JP2007059525A - Laminated piezoelectric element and apparatus using same, and method of manufacturing laminated piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated piezoelectric element where a laminate of a piezoelectric layer and an inner electrode layer is hard to be peeled from an insulating film formed on a side of the laminate. <P>SOLUTION: The element is provided with: the laminate where a plurality of piezoelectric layers 10 and a plurality of electrode layers 11a and 11b are alternately arranged; the insulating film 14a formed at least in a part of the end face of the electrode layer 11a by a piezoelectric material in a first side region of the laminate; the insulating film 14b formed at least in a part of the end face of the second electrode layer 11b, which is alternately arranged with the electrode layer 11a by the piezoelectric material in a second side region different from the first side region of the laminate; a side electrode 15a formed in the first side region, is insulated from the electrode layer 11a by the insulating film 14a, and is electrically connected to the electrode layer 11b; and a side electrode 15b formed in the second side region, is insulated from the electrode layer 11b by the insulating film 14b, and is electrically connected to the electrode layer 11a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric element (laminated piezoelectric element) having a laminated structure used as a piezoelectric actuator, an ultrasonic transducer, and the like, and a method for manufacturing the same. Furthermore, the present invention relates to an apparatus such as an ink jet head or an ultrasonic imaging apparatus using such a multilayer piezoelectric element.

  A piezoelectric body typified by a material having a lead-based perovskite structure such as PZT (lead zirconate titanate) produces a piezoelectric effect that expands and contracts when an electric field is applied. Piezoelectric elements that utilize such properties are used in various applications such as piezoelectric pumps, piezoelectric actuators, and ultrasonic transducers. The structure of the piezoelectric element is basically a single-layer structure in which electrodes are formed on both sides of one piezoelectric body, but the miniaturization and integration of the piezoelectric element accompanying the recent development of MEMS (micro electro mechanical system) related equipment. As a result, stacked piezoelectric elements in which a plurality of piezoelectric bodies and a plurality of electrodes are alternately stacked are also used.

  FIG. 10 is a cross-sectional view showing the structure of the multilayer piezoelectric element. This piezoelectric element is composed of alternately stacked piezoelectric layers 100 and internal electrode layers 101a and 101b, a lower electrode 102 and an upper electrode 103, and insulating films 104a and 104 formed alternately on the end faces of the internal electrode layers 101a and 101b. 104b and side electrodes 105a and 105b.

  The side electrode 105a is insulated from the internal electrode layer 101a by the insulating film 104a and is connected to the internal electrode layer 101b. On the other hand, the side electrode 105b is insulated from the internal electrode layer 101b by the insulating film 104b and connected to the internal electrode layer 101a. The lower electrode layer 102 is connected to the side electrode 105a, and the upper electrode layer 103 is connected to the side electrode 105b.

  By forming the electrodes of the piezoelectric elements in this way, the electrodes for applying an electric field to each of the plurality of piezoelectric layers 100 are connected in parallel. As a result, the inter-electrode capacity of the laminated structure as a whole increases, so that an increase in electrical impedance can be suppressed even if the size of the piezoelectric element is reduced.

  In the insulating films 104a and 104b shown in FIG. 10, for example, glass powder is attached to the end faces of the internal electrode layers 101a and 101b by electrophoresis, or paste containing glass powder is applied to a desired region by screen printing. It is formed by arranging. Therefore, when the piezoelectric layer 100 expands and contracts, the insulating films 104a and 104b cannot follow the displacement of the piezoelectric layer 100, and distortion occurs at the interface between them. As a result, the insulating films 104a and 104b are easily peeled off from the laminated body (the piezoelectric layer 100 and the internal electrode layers 101a and 101b), so that the reliability during operation of the piezoelectric element is low and the lifetime of the element is short. There is a problem.

  In view of the above, an object of the present invention is to provide a multilayer piezoelectric element in which an insulating film formed on a side surface of a multilayer body is difficult to peel from the multilayer body.

