater than the thickness of the internal electrode (4), and the thickness of the internal electrode (4) may be greater than the thickness of the charge-holding ceramic part (3) (that is, the thickness of the flexible member (2) may be greater than the thickness of the charge-holding ceramic part (3)). By adjusting the thicknesses of the respective layers in such an order, it becomes easier to exhibit greater flexibility and it becomes easier to bring about a greater flexoelectric effect. Here, the thickness of the charge-holding ceramic part (3) referred to here is the thickness of the charge-holding ceramic part located on either the upper side or the lower side of the internal electrode (4) in a cross-sectional view of the structure. Similarly, the thickness of the flexible member (2) also means the thickness of the flexible member located on either the upper side or the lower side of the internal electrode (4) in a cross-sectional view of the structure.

[0058] The flexoelectric coefficient of the structure (10) is, for example, greater than 1.3×10 -8 C / m, preferably greater than 5.0×10 -8 C / m, more preferably greater than 5.3×10 -8 C / m (for example, greater than 5.5×10 -8 C / m). When the flexoelectric coefficient is within such a range, a greater flexoelectric effect can be brought about by the structure of the present disclosure. The upper limit value of the flexoelectric coefficient of such a structure (10) is not particularly limited and may be 30×10 -8 C / m, 20×10 -8 C / m, 10×10 -8 C / m, 9×10 -8 C / m, 8×10 -8 C / m, etc. (the upper limit value may include the value itself).

[0059] The structure (10) can have a larger flexoelectric coefficient and can be provided as a hitherto unprecedented flexoelectric structure in that it can exhibit at least a suitable flexoelectric effect (preferably a more prominent flexoelectric effect), such as a ceramic electret.

[0060] Hereinafter, the "electret part (1)" and the "flexible member (2)" included in the structure (10) will be described in detail.

[0061] (Electret part) In the present disclosure, the "electret part" (1) is typically a part that can hold either a positive or negative charge on its surface. Therefore, the electret part can also be referred to as a "charge holding part". By holding either a positive or negative charge on its surface, the electret part (1) can polarize the surface of the flexible member (2).

[0062] In the structure of the present disclosure, the electret part (1) is a ceramic electret containing a ceramic component. The ceramic electret (1) includes a charge holding ceramic part (3) and an electrode, that is, an internal electrode (4), located inside or within this charge holding ceramic part (3) (see FIG. 1). In such a charge holding ceramic part (3), at least a ceramic component is included.

[0063] When the structure (10) receives an external force and the electret part (1) is displaced, particularly when a bending moment acts (see Fig. 9), the electret part (1) can have a radius of curvature of 5000 mm or less in its cross-sectional view. For example, it can have a radius of curvature of 4000 mm or less, 3000 mm or less, 2000 mm or less, 1500 mm or less, 1300 mm or less, 1200 mm or less, or 1100 mm or less, preferably 1000 mm or less. The radius of curvature within such a range of the electret part (1) means that a greater or more suitable flexibility can be brought to the structure, and therefore, a greater flexoelectric effect can be exerted on the structure. Although there is no particular limitation on the lower limit value of such a radius of curvature, it can be, for example, about 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, or 950 mm.

[0064] In the structure of the present disclosure, the ceramic electret located inside the flexible member may be a member thinner than the flexible member. That is, in the cross-sectional view of the structure, the thickness of the ceramic electret located inside the flexible member may be smaller than the thickness of the flexible member. Thereby, even though the electret contains a ceramic component, it becomes easier for the entire structure to exhibit suitable flexibility. That is, when the thickness of the relatively inner ceramic electret is smaller than the thickness of the relatively outer flexible member, the structure can be easily bent at an arbitrary radius of curvature when the structure is bent (preferably, it can be bent without cracking and / or chipping), and a suitable flexoelectric effect (preferably a more prominent flexoelectric effect) is likely to be brought to the structure.

[0065] (Ceramic electret) In the present disclosure, "ceramic electret" means an electret including a "ceramic component" described in detail below. There is no particular limitation on the specific ceramic component included in the ceramic electret as long as it can hold charges. In the present disclosure, the ceramic electret does not necessarily have to be entirely composed of ceramic components. For example, the ceramic electret may be composed of a ceramic component and other components (such as resin), or a partial region of the ceramic electret may be a non-ceramic region.

[0066] (Charge-holding ceramic part) In the present disclosure, the "charge-holding ceramic part" (3) can hold charges on its surface by dielectric polarization. In other words, the charge-holding ceramic part (3) may be a substance that can generate dielectric polarization when an electric field is applied, that is, a dielectric. Here, dielectric polarization refers to the phenomenon in which charges in a dielectric are separated into positive and negative poles by the action of an external electric field. In the present disclosure, dielectric polarization can be used as a term having the same meaning as electric polarization.

[0067] The charge-holding ceramic part is a member including a ceramic component, and may be provided with an electrode. For example, the charge-holding ceramic part (3) has an internal electrode (4) inside or within it, and such an internal electrode (4) can be used for grounding or GND connection. When, for example, the surface in contact with the internal electrode (4) of the charge-holding ceramic part (3) holds positive charges and the opposite surface holds negative charges, the positive charges are electrostatically shielded by the ground, and only negative charges can be held outside the charge-holding ceramic part (3). In the reverse case, only positive charges can be held outside the charge-holding ceramic part (3). In this way, when polarized by dielectric polarization or electric polarization, it can be charged with either positive or negative polarity.

[0068] There is no particular limitation on the position of the internal electrode (4) disposed inside or within the charge-holding ceramic part (3). In the aspect shown in FIG. 1, the internal electrode (4) is interposed in the charge-holding ceramic part (3) such that the charge-holding ceramic part (3) and the internal electrode (4) are in contact with each other. It can also be said that the internal electrode (4) is interposed so as to be sandwiched between two members of the charge-holding ceramic part (3). In a preferred aspect, the internal electrode (4) is positioned at the geometric center of the charge-holding ceramic part (3). For example, as shown in FIG. 1, the internal electrode (4) may be positioned such that it exists at an intermediate position in the thickness direction (overall thickness) of the charge-holding ceramic part (3).

[0069] There is no particular limitation on the shape of the charge-holding ceramic part (3). When more importance is attached to the charge density, the charge-holding ceramic part (3) may have a plate-like or sheet-like shape. That is, the charge-holding ceramic part (3) may have a form extending on the same plane. For example, the charge-holding ceramic part (3) may have a layer shape (preferably a form of a layer extending on the same plane or a form of a layer extending on a curved surface). Also, when more importance is attached to the charge density in the same way, the charge-holding ceramic part (3) may have an elongated shape, for example, a strip shape (preferably an elongated strip shape). Alternatively, when more importance is attached to flexibility and / or softness, the charge-holding ceramic part (3) may have a fiber shape (particularly an elongated shape). The shape of the cross-section of the charge-holding ceramic part (3) (for example, the outer contour in a cross-sectional view) may be square, rectangular, or circular, or any other geometric shape. For example, when more importance is attached to flexibility and / or softness, the charge-holding ceramic part (3) may have a circular contour or an elliptical contour (for example, a circular or elliptical outer contour) in its cross-sectional view. In a preferred aspect, the charge-holding ceramic part (3) has, for example, a cylindrical shape (see FIG. 8).

[0070] The charge-holding ceramic part (3) preferably has flexibility and / or softness. For example, the thickness of the charge-holding ceramic part (3) (the thickness dimension when viewed in cross-section) may be a thickness of 1 mm or less, for example, 0.005 mm or more and 1 mm or less, 0.005 mm or more and 0.5 mm or less, 0.005 mm or more and 0.3 mm or less, or 0.01 mm or more and 0.1 mm or less. The charge-holding ceramic part (3) having such a thickness is likely to exhibit suitable flexibility and / or softness.

