Piezoelectric element

Abstract

Disclosed is a piezoelectric element configured to be specialized for unidirectional performance. The disclosed piezoelectric element comprises: a laminated piezoelectric body in which a plurality of piezoelectric material sheets are laminated in a first axis direction; and a plurality of electrodes disposed on each of the plurality of piezoelectric material sheets, wherein, among the plurality of piezoelectric material sheets, a reference sheet divides the plurality of piezoelectric material sheets into a first region and a second region, and the first region and the second region are asymmetric with respect to the reference sheet.

Description

piezoelectric element

[0001] The present invention relates to a piezoelectric element, and more particularly, to a piezoelectric element having a bimorph structure.

[0002] Piezoelectric materials produce voltage (electrical energy) when pressure (mechanical energy) is applied (piezoelectric effect). Conversely, when voltage (electrical energy) is applied, the piezoelectric material experiences an increase or decrease in volume or length (mechanical energy) due to the change in pressure (inverse piezoelectric effect). In particular, applying the inverse piezoelectric effect can be used to create vibration devices or speakers (which generate sound through vibration).

[0003] Piezoelectric products that meet the haptic characteristics required for mobile and automotive applications must simultaneously meet both small volume and high performance compared to piezoelectric materials for other applications.

[0004] The matters described in the background art above are intended to help understand the background of the invention and may include matters that are not publicly disclosed prior art.

[0005] The present invention has been proposed in consideration of the above-mentioned conventional circumstances, and its purpose is to provide a piezoelectric element that specializes in unidirectional performance.

[0006] In order to achieve the above object, a piezoelectric element according to a preferred embodiment of the present invention includes: a laminated piezoelectric body in which a plurality of piezoelectric material sheets are laminated in a first axial direction; and a plurality of electrodes arranged on each of the plurality of piezoelectric material sheets; wherein a reference sheet among the plurality of piezoelectric material sheets divides the plurality of piezoelectric material sheets into a first region and a second region, and the first region and the second region are asymmetrical with respect to the reference sheet.

[0007] The number of piezoelectric material sheets in the first region and the number of piezoelectric material sheets in the second region may be different from each other.

[0008] The number of electrodes in the first region and the number of electrodes in the second region may be different from each other.

[0009] The thickness of the first region and the thickness of the second region may be different from each other.

[0010] The formation shape of the electrode in the first region and the formation shape of the electrode in the second region may be different from each other.

[0011] The force of contraction and expansion in the first region and the force of contraction and expansion in the second region may be different from each other.

[0012] The plurality of piezoelectric material sheets may include a first piezoelectric material sheet having a first electrode disposed on one surface; a second piezoelectric material sheet having a second electrode disposed on one surface and disposed under the first piezoelectric material sheet; a third piezoelectric material sheet having a third electrode disposed on one surface and disposed under the second piezoelectric material sheet; a fourth piezoelectric material sheet having a fourth electrode disposed on one surface and disposed under the third piezoelectric material sheet; and a fifth piezoelectric material sheet having a fifth electrode disposed on one surface and a sixth electrode disposed on the other surface and disposed under the fourth piezoelectric material sheet.

[0013] The third electrode and the fifth electrode may be connected to each other through a first via, and the fourth electrode and the fifth electrode may be connected to each other through a second via.

[0014] One end of the AC power supply is connected to the first electrode and the fourth electrode, the other end of the AC power supply is connected to the second electrode and the third electrode, and AC power from the AC power supply is applied to the first to fourth electrodes, so that contraction and expansion motions can be alternately performed in the remaining sheets except for the second piezoelectric material sheet.

[0015] The above reference sheet may be the second piezoelectric material sheet.

[0016] According to the present invention of this configuration, by asymmetrically configuring the upper and lower layers of the piezoelectric element, it is possible to improve (specialize) the performance in one direction (i.e., the direction in which the vibrating plate is attached) rather than in both directions.

[0017] By manufacturing piezoelectric elements with an asymmetric structure, performance control in a specific direction can be expected, and a reduction in process costs can be expected compared to piezoelectric elements with a symmetric structure.

