KR102626340B1 - Piezoelectric device, piezoelectric actuator including the device, and piezoelectric module including the actuator - Google Patents

Abstract

The piezoelectric element according to the embodiment includes a piezoelectric part; a first outer electrode disposed on a side surface of the piezoelectric unit and connected to a plurality of first electrodes and a second outer electrode connected to a plurality of second electrodes; first group electrodes alternately stacked at predetermined intervals within the piezoelectric unit and including a portion of the plurality of first electrodes and a portion of the plurality of second electrodes; and second group electrodes that are alternately stacked and spaced apart from each other at predetermined intervals within the piezoelectric unit and include a remaining portion of the plurality of first electrodes and a remaining portion of the plurality of second electrodes, One of the plurality of spacings formed between one electrode and the plurality of second electrodes is different from the other spacing, and the lowest electrode among the first group electrodes is the uppermost electrode among the second group electrodes. Although adjacent, the lowermost electrode and the uppermost electrode may be included in any one of the plurality of first electrodes and the plurality of second electrodes.

Description

Piezoelectric element, piezoelectric actuator including the element, and piezoelectric module including the actuator {Piezoelectric device, piezoelectric actuator including the device, and piezoelectric module including the actuator}

Embodiments relate to a piezoelectric element, a piezoelectric actuator including the element, and a piezoelectric module including the actuator.

In general, a piezoelectric element refers to an element that has the property of being able to change electrical energy and mechanical energy.

A piezoelectric speaker is a representative product of an acoustic component that generates sound in a desired frequency band by converting the mechanical movement of the piezoelectric element into acoustics using a diaphragm. At this time, the piezoelectric element generates voltage by the force applied to the piezoelectric ceramic, and the amount of voltage generated varies depending on the strength of the force.

In particular, the demand for piezoelectric speakers is increasing in recent mobile devices as there is a noticeable tendency to remove speaker holes that are exposed to the outside not only for waterproofing and dustproofing purposes but also for freedom of design. For example, these piezoelectric speakers are placed below the display of a mobile device such as a smartphone or smart tablet and vibrate the display panel itself to output sound.

In general, a piezoelectric speaker with good characteristics has high output, high sound pressure at each frequency, has a flat shape, and has a wide sound range. However, in the case of existing piezoelectric elements, resonance displacement is difficult to occur in the frequency range below 20Khz, so it is difficult to output low sounds.

Embodiments provide a piezoelectric element having a low resonance frequency but low power consumption and heat generation, a piezoelectric actuator including the element, and a piezoelectric module including the actuator.

A piezoelectric element according to an embodiment includes a piezoelectric part; a first outer electrode disposed on a side surface of the piezoelectric unit and connected to a plurality of first electrodes and a second outer electrode connected to a plurality of second electrodes; first group electrodes alternately stacked at predetermined intervals within the piezoelectric unit and including a portion of the plurality of first electrodes and a portion of the plurality of second electrodes; and second group electrodes that are alternately stacked and spaced apart from each other at predetermined intervals within the piezoelectric unit and include a remaining portion of the plurality of first electrodes and a remaining portion of the plurality of second electrodes, One of the plurality of spacings formed between one electrode and the plurality of second electrodes is different from the other spacing, and the lowest electrode among the first group electrodes is the uppermost electrode among the second group electrodes. Although adjacent, the lowermost electrode and the uppermost electrode may be included in any one of the plurality of first electrodes and the plurality of second electrodes.

For example, the piezoelectric part may include a dummy part defined between the lowermost electrode and the uppermost electrode.

For example, the spacing between the plurality of units may change from the dummy portion upward or downward in the thickness direction of the piezoelectric portion.

For example, the first group electrode may be disposed on the upper side of the dummy portion in the thickness direction of the piezoelectric portion, and the second group electrode may be disposed on the lower side of the dummy portion in the thickness direction.

For example, the piezoelectric unit includes a plurality of polarization portions defined by first and second electrodes adjacent to each other, and the polarization portion defined by the first group electrode among the plurality of polarization portions is the first group electrode. The polarization portion defined by the second group electrode among the plurality of polarization portions may be opposite to the direction of the electric field applied by the second group electrode.

For example, it may include a plurality of polarization portions defined by first and second electrodes adjacent to each other, and the polarization direction of each of the plurality of polarization portions may be opposite to that of the polarization portions adjacent to each other in the thickness direction of the piezoelectric portion. You can.

For example, the plurality of first electrodes are exposed to one of the sides of the piezoelectric unit and are electrically connected to the first outer electrode, and the plurality of second electrodes are exposed to the other side opposite to the one side. and can be electrically connected to the second outer electrode.

For example, the spacing between the plurality of units may decrease from the dummy portion upward or downward in the thickness direction of the piezoelectric portion.

For example, the reduction in the spacing between the plurality of units may be 8% to 15%.

For example, the piezoelectric unit may vibrate in a bending mode when power is applied through the first outer electrode and the second outer electrode, and may have at least one resonance frequency in a region of 10 kHz or less.

A piezoelectric actuator according to an embodiment includes a piezoelectric element; a display unit disposed on the piezoelectric element; an adhesive layer disposed between the piezoelectric element and the display unit; And it may include a cover member disposed on the display unit. Here, the piezoelectric element includes: a piezoelectric part; a first outer electrode disposed on a side surface of the piezoelectric unit and connected to a plurality of first electrodes and a second outer electrode connected to a plurality of second electrodes; first group electrodes alternately stacked at predetermined intervals within the piezoelectric unit and including a portion of the plurality of first electrodes and a portion of the plurality of second electrodes; and second group electrodes that are alternately stacked and spaced apart from each other at predetermined intervals within the piezoelectric unit and include a remaining portion of the plurality of first electrodes and a remaining portion of the plurality of second electrodes, One of the plurality of spacings formed between one electrode and the plurality of second electrodes is different from the other spacing, and the lowest electrode among the first group electrodes is the uppermost electrode among the second group electrodes. Although adjacent, the lowermost electrode and the uppermost electrode may be included in any one of the plurality of first electrodes and the plurality of second electrodes.

A piezoelectric module according to an embodiment includes a piezoelectric actuator; and a drive control unit that drives the piezoelectric actuator, wherein the piezoelectric actuator includes a piezoelectric element; a display unit disposed on the piezoelectric element; an adhesive layer disposed between the piezoelectric element and the display unit; And it may include a cover member disposed on the display unit. Here, the piezoelectric element includes a piezoelectric part; a first outer electrode disposed on a side surface of the piezoelectric unit and connected to a plurality of first electrodes and a second outer electrode connected to a plurality of second electrodes; first group electrodes alternately stacked at predetermined intervals within the piezoelectric unit and including a portion of the plurality of first electrodes and a portion of the plurality of second electrodes; and second group electrodes that are alternately stacked and spaced apart from each other at predetermined intervals within the piezoelectric unit and include a remaining portion of the plurality of first electrodes and a remaining portion of the plurality of second electrodes, One of the plurality of spacings formed between one electrode and the plurality of second electrodes is different from the other spacing, and the lowest electrode among the first group electrodes is the uppermost electrode among the second group electrodes. Although adjacent, the lowermost electrode and the uppermost electrode may be included in any one of the plurality of first electrodes and the plurality of second electrodes.

The piezoelectric element according to the embodiment, the piezoelectric actuator containing the element, and the piezoelectric module containing the actuator generate resonance displacement at a low frequency, resulting in excellent low-pitched sound output, and the capacitance between electrodes increases due to the increased spacing between piezoelectric layers. It has reduced power consumption and heat generation.