[0071] (Internal electrode) In the present disclosure, the "internal electrode" (4) has conductivity. In other words, the internal electrode is formed of at least a material having conductivity. For example, the internal electrode is formed of "metal" and / or the "conductive material" described below, and may contain other components as necessary.

[0072] Since the internal electrode (4) has conductivity, it can be used for grounding or ground (GND) connection as an electrode of the electret part. Therefore, when the charge-holding ceramic part (3) is polarized by dielectric polarization or electric polarization, the charge-holding ceramic part (3), particularly its surface, can be charged either positively or negatively. In the embodiment shown in FIG. 1, charge holding can be performed in such a manner that both of the two members of the charge-holding ceramic part (3) provided outside the internal electrode (4) to form a pair (that is, the member of the charge-holding ceramic part (3) located above the internal electrode (4) and the member of the charge-holding ceramic part (3) located below the internal electrode (4)) are positively charged, or both of the two members of the charge-holding ceramic part (3) are negatively charged. Preferably, in such a charge-holding ceramic part (3), either one of the charges can be held particularly over the entire surface thereof.

[0073] The "metal" that can be included in the internal electrode (4) may be a metal (for example, a single metal) or an alloy composed of the metal elements described below.

[0074] The metal or alloy that may be included in the internal electrode (4) may be a sintered body. A single metal consisting of a sintered body may be used for the internal electrode (4). In other words, the electrode of the structure of the present disclosure (that is, the "internal electrode" in the first embodiment) may be a sintered body. That is, in a preferred embodiment, the internal electrode is a sintered electrode. Even with such a sintered electrode, in the structure of the present disclosure, a flexible member is provided outside the internal electrode, which suitably contributes to the flexibility and / or softness of the structure.

[0075] In the present disclosure, the "sintered body" may generally be a sintered body (inorganic solid material body) obtained by heat-treating an inorganic substance (for example, a paste of a composition containing an inorganic substance) to harden it. For example, the electrode of the structure of the present disclosure (the "internal electrode" in the first embodiment) may be a sintered body formed by heat-treating a raw material powder (preferably an inorganic powder such as a metal raw material powder) or a paste obtained therefrom.

[0076] Examples of the "metal" that may be included in the electrode (the "internal electrode" in the first embodiment) in the structure of the present disclosure include at least one selected from the group consisting of gold (Au), silver (Ag), copper (Cu), iron (Fe), aluminum (Al), chromium (Cr), titanium (Ti), nickel (Ni), palladium (Pd), and platinum (Pt).

[0077] The "conductive material" that may be included in the electrode (the "internal electrode" in the first embodiment) in the structure of the present disclosure means a material having electrical conductivity, and there is no particular limitation on the specific type as long as it has electrical conductivity.

[0078] Examples of the "conductive material" include a "conductive filler". In a preferred embodiment, the conductive filler may be combined with a resin. That is, the conductive material that can be included in the electrode (the "internal electrode" in the first embodiment) in the structure of the present disclosure may be a composite of a conductive filler and a resin. When the conductive material is provided as a composite, it is easier to impart greater flexibility and / or softness to the internal electrode (4), and thus it is easier to further improve the flexibility of the ceramic electret and the structure.

[0079] The "conductive filler" means a material or substance that can impart conductivity (make it easier to conduct electricity / electrons) to a polymer material such as a resin. There is no particular limitation on the specific type as long as it can impart conductivity. For example, conductive fillers such as carbon-based, metal-based, and / or metal oxide-based fillers can be mentioned. Examples of the conductive filler may include conductive fillers containing carbon black, acetylene black, ketjen black, nanocarbon materials, gold, silver, platinum, nickel, copper, zinc, aluminum, tin, manganese, stainless steel, tin oxide, indium oxide, zinc oxide, nickel zinc oxide, magnesium, tungsten, cobalt, chromium, and / or titanium, etc.

[0080] The "resin" means a polymer material, for example. There is no particular limitation on the specific type of resin, and thermoplastic resins and / or thermosetting resins, etc. may be included in the electrode (the "internal electrode" in the first embodiment) in the structure of the present disclosure. The resin may be, for example, a resin having a volume resistivity of 10 14 [Ω·m] or less (resistivity under the temperature and humidity conditions of 23 ± 5°C and relative humidity of 50 ± 20%). For example, resins such as phenolic resins, epoxy resins, bismaleimide resins, vinyl chloride-based resins, urethane resins, nylon resins, ether resins, polyether resins, ketone resins, wholly aromatic polyester resins, polyamide resins, polyester resins, acrylic resins, polymethyl methacrylate resins, melamine resins, and / or silicone resins may be included in the electrode (the "internal electrode" in the first embodiment) in the structure of the present disclosure.

[0081] In the present disclosure, "composite" means a material in which two or more types of materials are combined, that is, a composite material. For example, the composite may be a material in which the above-mentioned "conductive filler" and "resin" are combined. However, in the present disclosure, it is not necessarily limited to the filler form. That is, the electrode of the structure of the present disclosure (the "internal electrode" in the first embodiment) preferably comprises a composite material, and the composite material may comprise a metal component, an alloy component and / or a carbon component, and a resin component. In the present disclosure, such a composite material may be a mixture (or blend) in which only two or more types of materials are simply mixed (or blended).

[0082] The ratio of the conductive filler to the resin in the composite used for the electrode of the structure (conductive filler / resin) is, for example, 99 / 1 to 1 / 99 on a weight basis, preferably 80 / 20 to 40 / 60.

[0083] There is no particular limitation on the shape of the internal electrode (4). When more importance is attached to the charge density, it may have a plate-like or sheet-like shape. That is, the internal electrode (4) may have a form extending on the same plane. For example, the internal electrode (4) may have a layer shape (preferably a form of a layer extending on the same plane or a form of a layer extending on a curved surface). Similarly, when more importance is attached to the charge density, the internal electrode (4) may have an elongated shape, for example, a strip shape (preferably an elongated strip shape). Alternatively, when more importance is attached to flexibility and / or softness, the internal electrode (4) may have a fibrous shape (particularly an elongated shape). The shape of the cross section of the internal electrode (4) (for example, the outer contour in a cross-sectional view) may be square, rectangular or circular, or any other geometric shape.

[0084] The internal electrode (4) preferably has flexibility and / or softness. For example, the thickness of the internal electrode (4) (the thickness dimension when viewed in cross-section) may be a thickness of 2 mm or less, 1.5 mm or less, 1 mm or less, 0.1 mm or less, or 0.05 mm or less. For example, it may be 0.005 mm or more and 2 mm or less, 0.005 mm or more and 1.5 mm or less, 0.01 mm or more and 1 mm or less, 0.01 mm or more and 0.5 mm or less, 0.01 mm or more and 0.3 mm or less, 0.01 mm or more and 0.1 mm or less, or 0.01 mm or more and 0.05 mm or less. The internal electrode (4) having such a thickness is likely to exhibit suitable flexibility and / or softness. The thickness of the internal electrode (4) may be greater than the thickness of the charge-holding ceramic part (3).

[0085] The internal electrode (4) may be a member that supports the charge-holding ceramic part (3). Thus, the internal electrode (4) makes it easier to increase the strength of the ceramic electret, and thus it becomes easier to increase the strength of the electret (1). Also, the internal electrode (4) may function as a shield. In such a case, the internal electrode (4) can be a shielding member.

[0086] In the structure (10) of the present disclosure, the internal electrode (4) includes a metal and / or a conductive filler, etc., and contributes to electrical connection with the outside. For example, after charging the charge-holding ceramic part (3) of the structure (10) of the present disclosure (after electretization), by grounding or connecting the internal electrode (4) to GND, a surface potential of either positive or negative can be provided at the charge-holding ceramic part (3) (preferably on the surface of the charge-holding ceramic part (3), more preferably over the entire surface thereof). In this way, the internal electrode (4) preferably prevents, for example, the two charge-holding ceramic parts (3) shown in FIG. 1 from canceling each other's charges, and a suitable flexoelectric effect (preferably a more prominent flexoelectric effect) can be brought about in the structure.