[0018] In addition, the embodiments of the present invention can be applied to various types of electric vehicles and mobile phone parts, and the process cost can be significantly reduced by eliminating the process required for dustproofing and waterproofing of existing physical buttons.

[0019] Figure 1 is an exploded perspective view of a conventional piezoelectric element in contrast to an embodiment of the present invention.

[0020] Figure 2 is a cross-sectional view of the piezoelectric element illustrated in Figure 1.

[0021] Figure 3 is a drawing for explaining polarization treatment for the piezoelectric element shown in Figure 1.

[0022] Figures 4 and 5 are drawings for explaining the operation of the piezoelectric element shown in Figure 1.

[0023] Figure 6 is an exploded perspective view of a piezoelectric element according to an embodiment of the present invention.

[0024] FIG. 7 is a cross-sectional view of a piezoelectric element according to an embodiment of the present invention illustrated in FIG. 6.

[0025] FIG. 8 is a drawing illustrating a state after polarization treatment is performed on a piezoelectric element according to an embodiment of the present invention.

[0026] Figure 9 is a drawing for explaining the operation of a piezoelectric element according to an embodiment of the present invention.

[0027] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0028] These examples are provided to more fully illustrate the present invention to those skilled in the art. The following examples may be modified in various ways, and the scope of the present invention is not limited to the examples described below. Rather, these examples are provided to further faithfully and completely convey the spirit of the present invention.

[0029] The terminology used herein is used to describe specific embodiments and is not intended to limit the present invention. In addition, the singular form in this specification may include the plural form unless the context clearly indicates otherwise. It should be understood that the terms "comprise," "include," and "have" in this application are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof of the invention, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] In the description of the embodiments, when each layer (film), region, pattern or structure is described as being formed "on" or "under" the substrate, each layer (film), region, pad or pattern, "on" and "under" include both being formed "directly" or "indirectly" through another layer. In addition, the reference for above or below each layer is, in principle, based on the drawing.

[0031] The drawings are intended solely to facilitate understanding of the invention and should not be construed as limiting the scope of the invention. Furthermore, relative thicknesses, lengths, and sizes in the drawings may be exaggerated for convenience and clarity of explanation.

[0032] FIG. 1 is an exploded perspective view of a conventional piezoelectric element in contrast to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the piezoelectric element illustrated in FIG. 1, FIG. 3 is a drawing for explaining polarization treatment for the piezoelectric element illustrated in FIG. 1, and FIGS. 4 and 5 are drawings for explaining the operation of the piezoelectric element illustrated in FIG. 1.

[0033] The conventional piezoelectric element (10) is a symmetrical piezoelectric element and includes a plurality of piezoelectric material sheets (30, 32, 34, 36, 40, 42, 44, 46) and electrodes (31, 33).

[0034] For example, each of a plurality of piezoelectric material sheets (30, 32, 34, 36, 40, 42, 44, 46) can be formed into a thin single-layer film by performing a polishing process on a piezoelectric ceramic in the form of a thick film.

[0035] A plurality of piezoelectric material sheets (30, 32, 34, 36, 40, 42, 44, 46) are sequentially laminated.

[0036] Each of the plurality of piezoelectric material sheets (30, 32, 34, 36, 40, 42, 44, 46) may include not only polycrystalline ceramics such as PZT, but also single-crystal piezoelectric materials such as PMN-PT, PZN-PT, PIN-PT, and PYN-PT, flexible piezoelectric polymer materials such as PVDF and PVDF-TrFE, and lead-free piezoelectric new materials such as BNT (BaNiTiO3) and BZT-BCT.

[0037] A first electrode (31) is formed on one side (e.g., the upper side) of a piezoelectric material sheet (30), and a second electrode (33) is formed on one side (e.g., the upper side) of a piezoelectric material sheet (32).

[0038] A first electrode (31) is formed on one surface (e.g., the upper surface) of a piezoelectric material sheet (34), and a second electrode (33) is formed on one surface (e.g., the upper surface) of a piezoelectric material sheet (36).