The drawings attached below are intended to aid understanding of the present invention and provide embodiments of the present invention along with a detailed description. However, the technical features of the present invention are not limited to specific drawings, and the features disclosed in each drawing may be combined to form a new embodiment.
Figure 1 is a diagram for explaining the deformation form according to the polarization direction and voltage (or electric field) direction of the piezoelectric material.
Figure 2 is a diagram for explaining resonance frequency band characteristics for each vibration mode.
Figure 3 shows a cross-sectional view of a piezoelectric element according to one embodiment.
FIG. 4 shows an example of an external perspective view of the piezoelectric element shown in FIG. 3.
Figure 5 is an enlarged cross-sectional view of portion 'A' of Figure 3.
Figure 6 is a flowchart showing the manufacturing process of a piezoelectric element according to an embodiment.
Figure 7 shows an example of a process perspective view according to an embodiment.
Figure 8 shows a cross-sectional view of a piezoelectric element according to a comparative example.
9 is a graph showing resonance characteristics of a piezoelectric element according to an example and a comparative example.
Figure 10 shows a cross-sectional view of a piezoelectric element according to another embodiment, and Figure 11 shows an example of an external perspective view of the piezoelectric element shown in Figure 10.
FIG. 12 shows a cross-sectional view of a piezoelectric element according to a comparative example, and FIG. 13 is a graph showing displacement characteristics of a piezoelectric element according to another embodiment and a piezoelectric element according to a comparative example.
Figure 14 shows a cross-sectional view of a piezoelectric element according to another embodiment, and Figure 15 shows an example of an external perspective view of the piezoelectric element shown in Figure 14.
Figure 16 is a graph showing the displacement difference according to the ratio of the vertical width and the horizontal width of the piezoelectric element according to the embodiment.
Figure 17 shows a cross-sectional view of a piezoelectric actuator according to an embodiment.
Figure 18 shows a cross-sectional view of a piezoelectric actuator according to another embodiment.
Figure 19 shows a perspective view of a piezoelectric module according to an embodiment.
Figure 20 is a flow chart to explain a driving method according to an embodiment of a piezoelectric element serving as a speaker.
Figure 21 is a flow chart to explain a driving method according to an embodiment of a piezoelectric element serving as a receiver.
Figure 22 is a flow chart for explaining a method for compensating for distortion of a first sound signal according to an embodiment.
Figure 23a schematically shows an external perspective view of an existing mobile phone, and Figure 23b shows an external perspective view of a mobile phone according to an embodiment.

Hereinafter, the present invention will be described with reference to embodiments to specifically explain the present invention, and will be described in detail with reference to the accompanying drawings to aid understanding of the invention. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. Embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

In the description of the embodiment according to the present invention, in the case where each element is described as being formed "on or under", the (on or under) includes both that two elements are in direct contact with each other or that one or more other elements are formed (indirectly) between the two elements. Additionally, when expressed as “up” or “on or under,” it can include not only the upward direction but also the downward direction based on one element.

In addition, relational terms such as “first” and “second,” “upper/upper/above” and “lower/lower/bottom” used below refer to any physical or logical relationship or relationship between such entities or elements. It may be used to distinguish one entity or element from another entity or element, without necessarily requiring or implying order.

Hereinafter, the piezoelectric elements (1000A, 1000B, 1000C) according to the embodiment, the piezoelectric actuators (2000A to 2000C) including the devices (1000A, 1000B, 1000C), and the piezoelectric module 3000 including the actuators are defined in a Cartesian coordinate system. Although described using , the embodiment is not limited thereto. That is, according to the Cartesian coordinate system, the x-axis, y-axis, and z-axis are orthogonal to each other, but the embodiment is not limited to this. That is, the x-axis, y-axis, and z-axis can intersect each other instead of being perpendicular.

Before describing the piezoelectric element according to the embodiments of the present invention, the piezoelectric actuator containing the element, and the piezoelectric module containing the actuator, the driving method of the resonance type piezoelectric actuator and the frequency characteristics for each vibration mode will be described. Description will be made with reference to FIGS. 1 and 2.

FIG. 1 is a diagram for explaining the deformation form according to the polarization direction and voltage (or electric field) direction of the piezoelectric material, and FIG. 2 is a diagram for explaining resonance frequency band characteristics for each vibration mode.

Resonant type piezoelectric actuators are driven by applying an alternating electric field to a piezoelectric material to generate periodic vibrations that repeat expansion and contraction similar to the natural frequency. For example, as shown on the left side of FIG. 1, when the polarization direction of the piezoelectric material 10 is indicated by the arrow direction, if the polarization direction and the voltage direction match, the piezoelectric material 10 expands in the vertical direction and expands in the plane direction. It shrinks. Conversely, as shown on the right side of FIG. 1, when the polarization direction and voltage direction of the piezoelectric material 10 are opposite, the piezoelectric material 10 expands in the plane direction and contracts in the vertical direction.

Next, referring to FIG. 2, the resonance modes of the piezoelectric material are flextural mode, length mode, area expansion mode, thickness shear mode, and thickness expansion mode. It can be divided into seven types, including Surface Acoustic Wave mode and BGS (Bleustein-Gulyaev-Shimizu)/SH (shear horizontal) wave mode. Seven different resonance modes each have a corresponding resonance frequency band. Ultimately, according to Table 2, it can be seen that only the bending mode has a low resonance frequency of 10 kHz or less.

Accordingly, in embodiments of the present invention, a piezoelectric element having excellent low sound output characteristics by causing the piezoelectric material to vibrate in a bending mode, a piezoelectric actuator including the element, and a piezoelectric module including the actuator are proposed.

FIG. 3 shows a cross-sectional view of a piezoelectric element 1000A according to an embodiment, and FIG. 4 shows an example of an external perspective view of the piezoelectric element 1000A shown in FIG. 3. Additionally, Figure 5 is an enlarged cross-sectional view of portion ‘A’ of Figure 3.

Referring to FIGS. 3 to 5, the piezoelectric element 1000A according to one embodiment includes a piezoelectric portion 100A, a first electrode portion PE1, a second electrode portion NE1, and outer electrode portions OE11 and OE12. may include.

The piezoelectric element 1000A according to the embodiment may operate as a type of speaker that converts electrical signals into acoustic signals. Additionally, the piezoelectric element 1000A according to the embodiment may operate as a type of receiver (or microphone) that converts acoustic signals into electrical signals.

The piezoelectric unit 100A may have a plate shape with a height (or thickness) (Z1), a horizontal width (Y1), and a longitudinal width (X1) in the Z-axis direction, but the embodiment is limited to a specific shape of the piezoelectric unit 100A. It doesn't work. Here, the horizontal width (Y1) and the vertical width (X1) may be at least greater than the height (Z1).

The piezoelectric portion 100A may include a ceramic-based piezoelectric material. Ceramic piezoelectric materials may be single crystalline or polycrystalline. For example, the single crystal ceramic-based piezoelectric material may include at least one of PZN-PT [Pb(Zn2/3Nb1/3)O3-PbTiO3] or PMN-PT [Pb(Mg2/3Nb1/3)O3-PbTiO3]. there is. Alternatively, the polycrystalline ceramic-based piezoelectric material may include a Pb-based or non-Pb-based basic composition. For example, the polycrystalline ceramic-based piezoelectric material having a Pb-based basic composition may include at least one of Pb(Zr, Ti)O3 or Pb Zirconate Titanate (PZT). Alternatively, the polycrystalline ceramic-based piezoelectric material having a non-Pb-based basic composition may include at least one of K0.5Na0.5NbO3 or KNN.

However, the material of the piezoelectric portion 100A is not limited to ceramic-based piezoelectric materials. That is, if stacking is possible and the first electrode portion (PE1), the second electrode portion (NE1), and the outer electrode portions (OE11, OE12) can be deposited, printed, or attached, the material of the piezoelectric portion 100A may be a specific material. It is not limited to types of piezoelectric materials. For example, at least one of the first electrode portion (PE1), the second electrode portion (NE1), and the outer electrode portions (OE11 and OE12) may be formed by printing using a screen printing technique.

According to another embodiment, the material of the piezoelectric portion 100A may be a polymer-based piezoelectric material.

Meanwhile, at least a portion of the first electrode portion PE1 and the second electrode portion NE1 overlap each other in the thickness direction (for example, the Z-axis direction) inside or outside the piezoelectric portion 100A, but in the thickness direction They are spaced apart from each other and can be placed side by side along the X-Y plane.

According to one embodiment, each of the first electrode portion PE1 and the second electrode portion NE1 may include a plurality of flat electrodes. For example, the first electrode unit PE1 includes a 1-1 electrode PE11 disposed on the upper surface of the piezoelectric portion 100A, a 1-2 electrode PE12 disposed inside the piezoelectric portion 100A, and a 1-2 electrode PE12 disposed inside the piezoelectric portion 100A. It may include a 1-3 electrode (PE13), a 1-4 electrode (PE14), and a 1-5 electrode (PE15) disposed on the bottom of the piezoelectric part (100A). Accordingly, at least the top surface of the 1-1 electrode (PE11) and the bottom surface of the 1-5 electrode (PE15) are exposed to the outside of the piezoelectric part (100A), and the 1-2 electrode (PE12) and the 1-3 electrode (PE13) and the 1-4th electrode (PE14) can be viewed as being disposed inside the piezoelectric part 100A. Of course, depending on the embodiment, at least a portion of the 1-2 electrode (PE12), the 1-3 electrode (PE13), and the 1-4 electrode (PE14) may be exposed to the side of the piezoelectric portion 100A. Additionally, according to another embodiment, at least one of the 1-1 electrode PE11 and the 1-5 electrode PE15 may be omitted.