[0087] (Flexible member) In the present disclosure, the "flexible member" (2) means a member having at least flexibility. The flexible member (2) may be a member that can be polarized by the above electret part (1), particularly the charged charge-holding ceramic part (3).

[0088] The flexible member (2) preferably comprises a resin component. For example, the resin component may be the most abundant component among the components of the flexible member (2) (in such a case, the flexible member may also be particularly referred to as a "resin member" or a "flexible resin member", etc.). By including a resin component in the flexible member (2), it becomes easier to impart more suitable flexibility and chargeability to the structure.

[0089] The resin that can be included in the flexible member (2) may be a polymer material. If it is a polymer material, there is no particular limitation on the specific type of resin, and thermoplastic resins and / or thermosetting resins, etc., may be included in the flexible member of the structure. More specific resin components of the flexible member include, for example, phenol resins, epoxy resins, bismaleimide resins, vinyl chloride-based resins, urethane resins, nylon resins, ether resins, polyether resins, ketone resins, wholly aromatic polyester resins, polyamide resins, polyester resins, acrylic resins, polymethyl methacrylate resins, melamine resins, silicone resins, fluorine-based resins (such as polyvinylidene fluoride (PVDF), and / or polytetrafluoroethylene (PTFE)), etc.

[0090] The thickness of the flexible member (2) (the thickness dimension when viewed in cross-section) may be 10 mm or less, or 5 mm or less. For example, it may have a thickness of 0.05 mm or more and 10 mm or less, 0.05 mm or more and 8 mm or less, 0.1 mm or more and 5 mm or less, 0.5 mm or more and 5 mm or less, 0.5 mm or more and 4 mm or less, 0.5 mm or more and 3 mm or less, 0.5 mm or more and 2 mm or less. When the thickness of the flexible member (2) is within the above range, the flexible member (2) is more likely to deform following the electret portion (1), and more suitable flexibility and / or softness is more likely to be provided to the structure. In terms of the point that the flexibility and / or softness of the structure can be more manifested, the thickness of the flexible member (2) (the thickness of each layer forming the layer) is preferably larger than the thickness of the internal electrode (4). In addition, when the thickness of the flexible member (2) is within the above range, it becomes easier to provide a flexible member as a member having a relatively larger thickness than the electret portion (1), and the amount of deformation or displacement in the flexible member can be made larger than that in the electret portion (1). Therefore, a more suitable flexoelectric effect (for example, a larger flexoelectric effect) is more likely to be provided to the structure.

[0091] (Ceramic component) As described above, the electret of the structure of the present disclosure contains a ceramic component. In particular, the charge-holding ceramic portion provided in the ceramic electret of the structure contains a ceramic component. In the present disclosure, "ceramic component" means an inorganic compound component (oxide, carbide, and / or nitride) containing a metal element. For example, the ceramic component may correspond to a sintered body (inorganic solid material body) obtained by heat-treating an inorganic substance (preferably a paste of a composition containing an inorganic substance) as a raw material and sintering it.

[0092] There are no particular restrictions on the specific examples of the "ceramic component". For example, ceramics such as alumina (aluminum oxide), zirconia (zirconium oxide), tricalcium phosphate, and / or apatite can be mentioned. For example, the ceramic component of the ceramic electret may be a component that can be used as a ceramic-based biomaterial. In particular, apatite, which has biocompatibility as a biomaterial and also has high mechanical strength, fracture toughness, and excellent electronic properties, may be used in the structure of the present disclosure (especially its ceramic electret). In such a case, apatite can provide specificity in that it is used in fields such as electrets despite being a ceramic known as a biomaterial.

[0093] "Apatite" is a ceramic known as a calcium phosphate-based functional inorganic material, and typically has phosphorus (P) and calcium (Ca) as its main components. Apatite generally has high mechanical strength and fracture toughness, and is excellent in electronic properties, biocompatibility, ion exchangeability, surface adsorbability, optical properties, etc. In the structure (10) of the present disclosure, by using such a material in a ceramic electret, it becomes easier to impart high mechanical strength and fracture toughness to the electret portion (1), and it also becomes easier to impart electronic properties such as the manifestation and control of flexibility and / or charge retention ability.

[0094] "Apatite" is preferably at least one selected from the group consisting of fluoroapatite, chloroapatite, and hydroxyapatite. Among them, it is particularly preferable to use hydroxyapatite. Hydroxyapatite can provide specificity in that it is used in fields such as electrets despite being a ceramic known as a biomaterial. Hydroxyapatite can impart excellent electronic properties such as charge retention ability as well as high mechanical strength and fracture toughness to the structure of the present disclosure.

[0095] "Fluorapatite" (FAp) is not limited to specific types. For example, fluorapatite may be represented by the chemical formula: Ca5(PO4)3F without particular limitation. Fluorapatite, also called "fluorapatite" or "fluorapatite", may be used.

[0096] "Chlorapatite" (CAp) is not limited to specific types. For example, chlorapatite may be represented by the chemical formula: Ca5(PO4)3Cl without particular limitation. Chlorapatite, also called "chlorapatite" or "chlorapatite", may be used.

[0097] "Hydroxyapatite" (HAp) is not limited to specific types. For example, hydroxyapatite may be represented by the chemical formula: Ca5(PO4)3OH without particular limitation. Hydroxyapatite, also called "hydroxyapatite" or "hydroxyapatite", may be used.

[0098] In another aspect, in the present disclosure, the "ceramic component" is not particularly limited as long as it is a component (element) that can constitute a ceramic (ceramic crystal, particularly metal oxide). For example, at least one selected from the group consisting of lithium (Li), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), yttrium (Y), zirconium (Zr), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), boron (B), aluminum (Al), silicon (Si), indium (In), tin (Sn), antimony (Sb), barium (Ba), tantalum (Ta), tungsten (W), lead (Pb), bismuth (Bi), lanthanum (La), cesium (Ce), neodymium (Nd), samarium (Sm), gadolinium (Gd), dysprosium (Dy), holmium (Ho), erbium (Er), oxygen (O), carbon (C), nitrogen (N), sulfur (S), phosphorus (P), fluorine (F), and chlorine (Cl) may be included in the ceramic electret as a semi-ceramic component. Further, the ceramic component may be, for example, lead, zirconium, titanium, and oxygen, or titanium, barium, and oxygen, or bismuth, sodium, titanium, and oxygen, or zirconium and oxygen, or yttrium, zirconium, and oxygen.

[0099] A glass component may be included as a ceramic component of the ceramic electret. Examples of such glass components include at least one selected from the group consisting of soda-lime glass, potash glass, borate glass, borosilicate glass, barium borosilicate glass, zinc borate glass, barium borate glass, bismuth borosilicate salt glass, bismuth zinc borate glass, bismuth silicate glass, phosphate glass, aluminophosphate glass, and zinc phosphate glass.

[0100] In a ceramic electret, the ceramic component may include crystal grains or microcrystals. Among them, the components of the ceramic electret may be lead zirconate titanate (PZT), barium titanate (BaTiO3) (BT), bismuth sodium titanate ((Bi 1 / 2 Na 1 / 2 )TiO3) (BNT), zirconia, yttrium-stabilized zirconia, or glass, and crystal grains or microcrystals containing such components may be included in the ceramic electret.

[0101] In the present disclosure, the "charge-holding ceramic part" (3) is a part or member containing the above ceramic component. Therefore, the charge-holding ceramic part (3) may be composed of the above ceramic component, or may be a composite composed of the above ceramic component and other components such as resin. When the charge-holding ceramic part (3) includes a composite, it is easier to impart flexibility and / or softness to the charge-holding ceramic part (3), and thus the flexibility of the ceramic electret and the structure is more likely to be improved.

[0102] The term "composite" means two or more types of materials. For the "charge-holding ceramic part" (3), it means a material (composite material) in which at least the "ceramic component" and the "other component" are combined. The composite used for the charge-holding ceramic part (3) may be a mixture (or blend) simply mixing (or blending) two or more types of materials.

