JP2000117975A - Ink jet head drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head drive device which prevents an electrode from being ruptured and thereby keeping the amount of change of the deformation part of a piezoelectric element uniform, even when a notched recessed part if formed by an etching process or the like after a baking step. SOLUTION: Piezoelectric body layers 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h which contribute to a deformation due to an electric strain effect and electrode layers 19a, 19b, 19c, 19d, 19e, 19f, 19g which contribute to a deformation due to the electric strain effect are laminated over each other. At the same time, a dummy piezoelectric body layer 30 as the piezoelectric body layer of a bottom layer, a dummy electrode layer 31 as the electrode layer of a bottom layer, a dummy piezoelectric body layer 32 as the piezoelectric body layer of a top layer and a dummy electrode layer 33 as the electrode layer of a top layer are laminated over each other. Under this constitution, the electrode layers which become thin even in a banking step after lamination are the dummy electrode layers 31, 33 and the electric characteristics of the deformation part of piezoelectric elements are not deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a driving device for an ink jet head comprising a laminated piezoelectric element.

[0002]

2. Description of the Related Art An ink jet head used in a conventional ink jet printer comprises a ceramic cavity plate having an ink pressure chamber partitioned by a plurality of partition walls, and a piezoelectric element joined to the cavity plate. The piezoelectric element causes a pressure fluctuation in the ink pressure chamber, and the ink in the ink pressure chamber is discharged from a nozzle formed in the cavity plate.

[0003] Various types of piezoelectric elements are used. One example is a laminated piezoelectric element. In this laminated piezoelectric element, positive and negative electrodes formed of a silver paste are screen-printed on a green sheet-shaped piezoelectric body, and several layers of the green sheet-shaped piezoelectric body formed with such electrodes are formed. After performing a binder removal / sintering process, polarizing the piezoelectric element in a predetermined direction, and further providing a plurality of cutout recesses so as to make the deformed portions of the piezoelectric element independent from each other. Is done.

Therefore, by applying a predetermined voltage to the positive and negative electrodes, the deformed portions of the piezoelectric element can be displaced independently of each other, and necessary pressure fluctuations in the plurality of ink pressure chambers can be suppressed. Can be caused.

[0005]

However, according to the above-mentioned prior art, the piezoelectric layer at the uppermost position and the piezoelectric layer below the piezoelectric layer, and the piezoelectric layer at the lowermost position, The electrode printed between the piezoelectric layer above the piezoelectric layer and the silver paste forming the electrode are transferred into the piezoelectric body of the piezoelectric layer at the uppermost position and the lowermost position in the firing step. Because of the diffusion, the electrode becomes thinner than the electrode formed on the intermediate layer. Therefore, when the piezoelectric element is subjected to a cutting process after firing and the notch recess is provided, the thinned electrode is torn by an impact during the cutting process, and the electric characteristics of the piezoelectric element are reduced. there were. As a result, there has been a problem that the amount of change in the deformed portion of the piezoelectric element becomes non-uniform, and the speed and volume of the discharged droplet become non-uniform.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and prevents the electrode from being broken even when a notch recess is formed by a cutting process or the like after the firing step, and maintains the uniformity of the variation of the deformed portion of the piezoelectric element. It is an object of the present invention to provide a driving device for an inkjet head that can be used.

[0007]

According to a first aspect of the present invention, there is provided a driving apparatus for an ink jet head which ejects the ink by applying a pressure fluctuation to ink stored in an ink pressure chamber. A driving device for an ink jet head, comprising: a piezoelectric layer stacked in two or more layers; and an electrode formed between the piezoelectric layers.
The piezoelectric layer and the electrode include a dummy piezoelectric layer and a dummy electrode that do not contribute to the deformation due to the electrostriction effect, in addition to the piezoelectric layer and the electrode that contribute to the deformation due to the electrostriction effect.

