JP5932458B2 - Piezoelectric vibration element, piezoelectric vibration device using the same, and portable terminal - Google Patents

Description

  The present invention relates to a piezoelectric vibration element, a piezoelectric vibration device using the same, and a portable terminal.

  Conventionally, a plate-like piezoelectric bimorph element and a vibration plate are arranged with a space therebetween, and one end in the length direction of the piezoelectric bimorph element is fixed to the vibration plate via a fixing jig, thereby vibrating the piezoelectric bimorph element. There is known a piezoelectric vibration device that transmits a vibration to a diaphragm (see, for example, Patent Document 1).

JP 2006-238072 A

  However, the above-described conventional piezoelectric vibration device requires a sufficient space between the piezoelectric bimorph element and the diaphragm so that the piezoelectric bimorph element and the diaphragm do not contact even when an impact is applied. There is a problem that it is difficult to reduce the thickness. In addition, the inventors have clarified that it is difficult to transmit strong vibration to the diaphragm when one main surface of the diaphragm is directly joined to one main surface of the piezoelectric bimorph element in order to reduce the thickness.

  The present invention has been devised in view of such problems, and an object of the present invention is to provide a piezoelectric vibration element capable of transmitting strong vibration to a vibration plate even when the vibration plate is directly bonded to the surface, and the piezoelectric vibration element. Another object is to provide a piezoelectric vibration device and a portable terminal using the above.

The piezoelectric vibration element of the present invention has at least a plurality of electrodes and a plurality of piezoelectric layers arranged alternately along the first direction, and the piezoelectric layer on one side of the first direction. the average polarization intensity, the rather low than the average polarization intensity of the piezoelectric layer at the other side of the first direction, the polarization intensity of the piezoelectric layer, toward the one side of the first direction It is characterized by being lowered step by step .

  The piezoelectric vibration device of the present invention includes at least the piezoelectric vibration element and a vibration plate having one main surface bonded to the surface on the one side in the first direction of the piezoelectric vibration element. It is. The portable terminal according to the present invention includes at least the piezoelectric vibration device and an electronic circuit that generates an electric signal input to the piezoelectric vibration element.

  According to the piezoelectric vibration element of the present invention, it is possible to obtain a piezoelectric vibration element that can transmit strong vibration to the vibration plate even if the vibration plate is directly bonded to the surface. According to the piezoelectric vibration device of the present invention, a thin piezoelectric vibration device capable of transmitting strong vibration can be obtained. According to the mobile terminal of the present invention, a thin mobile terminal capable of transmitting strong vibrations can be obtained.

1 is a perspective view schematically showing a piezoelectric vibration element of a first example of an embodiment of the present invention. (A)-(e) is a top view for demonstrating the structure of the piezoelectric vibration element shown in FIG. It is a figure for demonstrating the structure of the piezoelectric vibration element shown in FIG. It is a figure for demonstrating the structure of the piezoelectric vibration element of the 2nd example of embodiment of this invention. It is a perspective view which shows typically the piezoelectric vibration apparatus of the 3rd example of embodiment of this invention. It is a perspective view which shows typically the portable terminal of the 4th example of embodiment of this invention. FIG. 7 is a cross-sectional view taken along line A-A ′ in FIG. 6. FIG. 7 is a sectional view taken along line B-B ′ in FIG. 6.

  Hereinafter, a piezoelectric vibration element of the present invention, a piezoelectric vibration device using the same, and a portable terminal will be described in detail with reference to the accompanying drawings.

(First example of embodiment)
FIG. 1 is a perspective view schematically showing a piezoelectric vibration element 14 which is a first example of an embodiment of the present invention. As shown in FIG. 1, the piezoelectric vibration element 14 of this example has a first direction (z-axis direction in the drawing) as a thickness direction, and an x-axis direction in the drawing perpendicular to the first direction as a length direction. There is a rectangular parallelepiped shape in which the first direction and the y-axis direction in the drawing perpendicular to the x-axis direction in the drawing are the width direction. In addition, the piezoelectric vibration element 14 includes a laminate 20, a first terminal electrode 41, a second terminal electrode 42, a third terminal electrode (not shown), and a fourth terminal electrode (not shown). ) And a fifth terminal electrode (not shown).