[0103] The "resin" provided as another component of the composite used in the charge-holding ceramic part (3) may be a polymer material. If it is a polymer material, there is no particular limitation on the specific type of resin, and thermoplastic resins and / or thermosetting resins, etc. may be included in the charge-holding ceramic part. For example, resin components such as phenolic resins, epoxy resins, bismaleimide resins, polypropylene resins, polyimide resins, polyamideimide resins, and / or acrylonitrile resins may be included in the charge-holding ceramic part. The ratio of the ceramic component to the resin in the composite included in the charge-holding ceramic part (ceramic component / resin) is, on a volume basis, within the range of, for example, 99 / 1 to 1 / 99, preferably 64 / 36 to 1 / 99, more preferably 30 / 70 to 1 / 99, and even more preferably 20 / 80 to 1 / 99.

[0104] (Effect) The electret part (1) provided as a ceramic electret containing a ceramic component is composed of a charge-holding ceramic part (3) and an internal electrode (4), and it is easier to improve (preferably significantly improve) the strength and / or charge density of the flexo-electret structure as compared with conventional polymer electrets.

[0105] In the structure of the present disclosure, a flexible member (2) is provided outside the electret portion (1). More preferably, the flexible member (2) is provided so as to sandwich or surround the electret portion (1). For example, the flexible member (2) may be provided at positions in contact with and facing each other with respect to the electret portion (1) (for example, as shown in FIG. 1, both the first flexible member and the second flexible member provided as two members may be provided so as to be in contact with the outer main surface of the electret portion (1) and face each other). Thus, the electret portion (1) in the present disclosure is easily positioned at the center of the flexo-electret structure (10). Therefore, the electret portion (1) can be a member that is relatively difficult to deform with respect to the flexible member (2), while the flexible member (2) is relatively easy to deform with respect to the electret portion (1). In other words, the electret portion (1) can have a relatively high Young's modulus (for example, apparent Young's modulus) with respect to the flexible member (2), while the flexible member (2) can have a relatively low Young's modulus (for example, apparent Young's modulus) with respect to the electret portion (1). When assuming that the structure is bent, it can be said that the flexible member (2) is more preferably displaced. Therefore, in the flexo-electret structure of the present disclosure, the flexible member (2) can be largely displaced (preferably selectively largely displaced), and a larger strain gradient is likely to be brought about in the flexible member (2). As a result, the structure of the present disclosure can exhibit a more suitable (preferably more remarkable) flexo-electric effect and can achieve a larger electromotive force (can achieve an increase in power generation amount, an increase in sensor sensitivity, etc.). Note that, although not bound by a specific theory, in a conventional polymer flexo-electret, the Young's modulus can be uniform, so it may be different from the manifestation of flexo-electricity as described above.

[0106] Furthermore, a conventional polymer electret had a drawback in that it lost its charge when exposed to high temperatures. Also, when water and / or an organic solvent adhered, they shielded the electric field, making it impossible to form an external electric field. In this regard, the flexo-electret structure (10) of the present disclosure includes an electret portion (1), particularly a charge-holding ceramic portion (3), and a flexible member (2) that covers the charge-holding ceramic portion (3). Thus, the flexible member (2) can preferably protect the charge-holding ceramic portion (3) from water and / or an organic solvent. In other words, the flexible member (2) can function as a protective layer. As a result, the structure (10) of the present disclosure can exhibit more suitable durability such as weather resistance (preferably durability such as improved weather resistance) compared to conventional polymer electrets, and thus can be used even in harsher high-temperature environments including the outdoors (for example, in a vehicle).

[0107] (Modification of the structure 10) As a modification of the structure according to the first embodiment, a structure 10' is shown in FIG. 2. The structure 10' can basically correspond to the structure 10 shown in FIG. 1.

[0108] The electret portion 1' that can be included in the structure 10' shown in FIG. 2 can correspond to the electret portion 1 of the structure 10 shown in FIG. 1. The modification in FIG. 2 corresponds to an aspect in which the components of the structure are composed of sub-members. For example, in the structure 10' in FIG. 2, the charge-holding ceramic portion is composed of a plurality of sub-members. Specifically, in the structure 10' shown in FIG. 2, the charge-holding ceramic portion 3 included in the electret portion 1 is at least composed of a first charge-holding ceramic layer 3a and a second charge-holding ceramic layer 3b, and an internal electrode 4 is positioned between the first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b in the same manner as in the structure 10 shown in FIG. 1. The first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b can each be configured in the same manner as the charge-holding ceramic layer 3 included in the electret portion 1 of the structure 10 shown in FIG. 1. The first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b may be made of the same material as each other. Alternatively, the first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b may be made of different materials from each other. In any case, since the internal electrode 4 is positioned between the first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b, in the first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b, particularly on their surfaces, either positive or negative charges can be charged, and a more suitable electric effect (preferably a more remarkable electric effect) can be brought about. For example, the surfaces of the first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b can both have charges of the same sign (+ or -), and at least in that respect, a more suitable electric effect (preferably a more remarkable electric effect) can be brought about. The thicknesses of the first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b may be the same as each other. Alternatively, the thicknesses of the first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b may be different from each other. Since the structure 10' includes the first charge-holding ceramic layer 3a and the second charge-holding ceramic layer 3b in the electret portion 1', the Young's modulus (for example, the apparent Young's modulus) at the central portion of the structure 10' tends to be high, and it is easy to bring about an improvement in the strength of the structure together with the flexible member.

[0109] In the structure 10' shown in FIG. 2, the flexible member 2 is also composed of a plurality of sub-members. More specifically, in the structure 10' shown in FIG. 2, the flexible member 2 is at least composed of a first flexible member 2a and a second flexible member 2b, and the electret portion 1' is positioned between the first flexible member 2a and the second flexible member 2b. The first flexible member 2a and the second flexible member 2b may be made of the same material as each other. Alternatively, the first flexible member 2a and the second flexible member 2b may be made of different materials from each other. In any case, the first flexible member 2a and the second flexible member 2b in FIG. 2 can be configured in the same manner as the flexible member 2 included in the structure 10 shown in FIG. 1. In the structure 10', the thicknesses of the first flexible member 2a and the second flexible member 2b may be the same as each other. Alternatively, the thicknesses of the first flexible member 2a and the second flexible member 2b may be different from each other.

[0110] In the structure 10' shown in FIG. 2, the first charge-holding ceramic layer 3a, the second charge-holding ceramic layer 3b, and the internal electrode 4 included in the electret portion 1', as well as the first flexible member 2a and the second flexible member 2b, may each have a plate-like or sheet-like shape. For example, each of these members may have a form such that they extend on the same plane. For example, the structure 10' may be provided as a laminate in which the first charge-holding ceramic layer 3a, the second charge-holding ceramic layer 3b, the internal electrode 4, the first flexible member 2a, and the second flexible member 2b are laminated on each other. The first charge-holding ceramic layer 3a, the second charge-holding ceramic layer 3b, the internal electrode 4, the first flexible member 2a, and the second flexible member 2b may have an elongated shape, for example, a strip shape (particularly a long and narrow strip shape). In such a shape, the structure 10' shown in FIG. 2 is likely to have a plate-like or sheet-like shape as a whole, and a more suitable electric effect (preferably a more prominent electric effect) is likely to be brought about due to a higher charge density.

[0111] (Second Embodiment) FIG. 3 shows a structure 20 according to the second embodiment. The structure 20 can basically correspond to the structure 10 shown in FIG. 1. The electret portion 21 included in the structure 20 shown in FIG. 3 can correspond to the electret portion 1 of the structure 10 shown in FIG. 1. The second embodiment corresponds to an aspect in which the components of the structure are composed of sub-members and the flexible member is made of a resin member.

