piezoelectric element

Abstract

Provided is a piezoelectric element capable of being reliably electrically connected to an electrode layer. A piezoelectric element having a piezoelectric layer, electrode layers formed on both surfaces of the piezoelectric layer, and a protective layer laminated on a surface opposite to a surface on the side of a polymer composite piezoelectric body of the electrode layer, wherein the protective layer has a hole portion that penetrates from the surface to the electrode layer, the piezoelectric element having: a filling member composed of an electrically conductive material formed from the hole portion to a part of the surface of the protective layer and electrically connected to the electrode layer; an electrically conductive member covering at least a part of the filling member and electrically connected to the filling member; and a fixing member for fixing the electrically conductive member.

Description

Technical Field

[0001] This invention relates to a piezoelectric element. Background Technology

[0002] As displays such as liquid crystal displays (LCDs) and organic EL displays become increasingly thinner, there is a growing demand for lightweight and slimmer speakers used in these displays. Furthermore, in flexible displays, flexibility is also required to ensure integration with the flexible display without compromising lightweightness and flexibility. As such lightweight, thin, and flexible speakers, sheet-like piezoelectric elements (electroacoustic conversion films) with the property of expanding and contracting in response to applied voltage can be considered.

[0003] As a flexible sheet-like piezoelectric element, a piezoelectric element with an electrode layer and a protective layer on both surfaces of the piezoelectric layer has been proposed.

[0004] For example, Patent Document 1 describes an electroacoustic conversion film comprising a dielectric layer, thin film electrodes formed on two surfaces of the dielectric layer (piezoelectric layer), and a protective layer formed on the surfaces of the thin film electrodes. Furthermore, at least one of the protective layers has a thin layer portion that is thinner than the film thickness of the peripheral portion.

[0005] In this type of electroacoustic conversion film, in order to vibrate the electroacoustic conversion film by applying a voltage to the electrode layer, the thickness of the electrode layer needs to be very thin. For example, the electrode layer is suitable for vapor-deposited films with a thickness of less than 1 μm.

[0006] On the other hand, in order to actually install the electroacoustic conversion film as a speaker, it is necessary to bring out the electrode layer and connect the wiring there.

[0007] However, thin electrode layers, such as vapor-deposited films, are difficult to extend outwards from the electroacoustic conversion film. Furthermore, if such thin electrodes are exposed to the outside and stored in this state in order to connect them to wiring, the electrodes will oxidize depending on the storage environment, resulting in reduced conductivity.

[0008] In contrast, it is proposed to provide a hole in the protective layer, insert conductive material into the hole, and connect a lead to the conductive material.

[0009] For example, Patent Document 1 describes a structure in which a recess is provided in a protective layer, a conductive material is inserted into the recess, and a lead for electrically connecting an electrode layer and an external device is connected to the conductive material. Therefore, a reliable electrical connection between the electrode layer and the lead can be achieved, and since the entire surface of the electrode layer is covered by the protective layer, deterioration of the electrode layer caused by oxidation or the like can be prevented.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2016-015354 Summary of the Invention

[0013] The technical problem to be solved by the invention

[0014] However, according to the research of the inventors, when a liquid conductive material is coated onto the pores of the protective layer, the coating thickness may vary due to the viscosity of the coating liquid, making it difficult to ensure conductivity. Furthermore, since the protective layer is, for example, as thin as about 4 μm, the pore depth of the pores formed on the protective layer is also about 4 μm. Considering factors such as warping of the electroacoustic conversion film, it is difficult to reliably coat the pores with the coating liquid. Therefore, reliable electrical connection to the electrode layer may be difficult.

[0015] Furthermore, since silver paste used as a conductive material is expensive, it is desirable to reduce its usage, and it is difficult to reliably ensure the presence of conductive material within the hole by increasing the amount of conductive material used.

[0016] The objective of this invention is to address the problems of this prior art and to provide a piezoelectric element that can be reliably electrically connected to the electrode layer.

[0017] means for solving technical problems

[0018] To solve the above problems, the present invention has the following structure.

[0019] [1] A piezoelectric element comprising a piezoelectric layer, electrode layers formed on two surfaces of the piezoelectric layer, and a protective layer stacked on a surface of the electrode layers opposite to the piezoelectric layer side, wherein,

[0020] The protective layer has a hole extending from the surface to the electrode layer, and the piezoelectric element has:

[0021] The filling component is made of a conductive material that extends from inside the hole to a portion of the surface of the protective layer and is electrically connected to the electrode layer;

[0022] A conductive component that covers at least a portion of the filling component and is electrically connected to the filling component; and

[0023] Fixing components are used to fix conductive components.

[0024] [2] According to the piezoelectric element described in [1], the conductive component is a conductive sheet.

[0025] [3] According to the piezoelectric element of [1], the conductive component has a conductor connected to the filling component and a conductive wire or conductive sheet connected to the conductor.

[0026] [4] The piezoelectric element according to any one of [1] to [3], wherein the fixing member fixes the conductive member to the protective layer.

[0027] [5] The piezoelectric element according to any one of [1] to [4] has a protrusion formed at the edge of the hole in the protective layer.

[0028] [6] The piezoelectric element according to any one of [1] to [5], wherein the equivalent circle diameter of the hole varies in stages in the depth direction, and the equivalent circle diameter on the electrode layer side is smaller than the equivalent circle diameter on the conductive component side.

[0029] [7] The piezoelectric element according to any one of [1] to [6], wherein the amount of carbon on the surface of the electrode layer located in the hole is less in the central part in the planar direction than in the area other than the central part.

[0030] [8] The piezoelectric element according to any one of [1] to [7], wherein the amount of carbon on the surface of the electrode layer located in the hole is greater in the central part in the planar direction than in the area other than the central part.

[0031] [9] The piezoelectric element according to any one of [1] to [8], wherein the opening shape of the orifice is circular.

[0032]

[10] The piezoelectric element according to any one of [1] to [9], wherein the protective layer has a plurality of holes,

[0033] The piezoelectric element has multiple filling components formed in multiple orifices.

[0034]

[11] According to the piezoelectric element of

[10] , a plurality of filling components are connected on the surface of the protective layer.

[0035]

[12] The piezoelectric element according to any one of [1] to

[11] , wherein a surrounding member is provided on the surface of the protective layer to surround the hole.

[0036] The filling component is formed at least within the surrounding component.

[0037]

[13] The piezoelectric element according to any one of [1] to

[12] has a recess formed around the hole in the protective layer.

[0038]

[14] The piezoelectric element according to any one of [1] to

[13] , wherein the thickness of the protective layer is 3 μm to 100 μm.

[0039]

[15] The piezoelectric element according to any one of [1] to

[14] , wherein the thickness of the electrode layer is 0.05 μm to 10 μm.

[0040]

[16] The piezoelectric element according to any one of [1] to

[15] , wherein a gap is provided at the location of the hole and between the electrode layer and the piezoelectric layer.

[0041] The difference between the average height of the interface between the piezoelectric layer and the electrode layer in the location where no aperture is formed and the average height of the interface between the piezoelectric layer and the electrode layer in the location where an aperture is formed is less than 25 μm.

[0042]

[17] The piezoelectric element according to any one of [1] to

[16] , wherein the conductive component is strip-shaped.

[0043] The conductive component has a folded-back portion that folds back along its length.

[0044] The fixing component secures the conductive component and the protective layer in the area opposite to the connection position between the conductive component and the filling component, separated by the folded-back portion.

[0045]

[18] The piezoelectric element according to any one of [1] to

[17] , wherein the conductive component is elongated.

[0046] The conductive component is connected to the filling component at one end along its length.

[0047] The fixing component is positioned along the length of the conductive component at a location further away from one end than the connection point between the conductive component and the filling component.

[0048]

[19] The piezoelectric element according to

[18] has a second fixing member that fixes at least a portion of the edge of the region between one end of the conductive element and the fixing member to the protective layer.

[0049]

[20] A piezoelectric element according to any one of [1] to

[19] , wherein the piezoelectric layer is composed of a polymer composite piezoelectric body, the polymer composite piezoelectric body containing piezoelectric particles in a matrix comprising polymeric material.

[0050] Invention Effects

[0051] According to the present invention, a piezoelectric element capable of reliably being electrically connected to an electrode layer is provided. Attached Figure Description

[0052] Figure 1 This is a cross-sectional view schematically illustrating an example of the piezoelectric element of the present invention.

[0053] Figure 2 yes Figure 1 A top view of a piezoelectric element.

[0054] Figure 3 It is an enlarged representation Figure 1A cross-sectional view of a portion of the piezoelectric layer.

[0055] Figure 4 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0056] Figure 5 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0057] Figure 6 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0058] Figure 7 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0059] Figure 8 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0060] Figure 9 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0061] Figure 10 It is a conceptual diagram used to illustrate the average height of the interface.

[0062] Figure 11 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0063] Figure 12 This is a partial enlarged top view of another example of the piezoelectric element of the present invention.

[0064] Figure 13 This is a partial enlarged top view of another example of the piezoelectric element of the present invention.

[0065] Figure 14 This is a conceptual diagram illustrating an example of how a piezoelectric element is manufactured.

[0066] Figure 15 This is a conceptual diagram illustrating an example of how a piezoelectric element is manufactured.

[0067] Figure 16 This is a conceptual diagram illustrating an example of how a piezoelectric element is manufactured.

[0068] Figure 17 This is a conceptual diagram illustrating an example of how a piezoelectric element is manufactured.

[0069] Figure 18 This is a conceptual diagram illustrating an example of how a piezoelectric element is manufactured.