  As shown in FIG. 1, an electrode 23 is disposed on the end face of one side of the laminate 20 in the first direction (+ z direction side in the figure). Further, the first terminal electrode 41 and the second terminal electrode 42 are disposed on the end surface in the + x direction of the stacked body 20 in the figure, and the third end surface of the stacked body 20 has the third terminal electrode in the −x direction. A fifth terminal electrode (not shown) is arranged. And the electrode 25 is arrange | positioned at the end surface of the other side (-z direction side of a figure) of the 1st direction of the laminated body 20. As shown in FIG.

  2A to 2E are plan views schematically showing the shapes of the electrodes 21 to 25 included in the piezoelectric vibration element 14. FIG. 3 shows the basic positional relationship of the electrodes 21 to 25 in the first direction (the z-axis direction in the drawing) and the polarization state of the piezoelectric layer 27 disposed between the electrodes 21 to 25. It is a figure shown typically. In FIG. 3, the first to fifth terminal electrodes and the piezoelectric layer 27 are not shown. As shown in FIGS. 2 and 3, the stacked body 20 includes a plurality of piezoelectric layers 27 polarized in a first direction (z-axis direction in the figure) and a plurality of flat electrodes 21 to 25. They are arranged alternately along the first direction.

The electrode 21 has a structure in which one end of a rectangular lead portion 21b is connected to one end of a rectangular main body portion 21a formed at a distance from the side surface of the laminate 20. The other end of the lead portion 21 b is connected to the first terminal electrode 41. The electrode 22 has a structure in which one end of a rectangular lead portion 22b is connected to one end of a rectangular main body portion 22a formed at a distance from the side surface of the laminate 20. The other end of the lead portion 22 b is connected to the second terminal electrode 42. The electrode 23 has a structure in which one end of a rectangular lead portion 23b is connected to one end of a rectangular main body portion 23a formed at a distance from the side surface of the laminate 20. The other end of the lead portion 23b is connected to a third terminal electrode (not shown). The electrode 24 has a structure in which one end of a rectangular lead portion 24b is connected to one end of a rectangular main body portion 24a formed at a distance from the side surface of the laminate 20. The other end of the lead portion 24b is connected to a fourth terminal electrode (not shown). The electrode 25 has a structure in which one end of a rectangular lead portion 25b is connected to one end of a rectangular main body portion 25a formed at a distance from the side surface of the laminate 20. The other end of the lead portion 25b is connected to a fifth terminal electrode (not shown).

  Further, the piezoelectric layer 27 disposed between the electrodes 21 to 25 is polarized as shown by arrows in FIG. Arrows P1 to P4 indicate the state of rough polarization of the piezoelectric layer 27 at each position as a vector, and the direction of the polarization is indicated by the direction of the arrow, and the strength of the polarization is indicated by the size of the arrow. Is shown.

  The piezoelectric layer 27 is polarized in the direction from the electrodes 24 and 25 toward the electrode 22 on the other side in the first direction (the −z direction side in the figure), and is one side in the first direction (the + z direction in the figure). On the direction side), it is polarized in a direction from the electrode 21 toward the electrodes 23 and 24. When the piezoelectric vibration element 14 is vibrated, for example, the electrodes 21 and 32 are at the same potential, the electrodes 23, 24 and 25 are at the same potential, and between the electrodes 21 and 32 and the electrodes 23, 24 and 25. An AC voltage is applied to the first to fifth terminal electrodes so that a potential difference is generated in the first to fifth terminal electrodes. Thereby, the piezoelectric vibrating element 14 is configured such that the polarization direction with respect to the direction of the electric field applied at a certain moment is reversed between one side and the other side in the first direction (z-axis direction in the figure).

  Therefore, when an electrical signal is applied and one side (the + z-direction side in the figure) of the first direction extends in the length direction (the x-axis direction in the figure) of the piezoelectric vibration element 14 at a certain moment, the first The other side of this direction (the −z direction side in the figure) is configured to shrink in the length direction of the piezoelectric vibration element 14. Thereby, the piezoelectric vibration element 14 is flexibly vibrated in the first direction (the z-axis direction in the figure) so that the amplitude changes in the x-axis direction in the figure when an electric signal is applied. Thus, the piezoelectric vibration element 14 is configured by a piezoelectric body (piezoelectric bimorph element) having a bimorph structure.