[0039] A first electrode (31) is formed on one side (e.g., the upper side) of a piezoelectric material sheet (40), a second electrode (33) is formed on one side (e.g., the upper side) of a piezoelectric material sheet (42), a first electrode (31) is formed on one side (e.g., the upper side) of a piezoelectric material sheet (44), and a second electrode (33) is formed on one side (e.g., the upper side) of a piezoelectric material sheet (46).

[0040] The first electrode (31) and the second electrode (33) may be composed of various printable electrodes containing a conductor such as silver.

[0041] Additionally, a via (32a) of a predetermined diameter is formed in the piezoelectric material sheet (32), and the via (32a) is formed to be spaced apart from the second electrode (33) formed in the piezoelectric material sheet (32).

[0042] A via (34a) of a predetermined diameter is formed in the piezoelectric material sheet (34), and the via (34a) is formed to be spaced apart from the first electrode (31) formed in the piezoelectric material sheet (34).

[0043] A via (42a) of a predetermined diameter is formed on the piezoelectric material sheet (42), and the via (42a) is formed to be spaced apart from the second electrode (33) formed on the piezoelectric material sheet (42).

[0044] A via (44a) of a predetermined diameter is formed on the piezoelectric material sheet (44), and the via (44a) is formed to be spaced apart from the first electrode (31) formed on the piezoelectric material sheet (44).

[0045] The interior of the above-described vias (32a, 34a, 42a, 44a) can be filled with a conductive material.

[0046] When the piezoelectric material sheets (30, 32, 34, 36, 40, 42, 44, 46) on which the above-described electrodes are formed are prepared, the piezoelectric material sheet (46) is made as the lowest layer, the piezoelectric material sheet (44) is laminated on the piezoelectric material sheet (46), the piezoelectric material sheet (42) is laminated on the piezoelectric material sheet (44), the piezoelectric material sheet (40) is laminated on the piezoelectric material sheet (42), the piezoelectric material sheet (36) is laminated on the piezoelectric material sheet (40), the piezoelectric material sheet (34) is laminated on the piezoelectric material sheet (36), the piezoelectric material sheet (32) is laminated on the piezoelectric material sheet (34), and the piezoelectric material sheet (30) is laminated on the piezoelectric material sheet (32).

[0047] After all piezoelectric material sheets (30, 32, 34, 36, 40, 42, 44, 46) are laminated, they are pressurized at a predetermined pressure at room temperature to become integrated.

[0048] Then, the sintering is continued for a predetermined time (e.g., about 15 minutes) at the final sintering temperature (e.g., about 875°C).

[0049] When the firing is completed, a laminated piezoelectric body (11) having a cross-sectional structure as in Fig. 2 is completed.

[0050] And, as in Fig. 3, by applying a DC voltage for a predetermined time with the first electrode (31) as the positive (+) pole and the second electrode (33) as the negative (-) pole to the laminated piezoelectric body (11), a polarization phenomenon occurs in the laminated piezoelectric body (11).

[0051] Due to the polarization phenomenon, as shown in Fig. 3, the positive and negative ions in the laminated piezoelectric body (11) are aligned in a certain direction according to the direction of the applied voltage. In this way, in the laminated piezoelectric body (11), the piezoelectric material sheet (30, 32, 34) region will become the upper layer (12), and the piezoelectric material sheet (40, 42, 44) region will become the lower layer (13).

[0052] As an example of a conventional piezoelectric element, a piezoelectric element in which the upper layer (12) and the lower layer (13) are symmetrical to each other was mentioned, and since the piezoelectric material sheet (46) can be omitted, the area of ​​the piezoelectric material sheet (46) is assumed to be absent in FIGS. 2 and 3. That is, the first electrode (31) is formed on the upper surface of the piezoelectric material sheet (44) in FIG. 1, and the second electrode (33) is formed (arranged) on the lower surface of the piezoelectric material sheet (44).