[0070] Figure 19 This is a conceptual diagram illustrating an example of how a piezoelectric element is manufactured.

[0071] Figure 20 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0072] Figure 21 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0073] Figure 22 This is a schematic diagram of an example of an article comprising the piezoelectric element of the present invention.

[0074] Figure 23 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0075] Figure 24 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0076] Figure 25 yes Figure 24 Top view.

[0077] Figure 26 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention.

[0078] Figure 27 This is a partially enlarged cross-sectional view of another example of the piezoelectric element of the present invention. Detailed Implementation

[0079] Hereinafter, the piezoelectric element of the present invention will be described in detail based on the preferred embodiment shown in the accompanying drawings.

[0080] The following description of the constituent elements is sometimes based on representative embodiments of the present invention, but the present invention is not limited to these embodiments.

[0081] In addition, in this specification, the numerical range represented by “~” refers to the range including the values ​​recorded before and after “~” as the lower limit and upper limit.

[0082] [Piezoelectric element]

[0083] The piezoelectric element of the present invention comprises a piezoelectric layer, electrode layers formed on two surfaces of the piezoelectric layer, and a protective layer stacked on the surface of the electrode layers opposite to the piezoelectric layer side. In the piezoelectric element,

[0084] The protective layer has a hole extending from the surface to the electrode layer, and the piezoelectric element has:

[0085] The filling component is made of a conductive material that extends from inside the hole to a portion of the surface of the protective layer and is electrically connected to the electrode layer;

[0086] A conductive component that covers at least a portion of the filling component and is electrically connected to the filling component; and

[0087] Fixing components are used to fix conductive components.

[0088] Furthermore, in the piezoelectric element of the present invention, the conductive component can be a conductive sheet such as copper foil. Alternatively, the conductive component can be composed of multiple conductive components combined. For example, a structure having a conductor and a conductive wire or conductive sheet connected to the conductor is illustrated.

[0089] In the piezoelectric element of the present invention, a fixing member fixes the conductive member to a predetermined location. The fixing member can fix the conductive member to a protective layer or to other parts of the piezoelectric element. Alternatively, the fixing member can fix the conductive member to other components. For example, such as... Figure 22 As shown, when the piezoelectric element 10 is fixed to the vibrating plate 100, the fixing member 74 can fix the conductive member 72 to the vibrating plate 100.

[0090] Figure 1 An example of the piezoelectric element of the present invention is schematically shown in a cross-sectional view. Figure 2 The image shows a view from above. Figure 1 A top view of a piezoelectric element. Figure 3 The middle shows an expansion Figure 1 A cross-sectional view of a portion of a piezoelectric element.

[0091] Figures 1-3 The piezoelectric element 10 shown includes a piezoelectric sheet, i.e., a piezoelectric layer 20, a lower electrode 24 stacked on one side surface of the piezoelectric layer 20, a lower protective layer 28 stacked on the lower electrode 24, an upper electrode 26 stacked on the other side surface of the piezoelectric layer 20, an upper protective layer 30 stacked on the upper electrode 26, a filling member 70, a conductive member 72, and a fixing member 74.

[0092] Figure 1 The piezoelectric layer 20 shown contains piezoelectric particles 36 within a matrix 34 comprising polymer material. Furthermore, the lower electrode 24 and upper electrode 26 are electrode layers in this invention. Additionally, the lower protective layer 28 and upper protective layer 30 are protective layers in this invention.

[0093] As described below, in a preferred embodiment, the piezoelectric element 10 (piezoelectric layer 20) is polarized in the thickness direction.

[0094] The piezoelectric element of the present invention has a hole in a protective layer, and includes a filling member formed in the hole, a conductive member connected to the filling member, and a fixing member for fixing the conductive member. Regarding this, using... Figure 3 Please provide an explanation. Additionally... Figure 3This is an enlarged view showing a portion of the upper protective layer 30 side, but the same structure is also present on the lower protective layer 28 side. In the following description, the upper protective layer 30 and the upper electrode 26 side will be used as examples.

[0095] like Figure 3 As shown, the upper protective layer 30 has a hole 31 extending from its surface to the upper electrode 26. That is, the hole 31 is formed from the surface opposite to the upper electrode 26, penetrating the upper protective layer 30 to the interface on the side of the upper electrode 26. Figure 1 and Figure 2 As shown, the hole 31 is formed in the surface direction near the end of the upper protective layer 30.

[0096] Furthermore, in Figure 3 In the example shown, as a preferred embodiment, a protrusion 32 is formed at the edge of the hole 31. The protrusion 32 is formed in a generally annular shape at the edge of the hole 31 in a manner that surrounds the hole 31.

[0097] The filling member 70 is made of a conductive material and is filled within the hole 31, and is formed in such a way that it covers a portion of the surface of the upper protective layer 30. Hereinafter, the portion of the filling member 70 extending out of the hole 31 is also referred to as the protrusion 71. The filling member 70 contacts and is electrically connected to the upper electrode 26 within the hole 31.

[0098] Furthermore, in Figure 3 In the example shown, the upper protective layer 30 has a protrusion 32, and the protrusion 71 of the filling member 70 is formed from the hole 31 to the outside of the protrusion 32.

[0099] The conductive component 72 is configured to cover at least a portion of the filling component 70 and is electrically connected to the filling component 70. In the example shown, when viewed from a direction perpendicular to the surface of the upper protective layer 30, the conductive component 72 is configured to cover the entire surface of the filling component 70.

[0100] like Figure 1 and Figure 2 As shown, the conductive member 72 is a long strip of conductive sheet, and one end of it is connected to the filling member 70 in the longitudinal direction. Furthermore, the conductive member 72 is arranged such that its other end in the longitudinal direction extends to the outside of the upper protective layer 30 in the planar direction.

[0101] The fixing member 74 fixes the conductive member 72 and the upper protective layer 30 at the position where the conductive member 72 is not covered by the filling member 70. Figure 3In the example shown, the fixing member 74 is positioned along the length of the conductive member 72 at an end further away from the filling member 70 than the connection point between the conductive member 72 and the filling member 70. Furthermore, the fixing member 74 is positioned along the length of the conductive member 72 between the connection point between the conductive member 72 and the filling member 70 and the end edge of the upper protective layer 30. In the example shown, the fixing member 74 is positioned between the upper protective layer 30 and the conductive member 72, and adheres to both the upper protective layer 30 and the conductive member 72.

[0102] Thus, in the piezoelectric element 10, the conductive part 72 is electrically connected to the filling part 70, and the filling part 70 is electrically connected to the upper electrode 26. Therefore, the conductive part 72 can be used as a lead, and wiring can be connected to the conductive part 72.

[0103] As described above, when a liquid conductive material is applied to the pores of the protective layer, the coating thickness may vary due to the viscosity of the coating material, making it difficult to ensure conductivity. Furthermore, since the protective layer is, for example, as thin as about 4 μm, the pore depth of the pores in the protective layer is also about 4 μm. Considering factors such as warping of the electroacoustic conversion film, it is difficult to reliably apply the coating material above the pores. Moreover, since silver paste used as the conductive material is expensive, it is desirable to reduce its usage; it is difficult to reliably maintain the conductive material within the pores by increasing the amount of conductive material used.

[0104] In contrast, the piezoelectric element of the present invention has a hole in the protective layer, and includes a filling member formed in the hole, a conductive member covering the filling member, and a fixing member for fixing the conductive member and the protective layer. In this piezoelectric element structure, the filling member is formed by coating the hole in the protective layer with a coating liquid of conductive material, covering the conductive member on top of the coating liquid, and then drying and curing the coating liquid. When the conductive member is covered on top of the coating liquid, the conductive member and the protective layer are fixed by the fixing member, thus preventing the conductive member from shifting while the coating liquid is not cured. Furthermore, by covering the conductive member on the coating liquid, the coating liquid is prevented from moving from above the hole, and the filling member is reliably present within the hole. Therefore, the piezoelectric element of the present invention can reliably perform electrical connection between the conductive member 72 and the filling member 70, and electrical connection between the filling member 70 and the upper electrode 26.

[0105] Furthermore, since the filling component can be reliably present within the hole, there is no need to increase the amount of conductive material used.

[0106] The shape of the opening surface of the hole 31 is not limited and can be various shapes such as circle, ellipse, rectangle, polygon, and irregular shape. From the viewpoint of ease of formation, a circle is preferred.

[0107] Furthermore, the size of the opening surface of the hole 31 is not particularly limited, as long as it ensures electrical connection with the filling member 70 and allows the piezoelectric element to operate normally. The equivalent circle diameter of the opening surface of the hole 31 is preferably 0.5 mm to 20 mm, more preferably 1.5 mm to 5 mm, and even more preferably 2 mm to 3 mm.

[0108] Furthermore, the height of the portion of the filling member 70 protruding from the hole 31 (the height from the surface of the upper protective layer 30, hereinafter also referred to as the "height of the filling member") is not particularly limited as long as it ensures electrical connection with the conductive member 72. The height of the filling member is preferably 2μm to 200μm, more preferably 10μm to 100μm, and even more preferably 20μm to 50μm.

[0109] Furthermore, the size (size in the planar direction) of the protrusion 71 of the filling member 70 is not particularly limited as long as it can ensure electrical connection with the conductive member 72. The equivalent circle diameter of the protrusion 71 is preferably 1 mm to 40 mm, more preferably 2 mm to 30 mm, and even more preferably 2 mm to 20 mm.