  In order to solve the above problems, a multilayer piezoelectric element according to one aspect of the present invention includes a multilayer body in which a plurality of piezoelectric layers and a plurality of electrode layers are alternately arranged, and a first side surface of the multilayer body. In the region, a first insulating film formed of a piezoelectric material on at least a part of the end surface of the first electrode layer of the plurality of electrode layers and a first side region different from the first side surface region of the stacked body. A second insulating film formed of a piezoelectric material on at least a part of an end surface of the second electrode layer alternately arranged with the first electrode layer among the plurality of electrode layers in the two side surface regions; And a side electrode formed in the first side region, the first side surface being insulated from the first electrode layer by the first insulating film and electrically connected to the second electrode layer An electrode and a side electrode formed in the second side surface region, wherein the second insulating film While being insulated from the second electrode layer comprises a first electrode layer and the second side electrode electrically connected.

  In addition, a method for manufacturing a multilayer piezoelectric element according to one aspect of the present invention includes a step (a) of forming a multilayer body by alternately arranging a plurality of piezoelectric layers and a plurality of electrode layers; A step (b) of forming a first insulating film with a piezoelectric material on at least a part of an end surface of the first electrode layer of the plurality of electrode layers in the first side surface region of the body; In a second side surface region different from the first side surface region of the plurality of electrode layers, at least a part of the end surface of the second electrode layer alternately arranged with the first electrode layer is piezoelectric. A step (c) of forming a second insulating film by a material, and being electrically insulated from the first electrode layer by the first insulating film and electrically connected to the second electrode layer in the first side surface region; Forming a first side electrode to be formed, and a second insulating region in the second side region. While it is insulated from the second electrode layer by a membrane, comprising a step (e) forming a second side surface electrodes which are connected to the first electrode layer and electrically.

  According to the present invention, since the insulating film is formed of the piezoelectric material, the insulating film expands and contracts following the displacement of the piezoelectric layer, so that peeling between the insulating film and the laminate can be suppressed. . As a result, the reliability of the operation of the piezoelectric element can be improved, and the lifetime of the piezoelectric element and the device including the piezoelectric element can be extended.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a partial cross-sectional perspective view showing the structure of a multilayer piezoelectric element according to an embodiment of the present invention.
As shown in FIG. 1, the multilayer piezoelectric element according to this embodiment is a columnar structure having, for example, a side of the bottom surface of about 200 μm to 1.0 mm and a height of about 300 μm to 1.0 mm. The multilayer piezoelectric element includes a plurality of piezoelectric layers 10, a plurality of internal electrode layers 11a and 11b, a lower electrode layer 12, an upper electrode layer 13, insulating films 14a and 14b, side electrodes 15a and 15b. The piezoelectric layers 10 and the internal electrode layers 11 a and 11 b are alternately arranged, and together with the lower electrode layer 12 and the upper electrode layer 13, form a laminate.

  The piezoelectric layer 10 has a thickness of about 100 μm, for example, and is formed of a complex oxide having a lead-based perovskite structure such as PZT (lead zirconate titanate). In FIG. 1, three piezoelectric layers 10 are shown. However, the piezoelectric layers may be at least two layers, and may be four or more layers.

The internal electrode layers 11a and 11b have a thickness of, for example, about 3 μm, and are aluminum (Al), gold (Ag), platinum (Pt), ruthenium (Ru), iridium (Ir), rhenium (Re). , Osmium (Os), rhodium (Rh), and other metal materials, alloys (for example, silver palladium), and metal oxides including at least one of these metals. The internal electrode layers 11a and 11b may be formed of one type of material or may have a multi-layer structure formed of a plurality of different materials. As an example of the latter, by forming a titanium oxide (TiO ₂ ) layer of about 50 nm as an adhesion layer on the piezoelectric layer 10 and forming a platinum (Pt) layer of about 3 μm as a conductive layer thereon, The adhesion between the conductive layer and the piezoelectric layer 10 can be improved.
When four or more piezoelectric layers 10 are arranged, the internal electrode layers 11a and the internal electrode layers 11b are alternately arranged with the piezoelectric layers 10 interposed therebetween.