According to the first aspect of the present invention, since the dummy piezoelectric layer and the dummy electrode do not contribute to the deformation due to the electrostrictive effect, two or more layers contribute to the deformation due to the electrostrictive effect. With respect to the piezoelectric layers and the electrodes stacked in the stacking direction, it is located on the outermost side in the stacking direction. On the other hand, since the inkjet head driving device of the present invention is manufactured by firing the laminated piezoelectric layers and electrodes including the dummy piezoelectric layers and the dummy electrodes, it is located at the outermost position in the laminating direction. The material for forming the electrode is diffused into the outermost piezoelectric layer in the laminating direction during the firing step, and the electrode becomes thinner. However, the outermost electrode in the stacking direction is a dummy electrode that does not contribute to deformation due to the electrostriction effect, and the outermost piezoelectric layer in the stacking direction is a dummy piezoelectric layer. During the firing step, the dummy electrode diffuses into the dummy piezoelectric layer, and the dummy electrode becomes thin. Therefore, if a cutting process or the like is performed thereafter, the dummy electrode will be torn. On the other hand, the piezoelectric layer and the electrodes other than the dummy piezoelectric body and the dummy electrode are not affected by the diffusion, so that the electrode is not torn and the electric deformation of the deformed portion composed of the piezoelectric layer and the electrode is not caused. The properties do not degrade. As a result, good deformation due to the electrostrictive effect is obtained.

According to a second aspect of the present invention, there is provided an ink jet head driving apparatus according to the first aspect, wherein the dummy piezoelectric layer is formed by the electrostrictive effect. The dummy electrode layer is provided at an uppermost position and a lowermost position so as to sandwich the piezoelectric layer contributing to deformation, and the dummy electrode layer and the piezoelectric layer contributing to deformation due to the electrostrictive effect are provided. It is characterized by being formed between the body layer.

According to a second aspect of the present invention, the dummy electrode contributes to the deformation of the dummy piezoelectric layer and the electrostrictive effect at both the uppermost position and the lowermost position. And the piezoelectric layer. Therefore, the diffusion that occurs in both the uppermost layer position and the lowermost layer position occurs between the dummy electrode and the dummy piezoelectric layer. as a result,
The effect of the diffusion of the piezoelectric layer and the electrode, which contributes to the deformation due to the electrostriction effect, is more reliably prevented, and the deterioration of the electrical characteristics of the deformed portion composed of the piezoelectric layer and the electrode due to the rupture of the electrode is more reliably. Is prevented. As a result, a better deformation due to the electrostriction effect can be obtained.

According to a third aspect of the present invention, there is provided an ink jet head driving apparatus according to the first or second aspect, wherein the piezoelectric layer is polarized in a laminating direction. The electric field parallel to the polarization direction causes a deformation in a stretching mode.

According to a third aspect of the present invention, the piezoelectric layer is polarized in the laminating direction,
By applying a predetermined voltage to each of the electrodes,
An electric field parallel to the polarization direction is generated, and the electric field deforms the piezoelectric body in the expansion and contraction mode. Therefore, by providing a dummy piezoelectric layer and a dummy electrode that do not contribute to the deformation due to the electrostriction effect at the outermost position in the lamination direction, the deformation in the outward direction due to the expansion and contraction mode is restricted, The amount of deformation in the direction opposite to the outward direction is increased. As described above, the dummy piezoelectric layer and the dummy electrode not only function as a dummy for reducing the thickness of the electrode due to diffusion, but also compensate for deformation of the deformed portion.

According to a fourth aspect of the present invention, there is provided a driving apparatus for an ink-jet head which discharges the ink by applying pressure fluctuation to ink stored in an ink pressure chamber in order to solve the above problem. Comprising a piezoelectric layer laminated in two or more layers, an electrode formed between the piezoelectric layers, the thickness of the electrodes formed on the uppermost layer and the lowermost layer of the piezoelectric layer, It is characterized in that the thickness is larger than the thickness of the electrodes formed on the other piezoelectric layers.