[0053] Thereafter, an AC voltage having a cycle as exemplified in FIG. 4 (e.g., having a +peak voltage of +20 V and a -peak voltage of -20 V) is applied to the polarized laminated piezoelectric body (11). At this time, it is assumed that the external power source (i.e., the AC voltage) and the electrodes (31, 33) are connected in a connection relationship as in FIG. 5. In the cases of (a) and (b) of FIG. 5, the area of ​​the piezoelectric material sheet (36) in the laminated piezoelectric body (11) neither contracts nor expands. Therefore, the area of ​​the piezoelectric material sheets (30, 32, 34) can be referred to as the upper layer (12) based on the area of ​​the piezoelectric material sheet (36), and the area of ​​the piezoelectric material sheets (40, 42, 44) can be referred to as the lower layer (13).

[0054] As shown in Fig. 5, the laminated piezoelectric material (11) causes the upper layer (12) and the lower layer (13) to periodically contract / expand in opposite directions due to the applied AC voltage, thereby deforming the vibration plate (20). In Fig. 5, reference numeral 50 may be an FPCB.

[0055] Haptic performance mostly requires characteristics in the direction in which the vibration plate (20) is attached (connected). However, in the conventional symmetrical bimorph piezoelectric structure described above, kinetic energy is dissipated in both directions (i.e., the upper layer connected to the FPCB (50) and the lower layer connected to the vibration plate (20), resulting in a waste of approximately 50% or more. Therefore, when a demand for improved characteristics arises, development of a new piezoelectric material is required to increase the permittivity, which may result in additional process development costs and increased development difficulty.

[0056] To address this, embodiments of the present invention configure the layer thicknesses and stacking quantities of the upper and lower layers of the piezoelectric element asymmetrically. Embodiments of the present invention are described below.

[0057] FIG. 6 is an exploded perspective view of a piezoelectric element according to an embodiment of the present invention, and FIG. 7 is a cross-sectional view of the piezoelectric element according to an embodiment of the present invention illustrated in FIG. 6.

[0058] A piezoelectric element (60) according to an embodiment of the present invention is an asymmetrical piezoelectric element, and includes a laminated piezoelectric body (61) in which a plurality of piezoelectric material sheets (70, 72, 80, 82, 84, 86) are laminated, and electrodes (34, 35, 36, 37, 38, 39).

[0059] For example, each of the plurality of piezoelectric material sheets (70, 72, 80, 82, 84, 86) can be formed into a thin single-layer film by performing a polishing process on a piezoelectric ceramic in the form of a thick film.

[0060] A plurality of piezoelectric material sheets (70, 72, 80, 82, 84, 86) are sequentially laminated.

[0061] Each of the plurality of piezoelectric material sheets (70, 72, 80, 82, 84, 86) may include not only polycrystalline ceramics such as PZT, but also single-crystal piezoelectric materials such as PMN-PT, PZN-PT, PIN-PT, and PYN-PT, flexible piezoelectric polymer materials such as PVDF and PVDF-TrFE, and lead-free piezoelectric new materials such as BNT (BaNiTiO3) and BZT-BCT.

[0062] A first electrode (34) is formed (arranged) on one side (e.g., upper side) of a first piezoelectric material sheet (70), and a second electrode (35) is formed (arranged) on one side (e.g., upper side) of a second piezoelectric material sheet (72).

[0063] A third electrode (36) is formed (arranged) on one side (e.g., upper side) of the third piezoelectric material sheet (80), and a fourth electrode (37) is formed (arranged) on one side (e.g., upper side) of the fourth piezoelectric material sheet (82).

[0064] A fifth electrode (38) is formed (arranged) on one surface (e.g., upper surface) of the fifth piezoelectric material sheet (84), and a sixth electrode (39) is formed (arranged) on one surface (e.g., upper surface) of the sixth piezoelectric material sheet (86).

[0065] In FIG. 6, the sixth electrode (39) is formed (arranged) on the upper surface of the sixth piezoelectric material sheet (86), but the sixth piezoelectric material sheet (86) may be omitted if necessary. For example, instead of employing the sixth piezoelectric material sheet (86), the fifth electrode (38) may be formed on the upper surface of the fifth piezoelectric material sheet (84) and the sixth electrode (39) may be formed (arranged) on the lower surface of the fifth piezoelectric material sheet (84).