In addition, as shown in FIG. 5, the bottom surface of the electrode disposed at the outermost part of the piezoelectric part 100A, for example, the 1-1 electrode PE11, may be lower than the top surface of the piezoelectric part 100A. That is, at least a portion of the 1-1 electrode PE11 may be embedded in the piezoelectric portion 100A. Of course, according to another embodiment, the bottom surface of the 1-1 electrode PE11 may be parallel to the top surface of the piezoelectric portion 100A. Through this, the adhesion between the 1-1 electrode PE11 and the piezoelectric unit 100A can be improved, thereby improving the reliability of the piezoelectric element 1000A.

The second electrode unit (NE1) includes a 2-1 electrode (NE11), a 2-2 electrode (NE12), a 2-3 electrode (NE13), and a 2-4 electrode ( NE14) may be included. At this time, each electrode of the second electrode part NE1 is spaced apart from each other in the thickness direction (for example, Z-axis) of the piezoelectric part 100A and each electrode of the first electrode part PE1 alternately repeats. can be placed.

The outer electrode portions OE11 and OE12 may include a first outer electrode OE11 and a second outer electrode OE12. The first outer electrode OE11 may be disposed on one side of the piezoelectric portion 100A, and the second outer electrode OE12 may be disposed on the other side opposite to the side on which the first outer electrode OE11 is disposed. . Here, the side of the piezoelectric unit 100A may mean a surface defined by the height Z1 and the vertical width X1 in FIG. 3.

The first outer electrode OE11 is electrically connected to one end of the flat electrodes of the first electrode portion PE1 exposed to one side of the piezoelectric portion 100A, and the second outer electrode OE12 is electrically connected to the piezoelectric portion 100A. ) is electrically connected to one end of the plate-shaped electrodes of the second electrode portion (NE1) exposed on the other side. To this end, the flat electrodes of the first electrode unit (PE1) are spaced apart from the other side of the piezoelectric unit (100A) in the Y-axis direction, and the flat electrodes of the second electrode unit (NE1) are one part of the piezoelectric unit (100A). separated from the side. Through this, signals can be efficiently transmitted with the drive control unit 2500, which will be described later.

In addition, the first electrode portion (PE1) and the first outer electrode (OE11) may be a positive (+) electrode, and the second electrode portion (NE1) and the second outer electrode (OE12) may be a negative (-) or ground electrode. there is. Alternatively, the first electrode portion (PE1) and the first outer electrode (OE11) are negative (-) or ground electrodes, and the second electrode portion (NE1) and the second outer electrode (OE12) are positive (+) electrodes. You can.

The piezoelectric part 100A may include a plurality of polarized parts (or polarized piezoelectric layers). Each polarization portion may be defined through electrodes of the first electrode portion (PE1) and the second electrode portion (NE1) that are adjacent to each other and face each other. For example, a portion of the piezoelectric portion 100A located between the 1-1 electrode PE11 and the 2-1 electrode NE11 may be viewed as a polarization portion. As another example, a portion of the piezoelectric portion 100A located between the 2-1 electrode NE11 and the 1-2 electrode PE12 may also be viewed as a polarization portion. Accordingly, the piezoelectric unit 100A can be viewed as a plurality of plate-shaped polarization parts having the same planar shape (for example, a square planar shape) stacked in the thickness direction, and in the case of FIG. 3, a total of eight polarization parts exist. It can be seen as

The piezoelectric unit 100A may be polarized in the thickness direction (eg, Z-axis direction) in units of polarization units, and as shown in FIG. 3, the polarization direction may be alternately changed along the thickness direction. At this time, the polarization direction of each polarization unit may be the same direction as the direction of the electric field applied to the electrodes disposed above and below the corresponding polarization unit.

In addition, the thickness direction separation distance (i.e., the thickness of each polarization portion) between two electrodes of the first electrode portion (PE1) and the second electrode portion (NE1) adjacent to each other and facing each other is along the thickness direction of the piezoelectric portion (100A). Things can change as you go to the center. For example, in the piezoelectric element 1000A shown in FIGS. 3 and 4, the distance T1 to T8 between two adjacent electrodes may gradually increase in one direction along the thickness direction. This may mean that the thickness of each of the plurality of polarization parts increases in one direction along the vertical direction. Through this, a bending mode can be formed due to the different expansion/contraction rates of each polarization section.

At this time, the thickness variation between adjacent polarization parts may be 1% to 50%. However, if the thickness fluctuation range is too large, the overall displacement of the piezoelectric part 100A decreases, and if the thickness fluctuation range is too small, the vibration corresponding to the bending mode in the piezoelectric part 100A becomes weak. Therefore, the thickness variation range may be 15% to 25%, and more preferably 8% to 15%. For example, in FIG. 3, the distance between each electrode (T1 to T8) can be set as shown in Table 1 below.

division T1 T2 T3 T4 T5 T6 T7 T8 Thickness (um) 36 40 44 50 55 61 67 74

Table 1 shows cases where the thickness varies for each polarization portion, but is not necessarily limited to this. For example, the thickness relationship of the polarization layer is “T1=T2<T3=T4<T5…” ”, two (or N, natural numbers where N>1) adjacent polarization layers may have regularity, such as having the same thickness, or may increase in an irregular pattern.

As described above, because the spacing between electrodes (or the thickness of the polarization portion) changes along the thickness direction, bending mode operation can be guaranteed when power is applied to the piezoelectric element 1000A. For example, assuming that the structure shown in FIG. 3 has the polarization portion thickness variation as shown in Table 1, since the polarization direction and the electric field direction are the same, the piezoelectric portion 100A deforms as shown on the left side of FIG. 1. At this time, the polarization portion located on the upper side of the piezoelectric portion 100A has a relatively smaller thickness than the polarization portion located on the lower side, so the extent of deformation is small. Therefore, because the lower side of the piezoelectric portion 100A shrinks more in the plane direction than the upper side, the center of the piezoelectric portion 100A rises relatively on the plane and the edges relatively fall, causing bending in the piezoelectric portion 100A. I do it.

For sufficient sound output, the thickness of the piezoelectric part 100A is preferably greater than 40um. This is to create sufficient displacement in the display panel, which generally has a thickness of about 500 um, assuming that the piezoelectric element 1000A according to the embodiment is disposed at the bottom of the display. Additionally, the piezoelectric portion 100A preferably includes five or more polarization portions in the thickness direction. This is because, in the manufacturing process to be described later, it is difficult to manufacture the piezoelectric thin film corresponding to one polarization part with a thickness of 10 um or less.

Meanwhile, although not shown, the piezoelectric element 1000A according to the embodiment may further include a protection layer (passivation layer) on at least a portion of the outermost portion to prevent damage to each electrode portion and the piezoelectric portion 100A. there is. The protective part can be made of a material with excellent electrical insulation and waterproofing properties. In addition, the protective part can be made of a material with high adhesion and low mechanical strain. For example, the protective part may include at least one of Urethane, Epoxy, Silicone, or Acryl, but the embodiment is not limited thereto.

In addition, the protective portion may have a modulus of 2 MPa to 300 MPa, an adhesive force of 5 MPa to 45 MPa, a hardness of 30 to 70, a thickness (t1) of 20 ㎛ to 70 ㎛, and an insulation coefficient of 1x109Ω or more. . By arranging the above-described protection portion 400, the phenomenon of breaking or lifting of the outer electrodes (OE11, OE12) of the piezoelectric element (1000A) that vibrate at a large amplitude can be prevented, and each electrode portion (PE1, NE1) from the outside By completely insulating, the bending strength of the piezoelectric portion 100A can be strengthened.

In addition, as will be explained later, when the outer electrodes OE11 and OE12 are connected to the drive control unit 2500 through the wires 2610 and 2620, the outer electrodes OE11 and OE12 and the wires 2610 and 2620 are joined. By arranging the joint (for example, soldering portion) to be surrounded by a protective portion, the adhesion of the joint may be strengthened.

Hereinafter, the manufacturing method of the piezoelectric element 1000A shown in FIGS. 3 to 5 will be described with reference to the attached FIGS. 6 to 7. However, the piezoelectric element 1000A shown in FIGS. 3 to 5 may be manufactured by a method different from that of FIGS. 6 to 7.

FIG. 6 is a flowchart showing a manufacturing process 600 of a piezoelectric element 1000A according to an embodiment, and FIG. 7 shows an example of a process perspective view according to an embodiment.

Referring to FIG. 6, first, a piezoelectric material in powder form may be mixed with a solvent (610).

The result of mixing may be in the form of a slurry, and a piezoelectric thin film can be manufactured with this result through a method such as roller extrusion (620). Here, when one layer of the piezoelectric thin film undergoes a polarization process to be described later, it can correspond to one polarization portion, and the thickness of the piezoelectric thin film can be controlled by adjusting the gap between rollers during extrusion.