Similarly to the internal electrode layers 11a and 11b, the lower electrode layer 12 and the upper electrode layer 13 may have a single-layer structure, or may have a multi-layer structure including an adhesion layer and a conductive layer.
The insulating film 14a is formed by a piezoelectric material such as PZT so as to cover the end surface of the internal electrode layer 11a exposed on one side surface of the multilayer body. The insulating film 14b is formed by a piezoelectric material such as PZT so as to cover the end surface of the internal electrode layer 11b exposed on the opposite side surface of the multilayer body. In order to enhance the insulating function of the insulating films 14a and 14b, it is desirable to form the insulating films 14a and 14b not only on the end surfaces of the internal electrode layers 11a and 11b but also on a partial region of the adjacent piezoelectric layer 10. . Therefore, in the present embodiment, the insulating films 14a and 14b are formed so as to protrude by about 3 μm on the upper and lower piezoelectric layers 10 side with respect to the internal electrode layer having a thickness of about 3 μm. Further, if the insulating films 14a and 14b are too thin, dielectric breakdown or polarization inversion may occur. Therefore, in the present embodiment, the thickness of the insulating films 14a and 14b is about 10 μm.

  The side electrode 15a is formed on the side surface of the stacked body so as to pass through the surface of the insulating film 14a, thereby being insulated from the internal electrode 11a and connected to the internal electrode 11b. Further, the side electrode 15b is formed on another side surface of the stacked body so as to pass through the surface of the insulating film 14b, thereby being insulated from the internal electrode 11b and connected to the internal electrode 11a. Further, the side electrode 15 a is connected to the lower electrode layer 12, and the side electrode layer 15 b is connected to the upper electrode layer 13.

  When a voltage is supplied to such a laminated piezoelectric element via the lower electrode layer 12 and the upper electrode layer 13, a first group of electrodes including the lower electrode layer 12 and the internal electrode layer 11b, and the upper electrode layer 13 and the second group of electrodes including the internal electrode layer 11a apply an electric field to each piezoelectric layer 10. As a result, the multilayer piezoelectric element expands and contracts as a whole due to the piezoelectric effect in each piezoelectric layer 10.

Next, the reason why the insulating films 14a and 14b are formed of a piezoelectric material will be described with reference to FIG. The arrows shown in FIG. 2 indicate the directions of polarization of the piezoelectric layer 10 and the insulating films 14a and 14b shown in FIG.
Here, the direction of polarization means that a large number of electronic dipoles in an insulator (or a dielectric, including a piezoelectric layer and an insulating film in this embodiment) are aligned in a predetermined direction (polarized). The direction of the charge from the negative charge side toward the positive charge side in the bias of the charge generated in the entire insulator. This direction is determined by the vector sum of all electric dipole moments in the insulator. Therefore, even when there are some electric dipoles in the insulator that are oriented in a different direction from the whole insulator, the direction based on the charge bias in the whole insulator is the polarization of the insulator. It becomes the direction.

  In the present embodiment, the polarizations of the insulating films 14 a and 14 b formed of the piezoelectric material are determined according to the polarization direction of the piezoelectric layer 10. That is, as shown in FIG. 2, when the polarization of two piezoelectric layers sandwiching one internal electrode layer faces the internal electrode layer side (in FIG. 2, internal electrode layer 11a), the internal electrode The insulating film formed on the end face of the layer is polarized so as to face the opposite side of the internal electrode layer (the insulating film 14a in FIG. 2). On the other hand, when the polarization of two piezoelectric layers sandwiching one internal electrode layer is directed to the opposite side of the internal electrode layer (in FIG. 2, internal electrode layer 11b), it is formed on the end face of the internal electrode layer. The applied insulating film is polarized so as to face the internal electrode layer side (the insulating film 14b in FIG. 2).

