JPH08309979A - Ink jetting apparatus and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an ink ejecting apparatus which is excellent in mass productivity and reliability and which can be easily electrically connected. A piezoelectric laminated body is formed by integrally laminating a lower piezoelectric ceramics layer 4 made of a piezoelectric material having a Curie temperature T1 and an upper piezoelectric ceramics layer 5 made of a piezoelectric material having a Curie temperature T2 lower than the Curie temperature. 20
And Then, an electric field is applied to the stacking method of each layer in oil having a temperature T3 lower than T1 and higher than T2. Then, an electric field in the direction opposite to the pre-polarization step is applied in the stacking direction in oil at a temperature T4 lower than T2. As a result, the lower piezoelectric ceramics layer 4 and the upper piezoelectric ceramics layer 5 become a piezoelectric laminate 20 having opposite polarization directions. The piezoelectric ceramic plate 2 including the laminated body 20, the cover plate 3, and the nozzle plate form the ink ejecting apparatus 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Among the non-impact type printers, which have been expanding the market to replace the impact type printers used up to now, the principle is the simplest, and multi-gradation and colorization are possible. An example of a printer that is easy to perform is an inkjet printer. Above all, a drop that ejects only the ink drops used for printing
The on-demand type is rapidly spreading due to its good injection efficiency and low running cost.

The Kaiser type disclosed in Japanese Patent Publication No. 53-12138 as a drop-on-demand type,
Alternatively, a thermal jet type disclosed in Japanese Patent Publication No. 61-59914 is a typical method.
Of these, the former is difficult to miniaturize, and the latter requires a high heat resistance of the ink in order to apply high heat to the ink, and each has a very difficult problem.

A method proposed at the same time to solve the above problems is disclosed in Japanese Patent Laid-Open No. 63-24705.
It is a shear mode type using the piezoelectric ceramics disclosed in Japanese Patent Laid-Open No.

As shown in FIG. 11, the shear mode type ink jet apparatus 600 comprises a bottom wall 601, a top wall 602 and a shear mode actuator wall 603 therebetween. The actuator wall 603 is bonded to the bottom wall 601 and is polarized in the direction of arrow 611.
And an upper wall 605 bonded to the ceiling wall 602 and polarized in the direction of arrow 609. The actuator walls 603 are paired to form an ink flow path 613 therebetween, and a space 615 narrower than the ink flow path 613 is formed between the next pair of actuator walls 603.

The nozzle 6 is provided at one end of each ink flow path 613.
A nozzle plate 617 having 18 is fixed, and electrodes 619 and 621 are provided as metal layers on both side surfaces of each actuator wall 603. Each electrode 619, 621 is covered with an insulating layer (not shown) for insulating the ink. The electrode 621 facing the space 615 is connected to the ground 623, and the electrode 619 provided in the ink flow path 613 is connected to the silicon chip 625 which provides the actuator drive circuit.

Next, a method for manufacturing the ink jet device 600 will be described. First, the piezoelectric ceramic layer polarized in the arrow 611 is bonded to the bottom wall 601, and the piezoelectric ceramic layer polarized in the arrow 609 is bonded to the ceiling wall 602. The thickness of each piezoelectric ceramic layer is as follows.
Equal to 5 height. Next, parallel grooves are formed in the piezoelectric ceramics layer by rotating a diamond cutting disk or the like to form a lower wall 607 and an upper wall 605. Then, the electrode 61 is formed on the side surface of the lower wall 607 by vacuum deposition.
9 is formed, and the insulating layer is provided on the electrode 619.
Similarly, an electrode 621 is formed on the side surface of the upper wall 605,
The insulating layer is provided thereon.

The zenith of the upper wall 605 and the zenith of the lower wall 607 are adhered to each other to form an ink flow path 613 and a space 615. Next, a nozzle plate 617 on which the nozzles 618 are formed is adhered to one end of the ink flow passage 613 and the space 615 so that the nozzles 618 correspond to the ink flow passages 613, and the ink flow passages 613 and the space 615 are connected. The other end is connected to silicon chip 625 and ground 623.

Then, the electrode 61 of each ink flow path 613
When the silicon chip 625 applies a voltage to 9, 621, each actuator wall 603 undergoes piezoelectric thickness slip deformation in a direction of increasing the volume of the ink flow path 613, and after a predetermined time, the voltage application is stopped and the ink flow is stopped. Road 613
Of the ink flow path 61 from the increased state to the natural state.
Pressure is applied to the ink in the nozzle 3, and ink drops are generated in the nozzle 61.
It is injected from 8.