When piezoelectric thin films having different thicknesses are prepared, the piezoelectric thin films and electrodes may be stacked in alternating order (630). For example, as shown in FIG. 7 , one electrode (eg, NE14) constituting the second electrode portion (NE1) may be created on one piezoelectric thin film (PF1). After the electrode NE14 is created, the piezoelectric thin film PF2 is stacked again on the NE14, and one electrode (for example, PE14) constituting the first electrode portion PE1 is formed on the PF2. can be created.

When the alternating stacking of the piezoelectric thin films and electrodes is completed, the solvent is volatilized through dry firing and the boundary between the contact surfaces between adjacent piezoelectric thin films disappears, and through this, the shape of the piezoelectric portion 100A can be fixed (640) .

Thereafter, outer electrodes may be attached to the two opposing sides of the piezoelectric portion 100A, and the piezoelectric portion 100A may be polarized in units of polarization portions by applying a voltage to the outer electrodes (S650). For example, the polarization process applies a voltage equivalent to 1 to 2.5 kV/mm based on the thickness direction separation distance between electrodes at a temperature equivalent to about 1/3 of the Curie temperature of the piezoelectric material constituting the piezoelectric part 100A. It can be performed by applying it for 15 minutes to 1 hour.

Hereinafter, with reference to FIGS. 8 and 9, the effect of the piezoelectric element 1000A according to the embodiment will be described through comparison with a comparative example.

FIG. 8 shows a cross-sectional view of a piezoelectric element (1000A') according to a comparative example, and FIG. 9 is a graph showing resonance characteristics of the piezoelectric element (1000A') according to an embodiment and the piezoelectric element (1000A') according to a comparative example.

Referring to FIG. 8, it is assumed that the piezoelectric element 1000A' according to the comparative example has substantially the same size as the piezoelectric element 1000A according to the embodiment shown in FIG. 3. However, in the piezoelectric element 1000A according to the embodiment, the distance between two adjacent electrodes varies along the thickness direction, but in the piezoelectric element 1000A' according to the comparative example, the distance between two adjacent electrodes along the thickness direction is the same (i.e. , it is assumed that the thickness of the plurality of polarization parts is uniform.

For example, assuming that the distance (T') between two adjacent electrodes is both 36um and the total height of the piezoelectric part (100A') is about 430um (i.e., similar to the sum of T1 to T8 in Table 1) , the piezoelectric element (1000A) according to the comparative example has a total of 12 polarization parts. Accordingly, the number of electrodes constituting the first electrode unit (PE1') and the second electrode unit (NE1') also increases. In this case, since there is no difference in the thickness of the polarization part in the vertical direction, when power is applied to each electrode, the vibration of the piezoelectric part (100A') is unlikely to be in the form of a bending mode, and the larger of the longitudinal and transverse widths of the piezoelectric part (100A') It appears in the form of length mode for width.

Under the above-described assumption, when the same voltage is applied to the piezoelectric element 1000A according to the embodiment and the piezoelectric element 1000A′ according to the comparative example, the resonance characteristics are shown in FIG. 9. In Figure 9, two graphs are shown, where the horizontal axis represents frequency and the vertical axis represents admittance (i.e., the reciprocal of impedance).

First, referring to the upper graph corresponding to the comparative example, the resonance frequency does not appear below 10 kHz, and assuming that the length of the long side among the vertical and horizontal widths of the piezoelectric part 100A' is 40 to 50 mm, in the range of 20 to 30 kHz It can be expected that length mode resonance will occur first. This is because, assuming that the long side is L and f is the resonance frequency, “L= λf” is satisfied, and λ corresponds to 2L.

Unlike the comparative example, referring to the bottom graph corresponding to the example, it can be seen that resonance displacement occurs in the 680Hz area and another resonance displacement occurs in the 4.9kHz area. These admittance changes correspond to resonance displacements of 1.12 mm and 0.32 mm, respectively, assuming that the long side length of the piezoelectric part 100A is 40 to 50 mm as in the comparative example.

Accordingly, since the piezoelectric element 1000A according to the embodiment has a plurality of resonance frequencies below 10 kHz, it can be seen that bending mode vibration occurs in the low-pitched sound region, resulting in excellent low-pitched sound output performance.

In addition, when constructing a piezoelectric body of the same size, the embodiment has fewer polarization parts, that is, fewer electrodes, than the comparative example, so process efficiency during manufacturing can be improved.

In addition, in the embodiment, as the distance between electrodes gradually changes in the thickness direction, the distance between electrodes becomes relatively larger than the comparative example. Capacitance is inversely proportional to the spacing between electrodes, which means that the capacitance of each polarization portion according to the embodiment decreases compared to the comparative example. Ultimately, when the applied AC power is the same, the current flowing through all devices is proportional to the capacitance (i.e., I _Peak = 2π xfx C x V _Peak ), so the current value in the example is lower than in the comparative example. However, a lower current value means lower power consumption (i.e., P _Avg = π/4 xfx C x V _pp ^2), which also means lower heat generation amount (i.e., P _Heat = P _Avg x tanδ). do. Therefore, it can be seen that the piezoelectric element 1000A according to the embodiment has low power consumption and low heat generation compared to the comparative example, and also has high energy efficiency and excellent heat generation characteristics.

In the above-described embodiment, the distance between electrodes was gradually changed along the thickness direction of the piezoelectric part. In contrast, according to another embodiment of the present invention, the distance between electrodes may gradually change from the center of the piezoelectric part in the thickness direction to the outside. In addition, in the thickness direction based on the center, the polarization direction of the piezoelectric part and the direction of the electric field may coincide with the direction of the electric field on one side, and the polarization direction of the piezoelectric part and the direction of the electric field may be opposite to the direction of the electric field on the other side.

This will be explained with reference to FIGS. 10 and 11.

FIG. 10 shows a cross-sectional view of a piezoelectric element 1000B according to another embodiment, and FIG. 11 shows an example of an external perspective view of the piezoelectric element 1000B shown in FIG. 10.

Referring to FIGS. 10 and 11 , the piezoelectric element 1000B according to another embodiment includes a piezoelectric portion 100B, a first electrode portion PE2, a second electrode portion NE2, and outer electrode portions OE21 and OE22. may include.

The piezoelectric element 1000B according to another embodiment may also operate as a type of speaker that converts electrical signals into acoustic signals. In addition, the piezoelectric element 1000B according to another embodiment may operate as a type of receiver (or microphone) that converts acoustic signals into electrical signals.

The piezoelectric unit 100B may have a plate shape with a height (or thickness) (Z2), a horizontal width (Y2), and a longitudinal width (X2) in the Z-axis direction, but the embodiment is limited to a specific shape of the piezoelectric unit 100B. It doesn't work. Here, the horizontal width (Y2) and the vertical width (X2) may be at least greater than the height (Z2).

Since the material of the piezoelectric portion 100B is the same as that of the piezoelectric portion 100A according to the above-described embodiment, redundant description will be omitted.

The first electrode portion PE2 and the second electrode portion NE2 overlap each other at least partially in the thickness direction (e.g., Z-axis direction) inside or outside the piezoelectric portion 100B, but are spaced apart from each other in the thickness direction. and can be placed side by side along the X-Y plane.

According to one embodiment, each of the first electrode portion (PE2) and the second electrode portion (NE2) may include a plurality of flat electrodes. For example, the first electrode portion PE2 includes a 1-1 electrode PE21 disposed on the upper surface of the piezoelectric portion 100B, a 1-2 electrode PE22 disposed inside the piezoelectric portion 100B, and a 1-2 electrode PE22 disposed inside the piezoelectric portion 100B. It may include a 1-3 electrode (PE23), a 1-4 electrode (PE24), a 1-5 electrode (PE25), and a 1-6 electrode (PE26) disposed on the bottom of the piezoelectric part 100B. Accordingly, at least the top surface of the 1-1 electrode (PE21) and the bottom surface of the 1-6 electrode (PE26) are exposed to the outside of the piezoelectric portion (100B), and the 1-2 electrode (PE22) and the 1-3 electrode (PE23), the 1-4th electrode (PE24), and the 1-5th electrode (PE25) can be viewed as being disposed inside the piezoelectric portion (100B). Of course, depending on the embodiment, at least a portion of the 1-2 electrode (PE22), the 1-3 electrode (PE23), the 1-4 electrode (PE24), and the 1-5 electrode (PE25) are formed in the piezoelectric portion 100B. It may be exposed to the side of. Additionally, according to another embodiment, at least one of the 1-1 electrode PE21 and the 1-6 electrode PE26 may be omitted.