  The advantages of determining the polarization directions of the insulating films 14a and 14b are as follows. When an electric field having a predetermined polarity is applied to the laminated piezoelectric element, for example, when the two piezoelectric layers 10 sandwiching the internal electrode layer 11a contract, the insulating film 14a has the internal electrode layer 11a, the side electrode 15a, A piezoelectric effect is generated by the electric field formed by the above, and it expands in the horizontal direction in the figure and contracts in the vertical direction. On the contrary, when the two piezoelectric layers 10 are expanded by applying an electric field having a reverse polarity to the stacked piezoelectric element, the insulating film 14a contracts in the left-right direction in the figure and expands in the vertical direction in the figure. . That is, when the polarization directions of the insulating films 14a and 14b and the polarization direction of the piezoelectric layer 10 are in the relationship shown in FIG. 2, the insulating films 14a and 14b follow the expansion and contraction of the piezoelectric layer 10. Expand and contract. Thereby, since distortion at the interface between the insulating films 14a and 14b and the stacked body is suppressed, peeling of the insulating films 14a and 14b can be prevented.

Next, a method for manufacturing the multilayer piezoelectric element according to this embodiment will be described with reference to FIGS.
First, as shown in FIG. 3A, a piezoelectric laminate 20 and internal electrode layers 21a and 21b are laminated to produce a sheet-like laminate. As a method for producing a laminate sheet, a method of superimposing a bulk material of a piezoelectric material on which an electrode layer is formed, a green sheet method, a method of sequentially forming a piezoelectric layer and an electrode layer on a substrate by film formation, etc. Any of these methods may be used. As a film forming method, a known method such as a sputtering method, a CVD method, a sol-gel method, an aerosol deposition (AD) method, a screen printing method, or the like can be used. Here, the AD method is to generate an aerosol by dispersing a raw material powder (raw material powder) in a gas, and injecting it from the nozzle toward the substrate to collide with the lower layer, thereby bringing the raw material onto the substrate. It is a film forming method to be deposited on the substrate and is also called a jet deposition method or a gas deposition method. When the piezoelectric layer 20 is formed by the AD method, in order to improve the crystallinity of the piezoelectric material, a heat treatment (post) is performed in an oxygen atmosphere or air at a predetermined temperature (for example, about 500 ° C. to 1000 ° C.). Annealing).
Furthermore, as shown with the broken line of (a) of FIG. 3, the workpiece of a predetermined magnitude | size is cut out from a laminated body sheet | seat.

  Next, as shown in FIG. 3B, insulating films 22a and 22b are formed so as to alternately cover the end surfaces of the internal electrode layers 21a and 21b exposed on the two opposite side surfaces of the workpiece. The formation method of the insulating films 22a and 22b is not particularly limited, but it is desirable to perform an AD method using a piezoelectric material powder as a raw material powder. According to the AD method, it is possible to form a piezoelectric film having a desired thickness in a desired region by using a nozzle having an opening having a predetermined size and shape.

Next, as shown in FIG. 3C, side electrodes 23a and 23b, a lower electrode layer 24, and an upper electrode layer 25 are formed. As a method of forming these electrodes, a resist mask is formed in advance on the insulating portion between the side electrode 23a and the upper electrode layer 25 and the insulating portion between the side electrode 23b and the lower electrode layer 24, and plating is performed. The method etc. which apply can be used.
Note that the lower electrode layer 24 and the upper electrode layer 25 may be formed first in the step of manufacturing the laminate sheet shown in FIG.

Next, as shown to (a) and (b) of FIG. 4, the 1st and 2nd polarization process is performed to the workpiece in which the side surface electrode was formed.
In the polarization treatment, electrodes for polarization treatment are arranged on the lower electrode layer 24 and the upper electrode layer 25 of the workpiece, the workpiece is immersed in silicon oil together with the electrode for polarization treatment, and the silicon oil is heated to a predetermined temperature by a heater. The heating is performed by applying an electric field to the workpiece by the power supply device for a predetermined time. Thus, in each piezoelectric layer 20, the electric dipoles are aligned in a predetermined direction according to the polarities of the lower electrode layer 24, the internal electrodes 21 a and 21 b, and the upper electrode layer 25. In each of the insulating films 22a and 22b, the electric dipoles are aligned in a predetermined direction according to the polarities of the internal electrodes 21a and 21b and the side electrodes 23a and 23b. Further, after elapse of a predetermined time, the workpiece is cooled in silicon oil with an electric field applied to the workpiece. Here, the electric field is applied to the workpiece in the silicon oil by increasing the temperature of the piezoelectric layer 20 and the insulating films 22a and 22b to facilitate polarization, and in the region where the side electrode is not formed. It is for preventing. In addition, the work piece is gradually cooled while applying an electric field. If the voltage is lowered before the work piece is cooled, the aligned electric dipoles may return to the original state again. Because there is.