[0066] For example, the above-described electrodes (34, 35, 36, 37, 38, 39) may be made of a metal material including silver (Ag), magnesium (Mg), aluminum (Al), copper (Cu), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), and chromium (Cr). Alternatively, the electrodes (34, 35, 36, 37, 38, 39) may also include a transparent conductive oxide including ITO (InSnO), IZO (InZnO), IZTO (InZnSnO), ZnO, and In2O3. On the other hand, the electrodes (34, 35, 36, 37, 38, 39) may include conductive polymers including polyaniline, polypyrrole, and polythiopene.

[0067] In addition, a via (82a) having a predetermined diameter is formed in the fourth piezoelectric material sheet (82), and the via (82a) is formed to be spaced apart from the fourth electrode (37) of the fourth piezoelectric material sheet (82). The interior of the via (82a) may be filled with a conductive material. Here, the via (82a) is for connecting the third electrode (36) formed on the upper surface of the third piezoelectric material sheet (80) and the fifth electrode (38) formed on the upper surface of the fifth piezoelectric material sheet (84) to each other. The via (82a) may be the first via described in the claims of the present invention. Of course, although not shown, in order for the third electrode (36) and the fifth electrode (38) to be connected to each other, a via must be formed in the third piezoelectric material sheet (80) at a position facing the first via (82a) in the vertical direction.

[0068] A via (84a) having a predetermined diameter is formed in the fifth piezoelectric material sheet (84), and the via (84a) is formed to be spaced apart from the fifth electrode (38) formed in the fifth piezoelectric material sheet (84). The interior of the via (84a) may be filled with a conductive material. Here, the via (84a) is for connecting the fourth electrode (37) formed on the upper surface of the fourth piezoelectric material sheet (82) and the sixth electrode (39) formed on the upper surface of the sixth piezoelectric material sheet (86) (or the lower surface of the fifth piezoelectric material sheet (84)). The via (84a) may be the second via described in the claims of the present invention. Of course, although not shown, in order for the fourth electrode (37) and the sixth electrode (39) to be connected to each other, a via must be formed in the fourth piezoelectric material sheet (82) at a position facing the second via (84a) in the vertical direction.

[0069] In the above-described embodiment of the present invention, the third electrode (36) and the fifth electrode (38) are connected to each other and the fourth electrode (37) and the sixth electrode (39) are connected to each other using vias (82a, 84a) that are not exposed to the outside of the laminated piezoelectric body (61). The present invention is not limited thereto. The third electrode (36) and the fifth electrode (38) may be connected to each other and the fourth electrode (37) and the sixth electrode (39) may be connected to each other using a connection structure of a different form than the above-described vias (82a, 84a).

[0070] When the piezoelectric material sheets (70, 72, 80, 82, 84, 86) on which the above-described electrodes are formed are prepared, the sixth piezoelectric material sheet (86) is the lowest layer, the fifth piezoelectric material sheet (84) is laminated on the sixth piezoelectric material sheet (86), the fourth piezoelectric material sheet (82) is laminated on the fifth piezoelectric material sheet (84), the third piezoelectric material sheet (80) is laminated on the fourth piezoelectric material sheet (82), the second piezoelectric material sheet (72) is laminated on the third piezoelectric material sheet (80), and the first piezoelectric material sheet (70) is laminated on the second piezoelectric material sheet (72).

[0071] That is, the piezoelectric material sheets (70, 72, 80, 82, 84, 86) are laminated in the first axial direction (i.e., the up-down direction or the vertical direction).

[0072] After all piezoelectric material sheets (70, 72, 80, 82, 84, 86) are laminated, they are pressurized at room temperature at a predetermined pressure to become integrated.

[0073] Then, the sintering is continued for a predetermined time (e.g., about 15 minutes) at the final sintering temperature (e.g., about 875°C).

[0074] When the firing is completed, a laminated piezoelectric body (61) having a cross-sectional structure as in Fig. 7 is completed.