[0110] Among them, Figure 3 In the example shown, the upper protective layer 30 is configured to have a protrusion 32 at the edge of the hole 31, but it is not limited to this and may not have the protrusion 32. In addition, by configuring it to have the protrusion 32, the depth of the hole 31 can be made deeper than the thickness of the upper protective layer 30, and the coating liquid of the conductive material can be easily accumulated, and the contact area between the filling member 70 and the upper electrode 26 and between the filling member 70 and the conductive member 72 can be ensured.

[0111] The height of the protrusion 32 is preferably 0.2μm to 100μm, more preferably 0.5μm to 50μm, and even more preferably 0.7μm to 10μm.

[0112] Among them, Figure 3 In the example shown, the structure is provided with one hole 31 and one filling member 70, but it is not limited to this and may have multiple holes 31 and filling members 70.

[0113] For example, in Figure 4In the example shown, there are two holes 31, and two filling members 70 respectively disposed in the two holes 31. The two holes 31 are arranged adjacent to each other in the longitudinal direction of the conductive member 72. The two filling members 70 are filled in the holes 31 in the same way as the filling members, and are formed in a way that covers a portion of the surface of the upper protective layer 30. The conductive member 72 is arranged to cover the two filling members 70 disposed in the two holes 31. Furthermore, the two filling members 70 have protrusions 71 connected to the surface of the upper protective layer 30.

[0114] Furthermore, in Figure 5 In the example shown, there are five holes 31 arranged in a cross shape, and filling members 70 are respectively arranged in the five holes 31. The filling members 70 have protrusions 71 integrally connected to the surface of the upper protective layer 30. Furthermore, the protrusions 71 of the filling members 70 are formed in such a way that they cover the entire inner area of ​​the surface of the upper protective layer 30 surrounded by the five holes 31.

[0115] When a piezoelectric element has a structure with multiple filling parts 70, it is sufficient for at least one filling part 70 to have a protrusion 71, but it is preferable that all filling parts 70 have a protrusion 71.

[0116] Furthermore, the piezoelectric element of the present invention has a surrounding member on the surface of the protective layer for surrounding the hole, and the filling member can be formed within the surrounding member.

[0117] For example, in Figure 6 In the example shown, the outer periphery of the hole 31 and the protrusion 32 on the surface of the upper protective layer 30 has a surrounding member 76 for surrounding the hole 31. In the area surrounded by the surrounding member 76, there is a protrusion 71 of the filling member 70. Furthermore, the surrounding member 76 covers the upper surface (the surface opposite to the side of the upper protective layer 30) with the conductive member 72.

[0118] The surrounding member 76 is, for example, an annular member, and its height (thickness) is greater than that of the protrusion 32. Furthermore, it is preferably configured such that the filling member 70 formed inside the surrounding member 76 contacts the conductive member 72, and the height of the surrounding member 76 is equal to or less than the height of the filling member 70.

[0119] By having the surrounding member 76, when applying a coating liquid containing a conductive material, it is possible to prevent the coating liquid from moving from the hole 31, and to ensure that the filling member 70 is reliably present in the position of the hole 31.

[0120] The shape of the opening of the surrounding component 76 is not limited to a circle, and can be set to various shapes such as ellipse, rectangle, polygon, and irregular shape.

[0121] Furthermore, when the upper protective layer 30 has multiple holes 31, it may have multiple surrounding members 76 disposed at the positions of each hole 31, or it may be configured as a single surrounding member 76 having the size to surround the multiple holes 31.

[0122] The size (diameter) and height of the surrounding member 76 can be appropriately set according to the size of the hole 31, the height of the protrusion 32, and the size and height of the protrusion 71 of the filling member 70.

[0123] The equivalent circle diameter of the surrounding component 76 is preferably 3mm to 60mm, more preferably 5mm to 50mm, and even more preferably 5mm to 40mm.

[0124] The height of the surrounding component 76 is preferably 0.01mm to 1mm, more preferably 0.1mm to 0.5mm, and even more preferably 0.1mm to 0.3mm.

[0125] The surrounding component 76 is preferably bonded to the upper protective layer 30 by an adhesive or the like. It is also preferably bonded to the conductive component 72 by an adhesive or the like.

[0126] Furthermore, the piezoelectric element of the present invention may have a recess formed around the hole in the protective layer.

[0127] For example, in Figure 7 In the example shown, the surface of the upper protective layer 30 has a hole 31 and a protrusion 32 on the outer periphery, and a recess 33 around the hole 31. A protrusion 71 of the filling member 70 is located within the recess 33. By having the recess 33, when applying a coating liquid containing a conductive material, the coating liquid can be concentrated at the location of the hole 31, and the filling member 70 can be reliably present at the location of the hole 31.

[0128] When the upper protective layer 30 has a protrusion 32, the recess 33 is formed on the outer periphery side of the protrusion 32. Furthermore, when the surrounding member 76 is included, the recess 33 is formed on the inner side of the surrounding member 76.

[0129] The depth of the recess 33 from the surface of the upper protective layer 30 is preferably 0.1 μm to 3 μm, more preferably 0.5 μm to 2 μm, and even more preferably 1 μm to 2 μm.

[0130] The equivalent circle diameter of the hole varies in stages along the depth direction, and preferably the equivalent circle diameter on the electrode layer side is smaller than that on the conductive component side.

[0131] For example, in Figure 8In the example shown, the size of the hole 31 changes midway along the depth direction, and the equivalent circle diameter D2 in the region on the upper electrode 26 side is smaller than the equivalent circle diameter D1 in the region on the surface side (conductive component side). Additionally, in Figure 8 The diagram of conductive components is omitted.

[0132] As will be described in detail later, the holes formed in the protective layer are created through laser processing. Because heat is generated during laser processing, the protective layer and piezoelectric layer near the holes also become heated, causing the electrode layer at the hole location to easily lose strength. In particular, the electrode layer is prone to damage at the boundary between the hole and the protective layer.

[0133] In contrast, by reducing the size of the pores in the region on the electrode layer side, heating of the electrode layer can be suppressed, and a decrease in the strength of the electrode layer can be prevented. Furthermore, by increasing the size of the pores in the region on the surface side, the coating liquid of the conductive material can be appropriately concentrated within the pores.

[0134] Furthermore, when holes are formed in the protective layer through laser processing, although the electrode layer and piezoelectric layer expand due to heat, the difference in thermal expansion rate and thermal conductivity between the electrode layer and the piezoelectric layer sometimes creates voids between them within the hole due to expansion caused by heating and contraction caused by slow heating. In particular, since heat tends to accumulate in the central part of the hole, voids are more likely to form in the central part.

[0135] For example, such as Figure 9 As shown, the piezoelectric layer 20 has voids 80 formed by deformation.

[0136] In addition, Figure 9 The illustrations of the filling component 70 and the conductive component 72 are omitted.

[0137] Since the presence of such a gap 80 causes a change in the relative permittivity between the electrode layers, it may lead to a reduction in the performance of the piezoelectric element.

[0138] In contrast, the difference d between the average height of the interface between the piezoelectric layer and the electrode layer in locations where no aperture is formed and the average height of the interface between the piezoelectric layer and the electrode layer in locations where an aperture is formed is preferably set to 25 μm or less, more preferably 0 μm to 20 μm, and even more preferably 0 μm to 15 μm. Furthermore, this difference d is preferably 50% or less of the average thickness of the piezoelectric layer, more preferably 0% to 40%, and even more preferably 0% to 30%.

[0139] Regarding the method for measuring this difference d, the following is used: Figure 10 Please provide an explanation.

[0140] The piezoelectric layer, including the holes, is cut to any size and embedded in epoxy resin or similar material, then cured. Next, the piezoelectric layer in the resin is cut using a focused ion beam (FIB) or similar method, exposing its cross-section. This cross-section is observed using an optical microscope, and image conversion software is used to convert the boundary line (interface) between the piezoelectric layer and the electrode layer, approximately 40 mm in length, into a curve formula. For example... Figure 10 As shown, the interface between the piezoelectric layer and the electrode layer has roughness.

[0141] In this cross section, the arithmetic mean roughness Ra of the boundary lines in the parts other than the holes is calculated based on image analysis in about 10 sections, and the average height d0 of the piezoelectric layer interface in the parts other than the holes is calculated by calculating the average value.

[0142] Similarly, the average height d1 of the piezoelectric layer interface is calculated from the image analysis of the boundary lines in the aperture portion.

[0143] The difference d in average height is obtained by calculating the difference between the calculated average height d0 and the average height d1.

[0144] Specifically, the average height (Rc) of the roughness curve elements described in JIS B 0601-2001 is calculated for the portion excluding the hole. Then, the average height d0 of the left and right interfaces of the hole is calculated from the profile curve. Similarly, the average height d1 of the piezoelectric layer interface is calculated from the image analysis of the boundary lines in the hole portion. For the left and right sides, the larger deviation between d1 and d0 is designated as d.

[0145] Furthermore, when holes are formed in the protective layer through laser processing, sometimes the protective layer is not completely removed, leaving residue on the surface of the electrode layer. This residue tends to remain on the surface of the electrode layer due to factors such as the conditions of laser processing.

[0146] For example, because heat from laser processing tends to accumulate in the center of the hole, the residue in the protective layer tends to be less than that at the periphery. On the other hand, it is also possible to design a structure where the residue in the protective layer is more in the center of the hole and less at the periphery, depending on the laser processing conditions.

[0147] In a structure where the residue of the protective layer is less in the central part of the hole than in the peripheral part, it is possible to ensure the electrical connection between the filling component in the central part and the electrode layer, and to suppress the reduction of the strength of the electrode layer in the peripheral part.

[0148] On the other hand, in a structure where the residue of the protective layer is more in the central part of the hole than in the peripheral part, the heat accumulation in the central part during laser processing can be suppressed, thus suppressing the formation of the aforementioned voids and suppressing changes in the relative permittivity.