  In the piezoelectric vibration element 14 of this example, the average polarization intensity of the piezoelectric layer 27 on one side in the first direction (the + z direction side in the figure) is the other side in the first direction (the −z direction in the figure). And the average polarization intensity of the piezoelectric layer 27 on the side). Note that one side in the first direction is a part on one side of the center in the first direction, and the other side in the first direction is a part on the other side of the center in the first direction. is there. In the case shown in FIG. 3, the electrode 24 is located in the center of the piezoelectric vibration element 14 in the first direction (z-axis direction in the figure).

  Therefore, the average polarization intensity of the piezoelectric layer 27 on the other side in the first direction is A1, the polarization intensity of the piezoelectric layer 27 positioned between the electrode 25 and the electrode 22 is | P1 | If the polarization intensity of the piezoelectric layer 27 positioned between the electrodes 24 is | P2 |, A1 = (| P1 | + | P2 |) / 2.

  The average polarization intensity of the piezoelectric layer 27 on one side in the first direction is A2, the polarization intensity of the piezoelectric layer 27 located between the electrode 24 and the electrode 21 is | P3 | When the polarization strength of the piezoelectric layer 27 located between the electrodes 23 is | P4 |, A2 = (| P3 | + | P4 |) / 2.

  In the piezoelectric vibration element 14 of this example, the average polarization intensity A2 of the piezoelectric layer 27 on one side in the first direction is greater than the average polarization amplitude A1 of the piezoelectric layer 27 on the other side in the first direction. Is also lower (smaller). Thus, the vibration device is configured to join the main surface of the vibration plate to the surface of the piezoelectric vibration element 14 on one side in the first direction (+ z direction side in the drawing) and transmit the vibration of the piezoelectric vibration element 14 to the vibration plate. When it is done, strong vibration can be transmitted to the diaphragm.

The reason why this effect is obtained can be estimated as follows. That is, for example, when the piezoelectric vibration element 14 is bent so that the −z direction side is convex, as described above, the + z direction side of the piezoelectric vibration element 14 contracts in the x-axis direction. Then, since the surface of the diaphragm bonded to the surface on the + z direction side of the piezoelectric vibration element 14 also contracts in the x-axis direction, the diaphragm tends to deform so that the + z direction side is convex. Therefore, the direction in which the piezoelectric vibration element 14 tries to bend and the direction in which the vibration plate tries to bend are reversed, the vibration of the piezoelectric vibration element 14 is hindered, and the vibration of the piezoelectric vibration element 14 is weakened. Thereby, the vibration transmitted to the diaphragm is weakened.

  In the piezoelectric vibration element 14 of this example, the average polarization intensity of the piezoelectric layer 27 on one side in the first direction (the + z direction side in the figure) is the other side in the first direction (the −z direction side in the figure). Is lower than the average polarization intensity of the piezoelectric layer 27. As a result, when an equal potential difference is applied between the adjacent electrodes, the amount of expansion / contraction on one side in the first direction is smaller than the amount of expansion / contraction on the other side in the first direction. As a result, the force to bend the vibration plate bonded to the surface of the piezoelectric vibration element 14 on one side in the first direction in the direction opposite to that of the piezoelectric vibration element 14 is reduced. Therefore, the action which prevents the vibration of the piezoelectric vibration element 14 is reduced, and the piezoelectric vibration element 14 can vibrate strongly. Therefore, strong vibration can be transmitted to the diaphragm. In addition, since the deformation on one side in the first direction when the piezoelectric vibration element 14 undergoes flexural vibration is smaller than the deformation on the other side in the first direction, the surface on the one side in the first direction Even when the vibration of the bonded diaphragm is suppressed, the vibration of the piezoelectric vibration element 14 is not significantly suppressed, and a strong vibration can be transmitted to the diaphragm.

  For example, when the center in the first direction (the z-axis direction in the drawing) is located in one piezoelectric layer 27A, the piezoelectric layer 27A may be excluded. That is, the average polarization intensity of the piezoelectric layer 27 located on one side in the first direction (the + z direction side in the drawing) from the piezoelectric layer 27A is expressed as “the piezoelectric layer 27 on one side in the first direction. The average of the polarization intensity of the piezoelectric layer 27 located on the other side in the first direction (the −z direction side in the drawing) from the piezoelectric layer 27A is referred to as “first direction”. The average of the polarization intensity of the piezoelectric layer 27 on the other side ”may be used.