In addition, similar to that shown in FIG. 5, in another embodiment of the present invention, the bottom surface of the electrode disposed on the outermost side of the piezoelectric portion 100B, for example, the 1-1 electrode PE21, is the piezoelectric portion 100B. ) may be lower than the upper surface of That is, at least a portion of the 1-1 electrode PE21 may be embedded in the piezoelectric portion 100B. Of course, according to another embodiment, the bottom surface of the 1-1 electrode PE21 may be parallel to the top surface of the piezoelectric portion 100B.

The second electrode unit (NE1) includes a 2-1 electrode (NE21), a 2-2 electrode (NE22), a 2-3 electrode (NE23), and a 2-4 electrode ( NE24) may be included. At this time, each electrode of the second electrode part NE1 is spaced apart from each other in the thickness direction (for example, Z-axis) of the piezoelectric part 100B and each electrode of the first electrode part PE2 alternately repeats each other. can be placed. However, only two electrodes corresponding to one of the first electrode part PE2 and the second electrode part NE2 are located above and below the polarization part DL (for example, in FIG. 10, 1-3). Electrodes (PE23) and first to fourth electrodes (PE24) are disposed.

The outer electrode portions OE21 and OE22 may include a first outer electrode OE1 and a second outer electrode OE2. The first outer electrode OE11 may be disposed on one side of the piezoelectric portion 100A, and the second outer electrode OE22 may be disposed on the other side opposite to the side on which the first outer electrode OE21 is disposed. . Here, the side of the piezoelectric unit 100B may mean a surface defined by the height Z2 and the vertical width X2 in FIG. 11.

The first outer electrode OE21 is electrically connected to one end of the flat electrodes of the first electrode portion PE2 exposed to one side of the piezoelectric portion 100B, and the second outer electrode OE22 is connected to the piezoelectric portion 100B. ) is electrically connected to one end of the flat electrodes of the second electrode portion (NE2) exposed on the other side. To this end, the flat electrodes of the first electrode unit (PE2) are spaced apart from the other side of the piezoelectric unit (100B) in the Y-axis direction, and the flat electrodes of the second electrode unit (NE2) are one part of the piezoelectric unit (100B). separated from the side.

In addition, the first electrode portion (PE2) and the first outer electrode (OE21) may be a positive (+) electrode, and the second electrode portion (NE2) and the second outer electrode (OE22) may be a negative (-) or ground electrode. there is. Alternatively, the first electrode portion (PE2) and the first outer electrode (OE21) are negative (-) or ground electrodes, and the second electrode portion (NE2) and the second outer electrode (OE22) are positive (+) electrodes. You can.

The piezoelectric part 100B may include one dummy part DL and a plurality of polarized parts (or polarized piezoelectric layers).

Here, the dummy portion DL may be located at the center in the thickness direction of the piezoelectric portion 100B, and may correspond to either the first electrode portion PE2 or the second electrode portion NE2 but are adjacent to and face each other. It can be defined through two electrodes. For example, a portion of the piezoelectric portion 100B located between the 1-3 electrode PE23 and the 1-4 electrode PE24 corresponds to the dummy portion DL. Unlike the polarization portion, the dummy portion DL is located between two electrodes having the same polarity, so an electric field may not be applied and the dummy portion DL may not be polarized. Additionally, the thickness T15 of the dummy portion in the vertical direction (eg, Z-axis) may be greater than the thicknesses T11 to T14 and T16 to T19 of each of the plurality of polarization portions.

Each polarization portion may be defined through electrodes of the first electrode portion (PE2) and the second electrode portion (NE2) that are adjacent to each other and face each other. For example, a portion of the piezoelectric portion 100B located between the 1-1 electrode PE21 and the 2-1 electrode NE21 may be viewed as one polarization portion. As another example, a portion of the piezoelectric portion 100B located between the 2-1 electrode NE21 and the 1-2 electrode PE22 may also be viewed as a polarization portion. Accordingly, the piezoelectric part 100B can be viewed as a plurality of plate-shaped polarization parts having the same planar shape (for example, a square planar shape) stacked in the thickness direction, and in the case of FIG. 10, there are a total of eight polarization parts. It can be seen as

Each of the plurality of polarization units may be polarized in the thickness direction (e.g., Z-axis direction) in units of polarization units, and as shown in FIG. 10, the polarization direction extends from the dummy portion DL along the thickness direction. The order may change depending on the order. At this time, the polarization direction of each polarization unit may be the same direction or the opposite direction to the direction of the electric field applied to the electrodes disposed above and below the corresponding polarization unit. For example, as shown in FIG. 10, the polarization portions located above the dummy portion DL in the thickness direction match the electric field direction and the polarization direction, but have a thickness direction relative to the dummy portion DL. The polarization portions located on the lower side of may have opposite polarization directions to the direction of the electric field.

In addition, the thickness direction separation distance (i.e., the thickness of each polarization portion) between two electrodes of the first electrode portion (PE1) and the second electrode portion (NE1) adjacent to each other and facing each other is along the thickness direction of the piezoelectric portion (100B). It can change as you go from the center to the top or bottom. For example, in the piezoelectric element 1000B shown in FIGS. 10 and 11, the distance (T11 to T14) between two adjacent electrodes may gradually decrease from the center to the top along the thickness direction of the piezoelectric portion 100B. there is. This may mean that the thickness of each of the plurality of polarization units becomes smaller from the center to the top.

Additionally, in the piezoelectric element 1000B, the distance T16 to T19 between two adjacent electrodes may gradually decrease from the center to the bottom along the thickness direction of the piezoelectric portion 100B. This may mean that the thickness of each of the plurality of polarization units decreases from the center to the bottom.

At this time, the thickness variation between adjacent polarization parts may be 1% to 50%. However, if the thickness fluctuation range is too large, the overall displacement of the piezoelectric part 100B decreases, and if the thickness fluctuation range is too small, the vibration corresponding to the bending mode in the piezoelectric part 100B becomes weak. Therefore, the thickness variation range may be 15% to 25%, and more preferably 8% to 15%. For example, in FIG. 10, the distance between each electrode (T11 to T19) can be set as shown in Table 2 below.

division T11 T12 T13 T14 T15 T16 T17 T18 T19 Thickness (um) 36 41 47 54 62 54 47 41 36

Table 2 shows cases where the thickness varies for each polarization portion, but is not necessarily limited to this. For example, the thickness relationship of the polarization layer is “T11=T12<T13=T14<T15…” ”, etc., two (or N, natural numbers with N>1) adjacent polarization layers may have regularity, such as having the same thickness, or may increase toward the center in the thickness direction in an irregular pattern.

As the spacing between electrodes (or the thickness of the polarization portion) changes along the thickness direction and the polarization direction is reversed with respect to the dummy portion DL, bending mode operation is guaranteed when power is applied to the piezoelectric element 1000B. It can be. For example, assuming that the structure shown in FIG. 10 has the thickness variation of the polarization part as shown in Table 2, the polarization part located on the upper side of the piezoelectric part 100B with respect to the dummy part DL has the polarization direction and the direction of the electric field. In this same manner, deformation of the piezoelectric portion 100B as shown on the left side of FIG. 1 occurs. In addition, the polarization part located below the piezoelectric part 100B with respect to the dummy part DL has a polarization direction and the direction of the electric field opposite to each other, so the piezoelectric part 100B is deformed as shown on the right side of FIG. 1.

Accordingly, the polarization portion located above the piezoelectric portion 100B with respect to the dummy portion DL shrinks in the plane direction, and the polarization portion located below the piezoelectric portion 100B with respect to the dummy portion DL Expansion occurs in the plane direction. In addition, since the thickness of each polarization portion is different, the deformation principle of the piezoelectric portion 100A according to one embodiment is added. As a result, because the expansion of the lower side of the piezoelectric portion 100B in the plane direction is greater than the upper side, the center of the piezoelectric portion 100B on the plane is relatively lowered and the edges are relatively raised, causing a bend in the piezoelectric portion 100B. It happens.

For sufficient sound output, the thickness of the piezoelectric portion 100B is preferably greater than 40um. This is to create sufficient displacement in the display panel, which generally has a thickness of about 500 um, assuming that the piezoelectric element 1000B according to the embodiment is disposed below the display. Additionally, the piezoelectric portion 100B preferably includes five or more polarization portions in the thickness direction. This is because, in the manufacturing process to be described later, it is difficult to manufacture the piezoelectric thin film corresponding to one polarization part with a thickness of 10 um or less.

Meanwhile, although not shown, the piezoelectric element 1000B according to the embodiment may further include a protection layer (passivation layer) on at least a portion of the outermost portion to prevent damage to each electrode portion and the piezoelectric portion 100B. there is. Since the characteristics and materials of the protection part are the same as those described in the piezoelectric element 1000A according to an embodiment, redundant description will be omitted.