According to a fourth aspect of the present invention, the inkjet head driving apparatus of the present invention is manufactured by firing the laminated piezoelectric layers and electrodes. The material forming the electrodes formed on the uppermost layer and the lowermost layer of the layer diffuses into the piezoelectric material of the uppermost layer and the lowermost layer during the firing step, and the electrodes become thinner. However, since the electrodes formed on the uppermost layer and the lowermost layer of the piezoelectric layer are thicker than the electrodes formed on the other piezoelectric layers, it is assumed that the electrodes are thinner due to the diffusion. Also, the thickness of the electrodes does not become thinner than the electrodes formed on the other piezoelectric layers. As a result, the electrodes formed on the uppermost layer and the lowermost layer of the piezoelectric layer do not fracture, and the electrical characteristics of the deformed portion including the piezoelectric layer and the electrode do not deteriorate. As a result, good deformation due to the electrostrictive effect is obtained.

[0015]

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

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. 7 and 8 showing a conventional example for comparison with the present embodiment.

FIG. 1 is a perspective view showing a state before a firing step of the laminated piezoelectric body of the present embodiment, and FIG. 2 is a perspective view showing a completed state of the piezoelectric element of the present embodiment.

Hereinafter, the structure of the piezoelectric element 1 according to the present embodiment will be described together with the manufacturing method.

In manufacturing the piezoelectric element 1 of this embodiment, first, PZT (lead zircon titanate (Pb (Z
A green sheet-shaped dummy piezoelectric layer 30 made of a piezoelectric material such as r, Ti) O ₃ )) is provided, and a silver paste is screen-printed on the entire surface of the dummy piezoelectric layer 30 to form a dummy electrode layer 31. Form. The dummy piezoelectric layer 30 is formed thicker than other piezoelectric layers that contribute to deformation due to the electrostriction effect,
The dummy electrode layer 31 is formed to have the same thickness as other electrode layers that contribute to deformation due to the electrostriction effect.

Next, a green sheet-like piezoelectric layer 20a thinner than the dummy piezoelectric layer 30 is laminated on the dummy electrode layer 31, and the same layer as the dummy electrode layer 31 is formed on the piezoelectric layer 20a. The electrode layer 19a is formed by screen-printing a silver paste having a thickness.

Hereinafter, green sheet-like piezoelectric layers 20b, 20c, 20d, and 20 having the same thickness as the piezoelectric layer 20a will be described.
e, 20f, 20g, and 20h, and the electrode layer 19a
Electrode layers 19b, 19c, 19d, 19e having the same thickness as
19f and 19g are laminated in the same procedure.

At this stage, a dummy electrode layer 33 is formed on the uppermost piezoelectric layer 20h by screen printing a silver paste having the same thickness as the other electrode layers.

On the dummy electrode layer 33, the piezoelectric layers 20a, 20c, 20d, 20e, 20f, 20f
g and a green sheet-like dummy piezoelectric layer 32 thicker than 20h.

Next, the entire laminated body as described above is heated and pressed, and a laminated piezoelectric body is obtained through steps such as binder removal and firing. In this firing step, the silver paste forming the uppermost and lowermost electrode layers diffuses into the uppermost and lowermost piezoelectric bodies formed thicker than the middle piezoelectric layer. However, there is a phenomenon that the electrode layer becomes thinner than the electrode layer located in the intermediate layer. As described above, in the piezoelectric element 1 of the present embodiment, the dummy electrode layer 31 is the lowermost electrode layer, and the dummy electrode layer 33 is the uppermost electrode layer. The dummy piezoelectric layer 30 is the lowermost piezoelectric layer, and the dummy piezoelectric layer 32 is the uppermost piezoelectric layer. Therefore, the silver paste forming the lowermost dummy electrode layer 31 diffuses into the piezoelectric material of the lowermost dummy piezoelectric layer 30, and the silver paste forming the uppermost dummy electrode layer 33 is the uppermost dummy piezoelectric layer 32. In the piezoelectric material. As a result, the dummy electrode layers 31 and 33 are thinner than the other electrode layers. On the other hand, the dummy electrode layers 31 and 3
Since the electrode layers other than 3 do not cause the diffusion as described above,
It remains at the thickness before the firing step.