[0149] Furthermore, since the protective layer is composed of a resin film such as polyethylene terephthalate (PET), the residue in the protective layer contains carbon. Therefore, when measuring the amount of residue in the protective layer on the surface of the electrode layer, it is sufficient to measure the amount of carbon on the surface of the electrode layer.

[0150] The amount of carbon on the electrode layer surface can be determined by peeling the conductive component from the piezoelectric element, etching the surface of the filling component, and performing elemental analysis using XPS (X-ray photoelectron spectroscopy) to observe the presence of carbon.

[0151] That is, a structure in which the residue of the protective layer is less in the central part of the hole than in the peripheral part is a structure in which the amount of carbon in the surface of the electrode layer within the hole is less in the central part of the plane than in the areas excluding the central part. Furthermore, a structure in which the residue of the protective layer is more in the central part of the hole than in the peripheral part is a structure in which the amount of carbon in the surface of the electrode layer within the hole is more in the central part of the plane than in the areas excluding the central part.

[0152] Furthermore, the central portion of the hole refers to the area encompassing 1 / 16 of the hole's area, centered on the centroid of the hole in the surface direction. The peripheral portion refers to the area excluding the central portion. The amount of residue in the protective layer is the average value measured at 10 points within this range.

[0153] The piezoelectric element of the present invention can be configured as follows: the conductive component is elongated, the conductive component has a folded-back portion in the length direction, and the fixing component fixes the conductive component and the protective layer in a region opposite to the connection position between the conductive component and the filling component, with the folded-back portion between them.

[0154] Regarding this structure, use Figure 11 Please provide an explanation.

[0155] Figure 11 This is an enlarged cross-sectional view showing a portion of another example of the piezoelectric element of the present invention.

[0156] exist Figure 11 In this context, due to the fact that, apart from the shape of the conductive component 72, it has the same characteristics as... Figure 3 The piezoelectric element shown below has the same structure, so the differences will be explained mainly below.

[0157] exist Figure 11 In the middle, the conductive component 72 is folded back in the length direction. If one region sandwiched in the middle by the folded part 73 is designated as region 72a and the other region is designated as region 72b, then one surface of region 72a is connected to the filling component 70 and one surface of region 72b is connected to the fixing component 74.

[0158] That is, the region 72b, where the conductive component 72 is fixed to the upper protective layer 30 by the fixing component 74, is on the opposite side of the region 72a, which sandwiches the folded-back portion 73 and is connected to the filling component 70.

[0159] like Figure 11 As shown, regarding the conductive member 72, region 72a is shorter than region 72b, and the shorter region 72a is disposed on the filling member 70 facing the filling member 70. Furthermore, region 72b of the conductive member 72 is fixed to the upper protective layer 30 by a fixing member 74 at a position that does not overlap with region 72a.

[0160] Thus, by using a structure in which the bent conductive member 72 sandwiches the folded portion 73 in the middle, and one region 72a is fixed to the filling member 70, and another region 72b is fixed to the upper protective layer 30 by the fixing member 74, when a coating liquid of conductive material is applied to the hole provided in the protective layer and the conductive member 72 is placed over the coating liquid, since a force is applied to region 72a toward the coating liquid side, it is possible to ensure a tight seal between the conductive member 72 and the coating liquid, and a reliable electrical connection between the conductive member 72 and the filling member 70 can be obtained.

[0161] Furthermore, when a tensile force or other force is applied to region 72b of the conductive member 72, it is difficult to transmit the force to region 72a, thus enabling a reliable electrical connection between the conductive member 72 and the filling member 70.

[0162] In addition, in cases with multiple holes and filling components, such as Figure 12 As shown, the region 72a of the conductive component 72 can be configured by adjusting the position of the folded portion 73 to cover multiple filling components 70.

[0163] Furthermore, it may also have a second fixing member that fixes the edge near the connection point between the conductive member and the filling member to the protective layer.

[0164] For example, in Figure 5 In the example shown, the conductive member 72 is elongated. The conductive member 72 is connected to the filling member 70 at one end along its length. The fixing member 74 is positioned along the length of the conductive member 72 at an end further away from the filling member 70 than the connection point between the conductive member 72 and the filling member 70. Furthermore, the three sides of the region between the filling member 70 end of the conductive member 72 and the fixing member 74 are fixed to the upper protective layer 30 by the second fixing member 82.

[0165] The second fixing member 82 is preferably disposed in the surface direction at a position that does not overlap with the filling member 70 (protrusion 71).

[0166] Thus, by having a second fixing member that fixes the edge near the connection point of the conductive component and the filling component to the protective layer, it is possible to suppress the peeling of the conductive component and the filling component.

[0167] In addition, Figure 3 and Figure 5 In this context, the fixing member 74 is configured as a so-called adhesive layer / gluing layer disposed between the conductive member 72 and the upper protective layer 30, but is not limited to this, such as... Figure 13 As shown, it can also be a so-called adhesive sheet fixed from above the conductive component 72 to the upper protective layer 30.

[0168] Similarly, in Figure 5 In this context, the second fixing member 82 is configured as an adhesive sheet fixed to the upper protective layer 30 from above the conductive member 72, but it is not limited to this, such as... Figure 13 As shown, the second fixing member 82 can also be configured as a so-called adhesive layer / gluing layer disposed between the conductive member 72 and the upper protective layer 30.

[0169] Furthermore, in the piezoelectric element of the present invention, at the connection position between the filling member 70 and the conductive member 72, the filling member 70 has a recess, and the conductive member 72 can be formed in a manner that bends along the recess.

[0170] For example, in Figure 20 In the example shown, a recess is formed on the surface of the filling member 70 on the side of the conductive member 72. Furthermore, the conductive member 72 bends along the recess formed on the filling member 70 to contact and connect with the filling member 70.

[0171] and, Figure 21 The example shown is one where the conductive component 72 has a folded-back portion 73. Figure 21 In the example shown, a recess is formed on the surface of the filling member 70 on the side of the conductive member 72. Furthermore, the region 72a of the conductive member 72 bends along the recess formed on the filling member 70 to contact and connect with the filling member 70.

[0172] Thus, at the connection position between the filling member 70 and the conductive member 72, the filling member 70 has a recess. By setting the conductive member 72 to bend along the recess, the contact area between the filling member 70 and the conductive member 72 can be increased, and the filling member 70 and the conductive member 72 can be reliably electrically connected.

[0173] In addition, Figure 20 and Figure 21In the example shown, the recess formed on the filling member 70 is configured to be formed at a position corresponding to the hole 31 of the protective layer, but it is not limited to this. For example, in the case where the filling members 70 formed on each hole 31 are connected by forming multiple holes 31 on the protective layer, a recess may also be formed at the position where the filling members 70 are connected.

[0174] Furthermore, the recess of the filling member 70 can be formed in the piezoelectric element manufacturing method described later by coating the conductive material used as the filling member 70 onto the hole portion 31, placing the conductive member 72 on top of the conductive material 84, and then pressing the conductive material 84 from above the conductive member 72.

[0175] Alternatively, a curved portion corresponding to the recess can be provided on the conductive component 72 in advance, the conductive component 72 can be placed such that the curved portion of the conductive component 72 is located above the conductive material 84, and the recess can be transferred to the conductive material 84, thereby forming the recess of the filling component 70.

[0176] Among them, Figure 3 In the examples shown, an example of a conductive component being a conductive sheet was described, but as mentioned above, a conductive component can be composed of multiple conductive components.

[0177] For example, Figure 23 The example shown is one in which a conductor 92 and a conductive line 86 are used as conductive components. The conductor 92 and the conductive line 86 are connected by solder 87. The conductor 92 is only connected to the top of the filler member 70 and is not fixed to the upper protective layer 30 or the like. The conductive line 86 is fixed to the upper protective layer 30 by a fixing member 74.

[0178] and, Figure 24 and Figure 25 The example shown is one in which a conductor 92 and a printed wiring board 98 are used as conductive components. For example... Figure 25 As shown, the printed wiring board 98 has wiring 96 printed on an insulating substrate 94 such as a plastic sheet. The wiring 96 of the printed wiring board 98 is connected to the conductor 92.

[0179] Conductor 92 is only connected to the top of filler 70 and is not fixed to the upper protective layer 30, etc. Printed wiring board 98 is fixed to the upper protective layer 30 by fixing member 74.

[0180] Thus, a conductive component can also be composed of multiple conductive components. In this case, it is sufficient that at least one of the components constituting the conductive component is fixed to a predetermined location by the fixing component 74.

[0181] Furthermore, the conductive component 72, which is made of conductive sheet material, can be further connected to conductive components such as conductive wires. Moreover, conductive components such as conductive wires can be connected to any position of the conductive component 72.

[0182] For example, in Figure 26 In the example shown, on the surface side of the conductive member 72, which is made of conductive sheet, where it is connected to the filler member 70, the conductive line 86 is fixed by solder 87. The conductive line 86 is fixed to the upper protective layer 30 by adhesive member 88 at a midpoint in its extension direction.

[0183] Figure 26 In the case of the structure shown, the conductive component 72, solder 87 and conductive wire 86 can also be regarded as conductive components in the present invention, and the adhesive component 88 can be regarded as fixing component in the present invention.

[0184] exist Figure 27 In the example shown, the conductive member 72, which is made of conductive sheet, has a conductive support 90 on its surface side where it is connected to the filling member 70, and a conductive wire 86 with a socket 89 that fits into the support at its front end. The conductive wire 86 is fixed to the upper protective layer 30 by an adhesive member 88 at a midway point in its extension direction.