[0010]

However, in the ink ejecting apparatus 600 having the above-described structure, the electrodes 619 and 621 facing the space 615 are connected to the ground 623,
Electrodes 619 and 62 provided in the ink flow path 613
1 is connected to a silicon chip 625, which provides the actuator drive circuit, but the specific configuration and method of its electrical connection are not disclosed. So, for example,
After bonding the upper wall 605 and the lower wall 607, the electrode 6
19 and 621 are electrically connected or the electrode 61
It is necessary to separately connect 9, 621 to the silicon chip 625 which provides the actuator drive circuit, but in both cases, there is a problem that the process takes time and mass productivity is poor.

Further, when the upper wall 605 and the lower wall 607 are bonded, it is necessary to perform highly accurate alignment,
This is also a cause of poor mass productivity. Further, in reality, even if the alignment is performed, a displacement of the girder is inevitable at the joint. Therefore, in the manufactured ink ejecting apparatus, variations in durability and ink ejecting characteristics easily occur,
The yield was not good.

The present invention has been made in order to solve the above-mentioned problems, and provides an ink ejecting apparatus in which electrodes can be easily taken out and which can be electrically connected with high reliability. An object of the present invention is to provide a method for manufacturing an ink ejecting apparatus which is easy to manufacture and has excellent mass productivity.

[0013]

In order to achieve this object, an ink ejecting apparatus of the present invention has at least an ink liquid chamber filled with ink and a piezoelectric portion which constitutes the ink liquid chamber and is polarized. It has a side wall partially formed and a drive electrode formed on the side wall for applying an electric field substantially orthogonal to the polarization direction to the piezoelectric portion, and receives a field applied from the drive electrode. , The side wall is deformed by a piezoelectric thickness sliding effect, and pressure is applied to the ink in the ink liquid chamber to eject the ink. Further, the piezoelectric portion forming the side wall includes two types of piezoelectric materials having different Curie temperatures. The materials are stacked in the standing direction of the side wall, and the two types of piezoelectric materials are polarized in directions parallel to the stacking direction and opposite to each other.

The two types of piezoelectric materials may be integrated by sintering.

In order to achieve the above object, the method of manufacturing an ink ejecting apparatus of the present invention is such that at least a part of an ink liquid chamber filled with ink and a piezoelectric portion which constitutes the ink liquid chamber and is polarized is polarized. A piezoelectric layer having a formed side wall and a drive electrode formed on the side wall for applying an electric field substantially orthogonal to the polarization direction to the piezoelectric portion, and receiving the electric field applied from the drive electrode, the piezoelectric thickness A method of manufacturing an ink ejecting apparatus in which the side wall is deformed by a sliding effect to apply pressure to the ink in the ink liquid chamber to eject the ink, wherein a first piezoelectric material exhibiting a Curie temperature Ta and A step of forming a laminated body by laminating a second piezoelectric material exhibiting a high Curie temperature Tb in a direction that is a standing direction of the side wall to form an integrated body; Are brought into close contact with respectively electrode plates, the Curie temperature Ta or more of said first piezoelectric material, and the second
In an environment below the Curie temperature Tb of the piezoelectric material of
Applying an electric field between the electrode plates to polarize the second piezoelectric material; and a Curie temperature Ta of the first piezoelectric material.
Under an environment of less than, applying a field having a polarity opposite to that of the previous step between the electrode plates to polarize the first piezoelectric material in a direction opposite to the polarization direction of the second piezoelectric material,
A step of forming a groove portion in the laminated body having a depth in the laminating direction and extending to a piezoelectric material located in a lower layer; a step of forming a conductive film on at least a side wall surface of the groove portion; and an opening portion of the groove portion. And a step of adhering a cover plate to the upper layer of the laminate.