  As shown in FIG. 4A, in the first polarization process, a voltage of about 400 V is applied to the workpiece electrode in, for example, 200 ° C. silicon oil in order to align the polarization direction of each piezoelectric layer 20. Is applied. Here, in general, since the polarization treatment of PZT is performed at a voltage of 40 kV per cm (at 200 ° C.), as in the present embodiment, when the thickness of each piezoelectric layer 20 is about 100 μm, The applied voltage is about 400 V (at 200 ° C.). By this polarization treatment, the insulating films 22a and 22b are also polarized in a predetermined direction.

As shown in FIG. 4B, in the second polarization process, in order to reverse only the polarization of the insulating films 22a and 22b, for example, the polarity of each electrode is reversed from that of the first polarization process. This is performed by applying a voltage of about 60 V to the electrode of the workpiece in silicon oil. Here, in order to polarize the insulating films 22a and 22b having a thickness of about 10 μm, a voltage of about 40 V is sufficient in silicon oil at 200 ° C., but in this embodiment, polarization is performed in silicon oil at room temperature. In order to reverse the voltage, the voltage is set high.
Furthermore, the multilayered piezoelectric element according to this embodiment is completed by taking out the workpiece subjected to the first and second polarization treatments from the silicon oil and washing it.

FIG. 5 is a perspective view showing a modification of the multilayer piezoelectric element according to the present embodiment.
Here, in the stacked piezoelectric element shown in FIG. 1, the side electrodes 15a and 15b are formed in the entire depth direction of the side surface of the stacked body, but the internal electrodes 11a and 11b, the lower electrode 12, and the upper electrode are formed. If a predetermined wiring for connecting 13 can be formed, it is not always necessary to form the entire wiring.

  As shown in FIG. 5, in this modification, insulating films 30a and 30b are respectively formed on part of the end faces of the internal electrode layers 11a and 11b, and the side electrodes 31a and 31b are formed of the insulating films 30a and 31b. By being arranged so as to pass through the surface of 30b, the internal electrode layers 11a and 11b are insulated from each other.

  In the case where the insulating film and the side electrode are formed on a part of the side surface of the laminate as in this modification, the region where the two side electrodes are not necessarily in contact with each other unless the two side electrodes are in contact with each other. It does not have to be on one side. For example, the insulating film 30a and the side electrode 31a, and the insulating film 30b and the side electrode 31b may be formed on two adjacent side surfaces, or may be formed on one side surface.

  Next, a driving method of the multilayer piezoelectric element according to the present embodiment will be described with reference to FIGS. In the following description, a voltage lower than a voltage that generates a coercive electric field (an electric field having a magnitude that reverses polarization) of the insulating films 14a and 14b is referred to as a low voltage, and a voltage that generates a coercive electric field of the insulating films 14a and 14b. A large voltage is called a high voltage.

(1) When driving at a low voltage As shown in FIG. 6A, when the direction of the electric field formed in each piezoelectric layer 10 is opposite to the direction of polarization of the piezoelectric layer 10 Each piezoelectric layer 10 contracts. At that time, since the direction of the electric field formed in the insulating films 14a and 14b is aligned with the direction of polarization of the insulating films 14a and 14b, the insulating films 14a and 14b expand in the horizontal direction and contract in the vertical direction in the figure. . On the other hand, as shown in FIG. 6B, when the direction of the electric field formed in each piezoelectric layer 10 is aligned with the direction of polarization of each piezoelectric layer 10, each piezoelectric layer 10 expands. To do. At that time, the insulating films 14a and 14b contract in the left-right direction in the figure and extend in the up-down direction. Thus, when the stacked piezoelectric element is driven at a low voltage, the insulating films 14a and 14b can follow the displacement of each piezoelectric layer 10 regardless of the polarity of the applied electric field. it can. Therefore, in this case, the stacked piezoelectric element can be bipolar driven, or unipolar driven with any polarity.