[0185] Figure 27 In the case of the structure shown, the conductive component 72, the support 90, the socket 89 and the conductive wire 86 can also be regarded as conductive components in the present invention, and the adhesive component 88 can be regarded as fixing components in the present invention.

[0186] Among them, Figure 2 In the example shown, as a preferred embodiment, the conductive member 72 electrically connected to the upper electrode 26 on the upper protective layer 30 side, separated by the filling member 70, and the conductive member 72 electrically connected to the lower electrode 24 on the lower protective layer 28 side, separated by the filling member 70, are arranged such that their positions in the planar direction do not overlap. Therefore, short circuits can be suppressed by the contact between the conductive member 72 on the upper electrode side 26 and the conductive member 72 on the lower electrode 24 side.

[0187] As an example, in various audio devices (audio equipment) such as pickups used in loudspeakers, microphones and musical instruments such as guitars, this piezoelectric element 10 is used to generate (play) sound caused by vibrations of corresponding electrical signals or to convert vibrations caused by sound into electrical signals.

[0188] In addition, piezoelectric elements can also be used in pressure sensors and power generation components.

[0189] Furthermore, for example, when the piezoelectric element 10 is used in a loudspeaker, it can also be used to generate sound through the vibration of the thin-film piezoelectric element 10 itself. Alternatively, the piezoelectric element 10 can also be used as an exciter that is attached to a diaphragm and generates sound by vibrating the diaphragm through the vibration of the piezoelectric element 10.

[0190] The constituent elements of the piezoelectric element of the present invention will be described below.

[0191] [Piezoelectric layer]

[0192] The piezoelectric layer 20 can be any layer composed of a known piezoelectric material. In this invention, the piezoelectric layer 20 is preferably a polymer composite piezoelectric material containing piezoelectric particles 36 in a matrix 34 containing polymer materials.

[0193] The material used for the matrix 34 (matrix and binder) of the polymer composite piezoelectric body constituting the piezoelectric layer 20 is preferably a polymer material that has viscoelasticity at room temperature.

[0194] The piezoelectric element 10 of the present invention is preferably used in flexible display speakers, flexible speakers, etc. The polymer composite piezoelectric material (piezoelectric layer 20) used in a flexible speaker preferably possesses the following characteristics. Therefore, as a material possessing these characteristics, a polymer material that is viscoelastic at room temperature is preferred.

[0195] In addition, in this instruction manual, "normal temperature" refers to a temperature range of approximately 0 to 50°C.

[0196] (i) Flexibility

[0197] For example, when held in a portable container with a slow, flexible feel, like a news or magazine document, it is subjected to relatively slow but large bending deformations below a few Hz from the outside. In this situation, if the polymer composite piezoelectric is too stiff, it will generate relatively large bending stress, leading to cracking at the interface between the matrix and the piezoelectric particles, potentially causing damage. Therefore, appropriate flexibility is required for the polymer composite piezoelectric. Furthermore, if the strain energy can diffuse outwards as heat, the stress can be relaxed. Therefore, a sufficiently large loss tangent is required for the polymer composite piezoelectric.

[0198] (ii) Sound quality

[0199] The loudspeaker vibrates piezoelectric particles in the 20Hz–20kHz audio frequency band, and the vibrational energy causes the entire polymer composite piezoelectric element to vibrate as a whole to produce sound. Therefore, to improve the efficiency of vibrational energy transfer, the polymer composite piezoelectric element requires appropriate stiffness. Furthermore, if the loudspeaker's frequency response is smooth, the change in sound quality when the lowest resonant frequency changes with curvature is also reduced. Therefore, the polymer composite piezoelectric element requires a sufficiently large loss tangent.

[0200] In summary, the polymer composite piezoelectric material is required to have a relatively stiff response to vibrations in the 20Hz–20kHz range and a relatively soft response to vibrations below a few Hz. Furthermore, the loss tangent of the polymer composite piezoelectric material is required to be appropriately large relative to vibrations at all frequencies below 20kHz.

[0201] Typically, polymeric solids possess viscoelastic relaxation mechanisms, and with increasing temperature or decreasing frequency, large-scale molecular motion is observed as a decrease in the stored elastic modulus (Young's modulus) (relaxation) or a maximization of the loss elastic modulus (absorption). Among these, relaxation caused by the micro-Brownian motion of molecular chains in amorphous regions is called principal dispersion, and very large relaxation phenomena can be observed. This principal dispersion occurs at the glass transition point (Tg), where the viscoelastic relaxation mechanism is most clearly manifested.

[0202] In the polymer composite piezoelectric (piezoelectric layer 20), by using a polymer material with a glass transition point at room temperature—in other words, a polymer material that is viscoelastic at room temperature—in the matrix, a polymer composite piezoelectric is achieved that provides a stiffer action for vibrations in the range of 20 Hz to 20 kHz and a softer action for slow vibrations below a few Hz. In particular, to appropriately utilize this action, it is preferable to use a polymer material with a glass transition temperature at room temperature (0–50 °C) in the matrix of the polymer composite piezoelectric, within a frequency of 1 Hz.

[0203] As a viscoelastic polymer material at room temperature, various known polymer materials can be used as long as they possess dielectric properties. Preferably, the polymer material used has a maximum loss tangent of 0.5 or higher at a frequency of 1 Hz, obtained based on dynamic viscoelasticity testing, at room temperature (0°C to 50°C).

[0204] Therefore, when a polymer composite piezoelectric is slowly bent by an external force, the stress concentration at the interface between the matrix and the piezoelectric particles in the part with the maximum bending moment is relaxed, resulting in good flexibility.

[0205] Furthermore, the stored elastic modulus (E') of the polymer material at a frequency of 1 Hz, obtained based on dynamic viscoelasticity measurements, is preferably 100 MPa or more at 0°C and 10 MPa or less at 50°C.

[0206] Therefore, it can reduce the bending torque generated when the polymer composite piezoelectric is slowly bent by external force, while also being able to operate more rigidly for acoustic vibrations in the range of 20Hz to 20kHz.

[0207] Furthermore, it is even more preferable if the polymer material has more than 10 particles at a relative permittivity of 25°C. Therefore, when a voltage is applied to the polymer composite piezoelectric, a higher electric field is required for the piezoelectric particles in the matrix, thus a larger deformation can be expected.

[0208] However, on the other hand, if good moisture resistance is to be ensured, it is also preferable that the relative permittivity of the polymer material is less than 10 at 25°C.

[0209] Examples of polymeric materials that meet these conditions include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride acrylonitrile, polystyrene-vinyl polyisoprene block copolymer, polyvinyl methyl ketone, and polybutyl methacrylate. Furthermore, commercially available products such as Hibler5127 (manufactured by KURARAY CO.,LTD) are also preferred as these polymeric materials. Among these, materials containing cyanoethyl groups are preferred, and cyanoethylated PVA is particularly preferred.

[0210] In addition, these polymer materials can be used in combination (mixed) or with only one type.

[0211] The matrix 34 using this polymer material can be used in combination with multiple polymer materials as needed.

[0212] That is, for the purpose of adjusting dielectric or mechanical properties, a viscoelastic polymer material at room temperature is added to matrix 34. Other dielectric polymer materials may also be added as needed.

[0213] Examples of dielectric polymer materials that can be added include fluorinated polymers such as polyvinylidene fluoride, polyvinylidene fluoride-tetrafluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene copolymer, and polyvinylidene fluoride-tetrafluoroethylene copolymer; vinylidene cyanide-vinyl ester copolymer; cyanoethyl cellulose; cyanoethyl hydroxysucrose; cyanoethyl hydroxycellulose; cyanoethyl hydroxyfullerene; cyanoethyl methacrylate; cyanoethyl acrylate; cyanoethyl hydroxyethyl cellulose; cyanoethyl linear starch; cyanoethyl hydroxypropyl cellulose; cyanoethyl dihydroxypropyl cellulose; cyanoethyl hydroxypropyl linear starch; cyanoethyl polyacrylamide; cyanoethyl polyacrylate; cyanoethyl fullerene; cyanoethyl polyhydroxymethylene; cyanoethyl glycidyl fullerene; cyanoethyl sucrose; and cyanoethyl sorbitol, as well as synthetic rubbers such as nitrile rubber or chloroprene rubber.

[0214] Preferably, a polymer material containing cyanoethyl groups is used.

[0215] Furthermore, in the matrix 34 of the piezoelectric layer 20, the dielectric polymer material added when adding a viscoelastic polymer material such as cyanoethylated PVA at room temperature is not limited to one type, and multiple types can be added.

[0216] Furthermore, in order to adjust the glass transition point, in addition to dielectric polymer materials, thermoplastic resins such as vinyl chloride resin, polyethylene, polystyrene, methacrylic resin, polybutene and isobutene, as well as thermosetting resins such as phenolic resin, urea resin, melamine resin, alkyd resin and mica can be added to matrix 34.

[0217] In addition, adhesives such as rosin esters, rosin, terpenes, terpene phenols, and petroleum resins can be added to improve adhesion.

[0218] There is no particular limitation on the amount of materials other than viscoelastic polymers such as cyanoethylated PVA added to the matrix 34 of the piezoelectric layer 20, but it is preferred to be 30% by mass or less in proportion to the matrix 34.

[0219] Therefore, without compromising the viscoelastic relaxation mechanism in matrix 34, the properties of the added polymer material can be discovered, thus achieving preferred results in terms of high dielectric constant, improved heat resistance, and improved adhesion with piezoelectric particles 36 and electrode layers.