In addition, since the manufacturing method is similar to that described above with reference to FIGS. 6 and 7, redundant description will be omitted.

Hereinafter, with reference to FIGS. 12 and 13, the effect of the piezoelectric element 1000B according to the embodiment will be described through comparison with a comparative example.

Figure 12 shows a cross-sectional view of the piezoelectric element 1000B' according to a comparative example, and Figure 13 is a graph showing the displacement characteristics of the piezoelectric element 1000B' according to another embodiment and the piezoelectric element 1000B' according to the comparative example.

Referring to FIG. 12, it is assumed that the piezoelectric element 1000B' according to the comparative example has substantially the same size as the piezoelectric element 1000B according to the embodiment shown in FIG. 10. However, in the piezoelectric element 1000B according to the embodiment, the distance between two adjacent electrodes varies along the thickness direction, but in the piezoelectric element 1000B' according to the comparative example, the distance between two adjacent electrodes along the thickness direction is the same (i.e. , it is assumed that the thickness of the plurality of polarization parts is uniform.

For example, assuming that the distance (T”) between two adjacent electrodes is both 36um and the total height of the piezoelectric part (100B’) is about 430um (i.e., similar to the sum of T11 to T19 in Table 1) , the piezoelectric element 1000B according to the comparative example has a total of 11 polarization parts and one dummy part DL'. Accordingly, the number of each electrode constituting the first electrode part (PE2') and the second electrode part (NE2') also increases. In this case, when power is applied to each electrode, even though the expansion form of each polarization portion located above and below the thickness direction with respect to the dummy portion DL' is different, there is no difference in the thickness of the polarization portion in the vertical direction. It has a smaller displacement than the piezoelectric element 1000B shown in Figure 10.

Under the above-described assumption, when the same voltage is applied to the piezoelectric element 1000B according to the embodiment and the piezoelectric element 1000B′ according to the comparative example, the displacement characteristics are shown in FIG. 13.

Two graphs are shown in FIG. 13, where the horizontal axis represents harmonic magnitude and the vertical axis represents displacement in the Z-axis direction (i.e., thickness direction). In addition, in FIG. 13, the upper graph (second comparative example) shows the displacement of the piezoelectric element 1000B' according to the comparative example shown in FIG. 12, and the lower graph (second embodiment) shows the displacement of the piezoelectric element 1000B' according to the comparative example shown in FIG. 10. The displacement of the piezoelectric element 1000B according to the example is shown respectively.

Referring to FIG. 13, in the upper graph according to the comparative example, the maximum displacement is approximately 0.00259, and in the lower graph according to another embodiment, the maximum displacement is approximately 0.00574, and the piezoelectric element (1000B) according to the exemplary embodiment is shown as the comparative example (1000B). ') It can be seen that it has about twice the displacement. Therefore, it can be seen that the piezoelectric element 1000B according to the embodiment has greater sound output performance when the same driving voltage is applied. In addition, when constructing a piezoelectric body of the same size, the embodiment has fewer polarization parts, that is, fewer electrodes, than the comparative example, so process efficiency during manufacturing can be improved.

Meanwhile, according to another embodiment of the present invention, it has a structure similar to the piezoelectric element 1000B according to another embodiment described above, but more outer electrodes can be disposed.

This will be explained with reference to FIGS. 14 and 15.

FIG. 14 shows a cross-sectional view of a piezoelectric element 1000C according to another embodiment, and FIG. 15 shows an example of an external perspective view of the piezoelectric element 1000C shown in FIG. 14.

14 and 15, the piezoelectric element 1000C according to another embodiment includes a piezoelectric portion 100C, a first electrode portion PE3, a second electrode portion NE3, and outer electrode portions OE31 and OE32. , OE33, OE34), but excluding the outer electrode portions (OE31, OE32, OE33, OE34), the configuration is the same as described above with reference to FIGS. 10 and 11, so overlapping description will be omitted and the description will focus on the differences. I decided to do it.

The first electrode portion PE3 and the second electrode portion NE3 overlap each other at least partially in the thickness direction (e.g., Z-axis direction) inside or outside the piezoelectric portion 100C, but are spaced apart from each other in the thickness direction. and can be placed side by side along the X-Y plane.

According to this embodiment, the outer electrode units (OE31, OE32, OE33, and OE34) may include first outer electrodes (OE31, OE33) and second outer electrodes (OE32, OE34). The first outer electrodes OE31 and OE33 are disposed on one side of the piezoelectric unit 100A, and the second outer electrodes OE32 and OE34 are disposed on the other side opposite to the one side on which the first outer electrode OE21 is disposed. can be placed. Here, the side of the piezoelectric unit 100C may mean a surface defined by the height Z3 and the longitudinal width X3 in FIG. 15.

Additionally, the first outer electrodes (OE31, OE33) may include a 1-1 outer electrode (OE31) and a 1-2 outer electrode (OE32), and the second outer electrodes (OE32, OE34) may include a 2- It may include a first outer electrode (OE32) and a second-second outer electrode (OE34). Here, the 1-1st outer electrode OE31 and the 1-2nd outer electrode OE32 may be insulated from each other. For example, the 1-1st outer electrode OE31 and the 1-2nd outer electrode OE32 may be spaced apart in the thickness direction on one side of the dummy portion DL so as not to contact each other. Additionally, the 2-1st outer electrode OE32 and the 2-2nd outer electrode OE34 may be insulated from each other. For example, the 2-1st outer electrode OE32 and the 2-2nd outer electrode OE34 may be spaced apart in the thickness direction from the other side of the dummy portion DL so as not to contact each other. Accordingly, the 1-1 outer electrode OE31 is electrically connected to the 1-1 electrode PE31, the 1-2 electrode PE32, and the 1-3 electrode PE33 among the first electrodes PE3. , the 1-2 outer electrode OE33 is electrically connected to the 1-4 electrode PE34, the 1-5 electrode PE35, and the 1-6 electrode PE36 among the first electrodes PE3. In addition, the 2-1 outer electrode OE32 is electrically connected to the 2-1 electrode NE31 and the 2-2 electrode NE32 among the second electrodes NE3, and the 2-2 outer electrode OE34 ) is electrically connected to the 2-3 electrode (NE33) and the 2-4 electrode (NE34).

Meanwhile, along the thickness direction, the 1-1 outer electrode OE31 and the 2-1 outer electrode OE32 include electrodes PE31, PE32, PE33, NE31, and NE32 disposed on the upper side of the dummy portion DL. The 1-2 outer electrode OE33 and the 2-2 outer electrode OE34 are connected to the electrodes PE34, PE35, PE36, NE33, and NE34 disposed on the lower side of the dummy portion DL. Therefore, the electrodes PE31, PE32, PE33, NE31, and NE32 disposed on the upper side of the dummy portion DL along the thickness direction are referred to as “first group electrodes,” and the electrodes disposed on the lower side of the dummy portion DL (PE34, PE35, PE36, NE33, NE34) can be referred to as “second group electrodes.” In this case, the lowermost electrode PE33 of the first group electrode can be viewed as facing the uppermost electrode PE34 of the second group electrode with the dummy portion DL interposed therebetween. Of course, this classification of electrodes (i.e., first group electrodes and second group electrodes) can also be applied to the piezoelectric element 1000B shown in FIGS. 10 and 11.

The effect when the four outer electrodes are arranged as described above is explained as follows.

When driving the piezoelectric element 1000C according to this embodiment, power of different polarity is applied to the first outer electrodes OE31 and OE33 and the second outer electrodes OE32 and OE34. For example, the 1-1st outer electrode (OE31) and the 1-2nd outer electrode (OE32) are positive electrodes, and the 2-1st outer electrode (OE32) and the 2-2nd outer electrode (OE34) are negative electrodes. It may be an electrode of However, in the polarization process 650 described above with reference to FIG. 6, the direction of the electric field and the polarization direction are reversed with respect to the dummy portion DL in the thickness direction. Accordingly, the outer electrodes (OE31, OE32) connected to the first group electrodes (PE31, PE32, PE33, NE31, and NE32) have the same polarity in the polarization process 650 and in the driving situation, but the second group electrodes (PE34) have the same polarity in the driving situation. , PE35, PE36, NE33, and NE34), the outer electrodes (OE33, OE34) have opposite polarizations in the polarization process (650) and in the driving situation. In other words, the 1-1 outer electrode (OE31) becomes a positive electrode in both the polarization process (650) and the driving situation, and the 2-1 outer electrode (OE32) becomes a negative electrode in both the polarization process (650) and the driving situation. becomes the electrode of However, the first-second outer electrode OE33 becomes a negative electrode in the polarization process 650 and a positive electrode in a driving situation. Additionally, the 2-2 outer electrode OE34 becomes a positive electrode in the polarization process 650 and a negative electrode in a driving situation.