(2) When Driving at High Voltage As shown in FIG. 7A, the direction of the electric field formed in each piezoelectric layer 10 is opposite to the direction of polarization of the piezoelectric layer 10, and the insulating film 14a When the direction of the electric field formed on the insulating films 14 a and 14 b is aligned with the direction of polarization of the insulating films 14 a and 14 b, the insulating films 14 a and 14 b can follow the contraction of each piezoelectric layer 10. However, as shown in FIG. 7B, when the direction of the electric field formed in the insulating films 14a and 14b is opposite to the polarization direction of the insulating films 14a and 14b, the insulating films 14a and 14b Polarization is reversed by applying a high electric field. Then, when each piezoelectric layer 10 expands, the insulating films 14 a and 14 b contract in the vertical direction in the figure, and cannot follow the displacement of each piezoelectric layer 10. Therefore, in the case of driving at a high voltage, it is only possible to unipolarly drive the laminated piezoelectric element with the polarity shown in FIG.

  The multilayer piezoelectric element according to this embodiment described above is used as a piezoelectric pump, a piezoelectric actuator, an ultrasonic transducer that transmits and receives ultrasonic waves in an ultrasonic probe, and the like. In that case, the laminated piezoelectric element can be used alone or can be used as a piezoelectric element array by arranging the laminated piezoelectric elements in one or two dimensions.

  FIG. 8 is a cross-sectional view showing an example in which the multilayer piezoelectric element according to this embodiment is used as an actuator for driving an inkjet head. The ink jet head shown in FIG. 8 includes a plurality of stacked piezoelectric elements 40, a common wiring 41, a vibration plate 42, a partition wall 43, and a nozzle plate 44 that are two-dimensionally arranged. The ink jet head is connected to a drive circuit 47.

  The partition wall 43 partitions the space between the diaphragm 42 and the nozzle plate 44 into a plurality of regions. Thereby, a plurality of pressure chambers 45 filled with ink are formed at positions corresponding to the laminated piezoelectric element 40. The nozzle plate 44 has a plurality of discharge ports (nozzle portions) 46 corresponding to the plurality of pressure chambers 45.

  When printing is performed with such an ink jet head, a drive signal is generated in the drive circuit 47 and supplied to a predetermined laminated piezoelectric element 40. As a result, the laminated piezoelectric element 40 expands and contracts, so that the diaphragm 42 is deformed, and the volume of the pressure chamber 45 corresponding to the laminated piezoelectric element 40 changes. As a result, the ink filled in the pressure chamber 45 is pressurized and dropped from the ejection port 46.

  FIG. 9 is a diagram illustrating an example in which the multilayer piezoelectric element according to the present embodiment is used as an ultrasonic transducer. The ultrasonic imaging apparatus shown in FIG. 9 includes an ultrasonic probe used in contact with a subject and an ultrasonic imaging apparatus main body. The ultrasonic probe includes an ultrasonic transducer array 50, an acoustic matching layer 51, an acoustic lens 52, and a backing layer 53. These parts are housed in a housing 54. Further, the wiring drawn from the ultrasonic transducer array 50 is connected to the ultrasonic imaging apparatus main body 60 via the cable 55. The ultrasonic imaging apparatus main body 60 includes a control unit 61, a drive circuit 62, a transmission / reception switching circuit 63, a reception circuit 64, and a display unit 65.

  The ultrasonic transducer array 50 includes a plurality of stacked piezoelectric elements (ultrasonic transducers) 50a arranged in a two-dimensional matrix, and a filler 50b such as an epoxy resin arranged between them. The acoustic matching layer 51 is made of glass, ceramic, metal powder epoxy resin, or the like that can easily transmit ultrasonic waves, and can prevent acoustic impedance mismatch between the living body subject and the ultrasonic transducer. Let go. Furthermore, the acoustic lens 52 is made of, for example, silicon rubber, and focuses ultrasonic waves at a predetermined depth. The backing layer 53 is formed of a material having a large acoustic attenuation, such as a material in which ferrite or metal powder or PZT powder is mixed in epoxy resin or rubber, and is generated from the ultrasonic transducer array 50. Attenuate unnecessary ultrasonic waves quickly.