  In FIG. 3, when the polarization intensity of the piezoelectric layer 27 is sequentially described from the other side in the first direction (the −z direction side in the drawing) to the one side (the + x direction side in the drawing), | P1 | , | P2 |, | P3 |, | P4 |, but the relationship between these sizes is | P1 |> | P2 |> | P3 |> | P4 |. That is, in the piezoelectric vibration element 14 of this example, the polarization intensity of the piezoelectric layer 27 is gradually reduced toward one side in the first direction (the + z direction side in the figure). As a result, the amount of expansion / contraction of each piezoelectric layer 27 when the piezoelectric vibration element 14 undergoes flexural vibration gradually decreases toward one side in the first direction, so that the piezoelectric layer within the piezoelectric vibration element 14 The stress generated in the portion where the amount of expansion and contraction 27 changes can be reduced. Thereby, problems, such as generation | occurrence | production of a microcrack, can be reduced.

  When the material of the piezoelectric layer 27 is the same, the dielectric constant of the piezoelectric layer 27 is proportional to the polarization strength of the piezoelectric layer 27. Therefore, for example, instead of comparing the magnitude of polarization intensity (or its average value), the dielectric constant (or its average value) may be compared.

Thus, for example, the capacitance between the electrode 25 and the electrode 22 is C1, the facing area is S1, the interval is d1, the capacitance between the electrode 22 and the electrode 24 is C2, the facing area is S2, and the spacing is S2. Is d2, the capacitance between the electrode 24 and the electrode 21 is C3, the facing area is S3, the interval is d3, the capacitance between the electrode 21 and the electrode 22 is C4, and the facing area is S4. Is d4, B1 = C1 × d1 / S1, B2 = C2 × d2 / S2, B3 = C3 × d3 / S3, B4 = C4 × d4 / S4, E1 = (B1 + B2) / 2, E2 If = (B3 + B4) / 2, the magnitude relationship between A1 and A2 may be compared by comparing the magnitude relationship between E1 and E2. Further, by comparing the magnitude relationships of B1, B2, B3, B4, and B5, the magnitude relationships of | P1 |, | P2 |, | P3 |, | P4 |, and | P5 | Absent.

  In the piezoelectric vibration element 14 of this example, the laminate 20 can have a length of about 18 mm to 28 mm, a width of about 1 mm to 6 mm, and a thickness of about 0.2 mm to 1.0 mm, for example. The length of the main body of the electrodes 21 to 25 can be about 17 mm to 25 mm, for example, and the width of the main body of the electrodes 21 to 25 can be about 0.5 mm to 1.5 mm, for example.

  The piezoelectric layer 27 constituting the laminate 20 is preferably made of, for example, lead-free piezoelectric material such as lead titanate (PT), lead zirconate titanate (PZT), Bi layered compound, tungsten bronze structure compound, or the like. However, other piezoelectric materials may be used. The thickness of one layer of the piezoelectric layer 27 can be set to, for example, about 0.01 to 0.1 mm. The electrodes 21, 22, and 24 can be formed by suitably using, for example, a ceramic component or a glass component in addition to a metal component such as silver or an alloy of silver and palladium. You may form using a known metal material. The electrodes 23 and 25 and the first to fifth terminal electrodes desirably contain a metal component made of silver and a glass component, but may be a metal other than silver.

  Such a piezoelectric vibration element 14 can be manufactured by the following method, for example. First, a binder, a dispersant, a plasticizer, and a solvent are added to the piezoelectric material powder, and the mixture is agitated to produce a slurry. The obtained slurry is formed into a sheet shape to produce a green sheet. Next, a conductive paste is printed on the green sheet to form electrode patterns to be the electrodes 21, 22, and 24. The green sheets on which the electrode patterns are formed are stacked and pressed using a press device to form a laminated molded body Is made. Then, degreasing and baking are performed, and a laminated body is obtained by cutting to a predetermined dimension. Next, a conductor paste for forming the electrodes 23 and 25, the first terminal electrode 41, the second terminal electrode 42, and the third to fifth terminal electrodes (not shown) is printed at a predetermined temperature. After baking, the piezoelectric layer 27 is polarized by applying a DC voltage through the first to fifth terminal electrodes. At this time, the polarization intensity of each piezoelectric layer 27 can be made different by sequentially changing the two electrodes to which the voltage is applied and the voltage to be applied and performing the polarization in a plurality of times. In this way, the piezoelectric vibration element 14 can be obtained.

  For example, when a problem occurs when the electrode is exposed at the end face in the first direction (z-axis direction in the drawing) of the stacked body 20, a protective layer made of a piezoelectric body or the like may be provided. In that case, it is desirable to sufficiently reduce the thickness of the protective layer.