Ultimately, when four or more outer electrodes are prepared as in this embodiment, only the polarity of the power supply connected to each outer electrode needs to be changed in both the polarization process and the driving situation, so a separate outer electrode is required in the polarization process and the driving situation. Process efficiency can be improved as there is no need for additional placement or removal.

In another embodiment of the present invention described above, it is described that there are four outer electrodes, but this is an example and more outer electrodes may be provided by varying the electrical connection relationship with the individual electrodes.

Meanwhile, although not shown, the piezoelectric element 1000C according to this embodiment may further include a protection layer (passivation layer) on at least a portion of the outermost portion to prevent damage to each electrode portion and the piezoelectric portion 100C. It may be possible. Since the characteristics and materials of the protection part are the same as those described in the piezoelectric element 1000A according to an embodiment, redundant description will be omitted.

In addition, since the manufacturing method is similar to that described above with reference to FIGS. 6 and 7, redundant description will be omitted.

The description so far has focused on the effects of changes in the spacing between electrodes in the vertical direction and the thickness of the polarization portion. Below, the effect of changing the external shape of the piezoelectric elements (1000A, 1000B, 1000C), that is, the ratio of the vertical width (for example, X2 in FIG. 11) and the horizontal width (for example, Y2 in FIG. 11) will be described.

Assuming that the longitudinal width ( The smaller the difference in length, the better the displacement characteristics. For example, when the same power is applied to the piezoelectric element (1000B), the size of the displacement is larger when X:Y is 5:7 than when X:Y is 1:3, and is 1:7 than when X:Y is 5:7. The case of 1 appears largely. This is explained with reference to FIG. 16.

Figure 16 is a graph showing the displacement difference according to the ratio of the vertical and horizontal widths of the piezoelectric element according to the embodiment.

Two graphs are shown in FIG. 16, where the horizontal axis represents harmonic magnitude and the vertical axis represents displacement in the Z-axis direction (i.e., thickness direction). Additionally, in Figure 10, the upper graph shows a case where the X:Y ratio is 5:7, and the lower graph shows a case where the X:Y ratio is 1:1. Referring to Figure 10, in the top graph, the maximum displacement appears to be about 0.0045, and in the bottom graph, the maximum displacement is about 0.007, which is more than 50% larger when the X:Y ratio is 1:1 than when it is 5:7. It can be seen that it represents

As in the embodiment, when the vibration force of the piezoelectric elements (1000A, 1000B, 1000C) is high, the piezoelectric elements (1000A, 1000B, 1000C) can provide a haptic function in addition to a speaker or receiver, and can also be used as a proximity sensor. It can be applied.

Hereinafter, an embodiment of a piezoelectric actuator including piezoelectric elements (1000A, 1000B, 1000C) according to the above-described embodiment will be described with reference to the attached drawings.

Figure 17 shows a cross-sectional view of a piezoelectric actuator (2000A) according to an embodiment.

The piezoelectric actuator 2000A shown in FIG. 17 may include a cover member 1100, a display unit 1200A, an adhesive layer 1300, and a piezoelectric element 1400.

The display unit 1200A may be disposed below the cover member 1100.

The cover member 1100 may be rigid or flexible. Preferably, the cover member 1100 may be flexible such that it can be bent or folded.

For example, the cover member 1100 may include plastic or glass. In detail, the cover member 1100 includes reinforced or soft plastic such as polyimide (PI), polyethylene terephthalate (PET), propylene glycol (PPG), polycarbonate (PC), or sapphire. may include.

Additionally, the cover member 1100 may include an optically isotropic film. For example, the cover member 1100 may include Cyclic Olefin Copolymer (COC), Cyclic Olefin Polymer (COP), wide isotropic polycarbonate (PC), or wide isotropic polymethyl methacrylate (PMMA).

The display unit 1200A may be an organic electroluminescent display (OLED) panel substrate. In this case, the display unit 1200A includes a self-luminous element that does not require a separate light source.

The adhesive layer 1300 is disposed between the display unit 1200A and the piezoelectric element 1400 and serves to adhere them 1200A and 1400. For example, the adhesive layer 1300 may be an optically transparent adhesive, but the embodiment is not limited to a specific material of the adhesive layer 1300.

According to one embodiment, the piezoelectric element 1400 may correspond to the piezoelectric elements 1000A, 1000B, and 1000C according to the above-described embodiment. That is, the piezoelectric element 1400 may serve as a type of speaker that transmits sound signals generated by receiving pulses from the drive control unit 2500, which will be described later, and vibrating the piezoelectric units 100A, 100B, and 100C.

According to another embodiment, the piezoelectric element 1400 may include a plurality of piezoelectric elements 1000A, 1000B, and 1000C.

Figure 18 shows a cross-sectional view of a piezoelectric actuator (2000B) according to another embodiment.

The piezoelectric actuator 2000B shown in FIG. 18 may include a cover member 1100, a display unit 1200B, an adhesive layer 1300, a piezoelectric element 1400, and a back plate 1500.

The cover member 1100, adhesive layer 1300, and piezoelectric element 1400 shown in FIG. 18 correspond to the cover member 1100, adhesive layer 1300, and piezoelectric element 1400 shown in FIG. 17, respectively, and therefore refer to the same Symbols are used, and redundant explanations are omitted.

The display unit 1200B may be disposed below the cover member 1100 and may include a thin film transistor (TFT).

The back plate 1500 is disposed between the adhesive layer 1300 and the display unit 1200B and serves to protect the display unit 1200B.

17 and 18, when the piezoelectric element 1400 vibrates, the display units 1200A and 1200B disposed on top of the piezoelectric element 1400 also vibrate. At this time, the pixels of the display units 1200A and 1200B may be broken by vibration. However, as shown in FIGS. 17 and 18, when the adhesive layer 1300 is disposed between the display units 1200A and 1200B and the piezoelectric element 1400, the pixels of the display units 1200A and 1200B are damaged by vibration. The fear of breaking can be eliminated.

The lower surfaces of the display units 1200A and 1200B facing the piezoelectric element 1400 receive the vibration force of the piezoelectric element 1400 and vibrate. Sound can be generated by repeating contraction and expansion of the lower surface, and at this time, the display units 1200A and 1200B can function as a diaphragm of a flat speaker. Additionally, the waveform generated in the display units 1200A and 1200B may be in the form of a curved wave. Specifically, a distributed mode speaker can be implemented through methods such as arranging a single piezoelectric element 1400 asymmetrically up and down and/or left and right with respect to the display area, or using a plurality of piezoelectric elements 1400. . The distributed mode has low directivity and wide frequency characteristics, but tends to have low vibration power.

By applying the piezoelectric element 1400 of the embodiment, the vibration force can be increased and the resonance frequency can also be lowered, making it possible to implement a distributed mode planar speaker with smooth output in the audible frequency band.

Hereinafter, an embodiment of a piezoelectric module including a piezoelectric actuator according to the above-described embodiment will be described with reference to the attached drawings.

Figure 19 shows a perspective view of the piezoelectric module 3000 according to one embodiment.

The piezoelectric module 3000 shown in FIG. 19 may include a piezoelectric actuator, a drive control unit 2500, and wiring 2610 and 2620.

The piezoelectric actuator may correspond to the piezoelectric actuators 2000A to 2000B illustrated in FIGS. 17 to 18. For convenience of explanation, components other than the piezoelectric element in the piezoelectric actuator are omitted in FIG. 19.

The piezoelectric element shown in FIG. 19 may include a piezoelectric portion 100A including a first electrode and a second electrode and outer electrodes OE11 and OE12. The drive control unit 2500 serves to drive the piezoelectric actuator. In particular, the drive control unit 2500 is connected to the piezoelectric element through wires 2610 and 2620 and serves to drive the piezoelectric element. The wiring is a first wiring 2610 that electrically connects the drive control unit 2500 and the first outer electrode (OE11), and a second wire (2610) that electrically connects the drive control unit 2500 and the second outer electrode (OE12). 2620).

The driving control unit 2500 may be connected to a board (not shown) such as a Flexible Printed Circuit Board (FPCB). The FPCB may provide a pulse to be applied to the external electrode 300 from the drive control unit 2500, or may receive an electrical signal corresponding to the second acoustic signal provided from the drive control unit 2500. there is.

A detailed look at the operation of the drive control unit 2500 to drive the piezoelectric element of the piezoelectric actuator is as follows.

Figure 20 is a flowchart for explaining a driving method 3100 according to an embodiment of a piezoelectric element serving as a speaker.

First, when the piezoelectric element serves as a speaker, the drive control unit 2500 drives the piezoelectric element as follows.