[0112] In the structure 20, the charge-holding ceramic part 3 included in the electret part 1 of the structure 10 shown in FIG. 1 is composed of at least a first charge-holding ceramic layer 23a and a second charge-holding ceramic layer 23b, and an internal electrode 24 is positioned between the first charge-holding ceramic layer 23a and the second charge-holding ceramic layer 23b. With such a configuration, the Young's modulus (for example, the apparent Young's modulus) at the center of the structure 20 tends to be high, and it becomes easier to improve the strength of the structure together with the flexible member.

[0113] The first charge-holding ceramic layer 23a and the second charge-holding ceramic layer 23b can each be configured in the same manner as the charge-holding ceramic part 3 of the structure 10 shown in FIG. 1. In the structure 20 shown in FIG. 3, similar to the above-described structure, the first charge-holding ceramic layer 23a and the second charge-holding ceramic layer 23b may be made of the same material or different materials from each other. Similarly, the thicknesses of the first charge-holding ceramic layer 23a and the second charge-holding ceramic layer 23b may be the same or different.

[0114] The internal electrode 24 shown in FIG. 3 can also be configured in the same manner as the internal electrode 4 of the structure 10 shown in FIG. 1.

[0115] In the structure 20 shown in FIG. 3, the flexible member is composed of at least a first resin layer 22a and a second resin layer 22b, and an electret part 21 is positioned between the first resin layer 22a and the second resin layer 22b. Since the first resin layer 22a and the second resin layer 22b can have a relatively lower Young's modulus than the electret part 21, they are likely to be largely displaced (preferably selectively likely to be largely displaced), and a larger strain gradient can occur. Therefore, the electromotive force generated in the structure 20 is likely to be large.

[0116] The first resin layer 22a and the second resin layer 22b may each be a layer containing the above resin component. That is, each of the first resin layer 22a and the second resin layer 22b may be a member made of the above resin component.

[0117] In the structure 20 shown in FIG. 3, the first resin layer 22a and the second resin layer 22b may be made of the same material as each other. Alternatively, the first resin layer 22a and the second resin layer 22b may be made of different materials from each other. Also, the thicknesses of the first resin layer 22a and the second resin layer 22b may be the same as each other. Alternatively, the thicknesses of the first resin layer 22a and the second resin layer 22b may be different from each other.

[0118] In the structure 20 shown in FIG. 3, the first charge-holding ceramic layer 23a, the second charge-holding ceramic layer 23b, and the internal electrode 24 included in the electret portion 21, and the first resin layer 22a and the second resin layer 22b may each have a plate-like or sheet-like shape. For example, each of these members may have a form such that each extends on the same plane. For example, the structure 20 may be provided as a laminate in which the first charge-holding ceramic layer 23a, the second charge-holding ceramic layer 23b, the internal electrode 24, the first resin layer 22a, and the second resin layer 22b are laminated on each other. The first charge-holding ceramic layer 23a, the second charge-holding ceramic layer 23b, the internal electrode 24, the first resin layer 22a, and the second resin layer 22b may have an elongated shape, for example, a strip shape (particularly an elongated strip shape). By having such a shape, the structure 20 shown in FIG. 3 is likely to have a plate-like or sheet-like shape as a whole, and a more suitable electric effect (preferably a more remarkable electric effect) is likely to be brought about due to a higher charge density.

[0119] (Third Embodiment) FIG. 4 shows a structure 30 according to the third embodiment. The structure 30 can basically correspond to the structure 20 shown in FIG. 3. The electret portion 31 included in the structure 30 shown in FIG. 4 can correspond to the electret portion 21 of the structure 20 shown in FIG. 3. The third embodiment corresponds to an aspect in which the components of the structure are composed of sub-members, the flexible member is made of a resin member, and further, an external electrode is additionally provided.

[0120] The electret part 31 includes at least a first charge holding ceramic layer 33a and a second charge holding ceramic layer 33b, and an internal electrode 34 is positioned between the first charge holding ceramic layer 33a and the second charge holding ceramic layer 33b.

[0121] The first charge holding ceramic layer 33a and the second charge holding ceramic layer 33b can be configured in the same manner as the first charge holding ceramic layer 23a and the second charge holding ceramic layer 23b of the structure 20 shown in FIG. 3, respectively. In the structure 30 shown in FIG. 4, similar to the above-described structure, the first charge holding ceramic layer 33a and the second charge holding ceramic layer 33b may be made of the same material or different materials. Similarly, the thicknesses of the first charge holding ceramic layer 33a and the second charge holding ceramic layer 33b may be the same or different from each other.

[0122] The internal electrode 34 shown in FIG. 4 can be configured in the same manner as the internal electrode 24 of the structure 20 shown in FIG. 3.

[0123] The structure 30 shown in FIG. 4 includes a first resin layer 32a and a second resin layer 32b, and the electret part 31 is positioned between the first resin layer 32a and the second resin layer 32b.

[0124] The first resin layer 32a and the second resin layer 32b can be configured in the same manner as the first resin layer 22a and the second resin layer 22b of the structure 20 shown in FIG. 3, respectively. In the structure 30 shown in FIG. 4, the first resin layer 32a and the second resin layer 32b may be made of the same material or different materials. Also, the thicknesses of the first resin layer 32a and the second resin layer 32b may be the same or different from each other.

[0125] The structure 30 according to the third embodiment shown in FIG. 4 includes a first external electrode 5a on at least a part of the outer surface of the first resin layer 32a and a second external electrode 5b on at least a part of the outer surface of the second resin layer 32b.

[0126] The first external electrode 5a and the second external electrode 5b may each be an electrode for extracting the charges generated by the flexoelectric effect or measuring the generated potential in the structure 30.

[0127] The materials of the first external electrode 5a and the second external electrode 5b may include a conductive resin (for example, a volume resistivity of 10 14 [Ω·m] or less (resistivity under temperature and humidity conditions of 23 ± 5°C and relative humidity of 50 ± 20%)). The conductive resin may be a thermoplastic resin and / or a thermosetting resin, etc. Also, the materials of the first external electrode 5a and the second external electrode 5b may be a composite composed of a conductive filler and a resin. In such a case, the conductive filler may be a filler containing components such as carbon black, acetylene black, ketjen black, nanocarbon material, gold, silver, platinum, nickel, copper, zinc, aluminum, tin, manganese, stainless steel, tin oxide, indium oxide, zinc oxide, zinc nickel oxide, magnesium, tungsten, cobalt, chromium and / or titanium, etc. The resin may be, for example, a phenol resin, an epoxy resin, a bismaleimide resin, a vinyl chloride-based resin, a urethane resin, a nylon resin, an ether resin, a polyether resin, a ketone resin, a wholly aromatic polyester resin, a polyamide resin, a polyester resin, an acrylic resin, a polymethyl methacrylate resin, a melamine resin and / or a silicone resin, etc.). Also, conventionally known electrode materials may be used for the first external electrode 5a and the second external electrode 5b. For example, the first external electrode 5a and the second external electrode 5b may be formed from at least one metal element selected from the group consisting of gold (Au), silver (Ag), copper (Cu), iron (Fe), aluminum (Al), chromium (Cr), titanium (Ti), nickel (Ni), palladium (Pd) and platinum (Pt). Alternatively, the first external electrode 5a and the second external electrode 5b may be composed of a metal oxide film such as ITO.

[0128] There is no particular limitation on the shapes of the first external electrode 5a and the second external electrode 5b, and for example, they may be plate-shaped. Preferably, the first external electrode 5a and the second external electrode 5b have a thin film shape or a sheet shape.

[0129] The first external electrode 5a may be disposed on at least a part or the entire outer surface of the first resin layer 32a, and is preferably disposed at the geometric center of the outer surface of the first resin layer 32a. The second external electrode 5b may be disposed on at least a part or the entire outer surface of the second resin layer 32b, and is preferably disposed at the geometric center of the outer surface of the second resin layer 32b.