[0075] FIG. 8 is a drawing illustrating a state after polarization treatment is performed on a piezoelectric element according to an embodiment of the present invention.

[0076] The polarization treatment method may be the same as that described above with reference to FIG. 3.

[0077] That is, a direct current voltage is applied to the electrodes of the laminated piezoelectric body (61) of Fig. 7. For example, after connecting the positive (+) pole of the direct current power supply to the first electrode (34) and the third electrode (36) and connecting the negative (-) pole of the direct current power supply to the second electrode (35) and the fourth electrode (37), a direct current voltage is applied for a predetermined period of time, thereby causing a polarization phenomenon to occur in the laminated piezoelectric body (61).

[0078] By polarization, as shown in Fig. 8, positive and negative ions within the laminated piezoelectric body (61) are aligned in a certain direction according to the direction of the applied voltage. This polarization phenomenon is maintained in the laminated piezoelectric body even when the external power source is removed.

[0079] The piezoelectric element according to the embodiment of the present invention is said to be an asymmetrical piezoelectric element, and therefore, the sixth piezoelectric material sheet (86) may be omitted. Therefore, in FIGS. 7 and 8, the area of ​​the sixth piezoelectric material sheet (86) is assumed to be absent. That is, the fifth electrode (38) may be formed on the upper surface of the fifth piezoelectric material sheet (84) in FIG. 6, and the sixth electrode (39) may be formed (arranged) on the lower surface of the fifth piezoelectric material sheet (84).

[0080] A laminated piezoelectric material polarized in this manner can be called a piezoelectric element in an embodiment of the present invention.

[0081] Figure 9 is a drawing for explaining the operation of a piezoelectric element according to an embodiment of the present invention.

[0082] First, it is assumed that an AC voltage (e.g., having a +peak voltage of +20 V and a -peak voltage of -20 V) that changes continuously over time with a cycle as in Fig. 4 is applied to the laminated piezoelectric body (61).

[0083] In order to apply AC power to the laminated piezoelectric body (61), as shown in Fig. 9, one end of the AC power supply is connected to the first electrode (34) and the fourth electrode (37), and the other end of the AC power supply is connected to the second electrode (35) and the third electrode (36).

[0084] In the above connection structure, when the AC voltage of the AC power supply is applied to the second to fourth electrodes (34, 35, 36, 37), only the second piezoelectric material sheet (72) among the piezoelectric material sheets of the laminated piezoelectric body (61) neither contracts nor expands, as shown in (a) and (b) of FIG. 9. In other words, it can be seen that the reverse piezoelectric effect does not occur in the second piezoelectric material sheet (72).

[0085] Accordingly, the second piezoelectric material sheet (72) described above can be a reference sheet that divides a plurality of stacked piezoelectric material sheets into an upper layer (62) region and a lower layer (63) region. Accordingly, the upper region based on the second piezoelectric material sheet (72) can be referred to as the upper layer (62), and the lower region based on the second piezoelectric material sheet (72) can be referred to as the lower layer (63). Here, the upper layer (62) can be an example of the first region described in the claims of the present invention, and the lower layer (63) can be an example of the second region described in the claims of the present invention.

[0086] Accordingly, in the embodiment of the present invention, the number of piezoelectric material sheets of the upper layer (62) and the number of piezoelectric material sheets of the lower layer (63) are different. For example, in FIGS. 6 to 9, the number of piezoelectric material sheets of the upper layer (62) may be 1 (i.e., the first piezoelectric material sheet (70)), and the number of piezoelectric material sheets of the lower layer (63) may be 3 (i.e., the third to fifth piezoelectric material sheets (80, 82, 84)).

[0087] In addition, in an embodiment of the present invention, the number of electrodes of the upper layer (62) and the number of electrodes of the lower layer (63) are different. For example, in FIGS. 6 to 9, the number of electrodes of the upper layer (62) may be two (i.e., the first electrode (34), the second electrode (35)), and the number of electrodes of the lower layer (63) may be four (the third electrode (36), the fourth electrode (37), the fifth electrode (38), the sixth electrode (39)).