The drive control unit 2500 applies a drive pulse having an appropriate level to vibrate the piezoelectric unit 100 to the internal electrode 200 through the external electrode 300 (step 3102). For example, when the pulse signal is in the form of a voltage, a positive (+) voltage is applied to the first electrode portion (PE1) through the first outer electrode (OE11), and a negative (-) voltage is applied to the second outer electrode. It can be applied to the second electrode unit (NE1) through (OE12). Of course, the voltage direction may be applied in the opposite direction.

When positive and negative voltages are applied to the first electrode unit PE1 and the second electrode unit NE1, respectively, the piezoelectric unit 100 vibrates in a bending mode (step 3104).

At this time, the piezoelectric unit 100 vibrates, and when this vibration is transmitted to the display units 1200A and 1200B of the piezoelectric actuator through one surface defined by the horizontal width (W) and vertical width (L) of the piezoelectric element 100, The display units 1200A and 1200B vibrate at the exciting point, thereby transmitting an acoustic signal (step 3106). Here, the excitation point refers to the point where the piezoelectric actuator is placed.

Figure 21 is a flowchart for explaining a driving method 3200 according to an embodiment of a piezoelectric element serving as a receiver.

When the piezoelectric element shown in FIG. 19 functions as a receiver, the drive control unit 2500 drives the piezoelectric element as follows.

When the second acoustic signal is transmitted to the piezoelectric unit 100 from the outside, the piezoelectric unit 100 vibrates (step 3202).

These vibrations are converted into electrical signals through each electrode and transmitted to the drive control unit 2500 (step 3204).

The drive control unit 2500 detects an acoustic signal using an electrical signal generated corresponding to vibration (step 3206).

As described in FIGS. 20 and 21 , the piezoelectric element may convert an electrical signal into a first acoustic signal or a second acoustic signal into an electrical signal.

Meanwhile, while the first sound signal is being transmitted by vibration of the piezoelectric unit 100, the transmitted first sound signal may be distorted due to changes in external conditions. For example, if the user touches the display units 2100A and 2100B while the first sound signal is being transmitted, distortion may occur in the transmitted first sound signal.

Hereinafter, a distortion compensation method according to an embodiment for compensating for distortion of the first sound signal in a piezoelectric module will be described with reference to the attached drawings as follows.

FIG. 22 is a flowchart for explaining a method 3300 for compensating for distortion of a first sound signal according to an embodiment.

The drive control unit 2500 checks whether there is a change in the displacement of the panel of the display unit (hereinafter referred to as 'display panel') that transmits the first sound signal (step 3302).

If there is a change in displacement of the display panel, the amount of change in displacement is calculated (step 3304).

Thereafter, the level of the applied pulse, that is, the electrical signal, is adjusted to compensate for the change in displacement, and the pulse with the adjusted level is applied to the first and second electrodes through the wires 2610 and 2620 and the outer electrodes OE11 and OE12. Supply to (PE1, NE1) (step 3306). Accordingly, distortion of the first sound signal can be compensated.

The piezoelectric module according to the above-described embodiment can be applied to various devices having at least one of a speaker or a receiver. For example, piezoelectric modules according to embodiments may be used in mobile phones, multimedia Internet mobile phones, wireless devices, smart phones, Bluetooth devices, personal digital assistants (PDAs), portable computers, netbooks, laptops, smartbooks, and tablets. It may be included in electronic devices such as tablets, automotive display devices (including odometers and speedometers), cockpit control devices, and display devices, but embodiments are not limited thereto.

FIG. 23A schematically shows an external perspective view of an existing mobile phone 4000A, and FIG. 23B shows an external perspective view of a mobile phone 4000B according to an embodiment.

The existing mobile phone 4000A shown in FIG. 23A has a speaker 4100 for transmitting a first sound signal and a receiver 4200 for receiving a second sound signal from the outside. Therefore, the existing mobile phone 4000A must provide a hole for the speaker 4100 and the receiver 4200. In particular, when the receiver 4200 is placed on the bezel, the mobile phone 4000A necessarily requires a bezel, which limits the freedom of design.

On the other hand, the mobile phone 4000B according to the embodiment can transmit the first sound signal 4300 or receive the second sound signal 4300 using the piezoelectric element 1000, so as shown in FIG. 23A There is no need for a hole for the speaker 4100 or the receiver 4200. Therefore, it is possible to implement a high-output speaker with greater design freedom than before, such as by reducing the width of the bezel so that the display area occupies almost the entire display surface of the mobile phone (4000B).

In particular, in the case of the mobile phone (4000B), the internal space is small. When removing the hole, the display unit must be used as a vibrating plate, and the vibrating element must also be attached in a thin form, so a piezoelectric element in the form of a flat plate is needed. At least one of the rigidity, elasticity, or mass of the display that acts as a diaphragm is different from the diaphragm of the speaker used in the existing hall, and the display requires relatively more vibration force to generate vibration compared to the existing diaphragm. .

Although the above description focuses on examples, this is only an example and does not limit the present invention, and those skilled in the art will understand that the examples are as follows without departing from the essential characteristics of the present example. You will see that various variations and applications are possible. For example, each component specifically shown in the examples can be modified and implemented. And these variations and differences in application should be construed as being included in the scope of the present invention as defined in the appended claims.

10, 1000A, 1000B, 1000C, 1400: Piezoelectric element
100A, 100B, 100C: Piezoelectric part 1100: Cover member
1200A, 1200B: Display unit 1300: Adhesive layer
1500: back plate 1600: diaphragm
1700: Fixing plate 2000A, 2000B: Piezoelectric actuator
2500: drive control unit 2610, 2620: wiring
3000: Piezoelectric module 4000A, 4000B: Mobile phone
4100: Speaker 4200: Receiver

Claims (12)

Piezoelectric part;
a first outer electrode disposed on a side of the piezoelectric unit and connected to a plurality of first electrodes, and a second outer electrode connected to the plurality of second electrodes to apply a power having a polarity different from that of the first outer electrode;
first group electrodes alternately stacked at predetermined intervals within the piezoelectric unit and including a portion of the plurality of first electrodes and a portion of the plurality of second electrodes;
a dummy portion disposed below the first group electrode and not subject to an electric field;
They are stacked alternately and spaced apart at predetermined intervals within the piezoelectric part, and are disposed on the lower side of the dummy part, including the remaining part of the plurality of first electrodes and the remaining part of the plurality of second electrodes, and the first group electrode and Includes a second group of electrodes that are physically spaced apart and insulated,
Among the plurality of spacings formed between the plurality of first electrodes and the plurality of second electrodes, one spacing is different from the other spacing,
The lowermost electrode among the first group electrodes is adjacent to the uppermost electrode among the second group electrodes, and the lowermost electrode and the uppermost electrode are connected to either the first outer electrode or the second outer electrode. Piezoelectric element. delete According to claim 1,
A piezoelectric element wherein the plurality of spacing changes in the thickness direction of the piezoelectric part from the dummy part to the upper or lower side. According to claim 1,
The piezoelectric part,
It includes a plurality of polarization portions defined by first and second electrodes adjacent to each other,
Among the plurality of polarization portions, the polarization portion defined by the first group electrode coincides with the direction of the electric field applied by the first group electrode,
A piezoelectric element, wherein a polarization portion defined by the second group electrode among the plurality of polarization portions is opposite to the direction of the electric field applied by the second group electrode. According to claim 1,
It includes a plurality of polarization portions defined by first and second electrodes adjacent to each other,
The polarization direction of each of the plurality of polarization units is,
A piezoelectric element in a direction opposite to the polarization portions adjacent to each other in the thickness direction of the piezoelectric portion. According to claim 1,
The spacing between the plurality of objects decreases from the dummy portion upward or downward in the thickness direction of the piezoelectric portion,
A piezoelectric element in which the reduction in the spacing between the plurality of objects is 8% to 15%. According to claim 1,
The piezoelectric part,
Vibrates in a bending mode when power is applied through the first outer electrode and the second outer electrode,
A piezoelectric element having at least one resonance frequency in the region of 10 kHz or less. The piezoelectric element according to any one of claims 1, 3 to 7;
a display unit disposed on the piezoelectric element;
an adhesive layer disposed between the piezoelectric element and the display unit; and
A piezoelectric actuator comprising a cover member disposed on the display unit. Piezoelectric actuator; and
It includes a drive control unit that drives the piezoelectric actuator,
The piezoelectric actuator is
The piezoelectric element according to any one of claims 1, 3 to 7;
a display unit disposed on the piezoelectric element;
an adhesive layer disposed between the piezoelectric element and the display unit; and
A piezoelectric module comprising a cover member disposed on the display unit. delete delete delete