[0130] The thicknesses of the first external electrode 5a and the second external electrode 5b are, for example, 1 nm or more and 0.01 mm or less, respectively. When the thickness is within the above range, while ensuring the flexibility of the structure, it becomes easier to extract charges successfully. The thicknesses of the first external electrode 5a and the second external electrode 5b may be smaller than the thicknesses of the first resin layer 32a and the second resin layer 32b. In a certain preferred embodiment, the thicknesses of the first external electrode 5a and the second external electrode 5b are smaller than the respective thicknesses of any one, any two, any three, any four, or all of the first charge holding ceramic layer 33a, the second charge holding ceramic layer 33b, the internal electrode 34, the first resin layer 32a, and the second resin layer 32b.

[0131] In the structure 30 shown in FIG. 4, the first charge-holding ceramic layer 33a, the second charge-holding ceramic layer 33b, and the internal electrode 34 included in the electret portion 31, as well as the first resin layer 32a, the second resin layer 32b, the first external electrode 5a, and the second external electrode 5b preferably each have a plate-like or sheet-like shape. For example, these members may each have a form that extends on the same plane. The structure 30 may be provided as a laminate in which the first charge-holding ceramic layer 33a, the second charge-holding ceramic layer 33b, the internal electrode 34, the first resin layer 32a, the second resin layer 32b, the first external electrode 5a, and the second external electrode 5b are laminated on one another. The first charge-holding ceramic layer 33a, the second charge-holding ceramic layer 33b, the internal electrode 34, the first resin layer 32a, the second resin layer 32b, the first external electrode 5a, and the second external electrode 5b may have an elongated shape, for example, a strip shape (particularly an elongated strip shape). By having such a shape, the structure 30 shown in FIG. 4 is more likely to have a plate-like or sheet-like shape as a whole, and a more suitable electric effect (preferably a more prominent electric effect) is more likely to be brought about due to a higher charge density.

[0132] (Fourth Embodiment) FIG. 5 shows a structure 40 according to the fourth embodiment. The structure 40 can basically correspond to the structure 30 shown in FIG. 4. The electret portion 41 included in the structure 40 shown in FIG. 5 can correspond to the electret portion 31 of the structure 30 shown in FIG. 4. The fourth embodiment corresponds to an aspect particularly provided with a polarization electrode as an auxiliary electrode.

[0133] The electret portion 41 includes at least a first charge-holding ceramic layer 43a and a second charge-holding ceramic layer 43b, and an internal electrode 44 is positioned between the first charge-holding ceramic layer 43a and the second charge-holding ceramic layer 43b.

[0134] The first charge-holding ceramic layer 43a and the second charge-holding ceramic layer 43b can each be configured in the same manner as the first charge-holding ceramic layer 33a and the second charge-holding ceramic layer 33b of the structure 30 shown in FIG. 4. In the structure 40 shown in FIG. 5, similar to the above-described structure, the first charge-holding ceramic layer 43a and the second charge-holding ceramic layer 43b may be made of the same material as each other or may be different. Similarly, the thicknesses of the first charge-holding ceramic layer 43a and the second charge-holding ceramic layer 43b may be the same as each other or may be different.

[0135] The internal electrode 44 shown in FIG. 5 can be configured in the same manner as the internal electrode 34 of the structure 30 shown in FIG. 4.

[0136] The structure 40 includes a first resin layer 42a and a second resin layer 42b, and an electret portion 41 is positioned between the first resin layer 42a and the second resin layer 42b via a first polarization electrode 6a and a second polarization electrode 6b, which will be described in detail below.

[0137] The first resin layer 42a and the second resin layer 42b can each be configured in the same manner as the first resin layer 32a and the second resin layer 32b of the structure 30 shown in FIG. 4. In the structure 40 shown in FIG. 5, the first resin layer 42a and the second resin layer 42b may be made of the same material as each other or may be made of different materials. Also, the thicknesses of the first resin layer 42a and the second resin layer 42b may be the same as each other or may be different.

[0138] The structure 40 shown in FIG. 5 includes a first external electrode 45a on at least a part of the outer surface of the first resin layer 42a and a second external electrode 45b on at least a part of the outer surface of the second resin layer 42b. The first external electrode 45a and the second external electrode 45b can be configured in the same manner as the first external electrode 5a and the second external electrode 5b of the structure 30 shown in FIG. 4, respectively. In the structure 40 shown in FIG. 5, the first external electrode 45a and the second external electrode 45b may be made of the same material or different materials from each other. Also, the thicknesses of the first external electrode 45a and the second external electrode 45b may be the same or different from each other.

[0139] The structure 40 shown in FIG. 5 includes a polarization electrode. Specifically, it further includes a polarization electrode between the resin layer and the electret portion. In the structure 40 shown in FIG. 5, a first polarization electrode 6a is provided between the first resin layer 42a and the electret portion 41 (more specifically, between the first resin layer 42a and the first charge-holding ceramic layer 43a), and a second polarization electrode 6b is provided between the second resin layer 42b and the electret portion 41 (more specifically, between the second resin layer 42b and the second charge-holding ceramic layer 43b).

[0140] The first polarization electrode 6a and the second polarization electrode 6b may be electrodes for dielectric polarization or electric polarization of the first charge-holding ceramic layer 43a and the second charge-holding ceramic layer 43b in the structure 40, respectively. By adding such first and second polarization electrodes 6a and 6b, it becomes easier to dielectrically polarize or electrically polarize the first charge-holding ceramic layer 43a and the second charge-holding ceramic layer 43b after the manufacture of the structure 40.

[0141] The materials of the first polarization electrode 6a and the second polarization electrode 6b include conductive resin (for example, volume resistivity 10 14It may include resistivity below [[Ω·m]] (at temperature of 23 ± 5°C and relative humidity of 50 ± 20%). The conductive resin may be a thermoplastic resin and / or a thermosetting resin. Also, the materials of the first polarization electrode 6a and the second polarization electrode 6b may be a composite composed of a conductive filler and a resin. In such a case, the conductive filler may be a filler containing components such as carbon black, acetylene black, ketjen black, nanocarbon material, gold, silver, platinum, nickel, copper, zinc, aluminum, tin, manganese, stainless steel, tin oxide, indium oxide, zinc oxide, zinc nickel oxide, magnesium, tungsten, cobalt, chromium and / or titanium. The resin may be, for example, a phenolic resin, an epoxy resin, a bismaleimide resin, a vinyl chloride resin, a urethane resin, a nylon resin, an ether resin, a polyether resin, a ketone resin, an all-aromatic polyester resin, a polyamide resin, a polyester resin, an acrylic resin, a polymethyl methacrylate resin, a melamine resin and / or a silicone resin, etc.). Also, conventionally known electrode materials may be used for the first polarization electrode 6a and the second polarization electrode 6b. For example, the first polarization electrode 6a and the second polarization electrode 6b may be formed of at least one metal element selected from the group consisting of gold (Au), silver (Ag), copper (Cu), iron (Fe), aluminum (Al), chromium (Cr), titanium (Ti), nickel (Ni), palladium (Pd) and platinum (Pt). Alternatively, the first polarization electrode 6a and the second polarization electrode 6b may be a metal oxide film such as ITO.

[0142] There is no particular limitation on the shapes of the first polarization electrode 6a and the second polarization electrode 6b, but they may be plate-shaped. Preferably, the first polarization electrode 6a and the second polarization electrode 6b have a thin film or sheet shape.

[0143] The first polarization electrode 6a may be disposed on at least a part or the entire surface of the first charge holding ceramic layer 43a. The electrode 6b for the second polarization may be disposed on at least a part or the entire surface of the second charge holding ceramic layer 43b.

[0144] The thicknesses of the electrode 6a for the first polarization and the electrode 6b for the second polarization are, for example, each 1 nm or more and 0.01 mm or less. When the thickness is within the above range, while imparting flexibility to the structure, it becomes easier to successfully cause dielectric polarization or electric polarization in the charge holding ceramic layer 43a and the second charge holding ceramic layer 43b.