(Second example of embodiment)
FIG. 4 is a cross-sectional view schematically showing the structure of the piezoelectric vibration element 14a of the second example of the embodiment of the present invention. In FIG. 4, the piezoelectric layer and the first to fifth terminal electrodes are not shown in order to simplify the illustration. Moreover, in this example, a different point from the 1st example of embodiment mentioned above is demonstrated, the same referential mark is attached | subjected to the same component and the overlapping description is abbreviate | omitted.

  The piezoelectric vibration element 14a of this example is similar to the piezoelectric vibration element 14 of the first example of the above-described embodiment, and the polarization strength of the piezoelectric layer 27 on one side in the first direction (+ z direction side in the figure). Average A2 = (| P3 | + | P4 |) / 2 is the average polarization intensity of the piezoelectric layer 27 on the other side in the first direction (the −z direction side in the figure) A1 = (| P1 | + | It is lower than P2 |) / 2. As a result, when a vibration device is constructed in which the main surface of the diaphragm is joined to the surface on one side in the first direction (the + z direction side in the figure) and the vibration of the piezoelectric vibration element 14a is transmitted to the diaphragm. Strong vibration can be transmitted to the board. Further, even when vibration of the diaphragm is suppressed, strong vibration can be transmitted to the diaphragm.

  In the piezoelectric vibration element 14a of this example, the relationship of | P1 | = | P2 |> | P3 |> | P4 | is established in the polarization strengths P1, P2, P3, and P4 of the piezoelectric layer 27. That is, the polarization intensity of the piezoelectric layer 27 is constant on the other side in the first direction (the −z direction side in the drawing), and on the one side in the first direction (the + z direction side in the drawing) It goes down step by step toward one side of the direction.

  Since such a configuration is provided, the piezoelectric vibration element 14a of the present example can ensure a large amount of deformation on the other side in the first direction. As a result, when a piezoelectric vibration device in which the main surface of the diaphragm is attached to the surface on one side in the first direction (+ z direction side in the figure), stronger vibration can be transmitted to the diaphragm.

(Third example of embodiment)
FIG. 5 is a perspective view schematically showing a piezoelectric vibration device 15 according to a third example of the embodiment of the present invention. In FIG. 5, the detailed structure of the piezoelectric vibration element 14 is not shown for easy drawing. Moreover, in this example, a different point from the 1st example of embodiment mentioned above is demonstrated, the same referential mark is attached | subjected to the same component and the overlapping description is abbreviate | omitted. The piezoelectric vibration device 15 of this example includes the piezoelectric vibration element 14 and the diaphragm 12 of the first example of the above-described embodiment.

  The diaphragm 12 has a rectangular thin plate shape, and has one main surface (on the −z direction side in the figure) on the surface of one side (the + z direction side in the figure) of the piezoelectric vibration element 14 in the first direction. Are joined using an adhesive or the like. Such a diaphragm 12 can be preferably formed using a material having high rigidity and elasticity, such as acrylic resin or glass. Moreover, the thickness of the diaphragm 12 is set to about 0.4 mm to 1.5 mm, for example. The piezoelectric vibration device 15 of this example having such a configuration functions as a piezoelectric vibration device that flexibly vibrates the piezoelectric vibration element 14 by applying an electric signal and transmits the vibration to the vibration plate 12.

  In the piezoelectric vibration device 15 of this example, one main surface of the vibration plate 12 is bonded to the surface of one side (the + z direction side in the drawing) of the piezoelectric vibration element 14 in the first direction. In the piezoelectric vibration element 14, the average polarization intensity of the piezoelectric layer 27 on one side in the first direction (+ z direction side in the figure) is on the other side in the first direction (on the −z direction side in the figure). It is lower than the average polarization intensity of the piezoelectric layer 27. Thereby, even when the diaphragm 12 can vibrate freely, even when the vibration of the diaphragm 12 is suppressed, a thin piezoelectric vibration device that can transmit strong vibration to the diaphragm 12 can be obtained.