Next, the laminated piezoelectric element obtained as described above is immersed in an oil bath (not shown) filled with an insulating oil such as silicone oil at about 130 ° C., and the laminated piezoelectric element is polarized by an electrode for polarization. , An electric field of about 2.5 kV / mm is applied to perform polarization processing.

Next, a cutting process is performed by a dry etching method (shot blast method) using fine particles of silicon carbide or the like, and as shown in FIG. By forming a girder-shaped deformed portion, the piezoelectric element 1 is completed. When the cutting process is performed, an impact is generated during the processing, and the dummy electrode layer 31 and the dummy electrode layer 33, which are thinned by the diffusion, may be broken by the influence of the impact. However, since the dummy electrode layer 31 and the dummy electrode layer 33 are not electrode layers that contribute to the deformation of the piezoelectric body due to the electrostrictive effect, even if the tear occurs, the electrical characteristics of the piezoelectric element are not affected.

Next, the structure of an ink jet head using the piezoelectric element 1 manufactured as described above is shown in FIGS.
It will be described in detail based on. FIG. 3 is a sectional view of a plane perpendicular to the reciprocating axis of the ink jet head, and FIG.
It is a front view of the YY cross section in FIG.

As shown in FIG. 3, the ink jet head 5 of this embodiment has an ink reservoir 15 for temporarily storing ink I supplied from an ink supply device (not shown) and a plurality of ink reservoirs 15 in a direction perpendicular to the paper surface of FIG. A cavity plate 5a as a plate portion in which the ink pressure chambers 16 of the rows are formed; and ink discharge ports 17 corresponding to the respective ink pressure chambers 16 so as to cover the surface of the ink pressure chambers 16 opposite to the ink reservoir 15. Is formed on the nozzle plate 17, the above-described piezoelectric element 1, the support portion 5b as a support member for supporting the piezoelectric element 1, and the electrodes or electrode layers formed in the piezoelectric element 1. A driving unit 21 as a driving unit for applying a voltage of a predetermined polarity, and a recording corresponding to the recording information to be recorded by discharging the ink I by controlling the driving unit 21. It is constituted by a controller 22 as control means for performing.

In the piezoelectric element 1, a dummy piezoelectric layer 30 is adhered and attached to the support portion 5b with the opening of the space 26 generated when forming the girder-shaped deformed portion facing the support portion 5b. The layer 32 includes the partition wall 24 of the cavity plate 5a.
Are attached by gluing. Each of the girder-shaped deformed portions is disposed so as to come to a position corresponding to the ink pressure chamber 16 of the cavity plate 5a.

Each of the piezoelectric layers 20b, 20c, 20d, 20
e, 20f, 20g, and 20h are polarized in the directions shown in FIG. 4 by the above-described polarization processing when the inkjet head 5 is manufactured.

At the timing of pressurizing and ejecting the ink I, each of the electrode layers 19a,
A voltage having a polarity indicated by a positive mark or a negative mark in FIG. 2 is applied by the drive section 21 to 19b, 19c, 19d, 19e, 19f, 19g and the dummy electrode layers 31, 33.
That is, a positive voltage is applied to the electrode layers 19a, 19c, 19e and 19g and the dummy electrodes 31 and 33, and a negative voltage is applied to the electrode layers 19b, 19d, 19f and 23. At this time, the piezoelectric layers 20b, 2
0c, 20d, 20e, 20f, 20g, and 20h
Are the electrode layers 19a, 19b, 19c, 19d, 19e,
The dummy piezoelectric layer 30 is deformed in the expansion and contraction mode by the voltages applied to 19f and 19g, respectively, and the dummy piezoelectric layer 30 is deformed to reduce the volume in the ink pressure chamber 16 by this deformation.

Here, the expansion and contraction mode is a mode of deformation that occurs in a polarized piezoelectric body when an electric field is applied in parallel to the polarization direction of the piezoelectric body. This is a mode of deformation caused by expansion and contraction of the piezoelectric body itself.