[0145] In the structure 40 shown in FIG. 5, the first charge holding ceramic layer 43a, the second charge holding ceramic layer 43b, and the internal electrode 44 included in the electret portion 41, and the first resin layer 42a, the second resin layer 42b, the first external electrode 45a, the second external electrode 45b, the electrode 6a for the first polarization, and the electrode 6a for the second polarization may each have a plate-like or sheet-like shape. For example, each of these members may have a form such that they extend on the same plane. The structure 40 may be provided as a laminate in which the first charge holding ceramic layer 43a, the second charge holding ceramic layer 43b, the internal electrode 44, the first resin layer 42a, the second resin layer 42b, the first external electrode 45a, the second external electrode 45b, the electrode 6a for the first polarization, and the electrode 6a for the second polarization are laminated on one another. The first charge holding ceramic layer 43a, the second charge holding ceramic layer 43b, the internal electrode 44, the first resin layer 42a, the second resin layer 42b, the first external electrode 45a, the second external electrode 45b, the electrode 6a for the first polarization, and the electrode 6a for the second polarization may have an elongated shape, for example, a strip shape (particularly an elongated strip shape). By having such a shape, the structure 40 shown in FIG. 5 is likely to have a plate-like or sheet-like shape as a whole, and a more suitable electric effect (preferably a more remarkable electric effect) is likely to be brought about due to a higher charge density.

[0146] (Fifth Embodiment) FIG. 6 shows a structure 50 according to the fifth embodiment. The structure 50 can basically correspond to the structure 20 shown in FIG. 3. The electret part 51 that can be included in the structure 50 shown in FIG. 6 can correspond to the electret part 21 of the structure 20 shown in FIG. 3.

[0147] The electret part 51 includes at least a first charge-holding ceramic layer 53a and a second charge-holding ceramic layer 53b, and an internal electrode 54 is positioned between the first charge-holding ceramic layer 53a and the second charge-holding ceramic layer 53b. The first charge-holding ceramic layer 53a and the second charge-holding ceramic layer 53b can be configured in the same manner as the first charge-holding ceramic layer 23a and the second charge-holding ceramic layer 23b of the structure 20 shown in FIG. 3, respectively. In the structure 50 shown in FIG. 6, the materials of the first charge-holding ceramic layer 53a and the second charge-holding ceramic layer 53b may be the same as each other or different from each other. Also, the thicknesses of the first charge-holding ceramic layer 53a and the second charge-holding ceramic layer 53b may be the same or different.

[0148] In the fifth embodiment, the electret part is provided inside a flexible member. In the structure 50 shown in FIG. 6, the electret part 51 is positioned inside a resin member or a resin layer 52. In other words, a flexible member is provided so as to surround the electret part. Note that a part of the electret part 51 may not be covered with the resin member or the resin layer 52, and a part thereof may be exposed.

[0149] The resin member or the resin layer 52 may include the above resin component. That is, the resin layer 52 may be a surrounding member made of the above resin component.

[0150] The thickness of the resin member or resin layer 52 is, for example, 0.03 mm or more and 10 mm or less. The resin member or resin layer 52 may or may not be uniform. When the thickness of the resin member or resin layer 52 is within the above range, a more suitable electric effect (preferably a more remarkable electric effect) is likely to be brought to the structure 50.

[0151] In the structure 50 shown in FIG. 6, similar to the form shown in FIG. 5, an external electrode may be provided on at least a part of the outer surface of the resin layer 52 (see the external electrodes 45a and 45b shown in FIG. 5). A polarization electrode may be provided between the resin layer 52 and the electret portion 51, specifically, between the resin layer 52 and the charge holding ceramic layers (53a, 53b) (see the polarization electrodes 6a and 6b shown in FIG. 5).

[0152] (Sixth Embodiment) FIG. 7 shows a structure 60 according to the sixth embodiment. The structure 60 can basically correspond to the structure 50 shown in FIG. 6, but has a plurality of electret portions 61 instead of the electret portion 51 of the structure 50. By providing a plurality of electret portions 61, it becomes easier to further improve the flexibility of the structure 60. Therefore, the structure 60 according to the sixth embodiment is more likely to correspond to various deformation modes, and a more suitable electric effect (preferably a more remarkable electric effect) is likely to be brought about. There is no particular limitation on the number of the plurality of electret portions 61. Also, the plurality of electret portions 61 may be the same as or different from each other.

[0153] The electret portion 61 includes at least a first charge holding ceramic layer 63a and a second charge holding ceramic layer 63b, and an internal electrode 64 is positioned between the first charge holding ceramic layer 63a and the second charge holding ceramic layer 63b. The first charge holding ceramic layer 63a and the second charge holding ceramic layer 63b can be configured in the same manner as the first charge holding ceramic layer 53a and the second charge holding ceramic layer 53b of the structure 50 shown in FIG. 6, respectively.

[0154] The internal electrode 64 shown in FIG. 7 can be formed using the same material as the internal electrode 54 shown in FIG. 6. The resin member or resin layer 62 shown in FIG. 7 may contain the above resin components. That is, the resin layer 62 may be an enclosure member made of the above resin components. In the structure 60 shown in FIG. 7, similar to the form shown in FIG. 5, an external electrode may be provided on at least a part of the outer surface of the resin layer 62 (see the external electrodes 45a and 45b shown in FIG. 5). A polarization electrode may be provided between the resin layer 62 and the electret part 61 shown in FIG. 7, specifically, between the resin layer 62 and the charge holding ceramic layers (63a, 63b) (see the polarization electrodes 6a and 6b shown in FIG. 5).

[0155] (Seventh Embodiment) FIG. 8 shows a structure 70 according to the seventh embodiment. The structure 70 can basically correspond to the structure 10 shown in FIG. 1, where the shape of the electret part 1 of the structure 10 in FIG. 1 is changed to a fiber shape (preferably an elongated shape having a round cross-sectional contour or a curved cross-sectional contour), and includes a plurality of electret parts 71. There is no particular limitation on the number of electret parts 71 (hereinafter, the electret part 71 may also be referred to as an electret fiber 71).

[0156] The electret part 71 includes a charge holding ceramic part 73 and an internal electrode 74 located inside the charge holding ceramic part 73. The charge holding ceramic part 73 and the internal electrode 74 are preferably arranged concentrically with each other (for example, arranged concentrically with each other in a cross-sectional view as shown). The electret part 71 may have a fiber shape in which the charge holding ceramic part 73 has a cylindrical shape as a sheath part and the internal electrode 74 is provided as a core part. The internal electrode 74 may be, for example, a metal wire containing the above metal element.

[0157] The charge-holding ceramic part 73 can be formed using the same material as the charge-holding ceramic part 3 shown in FIG. 1. The internal electrode 74 shown in FIG. 8 can be formed using the same material as the internal electrode 4 shown in FIG. 1. There is no particular limitation on the cross-sectional area ratio (internal electrode / charge-holding ceramic part) between the internal electrode 74 and the charge-holding ceramic part 73, and it is, for example, 1 / 99 to 99 / 1, preferably 1 / 8 to 8 / 1.

[0158] A plurality of electret fibers 71 may be arranged parallel to each other. As flexible members, a first flexible member 72a and a second flexible member 72b may be arranged so as to sandwich such electret fibers 71 from above and below. The first flexible member 72a and the second flexible member 72b can each be configured in the same manner as the flexible member 2 shown in FIG. 1.

[0159] Between the first flexible member 72a and the second flexible member 72b, the portion where the electret fibers 71 do not exist may be a cavity (i.e., a hollow portion). A third flexible member 75 may be arranged between the first flexible member 72a and the second flexible member 72b. The third flexible member 75 may be configured in the same manner from the same material as the flexible member 2 shown in FIG. 1.

[0160] The materials constituting the first flexible member 72a, the second flexible member 72b, and the third flexible member 75 may be the same as or different from each other. When more importance is attached to uniformly polarizing and holding charges, the first flexible member 72a, the second flexible member 72b, and the third flexible member 75 may be formed from the same material as each other. The first flexible member 72a, the second flexible member 72b, and the third flexible member 75 may all be resin members.