(Fourth example of embodiment)
FIG. 6 is a perspective view schematically showing a portable terminal of the fourth example of the embodiment of the present invention. 7 is a cross-sectional view taken along line AA ′ in FIG. 8 is a cross-sectional view taken along line BB ′ in FIG. 7 and 8, the detailed structure of the piezoelectric vibration element 14 is not shown. Moreover, in this example, a different point from the 3rd example of embodiment mentioned above is demonstrated, the same referential mark is attached | subjected to the same component and the overlapping description is abbreviate | omitted. The portable terminal of this example includes the piezoelectric vibration device 15 of the third example of the embodiment shown in FIG. 5, an electronic circuit 17, a display 18, and a housing 19.

  The electronic circuit 17 generates an electrical signal that is input to the piezoelectric vibration element 14. The electronic circuit 17 may include other circuits such as a circuit for processing image information to be displayed on the display 18 and a communication circuit. The electronic circuit 17 and the piezoelectric vibration element 14 are connected via a wiring (not shown).

The display 18 is a display device having a function of displaying image information. For example, a known display such as a liquid crystal display, a plasma display, and an organic EL display can be suitably used. The display 18 may have an input device such as a touch panel.

  The housing 19 has a box shape with one surface opened. The housing 19 can be preferably formed using a material such as a synthetic resin having high rigidity and elasticity, but may be formed using another material such as a metal.

  In the portable terminal of this example, the diaphragm 12 is disposed outside the display 18 and integrated with the display 18, and functions as a cover that protects the display 18. Further, the diaphragm 12 has only one main surface (main surface on the −z direction side in the figure) around the casing 19 joined to the casing 19 with an adhesive or the like, and is attached to the casing 19 so as to vibrate. . The diaphragm 12 may have an input device such as a touch panel.

  The mobile terminal of this example having such a configuration can generate sound by vibrating the diaphragm 12 by vibrating the piezoelectric vibrating element 14. And the sound information can be transmitted to a person by this sound. In addition, audio information may be transmitted by transmitting vibration by bringing the diaphragm 12 or the casing 19 into contact with a part of a human body such as an ear directly or via another object.

  The portable terminal of this example uses a thin piezoelectric vibration device that can transmit strong vibration to the diaphragm 12 even when the diaphragm 12 can vibrate freely or when vibration of the diaphragm 12 is suppressed. ing. Thereby, even when the diaphragm 12 can vibrate freely, even when the vibration of the diaphragm 12 is suppressed, a thin mobile terminal capable of transmitting strong vibration to the diaphragm 12 can be obtained. Therefore, according to the portable terminal of this example, even when the diaphragm 12 is brought into contact with a human body such as an ear, strong vibration can be transmitted to the diaphragm 12 and voice information can be transmitted satisfactorily. A thin portable terminal can be obtained.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the scope of the present invention.

  For example, in the first and second examples of the above-described embodiment, the example in which the piezoelectric vibration element 14 has the five electrodes 21 to 25 is shown in order to simplify the illustration. However, the present invention is not limited to this, and a configuration having more electrodes may be used.

  In the third and fourth examples of the above-described embodiment, the example having the piezoelectric vibration element 14 of the first example of the embodiment has been described. However, the present invention is not limited to this. You may have the piezoelectric vibration element 14a of the 2nd example of embodiment, and the piezoelectric vibration element of another form.

  In the fourth example of the above-described embodiment, the example in which the cover of the display 18 functions as the diaphragm 12 is shown, but the present invention is not limited to this. For example, the display 18 itself may function as the diaphragm 12.

12: Vibration plates 14 and 14a: Piezoelectric vibration element 15: Piezoelectric vibration device 17: Electronic circuits 21, 22, 23, 24, 25: Electrode 24: Piezoelectric layer

Claims (4)

At least a plurality of electrodes and a plurality of piezoelectric layers arranged alternately along the first direction, the average polarization intensity of the piezoelectric layers on one side of the first direction is rather lower than the average polarization intensity of the piezoelectric layer on the other side of the first direction, the polarization intensity of the piezoelectric layer, which is stepwise lowered toward said one side of said first direction The piezoelectric vibration element characterized by the above-mentioned. The polarization intensity of the piezoelectric layer is constant on the other side of the first direction, and gradually decreases on the one side of the first direction toward the one side of the first direction. The piezoelectric vibration element according to claim 1 , wherein: The piezoelectric vibration element according to claim 1 or 2 , and a vibration plate having at least one main surface bonded to the surface on the one side in the first direction of the piezoelectric vibration element. Piezoelectric vibration device. A portable terminal comprising at least the piezoelectric vibration device according to claim 3 and an electronic circuit that generates an electric signal input to the piezoelectric vibration element.

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