[0220] The piezoelectric layer 20 is a polymeric composite piezoelectric material containing piezoelectric particles 36 in this matrix 34.

[0221] The piezoelectric particles 36 are composed of ceramic particles with perovskite or wurtzite crystal structures.

[0222] Examples of ceramic particles constituting piezoelectric particles 36 include lead zirconate titanate (PZT), lanthanum lead zirconate titanate (PLZT), barium titanate (BaTiO3), zinc oxide (ZnO), and a solid solution of barium titanate and bismuth ferrite (BiFe3) (BFBT).

[0223] These piezoelectric particles 36 can be used in single or multiple ways (mixed).

[0224] There is no limitation on the particle size of this piezoelectric particle 36; it can be appropriately selected according to the size and application of the polymer composite piezoelectric (piezoelectric element 10).

[0225] The particle size of the piezoelectric particles 36 is preferably 1 to 10 μm. By setting the particle size of the piezoelectric particles 36 within this range, optimal results can be obtained in the polymer composite piezoelectric (piezoelectric element 10) in terms of both high piezoelectric characteristics and flexibility.

[0226] In addition, Figure 1 In the piezoelectric layer 20, the piezoelectric particles 36 are uniformly and regularly dispersed in the matrix 34, but the present invention is not limited thereto.

[0227] That is, the piezoelectric particles 36 in the piezoelectric layer 20 can preferably be irregularly dispersed in the matrix 34 as long as they are uniformly dispersed.

[0228] In the piezoelectric layer 20 (polymer composite piezoelectric), the ratio of matrix 34 to piezoelectric particles 36 in the piezoelectric layer 20 is not limited. It can be appropriately set according to the size and thickness of the piezoelectric layer 20 in the surface direction, the application of the polymer composite piezoelectric, and the required characteristics of the polymer composite piezoelectric.

[0229] The volume fraction of piezoelectric particles 36 in the piezoelectric layer 20 is preferably 30-80%, more preferably 50% or more, and therefore even more preferably 50-80%.

[0230] By setting the ratio of matrix 34 to piezoelectric particles 36 within the aforementioned range, an optimal result can be obtained that balances high voltage characteristics and flexibility.

[0231] There is no limitation on the thickness of the piezoelectric layer 20, as long as it is appropriately set according to the application of the polymer composite piezoelectric body and the required characteristics in the polymer composite piezoelectric body. The thicker the piezoelectric layer 20, the more advantageous it is in terms of rigidity, such as the stiffness of the so-called sheet, but the voltage (potential difference) required to make the piezoelectric layer 20 expand and contract by the same amount becomes larger.

[0232] The thickness of the piezoelectric layer 20 is preferably 10–300 μm, more preferably 20–200 μm, and even more preferably 30–150 μm.

[0233] By setting the thickness of the piezoelectric layer 20 within the aforementioned range, a preferred result can be obtained while ensuring rigidity and appropriate flexibility.

[0234] [Electrode layer and protective layer]

[0235] like Figure 1 As shown in the figure, the piezoelectric element 10 is formed by having a structure in which a lower electrode 24 is provided on one surface of the piezoelectric layer 20, and a lower protective layer 28 is provided on its surface; an upper electrode 26 is provided on the other surface of the piezoelectric layer 20, and an upper protective layer 30 is provided on its surface. The upper electrode 26 and the lower electrode 24 form an electrode pair.

[0236] That is, the piezoelectric element 10 is formed by having an electrode pair, namely an upper electrode 26 and a lower electrode 24, sandwiching the two surfaces of the piezoelectric layer 20, and the laminate is sandwiched by a lower protective layer 28 and an upper protective layer 30.

[0237] Thus, in the piezoelectric element 10, the area sandwiched between the upper electrode 26 and the lower electrode 24 expands and contracts according to the applied voltage.

[0238] The lower protective layer 28 and the upper protective layer 30, while covering the upper electrode 26 and the lower electrode 24, also impart appropriate rigidity and mechanical strength to the piezoelectric layer 20. That is, in the piezoelectric element 10, the piezoelectric layer 20, composed of the matrix 34 and piezoelectric particles 36, exhibits excellent flexibility for slow bending deformation, but sometimes its rigidity or mechanical strength is insufficient depending on the application. The piezoelectric element 10 is provided with the lower protective layer 28 and the upper protective layer 30 to compensate for this.

[0239] There are no limitations on the lower protective layer 28 and the upper protective layer 30; various sheet materials can be used. For example, various resin films are preferably shown.

[0240] Among them, resin films composed of polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), polyetherimide (PEI), polyimide (PI), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), and cyclic olefin resins are appropriately used due to their excellent mechanical properties and heat resistance.

[0241] There are no restrictions on the thickness of the lower protective layer 28 and the upper protective layer 30. Furthermore, the thickness of the lower protective layer 28 and the upper protective layer 30 can be basically the same, but they can also be different.

[0242] If the lower protective layer 28 and the upper protective layer 30 are too rigid, it will not only restrict the expansion and contraction of the piezoelectric layer 20, but also impair its flexibility. Therefore, except in cases where mechanical strength or good operability as a sheet is required, the thinner the lower protective layer 28 and the upper protective layer 30 are, the more advantageous it is.

[0243] The thickness of the lower protective layer 28 and the upper protective layer 30 is preferably 3μm to 100μm, more preferably 3μm to 50μm, even more preferably 3μm to 30μm, and especially preferably 4μm to 10μm.

[0244] In the piezoelectric element 10, if the thickness of the lower protective layer 28 and the upper protective layer 30 is less than twice the thickness of the piezoelectric layer 20, then a preferred result can be obtained in terms of balancing rigidity and appropriate flexibility.

[0245] For example, if the thickness of the piezoelectric layer 20 is 50 μm and the lower protective layer 28 and the upper protective layer 30 are composed of PET, the thickness of the lower protective layer 28 and the upper protective layer 30 is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 25 μm or less.

[0246] In the piezoelectric element 10, a lower electrode 24 is formed between the piezoelectric layer 20 and the lower protective layer 28, and an upper electrode 26 is formed between the piezoelectric layer 20 and the upper protective layer 30.

[0247] A lower electrode 24 and an upper electrode 26 are provided to apply a driving voltage to the piezoelectric layer 20.

[0248] In this invention, the materials used to form the lower electrode 24 and the upper electrode 26 are not limited, and various conductors can be used. Specifically, examples include carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, titanium, chromium, and molybdenum, as well as alloys of these metals, laminates and composites of these metals and alloys, and indium tin oxide. Among these, copper, aluminum, gold, silver, platinum, and indium tin oxide are preferably used as the lower electrode 24 and the upper electrode 26.

[0249] Furthermore, there are no restrictions on the methods for forming the lower electrode 24 and the upper electrode 26. Various known methods can be used, such as films formed by vacuum evaporation and sputtering (vacuum film formation), electroplating, and methods for bonding foils formed from the aforementioned materials.

[0250] In particular, for reasons such as ensuring the flexibility of the piezoelectric element 10, the lower electrode 24 and the upper electrode 26 are preferably thin films of copper or aluminum formed by vacuum evaporation. In particular, the thin film of copper formed by vacuum evaporation is preferred.

[0251] There is no limitation on the thickness of the lower electrode 24 and the upper electrode 26. Furthermore, the thickness of the lower electrode 24 and the upper electrode 26 can be substantially the same, but they can also be different.

[0252] Similar to the lower protective layer 28 and the upper protective layer 30, if the rigidity of the lower electrode 24 and the upper electrode 26 is too high, it will not only restrict the expansion and contraction of the piezoelectric layer 20, but also impair its flexibility. Therefore, it is more advantageous for the lower electrode 24 and the upper electrode 26 to be as thin as possible without making the resistance too high. That is, the lower electrode 24 and the upper electrode 26 are preferably thin-film electrodes.

[0253] The thickness of the lower electrode 24 and the upper electrode 26 is thinner than that of the protective layer, preferably 0.05μm to 10μm, more preferably 0.05μm to 5μm, even more preferably 0.08μm to 3μm, and especially preferably 0.1μm to 2μm.

[0254] In the piezoelectric element 10, if the product of the thickness of the lower electrode 24 and the upper electrode 26 with Young's modulus is lower than the product of the thickness of the lower protective layer 28 and the upper protective layer 30 with Young's modulus, the flexibility will not be seriously impaired, and therefore it is preferred.

[0255] For example, if the lower protective layer 28 and the upper protective layer 30 are composed of PET (Young's modulus: about 6.2 GPa) and the lower electrode 24 and the upper electrode 26 are composed of copper (Young's modulus: about 130 GPa), and the thickness of the lower protective layer 28 and the upper protective layer 30 is set to 25 μm, then the thickness of the lower electrode 24 and the upper electrode 26 is preferably 1.2 μm or less, more preferably 0.3 μm or less, and preferably 0.1 μm or less.

[0256] The piezoelectric element 10 preferably has a maximum value of loss tangent (Tanδ) at a frequency of 1 Hz obtained based on dynamic viscoelasticity measurement at room temperature, and more preferably has a maximum value of 0.1 or more at room temperature.

[0257] Therefore, even if the piezoelectric element 10 is subjected to relatively slow and large bending deformation of less than a few Hz from the outside, it can effectively diffuse the strain energy to the outside as heat, thus preventing cracking at the interface between the matrix and the piezoelectric particles.

[0258] Regarding the piezoelectric element 10, the stored elastic modulus (E') at a frequency of 1 Hz, obtained based on dynamic viscoelasticity measurements, is 10 GPa to 30 GPa at 0°C, and preferably 1 GPa to 10 GPa at 50°C. Furthermore, this condition is the same as that for the piezoelectric layer 20.