[0161] In the structure 70 shown in FIG. 8, similar to the form shown in FIG. 5, at least a part of the outer surface of the first flexible member 72a may be provided with a first external electrode (see the first external electrode 45a shown in FIG. 5), and at least a part of the outer surface of the second flexible member 72b may be provided with a second external electrode (see the second external electrode 45b shown in FIG. 5). Further, a polarization electrode may be provided between the first flexible member 72a and the electret portion 71, more specifically, between the first flexible member 72a and the charge holding ceramic portion 73. Similarly, a polarization electrode may be provided between the second flexible member 72b and the electret portion 71, more specifically, between the second flexible member 72b and the charge holding ceramic portion 73.

[0162] The polarization electrode may be, for example, in a cylindrical shape and arranged in a sleeve shape outside the electret portion 71, more specifically, on the outer periphery of the charge holding ceramic portion 73, and may be arranged concentrically with the internal electrode 74.

[0163] The thickness of the polarization electrode is, for example, 1 nm or more and 0.01 mm or less. When the thickness is within the above range, while imparting flexibility to the structure, it becomes easier to successfully cause dielectric polarization or electric polarization in the charge holding ceramic portion 73.

[0164] Since the structure 70 includes a plurality of electret portions (electret fibers) 71 having a fiber-like shape, the strength of the structure 70 is ensured and the flexibility of the structure 70 is more easily improved, and a more suitable electric effect (preferably a more remarkable electric effect) is more likely to be brought about.

[0165] The radius of curvature when the electret fiber 71 is bent alone is, for example, about 1000 mm or less. Also, the tensile strength (breaking elongation load) of the electret fiber 71 is, for example, about 5 kgf / mm 2 or more.

[0166] As described above, the electret structure of the present disclosure has been illustrated from the first embodiment to the seventh embodiment. However, each configuration may be appropriately combined and used as necessary.

[0167] (Manufacturing method) There is no particular limitation on the manufacturing method of the flexoelectret structure of the present disclosure. For example, a ceramic electret (for example, the electret portion 1 shown in FIG. 1) including a charge-holding ceramic portion and an internal electrode located inside thereof may be integrally formed using techniques such as firing. Preferably, both flexibility and strength may be enhanced by simultaneously producing the charge-holding ceramic portion and the internal electrode by co-sintering. The internal electrode, the external electrode, the polarization electrode, and the like may also be integrally formed using techniques such as firing. Alternatively, the internal electrode, the external electrode, the polarization electrode, and the like may be formed using techniques such as lamination, coating, plating, vapor deposition, and / or sputtering. Further, the charge-holding ceramic portion may be formed using techniques such as lamination, coating, vapor deposition, and / or sputtering. The flexible member can be formed outside the electret portion using techniques such as resin coating and / or resin molding, for example.

[0168] (Regarding the flexoelectric coefficient) As described above, the flexoelectric coefficient of the structure of the present disclosure is preferably larger than 1.3×10 -8 C / m. The "flexoelectric coefficient" in the present disclosure is calculated based on Equation (III). TIFF0007704200000009.tif217170

Example

[0169] (Example 1) The flexoelectret structure 10 shown in FIG. 1 was fabricated by the following procedure. (A) Formation of the electret portion An electret part 1 (thickness: 180 μm) formed by sandwiching an internal electrode 4 (thickness: 30 μm) made of aluminum foil between two charge-holding ceramic parts 3 (thickness: 75 μm) made of ceramic (hydroxyapatite (HAp) as a typical ceramic in this example) was prepared. (B) Formation of flexible member After charging the surface of the charge-holding ceramic part 3 (HAp) of the electret part 1 negatively, a flexible member 2 (thickness: 1000 μm) made of resin (PET as a typical resin in this example) was formed on the upper side of the charge-holding ceramic part 3 (HAp), and a flexo-electret structure 10 in the form shown in FIG. 1 was fabricated (total thickness: 2180 μm). In the same manner as the external electrodes 5a and 5b shown in FIG. 4, electrodes for measurement (Cu foil electrodes in this example) were arranged on the surface of the flexible member 2, and the electromotive force of the flexo-electret structure 10 was measured. The results are shown in FIG. 12.

[0170] The flexoelectric coefficient of the flexo-electret structure 10 was 6×10 -8 C / m. Also, the radius of curvature of the flexo-electret structure 10 and the electret part 1 was 1000 mm.

[0171] Although the embodiments of the present invention have been described above, they are merely illustrative of typical examples. Therefore, it will be easily understood by those skilled in the art that the present invention is not limited thereto, and various aspects can be considered without changing the gist of the present invention.

Industrial Applicability

[0172] Although there is no particular limitation, the flexo-electret structure of the present disclosure can be used for sensors such as flexible sensors. The flexo-electret structure of the present disclosure can also be used, for example, in a field environment or in a high-temperature environment. In particular, the flexo-electret structure of the present disclosure can be used in vehicles and the like. In addition, the flexoelectret structure of the present disclosure can also be used in fields such as energy capture, artificial skin, and self-powered devices.

Explanation of Reference Numerals

[0173] 1, 21, 31, 41, 51, 61, 71 electret part 2 flexible member 2a, 72a first flexible member 2b, 72b second flexible member 3, 73 charge-holding ceramic part 3a, 23a, 33a, 43a, 53a, 63a first charge-holding ceramic layer 3b, 23b, 33b, 43b, 53b, 63b second charge-holding ceramic layer 4, 24, 34, 44, 54, 64, 74 internal electrode 5 external electrode 5a, 45a first external electrode 5b, 45b second external electrode 6 polarization electrode 6a first polarization electrode 6b second polarization electrode 10, 20, 30, 40, 50, 60, 70 structure 22, 32, 42, 52, 62 resin layer 22a, 32a, 42a first resin layer 22b, 32b, 42b second resin layer 75 third flexible member 100 flexoelectret 200 polymer flexoelectret 201 charged polymer thin film 202 polymer thin film

Claims

1. A structure having an electret part, wherein the structure has a flexible member outside the electret part, the electret part is a ceramic electret containing a ceramic component, and includes a charge-holding ceramic part and an internal electrode located inside the charge-holding ceramic part, the electret part has flexibility, and the structure is a flexoelectret.

2. The structure according to claim 1, wherein the flexible member is provided so as to sandwich or surround the electret part.

3. The structure according to claim 1 or 2, wherein the thickness of the ceramic electret located inside the flexible member is smaller than the thickness of the flexible member.

4. The structure according to any one of claims 1 to 3, wherein the charge-holding ceramic part is composed of at least a first charge-holding ceramic layer and a second charge-holding ceramic layer, and the internal electrode is positioned between the first charge-holding ceramic layer and the second charge-holding ceramic layer.

5. The structure according to any one of claims 1 to 4, wherein the charge-holding ceramic part is a composite containing a ceramic component and a resin.

6. The structure according to any one of claims 1 to 5, wherein the flexible member contains a resin component.

7. The structure according to any one of claims 1 to 6, wherein the flexible member is composed of at least a first resin layer and a second resin layer, and the electret part is positioned between the first resin layer and the second resin layer.

8. The structure according to claim 7, comprising a first external electrode on at least a part of the outer surface of the first resin layer and a second external electrode on at least a part of the outer surface of the second resin layer.

9. The structure according to claim 7 or 8, comprising a first polarization electrode between the first resin layer and the electret part and a second polarization electrode between the second resin layer and the electret part.

10. The flexoelectric coefficient of the structure is greater than 1.3×10 －８ C / m, and the structure according to any one of claims 1 to 9.

11. The structure according to any one of claims 1 to 10, wherein when the structure receives an external force and the electret part is displaced, the electret part has a radius of curvature of 1000 mm or less in cross-sectional view.

Images