  When performing ultrasonic imaging, first, the transmission / reception switching circuit 63 is switched to the transmission side under the control of the control unit 61. Then, the drive signal generated in the drive circuit 62 is supplied to each ultrasonic transducer 50 a via the cable 55. Thereby, each ultrasonic transducer 50a expands and contracts, and ultrasonic waves are transmitted toward the subject. Further, when the ultrasonic echo reflected from the subject propagates to the ultrasonic probe, each ultrasonic transducer 50a expands and contracts to generate an electrical signal. This electrical signal is transmitted to the ultrasonic imaging apparatus main body via the cable 55, and the transmission / reception switching circuit 63 is switched to the reception side under the control of the control unit 61, so that it is taken into the reception circuit 64 as an ultrasonic reception signal. It is. Further, the reception signal is subjected to predetermined signal processing such as TGC (time gain compensation) amplification and delay addition in the reception circuit 64, and is output to the display unit 65. In the display unit 65, an ultrasonic image is displayed on a screen such as a CRT based on the input received signal.

  The present invention can be used in a laminated piezoelectric element used as a piezoelectric actuator, an ultrasonic transducer, and the like and a manufacturing method thereof. Furthermore, the present invention can be used in apparatuses such as an inkjet head and an ultrasonic probe using such a multilayer piezoelectric element.

It is a partial cross section perspective view which shows the structure of the lamination type piezoelectric element which concerns on one Embodiment of this invention. It is a figure which shows the polarization direction of the piezoelectric material layer and insulating film in the laminated piezoelectric element shown in FIG. It is a figure for demonstrating the manufacturing method of the lamination type piezoelectric element shown in FIG. It is a figure for demonstrating the manufacturing method of the lamination type piezoelectric element shown in FIG. It is a perspective view which shows the modification of the lamination type piezoelectric element which concerns on one Embodiment of this invention. It is a figure for demonstrating the drive method in the case of driving the laminated piezoelectric element which concerns on one Embodiment of this invention by a low voltage. It is a figure for demonstrating the drive method in the case of driving the laminated piezoelectric element which concerns on one Embodiment of this invention by a high voltage. It is sectional drawing which shows the example which applies the multilayer piezoelectric element which concerns on one Embodiment of this invention to an inkjet head as an actuator. It is a figure which shows the example which applies the lamination type piezoelectric element which concerns on one Embodiment of this invention to an ultrasonic imaging apparatus as an ultrasonic transducer. It is sectional drawing which shows the structure of the conventional lamination type piezoelectric element.

Explanation of symbols

10, 20 Piezoelectric layers 11a, 11b, 21a, 21b Internal electrode layers 12, 24 Lower electrode layers 13, 25 Upper electrode layers 14a, 14b, 22a, 22b, 30a, 30b Insulating films 15a, 15b, 23a, 23b, 31a , 31b Side electrode 40 Multilayer piezoelectric element 41 Common wiring 42 Diaphragm 43 Partition wall 44 Nozzle plate 45 Pressure chamber 46 Discharge port (nozzle part)
47 Drive Circuit 50 Ultrasonic Transducer Array 50a Multilayer Piezoelectric Element (Ultrasonic Transducer)
50b Filler 51 Acoustic matching layer 52 Acoustic lens 53 Backing layer 54 Case 55 Cable 60 Ultrasonic imaging device main body 61 Control unit 62 Drive circuit 63 Transmission / reception switching circuit 64 Reception circuit 65 Display unit

Claims (9)