[0016]

In the ink ejecting apparatus according to the first aspect of the present invention having the above structure, a plurality of ink liquid chambers separated by the side wall are formed, and the piezoelectric portion constituting the side wall is
Two types of piezoelectric materials having different Curie temperatures are laminated in the standing direction of the side wall. The piezoelectric section uses the difference in Curie temperatures of two types of piezoelectric materials to
By performing the polarization process once, the stacked layers are polarized in the directions parallel to the stacking direction and opposite to each other. When a voltage is applied to the pair of drive electrodes formed on the piezoelectric portion so as to generate an electric field substantially orthogonal to the polarization direction,
Due to the piezoelectric thickness sliding effect of the piezoelectric portion, the side wall is deformed and pressure is applied to the ink in the ink liquid chamber to eject the ink.

In the ink jet device according to the second aspect, two types of piezoelectric elements are integrated by sintering.
Both are tightly coupled. Therefore, the actuator has high durability and high driving accuracy, and the ink ejecting apparatus provided with this actuator exhibits high printing quality.

In the method of manufacturing the ink jet device according to the third aspect of the present invention having the above-mentioned structure, the first piezoelectric material exhibiting the Curie temperature Ta and the second piezoelectric material exhibiting the Curie temperature Tb having a larger value than that. To form a laminated body by laminating the piezoelectric material and the piezoelectric material in a direction in which the side wall is erected, and contact the electrode plates to both end faces of the laminated body in the laminating direction. In an environment that is higher than the Curie temperature Ta and lower than the Curie temperature Tb of the second piezoelectric material, an electric field is applied between the electrode plates to polarize the second piezoelectric material. In addition, the first
In an environment below the Curie temperature Ta of the piezoelectric material of
An electric field having a polarity opposite to that in the previous step is applied between the electrode plates to polarize the first piezoelectric material in a direction opposite to the polarization direction of the second piezoelectric material. After that, a groove portion is formed in the laminated body with a depth in the laminating direction and extends to the piezoelectric material located in the lower layer, and a conductive film is formed on at least a side wall surface of the groove portion. Then, an ink ejecting apparatus is manufactured by bonding a cover plate to the upper layer of the laminated body so as to cover the opening of the groove.

In this method, two types of piezoelectric sheets are subjected to two polarization treatments by utilizing the difference in Curie temperature so that the laminated layers are parallel to the laminating direction and opposite to each other. Polarization can be easily performed. Also,
Since the grooves that will become the ink chambers are processed in the integrated laminated body, no digit shift occurs in each layer. Further, since there is no shift in the digits, the drive electrodes can be formed easily, and the electrical connection is ensured by the upper and lower piezoelectric layers.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the ink ejecting apparatus 1 is composed of a piezoelectric ceramic plate 2, a cover plate 3, and a nozzle plate (not shown) having nozzles (not shown).

The piezoelectric ceramics plate 2 is formed by laminating a lower piezoelectric ceramics layer 4 and an upper piezoelectric ceramics layer 5, and the lamination direction of the piezoelectric ceramics plate 2 is the depth, and the lower piezoelectrics ceramics plate 4 is arranged from the upper side in FIG. A plurality of grooves extending to the side walls 11 are provided.

The lower piezoelectric ceramics layer 4 and the upper piezoelectric ceramics layer 5 are made of a lead zirconate titanate (PZT) piezoelectric ceramics material having ferroelectricity, as shown by arrows 6 and 7, respectively. And are polarized in the stacking direction and in mutually opposite directions.

The grooves separated by the side wall 11 are alternately classified into a plurality of injection grooves 12 and non-injection grooves 13. A ground electrode 10 is formed on the inner surface of the ejection groove 12, and a drive electrode 9 is formed on the inner surface of the non-ejection groove 13. A separation groove 14 is formed at the bottom of the non-ejection groove 13 in order to electrically separate the drive electrode 9 into the ejection grooves 12.

A method of manufacturing the piezoelectric ceramic plate 2 will be described below with reference to FIGS.

First, as the piezoelectric material forming the lower piezoelectric ceramics layer 4, the Curie temperature T1, for example, 250 ° C.
A lead zirconate titanate (PZT) -based piezoelectric material having a temperature of less than the Curie temperature T1 is used as the piezoelectric material forming the upper piezoelectric ceramics layer 5.
2. A PZT piezoelectric material having a temperature of 100 ° C., for example, is prepared and formed into a sheet having a predetermined thickness by using a doctor blade method, a screen printing method or the like. Then, as shown in FIG. 2, two piezoelectric sheets made of the formed piezoelectric material are laminated, and subjected to pressure-bonding, degreasing, and sintering steps to form a piezoelectric laminate 20 which is an integral sintered body. At this stage, the spontaneous polarization directions of the lower piezoelectric ceramics layer 4 and the upper piezoelectric ceramics layer 5 are random and do not have piezoelectric characteristics. The Curie temperature referred to here is the temperature at which the piezoelectric ceramic loses its ferroelectricity above that temperature.