[0088] In addition, in an embodiment of the present invention, the thickness of the upper layer (62) is different from the thickness of the lower layer (63). For example, as shown in FIGS. 6 to 9, the number of laminated piezoelectric material sheets and electrodes of the lower layer (63) is greater than that of the upper layer (62), so the thickness of the upper layer (62) is thicker than that of the lower layer (63).

[0089] In addition, in an embodiment of the present invention, the formation shape of the electrode of the upper layer (62) is different from the formation shape of the electrode of the lower layer (63). For example, as shown in FIGS. 6 to 9, the electrodes (34, 35) of the upper layer (62) are formed from one end of one side (e.g., the upper surface) to the other end of the corresponding piezoelectric material sheet (70, 72), whereas the fourth electrode (37) of the lower layer (63) is formed by extending a predetermined distance from one end of one side (e.g., the upper surface) of the corresponding piezoelectric material sheet (82) toward the other end, and the fifth electrode (38) of the lower layer (63) is formed by extending a predetermined distance from the other end of one side (e.g., the upper surface) of the corresponding piezoelectric material sheet (84) toward the one end.

[0090] When comparing the number of piezoelectric material sheets, number of electrodes, thickness, etc. of the upper layer (62) and lower layer (63) described above, it can be seen that the upper layer (62) and lower layer (63) are configured (formed) in a ratio of approximately 1:3. Accordingly, the piezoelectric element (60) according to the embodiment of the present invention can be said to have an asymmetrical structure.

[0091] Of course, the upper layer (62) and the lower layer (63) may be configured (formed) in a ratio other than 1:3. For example, the upper layer (62) and the lower layer (63) may be configured in a ratio of 1:2, but in this case, compared to configuring them in a ratio of 1:3, there is a somewhat weaker aspect in specializing (improving) the characteristics (performance) of a specific direction (i.e., the direction in which the diaphragm is attached). On the other hand, the upper layer (62) and the lower layer (63) may be configured in a ratio of 1:4 or more. If the upper layer (62) and the lower layer (63) are configured at a ratio of 1:4 or more, it is possible to specialize (improve) the characteristics (performance) of a specific direction (i.e., the direction in which the vibration plate is attached) compared to configuring them at a ratio of 1:3, but the number of laminated piezoelectric material sheets and the number of electrodes of the lower layer (63) will increase, so the process cost will be higher compared to configuring the upper layer (62) and the lower layer (63) at a ratio of 1:3.

[0092] When an AC voltage such as that in Fig. 4 is applied to the laminated piezoelectric body (61), the laminated piezoelectric body (61) repeats expansion and contraction as in Fig. 9.

[0093] For example, in the case of section ① of FIG. 4, the laminated piezoelectric body (61) of the embodiment of the present invention undergoes a contraction and expansion movement as shown in (a) of FIG. 9. That is, in section ① of FIG. 4, the upper layer (62) of the laminated piezoelectric body (61) of the embodiment of the present invention can contract by the contraction movement, and the lower layer (63) of the laminated piezoelectric body (61) can expand by the expansion movement.

[0094] At this time, since the upper layer (62) and the lower layer (63) of the laminated piezoelectric body (61) can be configured asymmetrically at a ratio of approximately 1:3, in the case of section ① of FIG. 4, the expansion kinetic energy of the lower layer (63) is much greater than the contraction kinetic energy of the upper layer (62), as in (a) of FIG. 9. That is, the expansion force of the lower layer (63) is much stronger than the contraction force of the upper layer (62). In other words, the strength of the expansion force of the lower layer (63) is much greater than the strength of the contraction force of the upper layer (62).

[0095] Accordingly, in the case of section ① of FIG. 4, the laminated piezoelectric body (61) of the embodiment of the present invention is more specialized (improved) in the characteristics (performance) of the direction (or region) to which the vibration plate (20) is attached than in the characteristics of the direction (or region) to which the FPCB (50) is attached.