A laminate in which a plurality of piezoelectric layers and a plurality of electrode layers are alternately arranged;
A first insulating film formed of a piezoelectric material on at least a part of an end surface of the first electrode layer of the plurality of electrode layers in the first side surface region of the stacked body;
At least part of the end surface of the second electrode layer arranged alternately with the first electrode layer of the plurality of electrode layers in a second side surface region different from the first side surface region of the stacked body. A second insulating film formed of a piezoelectric material;
A side electrode formed in the first side region, wherein the first electrode is insulated from the first electrode layer by the first insulating film and electrically connected to the second electrode layer. Side electrodes of
A side electrode formed in the second side region, wherein the second electrode is insulated from the second electrode layer by the second insulating film and electrically connected to the first electrode layer. Side electrodes of
A laminated piezoelectric element comprising: Polarization of two piezoelectric layers adjacent to each other with the first electrode layer interposed therebetween is directed to the first electrode layer side, and two piezoelectric layers adjacent to each other with the second electrode layer interposed therebetween. The polarization of the body layer faces away from the second electrode layer;
The polarization of the first insulating film formed on the end surface of the first electrode layer is directed to the opposite side of the first electrode layer, and the first electrode formed on the end surface of the second electrode layer. The polarization of the insulating film 2 faces the second electrode layer side,
The multilayer piezoelectric element according to claim 1. The laminated piezoelectric element according to claim 1 or 2,
A drive circuit for bipolarly driving the multilayer piezoelectric element with a voltage that gives an electric field strength smaller than a coercive electric field to the first and second insulating films;
A device comprising: The laminated piezoelectric element according to claim 1 or 2,
A driving circuit for unipolarly driving the multilayer piezoelectric element with a voltage that gives an electric field strength smaller than a coercive electric field to the first and second insulating films;
A device comprising: The laminated piezoelectric element according to claim 1 or 2,
A driving circuit for unipolarly driving the laminated piezoelectric element with a voltage that gives a higher electric field strength than the coercive electric field to the first and second insulating films, and with a polarity that does not reverse the polarization of the first and second insulating films When,
A device comprising: A step (a) of forming a laminate by alternately arranging a plurality of piezoelectric layers and a plurality of electrode layers;
A step (b) of forming a first insulating film with a piezoelectric material on at least a part of an end surface of the first electrode layer of the plurality of electrode layers in the first side surface region of the stacked body;
At least part of the end surface of the second electrode layer arranged alternately with the first electrode layer of the plurality of electrode layers in a second side surface region different from the first side surface region of the stacked body. And (c) forming a second insulating film from the piezoelectric material,
Forming in the first side surface region a first side electrode that is insulated from the first electrode layer by the first insulating film and electrically connected to the second electrode layer ( d) and
Forming a second side surface electrode in the second side surface region, which is insulated from the second electrode layer by the second insulating film and electrically connected to the first electrode layer ( e) and
A method for manufacturing a laminated piezoelectric element comprising:   Steps (b) and (c) are performed by an aerosol deposition method in which an aerosol in which a powder of a piezoelectric material is dispersed in a gas is sprayed toward the side surface of the laminate to deposit the piezoelectric material in a predetermined region. The method of manufacturing a multilayer piezoelectric element according to claim 6, comprising forming each of the first and second insulating films. Applying a first electric field having a first polarity to the stacked body to perform at least a first polarization process for aligning the polarization of the plurality of piezoelectric layers in a predetermined direction;
Thereafter, by applying a second electric field smaller than the first electric field with a second polarity opposite to the first polarity to the stacked body, only the polarization of the first and second insulating films is inverted. A step (g) of applying a second polarization treatment for
The method for producing a laminated piezoelectric element according to claim 6 or 7, further comprising: In the step (f), the polarization of two piezoelectric layers adjacent to each other with the first electrode layer interposed therebetween is directed to the first electrode layer side, and adjacent to the second electrode layer therebetween. Applying a first polarization treatment such that the polarization of the two piezoelectric layers is directed to the opposite side of the second electrode layer,
In the step (g), the polarization of the first insulating film formed on the end face of the first electrode layer is opposite to the first electrode layer without inverting the polarization of the plurality of piezoelectric layers. And applying a second polarization treatment so that the polarization of the second insulating film formed on the end face of the second electrode layer faces the second electrode layer side,
The method for producing a multilayer piezoelectric element according to claim 8.

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