Next, as shown in FIG. 3, polarization electrodes 15 are formed on the upper and lower surfaces of the obtained piezoelectric laminate 20 by a known method such as a baking method, a sputtering method, an evaporation method or the like. continue,
As shown in FIG. 4, a temperature T3 lower than the Curie temperature T1 and higher than the Curie temperature T2, for example, 1
Polarization is performed in insulating oil such as silicon oil (not shown) at 50 ° C. In the polarization treatment, an electric field of about 10 to 35 kV / cm is applied to the upper piezoelectric ceramics layer 5 and the lower piezoelectric ceramics layer 4 via the polarization electrode 15. At this time, the upper piezoelectric ceramics layer 5
Is higher than the Curie temperature T2, it is not polarized by the application of an electric field, and only the lower piezoelectric ceramics layer 4 is polarized in the direction of arrow 6 in the figure.

Then, as shown in FIG. 5, the upper piezoelectric ceramics layer 5 is interposed through the polarization electrode 15 in an insulating oil (not shown) having a temperature T4 lower than the Curie temperature T2, for example, 50 ° C., And 10 to 35 kV / c in the lower piezoelectric ceramic layer 4 in the opposite direction to the polarization process.
An electric field of about m is applied. At this time, the upper piezoelectric ceramics layer 5 is polarized in the direction of arrow 7 by the application of an electric field, but the lower piezoelectric ceramics layer 4 has a high coercive electric field, so that polarization inversion hardly occurs at a low temperature and the polarization in the direction of arrow 6 occurs. Remain.

By the above-described two polarization processes with different temperature settings, the lower piezoelectric ceramics layer 4 and the upper piezoelectric ceramics layer 5 become the piezoelectric laminate 20 having the opposite polarization directions. After the polarization process is completed, the polarization electrode 14 is removed by grinding.

Next, the laminated body 20 is cut by a diamond blade or the like to have a depth of 300 μm, for example.
A plurality of grooves 22 having a width of 50 μm are formed to form the piezoelectric ceramic plate 2 shown in FIG. Further, the side wall 11 that is the side surface of the groove 11 has a width of 60 μm, for example. Groove 22
As shown in FIG. 6, an electrode 23 is formed on the inner surface of the substrate by sputtering, vapor deposition, plating or the like. And
As shown in FIG. 8, the grooves 22 are classified into the injection grooves 12 and the non-injection grooves 13 that are alternately arranged, and the electrodes 23 in the injection grooves 12 also serve as the ground electrodes 10 and the non-injection grooves 1 are formed.
The electrode 23 inside 3 becomes the drive electrode 9. Further, at the bottom of the non-ejection groove 13, a separation groove 14 having a width narrower than that of the non-ejection groove 13, for example, 30 μm is cut by a diamond blade or the like, and the drive electrode 9 is provided for each corresponding ejection channel (ejection groove). Electrically separated.

Then, the cover plate 3 is joined to the opening of the groove of the piezoelectric actuator 2 using an epoxy adhesive or the like, and a nozzle plate (not shown) having a nozzle (not shown) is attached to one end face in the longitudinal direction of the jet groove 12. By joining, the ink ejecting apparatus 1 shown in FIG. 1 is obtained.

Next, the configuration of the control unit of this embodiment will be described with reference to FIG. 9 showing a block diagram of the control unit. As shown in the figure, the drive electrode 9 and the ground electrode 10 of the ink ejecting apparatus 1 are individually connected to the LSI chip 51, and the clock line 52, the data line 53, the voltage line 54, and the ground line 55 are also the LSI chip. It is connected to 51. All the ground electrodes 10 are connected to the ground line 55. The LSI chip 51 has a clock line 52.
From the data appearing on the data line 53, which ejection groove 12
Then, it is determined whether or not ink droplets should be ejected. Then, the LSI chip 51 applies the voltage V of the voltage line 54 to the drive electrode 9 corresponding to the ejection groove 12 to be driven,
Driving electrodes 9 corresponding to the ejection grooves 12 other than the ejection groove 12
The ground line 55 is connected to and grounded.