[0259] Therefore, the piezoelectric element 10 can have a large frequency dispersion at the stored elastic modulus (E'). That is, it can operate more rigidly for vibrations in the range of 20 Hz to 20 kHz and more softly for vibrations below a few Hz.

[0260] Furthermore, regarding the piezoelectric element 10, the product of its thickness and the stored elastic modulus at a frequency of 1 Hz, obtained based on dynamic viscoelasticity measurements, is preferably 1.0 × 10⁻⁶ at 0°C. 5 ~2.0×10 6 (1.0E+05~2.0E+06) N / m, 1.0×10 at 50℃ 5 ~1.0×10 6 (1.0E+05~1.0E+06) N / m. Furthermore, this condition is the same as that for piezoelectric layer 20.

[0261] Therefore, the piezoelectric element 10 can possess appropriate rigidity and mechanical strength without compromising flexibility and acoustic properties.

[0262] Furthermore, regarding the piezoelectric element 10, the loss tangent obtained from the master curve obtained from dynamic viscoelasticity measurements is preferably 0.05 or higher at 25°C and a frequency of 1 kHz. This condition is also the same as that for the piezoelectric layer 20.

[0263] Therefore, the frequency response of the loudspeaker using the piezoelectric element 10 becomes smooth, which can reduce the change in sound quality when the lowest resonant frequency f0 changes with the curvature of the loudspeaker.

[0264] Furthermore, in this invention, the stored elastic modulus (Young's modulus) and loss tangent of the piezoelectric element 10 and piezoelectric layer 20 can be measured using known methods. For example, the dynamic viscoelasticity measuring device DMS6100 manufactured by SII Nano Technology Inc. can be used for measurement.

[0265] As an example, the measurement conditions are as follows: measurement frequency of 0.1Hz to 20Hz (0.1Hz, 0.2Hz, 0.5Hz, 1Hz, 2Hz, 5Hz, 10Hz and 20Hz), measurement temperature of -50 to 150℃, heating rate of 2℃ / min (in nitrogen atmosphere), sample size of 40mm × 10mm (including clamping area), and chuck spacing of 20mm.

[0266] [Filling component]

[0267] The filling component 70 is formed by solidifying a liquid conductive material.

[0268] As a conductive material used as a filler component 70, silver paste, metal nanoparticle ink (Ag, Au), etc. can be utilized.

[0269] The viscosity of the conductive material is preferably 10 mPa·s to 20 Pa·s, more preferably 0.1 Pa·s to 15 Pa·s, and even more preferably 0.5 Pa·s to 10 Pa·s.

[0270] The resistivity of the cured filler 70 is preferably 1×10^-6 (Ω·cm) to 1×10^-3 (Ω·cm), more preferably 1×10^-6 (Ω·cm) to 8×10^-4 (Ω·cm), and even more preferably 1×10^-6 (Ω·cm) to 1×10^-4 (Ω·cm).

[0271] [Conductive components]

[0272] (Conductive sheet)

[0273] The conductive sheet used as the conductive component 72 is, for example, a sheet formed from a conductive metallic material such as copper foil. Examples of materials for the conductive sheet include copper, aluminum, gold, and silver.

[0274] Furthermore, the shape of the conductive sheet is not particularly limited; as mentioned above, it is preferably elongated. Also, the size of the conductive sheet is not particularly limited, as long as it can cover the size of the filling component 70.

[0275] (Conductor)

[0276] As described above, the conductive component 72 may have a structure having a conductor and a conductive wire or conductive sheet connected to the conductor.

[0277] Examples of materials for conductors include copper, aluminum, gold, silver, and brass.

[0278] Furthermore, there are no particular limitations on the shape and size of the conductor, as long as it can be connected to the filling component 70 and to the conductive sheet or conductive wire.

[0279] (Conductive line)

[0280] A wire made of conductive materials such as copper, aluminum, gold, and silver.

[0281] There are no particular limitations on the diameter and length of the conductive wire, as long as it can be connected to a conductor and a reliable electrical connection can be made.

[0282] [Fixed component and second fixed component]

[0283] As a fixing component and a second fixing component, as long as it can fix the conductive component and the protective layer, various adhesive materials, bonding materials, double-sided tapes, and adhesive tapes can be used.

[0284] As described above, the fixing component and the second fixing component can be disposed between the conductive component and the protective layer, which is called an adhesive layer, or they can be fixed to the protective layer from above the conductive component, which is called an adhesive sheet.

[0285] The following is for reference. Figures 14-19 An example of a method for manufacturing the piezoelectric element 10 will be described.

[0286] First, such as Figure 14 As shown, a sheet 10a with a lower electrode 24 formed on the lower protective layer 28 is prepared. The sheet 10a can be fabricated by forming a copper thin film or the like on the surface of the lower protective layer 28 as the lower electrode 24 through vacuum evaporation, sputtering, electroplating, etc.

[0287] The lower protective layer 28 is very thin, and in cases of poor operability, a lower protective layer 28 with a partition (temporary support) can be used as needed. Alternatively, a partition made of PET or similar material with a thickness of 25 μm to 100 μm can be used. The partition can be removed after the upper electrode 26 and upper protective layer 30 are hot-pressed together and before any components are stacked on the lower protective layer 28.

[0288] On the other hand, a coating is prepared by dissolving a polymer material, which serves as the matrix material, in an organic solvent, further adding piezoelectric particles 36 such as PZT particles, and then stirring and dispersing the mixture.

[0289] There are no restrictions on the use of organic solvents other than those mentioned above; a variety of organic solvents can be used.

[0290] When the sheet 10a is prepared and the coating is made, the coating is cast onto the sheet 10a, and the organic solvent is evaporated and dried. Therefore, as... Figure 15 As shown, a laminate 10b is formed by having a lower electrode 24 on the lower protective layer 28 and forming a piezoelectric layer 20 on the lower electrode 24. Note that the lower electrode 24 refers to the electrode on the substrate side when the piezoelectric layer 20 is coated, and does not indicate a vertical positional relationship within the laminate.

[0291] There are no restrictions on the casting method of this coating; all known methods (coating devices) such as slide coaters and doctor knives can be used.

[0292] As described above, in addition to viscoelastic materials such as cyanoethylated PVA, dielectric polymer materials can also be added to the matrix 34 in the piezoelectric element 10.

[0293] When adding these polymer materials to matrix 34, simply dissolve the added polymer materials in the coating.

[0294] When a laminate 10b is fabricated having a lower electrode 24 above the lower protective layer 28 and a piezoelectric layer 20 formed above the lower electrode 24, it is preferable to perform a polarization treatment on the piezoelectric layer 20.

[0295] There are no restrictions on the method of polarization treatment of the piezoelectric layer 20, and known methods can be used.

[0296] In addition, prior to this polarization treatment, a calendering process can be performed to smooth the surface of the piezoelectric layer 20 using a heated roller or similar device. By performing this calendering process, the hot pressing step described later can be carried out smoothly.

[0297] Therefore, while performing polarization treatment on the piezoelectric layer 20 of the laminate 10b, a sheet 10c for forming an upper electrode 26 is prepared on the upper protective layer 30. This sheet 10c can be fabricated by forming a copper thin film or the like on the surface of the upper protective layer 30 through vacuum evaporation, sputtering, or electroplating to serve as the upper electrode 26.

[0298] Next, as Figure 16 As shown, the sheet 10c is stacked on the laminate 10b that has undergone polarization treatment of the piezoelectric layer 20 by aligning the upper electrode 26 with the piezoelectric layer 20.

[0299] In addition, the laminate of the laminate 10b and the sheet 10c is configured to sandwich the upper protective layer 30 and the lower protective layer 28, so that the hot pressing device or heating roller can perform hot pressing on each other.

[0300] The above steps are used to fabricate a laminate with electrode layers and protective layers stacked on both surfaces of the piezoelectric layer 20. The fabricated laminate can also be cut into desired shapes according to various applications.

[0301] This type of laminate can be manufactured using cut sheet materials or by roll-to-roll (hereinafter also known as RtoR).

[0302] Next, a hole is provided in the protective layer of the laminate, and a filling member is formed in the hole. A conductive member is provided above the filling member.

[0303] Specifically, firstly, such as Figure 17 As shown, a hole 31 is formed in the upper protective layer 30.

[0304] The hole 31 can be formed using laser-based processing methods (such as carbon dioxide gas lasers) or by removing the protective layer after making a cut along the depth direction through stamping (for example, when the thickness of the protective layer is 10 μm and the thickness of the electrode layer is 2 μm, a circular cut is made along the thickness direction of the protective layer to a depth of 8 to 9.5 μm, and then the circular portion is peeled off).

[0305] Furthermore, during processing, the protrusion 32 can be formed by applying heat or an outward external force to the periphery of the hole to force deformation of the protective layer.

[0306] Alternatively, a recess 33 may be formed around the hole 31 by means of laser processing or the like after machining the hole 31 or before machining it.

[0307] In the case where the hole 31 is formed using laser processing, the hole with the desired opening shape is formed by scanning the laser. At this time, when the opening shape of the hole is circular, since the laser can scan in a spiral shape from the center to the outside or from the outside to the center, the heat generated by the laser processing becomes difficult to accumulate, and the reduction in the strength of the electrode layer can be suppressed.

[0308] When multiple holes are provided, and the total area of ​​the holes is the same, the heat generated during laser processing is less likely to accumulate when multiple holes are provided compared to when there is only one hole. Therefore, the reduction in the strength of the electrode layer can be suppressed, which is preferable.