[0096] Meanwhile, in section ② of FIG. 4, the laminated piezoelectric body (61) of the embodiment of the present invention undergoes a contraction and expansion movement as shown in (b) of FIG. 9. That is, since the direction of current flow in section ② of FIG. 4 is opposite to the direction of current flow in section ① of FIG. 4, the upper layer (62) of the laminated piezoelectric body (61) can expand by the expansion movement, and the lower layer (63) of the laminated piezoelectric body (61) can contract by the contraction movement.

[0097] At this time, since the upper layer (62) and the lower layer (63) of the laminated piezoelectric body (61) can be configured asymmetrically at a ratio of approximately 1:3, in the case of section ② of FIG. 4, the contraction kinetic energy of the lower layer (63) is much greater than the expansion kinetic energy of the upper layer (62), as in (b) of FIG. 9. That is, the contraction force of the lower layer (63) is much stronger than the expansion force of the upper layer (62). In other words, the strength of the contraction force of the lower layer (63) is much greater than the strength of the expansion force of the upper layer (62).

[0098] Accordingly, in the case of section ② of Fig. 4, the laminated piezoelectric material (61) is more specialized (improved) in the characteristics (performance) of the direction (or area) to which the vibration plate (20) is attached than in the characteristics of the direction (or area) to which the FPCB (50) is attached.

[0099] As described above, when the upper layer (62) and the lower layer (63) of the piezoelectric element (60; more specifically, the laminated piezoelectric body (61)) are manufactured in an asymmetrical structure and an external power source (e.g., an AC voltage from an AC power source) is applied, the characteristics (performance) of the direction (or part) to which the vibration plate (20) is attached are further specialized, so that the deformation of the vibration plate (20) (e.g., the width of the up / down vibration in FIG. 9) can be maximized.

[0100] The above description is merely an illustrative illustration of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate, rather than limit, the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

Claims

1. A laminated piezoelectric material in which a plurality of piezoelectric material sheets are laminated in the first axis direction; and A plurality of electrodes arranged on each of the plurality of piezoelectric material sheets; Among the plurality of piezoelectric material sheets, a reference sheet divides the plurality of piezoelectric material sheets into a first region and a second region, The first region and the second region are asymmetrical with respect to the reference sheet. Piezoelectric element.

2. In paragraph 1, The number of piezoelectric material sheets in the first region and the number of piezoelectric material sheets in the second region are different from each other. Piezoelectric element.

3. In paragraph 1, The number of electrodes in the first region and the number of electrodes in the second region are different from each other. Piezoelectric element.

4. In paragraph 1, The thickness of the first region and the thickness of the second region are different from each other, Piezoelectric element.

5. In paragraph 1, The formation shape of the electrode of the first region and the formation shape of the electrode of the second region are different from each other. Piezoelectric element.

6. In paragraph 1, The force of contraction and expansion in the first region and the force of contraction and expansion in the second region are different from each other. Piezoelectric element.

7. In paragraph 1, The above multiple piezoelectric material sheets are, A first piezoelectric material sheet having a first electrode arranged on one surface; A second piezoelectric material sheet having a second electrode disposed on one surface thereof and disposed below the first piezoelectric material sheet; A third piezoelectric material sheet having a third electrode disposed on one surface thereof and disposed under the second piezoelectric material sheet; A fourth piezoelectric material sheet having a fourth electrode disposed on one side thereof and disposed below the third piezoelectric material sheet; and A fifth piezoelectric material sheet having a fifth electrode disposed on one side and a sixth electrode disposed on the other side, and disposed on the lower side of the fourth piezoelectric material sheet; Piezoelectric element.

8. In paragraph 7, The third electrode and the fifth electrode are connected to each other through the first via, The fourth electrode and the fifth electrode are connected to each other through the second via, Piezoelectric element.

9. In paragraph 8, One end of the AC power supply is connected to the first electrode and the fourth electrode, The other end of the AC power supply is connected to the second electrode and the third electrode, As the AC power from the AC power supply is applied to the first to fourth electrodes, the remaining sheets, excluding the second piezoelectric material sheet, alternately perform contraction and expansion movements. Piezoelectric element.

10. In paragraph 7, The above reference sheet is, The second piezoelectric material sheet, Piezoelectric element.

Images