Next, the operation of the ink ejecting apparatus 1 according to this embodiment will be described with reference to FIG. Injection groove 1 shown in FIG.
In order to eject ink droplets from 2b, the ejection groove 12b
A voltage is applied to the drive electrodes 9c and 9d corresponding to (the application of a voltage to a certain drive electrode 9 means applying a voltage to the drive electrode 9 and grounding the drive electrode 9 not instructed). Say). Then, the side walls 11c, 1
An electric field in the directions of arrows 24 and 25 is generated in 1d, and the side wall 11
c and 11d are jet grooves 12b due to the piezoelectric thickness sliding effect.
Moves in the direction of increasing the volume of. Then, the injection groove 12b
The pressure inside is reduced. As a result, ink is supplied from the ink supply source (not shown) into the ejection groove 12b through the manifold (not shown).

Next, when the application of the voltage to the drive voltage 9 is removed, the volume of the injection groove 12b is decreased from the increased state to the natural state, and the pressure in the injection groove 12b is increased.
As a result, the ink in the ejection groove 12b becomes an ink droplet and is ejected from a nozzle (not shown).

Further, in the above-described embodiment, first, the drive voltage is applied in the direction in which the volume of the ejection groove 12 is increased to supply the ink, and then the application of the drive voltage is stopped and the volume of the ejection groove 12 is set to the natural state. Although the ink droplets are ejected from the ejection groove 12 after being reduced to 1, the driving voltage is first applied so that the volume of the ejection groove 12 is reduced to eject the ink droplets from the ejection groove 12, and then the driving voltage is reduced. Is stopped to increase the volume of the injection groove 12 from the reduced state to the natural state,
Ink may be supplied inside.

As described above, in the ink ejecting apparatus 1 according to the manufacturing method of the present embodiment, the side wall 11 that deforms the piezoelectric thickness slip effect is made up of two types of piezoelectric materials having different Curie temperatures. It is laminated in the direction and sintered to form an integrated structure. Therefore, the actuator has high durability and high driving accuracy, and the ink ejecting apparatus provided with this actuator exhibits high printing quality.

Further, in the present embodiment, the respective piezoelectric ceramic layers are polarized twice by utilizing the difference in Curie temperature, so that the two kinds of piezoelectric materials are polarized in directions opposite to each other. There is. Therefore, with a minimum number of steps, reliable polarization is achieved without affecting the polarization characteristics of each layer.

Further, in this embodiment, the piezoelectric laminated body 20 which is sintered and integrated is subjected to groove processing to form the ejection groove 12 which becomes the ink liquid chamber and the non-ejection groove 13 which becomes the air chamber. To do. Therefore, the side wall 11 can be formed with high dimensional accuracy without causing a displacement in the joint surface of each layer.

Further, in this embodiment, since the electrode 23 is formed on the side wall 11 having a high dimensional accuracy, the electrodes are not separated between the upper piezoelectric ceramics layer 5 and the lower piezoelectric ceramics layer 4, and the electrodes are separated from the conventional example. Easy to take out electrodes,
In addition, the piezoelectric ceramic plate 2 having high reliability of electrical connection can be easily manufactured.

That is, the manufacturing method of this embodiment solves the problems such as the conventional alignment of the piezoelectric material, the formation of the internal electrodes, and the extraction of the electrodes, and is excellent in mass productivity.

Further, in the above embodiment, the injection groove 12
All the electrodes formed inside are always grounded, and no voltage difference is generated between each of the injection grooves 12. Therefore,
No electric field is applied to the ink, and the ejection groove 12 is formed by an electric effect.
The deterioration of the ink inside and the deterioration of the ground electrode 10 are not caused. As a result, there is no need to form an insulating layer on the ground electrode 10, which is conventionally provided. Even if the above driving method is not adopted, the gist of the present invention is not affected. For example, as in the conventional example, the electrodes formed in all the non-jet grooves 13 are always grounded, and normally the electrodes 1 formed in all the jet grooves 12 are formed.
25 may be grounded and a voltage V may be applied to the desired electrode of the ejection groove 12 during printing.