[0309] Furthermore, the laser scanning lines during laser processing can be spaced differently on the center and outer sides of the hole. By setting the laser scanning line spacing differently on the center and outer sides of the hole, the amount of residue in the protective layer in the central portion and the amount of residue in the protective layer in the peripheral portion can be adjusted.

[0310] Furthermore, by adjusting the spacing of the laser scanning lines on the center side and the outer side of the hole to be different, the size of the gap generated between the electrode layer and the piezoelectric layer can be reduced.

[0311] Furthermore, during laser processing, large-diameter holes can be formed up to the midpoint of the protective layer's thickness, and then smaller-diameter holes are formed in the remaining thickness up to the electrode layer. Therefore, as described above... Figure 8 As shown, the structure can be configured such that the equivalent circle diameter changes in stages, and the equivalent circle diameter on the electrode layer side is smaller than the equivalent circle diameter on the conductive component side.

[0312] After the hole 31 is provided in the protective layer, as follows Figure 18As shown, a liquid conductive material 84 is coated onto the hole portion 31. During the coating process, the conductive material 84 extends out from the hole portion 31.

[0313] The coating method for the conductive material 84 can utilize screen printing, dispensing based on a dispensing machine, brush-based coating, etc.

[0314] After the conductive material 84 is coated onto the hole 31, as follows: Figure 19 As shown, the conductive component 72 is placed on the conductive material 84. That is, the conductive component 72 is placed in a manner that covers the conductive material 84 before the conductive material 84 is cured.

[0315] Among them, such as Figure 19 As shown, a fixing member 74 is adhered to the surface of the upper protective layer 30 side of the conductive member 72, and the conductive member 72 is placed on top of the conductive material 84, thus fixing the conductive member 72 to the upper protective layer 30. This prevents misalignment of the conductive member 72 due to the conductive material 84 being in an uncured state. Furthermore, by covering the conductive material 84 with the conductive member 72, movement of the conductive material 84 above the hole 31 is prevented, and the filling member 70 is reliably present within the hole 31.

[0316] After the conductive component 72 is placed on top of the conductive material 84, the conductive material 84 is cured to form the filling component 70.

[0317] The curing method for conductive material 84 can be performed according to the method for conductive material 84. For example, heating and drying can be used as curing methods for conductive material 84.

[0318] The piezoelectric element of the present invention is manufactured through the above steps.

[0319] Regarding this piezoelectric element 10, if a voltage is applied to the lower electrode 24 and the upper electrode 26, the piezoelectric particles 36 will stretch and contract in the polarization direction according to the applied voltage. As a result, the piezoelectric element 10 (piezoelectric layer 20) shrinks along the thickness direction. At the same time, due to Pascal's ratio, the piezoelectric element 10 also stretches and contracts in the in-plane direction. This stretching and contraction is about 0.01 to 0.1%. In addition, as described above, it stretches and contracts isotropically in all directions in the in-plane direction.

[0320] As described above, the thickness of the piezoelectric layer 20 is preferably around 10 to 300 μm. Therefore, the maximum stretching in the thickness direction is only about 0.3 μm, which is very small.

[0321] In contrast, the piezoelectric element 10, i.e., the piezoelectric layer 20, has a dimension in the planar direction that is significantly larger than its thickness. Therefore, for example, if the length of the piezoelectric element 10 is 20 cm, the piezoelectric element 10 can expand or contract by a maximum of about 0.2 mm when a voltage is applied.

[0322] Furthermore, if pressure is applied to the piezoelectric element 10, electricity is generated through the action of the piezoelectric particles 36.

[0323] By taking advantage of this, as described above, the piezoelectric element 10 can be used in a variety of applications such as loudspeakers, microphones, and pressure sensors.

[0324] Among them, common piezoelectric elements made of polymer materials such as PVDF have in-plane anisotropy in their piezoelectric properties, and the amount of expansion and contraction in the plane direction when a voltage is applied is anisotropic.

[0325] In contrast, a piezoelectric layer composed of a polymer composite piezoelectric material containing piezoelectric particles in a matrix containing polymer materials does not exhibit in-plane anisotropy in its piezoelectric properties and stretches isotropically in all in-plane directions.

[0326] Based on the piezoelectric element 10, which expands and contracts isotropically in two dimensions, it can vibrate with greater force and produce a louder and more pleasant sound compared to the case of stacked piezoelectric elements such as PVDF that expand and contract significantly in only one direction.

[0327] exist Figure 1 In the example shown, a structure with one piezoelectric element 10 is provided, but it is not limited to this. It can also be a structure formed by stacking multiple piezoelectric elements 10 of the present invention. Furthermore, the piezoelectric element 10 of the present invention can be made into a structure with multiple layers by making it into a strip shape and folding it back more than once (preferably more) along the length direction.

[0328] The piezoelectric element of the present invention has been described in detail above. However, the present invention is not limited to the above examples. Various improvements or modifications can be made without departing from the spirit of the present invention, which is to be expected.

[0329] Industrial availability

[0330] It can be preferentially used in various applications such as audio equipment such as speakers and microphones, as well as pressure sensors.

[0331] Symbol Explanation

[0332] 10-Piezoelectric element; 10a, 10c-Sheet; 10b-Layer; 20-Piezoelectric layer; 24-Lower electrode; 26-Upper electrode; 28-Lower protective layer; 30-Upper protective layer; 31-Hole; 32-Protrusion; 33-Recess; 34-Matrix; 36-Piezoelectric particle; 70-Filling component; 71-Protrusion; 72-Conductive component; 72a, 72b-Region; 73-Foldback; 74-Fixing component; 76-Enclosing component; 80-Gap; 82-Second fixing component; 84-Conductive component; 86-Conductive wire; 87-Solder; 88-Bonding component; 90-Support; 92-Conductor; 94-Substrate; 96-Wiring; 98-Printed wiring board; 100-Vibrating plate.

Claims

1. A piezoelectric element comprising a piezoelectric layer, electrode layers formed on two sides of the piezoelectric layer, and a protective layer stacked on the side of the electrode layers opposite to the side of the piezoelectric layer, wherein, The protective layer has a hole extending from the surface to the electrode layer. The piezoelectric element has: A filling component made of conductive material is formed from inside the pore to a portion of the surface of the protective layer and is electrically connected to the electrode layer; A conductive component that covers at least a portion of the filling component and is electrically connected to the filling component; and A fixing component that fixes the conductive component to the side of the protective layer opposite to the electrode layer.

2. The piezoelectric element according to claim 1, wherein, The conductive component is a conductive sheet.

3. The piezoelectric element according to claim 1, wherein, The conductive component has a conductor connected to the filling component and a conductive wire or conductive sheet connected to the conductor.

4. The piezoelectric element according to any one of claims 1 to 3, wherein, The piezoelectric element has a protrusion formed at the edge of the hole in the protective layer.

5. The piezoelectric element according to any one of claims 1 to 3, wherein, The equivalent circle diameter of the hole varies in stages along the depth direction, and the equivalent circle diameter on the electrode layer side is smaller than that on the conductive component side.

6. The piezoelectric element according to any one of claims 1 to 3, wherein, The amount of carbon on the surface of the electrode layer located within the hole is less at the central portion in the planar direction than in the area outside the central portion.

7. The piezoelectric element according to any one of claims 1 to 3, wherein, The amount of carbon on the surface of the electrode layer located within the hole is greater at the central portion in the planar direction than in the area outside the central portion.

8. The piezoelectric element according to any one of claims 1 to 3, wherein, The opening of the hole is circular.

9. The piezoelectric element according to any one of claims 1 to 3, wherein, The protective layer has a plurality of the aforementioned holes. The piezoelectric element has a plurality of filling members formed in the plurality of said holes respectively.

10. The piezoelectric element according to claim 9, wherein, Multiple filling components are connected to the surface of the protective layer.

11. The piezoelectric element according to any one of claims 1 to 3, wherein, The surface of the protective layer has a surrounding member that surrounds the hole. The filling component is formed at least within the surrounding component.

12. The piezoelectric element according to any one of claims 1 to 3, wherein, The piezoelectric element has a recess formed around the hole in the protective layer.

13. The piezoelectric element according to any one of claims 1 to 3, wherein, The thickness of the protective layer is 3μm to 100μm.

14. The piezoelectric element according to any one of claims 1 to 3, wherein, The thickness of the electrode layer is 0.05 μm to 10 μm.

15. The piezoelectric element according to any one of claims 1 to 3, wherein, At the location of the hole, there is a gap between the electrode layer and the piezoelectric layer. The difference between the average height of the interface between the piezoelectric layer and the electrode layer at the location where the hole is not formed and the average height of the interface between the piezoelectric layer and the electrode layer at the location of the hole is less than 25 μm.

16. The piezoelectric element according to any one of claims 1 to 3, wherein, The conductive component is elongated. The conductive component has a folded-back portion that folds back along its length. The fixing member fixes the conductive component and the protective layer in a region on the side opposite to the connection position of the conductive component and the filling component, separated by the folded-back portion.

17. The piezoelectric element according to any one of claims 1 to 3, wherein, The conductive component is elongated. The conductive component is connected to the filling component at one end along its length. The fixing component is positioned along the length of the conductive component at a location further away from one end than the connection point between the conductive component and the filling component.

18. The piezoelectric element according to claim 17, wherein, The piezoelectric element has a second fixing member that fixes at least a portion of the edge of the region between one end of the conductive element and the fixing member to the protective layer.

19. The piezoelectric element according to any one of claims 1 to 3, wherein, The piezoelectric layer is composed of a polymer composite piezoelectric body, which contains piezoelectric particles within a matrix of polymer materials.

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