[0042]

As described above, in the method of manufacturing an ink jet device according to the present invention, it is possible to easily and surely perform polarization on the two-layer piezoelectric sheet. Further, since the grooves which will be the ink chambers are processed in the integrated laminated body, the digit shift does not occur in each layer. Further, since there is no shift in the digits, the drive electrodes can be formed easily, and the electrical connection is ensured by the upper and lower piezoelectric layers. Therefore, it is excellent in mass productivity.

In addition, the manufactured ink ejecting apparatus has improved reliability of electrical connection, excellent durability, and does not cause problems such as variations in ejection characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of an ink ejecting apparatus according to an embodiment of the invention.

FIG. 2 is a perspective view showing a manufacturing process of the ink ejecting apparatus.

FIG. 3 is a perspective view showing a manufacturing process of the ink ejecting apparatus.

FIG. 4 is a cross-sectional view showing a polarization process of the ink ejecting apparatus.

FIG. 5 is a cross-sectional view showing a polarization process of the ink ejecting apparatus.

FIG. 6 is a cross-sectional view showing a manufacturing process of the same ink ejecting apparatus.

FIG. 7 is a cross-sectional view showing a manufacturing process of the same ink ejecting apparatus.

FIG. 8 is a cross-sectional view showing a manufacturing process of the ink ejecting apparatus.

FIG. 9 is a block diagram showing a control unit of the ink ejecting apparatus according to the embodiment of the invention.

FIG. 10 is an explanatory diagram showing an operation of the ink ejecting apparatus.

FIG. 11 is a diagram showing a conventional ink ejecting apparatus.

[Explanation of symbols]

 1 Ink Ejector 2 Piezoelectric Ceramic Plate 3 Cover Plate 4 Lower Piezoelectric Ceramics Layer 5 Upper Piezoelectric Ceramics Layer 6 Polarization Direction 7 Polarization Direction 9 Drive Electrode 10 Ground Electrode 11 Sidewall 12 Jet Groove (Ink Liquid Chamber) 13 Non-jet Groove 24 Electric Field Direction 25 Electric field direction

Claims (3)

[Claims] 1. An ink liquid chamber filled with ink, a side wall that constitutes the ink liquid chamber and is at least partially formed by a polarized piezoelectric portion, and an electric field that is substantially orthogonal to the polarization direction. A driving electrode formed on the side wall for applying to the piezoelectric portion, and the side wall is deformed by a piezoelectric thickness sliding effect in response to an electric field applied from the driving electrode, and the ink in the ink liquid chamber is formed. In an ink ejecting device that applies pressure to eject ink, the piezoelectric portion forming the side wall has a different Curie temperature.
Ink characterized in that two kinds of piezoelectric materials are laminated in the standing direction of the side wall, and the two kinds of piezoelectric materials are polarized in directions parallel to the lamination direction and opposite to each other. Injection device. 2. The ink ejecting apparatus according to claim 1, wherein the two kinds of piezoelectric materials are integrated by sintering. 3. An ink liquid chamber filled with ink, a side wall that constitutes the ink liquid chamber and is at least partially formed by a polarized piezoelectric portion, and an electric field that is substantially orthogonal to the polarization direction. A driving electrode formed on the side wall for applying to the piezoelectric portion, and the side wall is deformed by a piezoelectric thickness sliding effect in response to an electric field applied from the driving electrode, and the ink in the ink liquid chamber is formed. In a method of manufacturing an ink ejecting apparatus that applies pressure to eject ink, a first piezoelectric material exhibiting a Curie temperature Ta and a second piezoelectric material exhibiting a Curie temperature Tb higher than the Curie temperature Ta are erected on the side wall. Forming a laminated body by laminating in the direction of the direction and forming an integrated body, and by making electrode plates adhere to both end faces of the laminated body in the laminating direction, the Curie temperature Ta of the first piezoelectric material. Above, and in an environment below the Curie temperature Tb of the second piezoelectric material, applying an electric field between the electrode plates to polarize the second piezoelectric material; and a Curie temperature of the first piezoelectric material. Applying an electric field having a polarity opposite to that of the previous step between the electrode plates in an environment of less than Ta to polarize the first piezoelectric material in a direction opposite to the polarization direction of the second piezoelectric material; Forming a groove in the laminated body, the groove extending to the piezoelectric material located in the lower layer, forming a conductive film on at least the side wall surface of the groove, and covering the opening of the groove. And a step of adhering a cover plate to the upper layer of the laminate as described above.