By the above-described deformation, the ink pressure chamber 1
6, the ink in the ink pressure chamber 16 is pressurized, and the ink is discharged from the ink discharge port 17.

In particular, in the piezoelectric element 1 of the present embodiment, since the dummy piezoelectric layers 30 and 32 and the dummy electrode layers 31 and 33 are formed, the piezoelectric element 1 is diffused in the firing step in the manufacturing process of the piezoelectric element 1. Since the dummy electrode layers 31 and 33 are thinned and are torn by the subsequent cutting process, the electrical characteristics of the piezoelectric element 1 are uniform without being reduced in any deformed portions. Therefore, uniform ink ejection is performed in any of the ink pressure chambers 16.

As described above, according to the present embodiment, excellent ink ejection can be performed. However, the excellent effect of the piezoelectric element of the present embodiment can be obtained by comparing with the conventional piezoelectric element. It becomes even more apparent.

FIG. 7 is a perspective view showing a configuration of a laminated piezoelectric body before a conventional firing step, and FIG. 8 is a perspective view showing a configuration of a piezoelectric element after a cutting process.

As shown in FIG. 7, in the conventional piezoelectric element, the piezoelectric layer 20a is the lowermost piezoelectric layer, and the piezoelectric layer 20h is the uppermost piezoelectric layer. The electrode layer 1
9a is the lowermost electrode layer, and 19g is the uppermost electrode layer.

Therefore, when such a laminated piezoelectric body is fired, the silver paste forming the lowermost electrode layer 19a diffuses into the piezoelectric body of the lowermost piezoelectric layer 20a, and the silver paste forming the lowermost electrode layer 19a also becomes thin. Is diffused into the piezoelectric material of the uppermost piezoelectric material layer 20h.
The layer thicknesses of 9a and 19g are thinner than the other electrode layers. As a result, when a cutting process is performed to form the deformed portion of the piezoelectric element into a shape as shown in FIG. 8, the thinned electrode layers 19a and 19g are torn by impact during the cutting process, and the piezoelectric element is broken. The electrical characteristics of the device are degraded. As a result, the deformation amount of each deformed portion becomes non-uniform, and the speed and volume of the discharged droplet become non-uniform for each nozzle.

On the other hand, in the piezoelectric element of the present embodiment, the dummy piezoelectric layers 30, 32,
Further, since the dummy electrode layers 31 and 33 are provided, the electrode layer after the firing step and the cutting process is not broken at any of the deformed portions, and the electric characteristics at each of the deformed portions can be made uniform. Therefore, the amount of deformation of each deformed portion is uniform, and the speed and volume of the ejected droplet can be made uniform.

As described above, according to the present embodiment, it is possible to provide a piezoelectric element capable of exhibiting extremely excellent ink ejection performance as compared with the related art.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 5 is a perspective view showing the configuration of the laminated piezoelectric element before the firing step in this embodiment, and FIG. 6 is a perspective view showing the configuration of the piezoelectric element after cutting processing in this embodiment.

In this embodiment, the dummy piezoelectric layer and the dummy electrode layer are not provided, but the lowermost electrode layer 19a and the uppermost electrode layer 19g are configured to be thicker than the other electrode layers. are doing. For example, other electrode layers 19
b, 19c, 19d, 19e and 19f have a thickness of about 2
３3 μm, while the electrode layers 19a and 19
g is formed to a thickness of about 10 μm.

With this configuration, even if the silver paste forming the electrode layers 19a and 19g diffuses into the piezoelectric bodies of the piezoelectric layers 20a and 20h in the firing step and becomes thinner, Like the other electrode layers, a thickness of about 2 to 3 μm can be maintained.

Therefore, even when a cutting process is performed thereafter, the electrode layer 19a and the electrode layer 19g do not break due to an impact during the cutting process, and the electrical characteristics of the piezoelectric element are made uniform in each deformed portion. be able to.

As a result, according to the present embodiment, the amount of deformation of each deformed portion of the piezoelectric element is uniform, and the speed and volume of the discharged droplet can be made uniform.

In each of the embodiments described above, an example was described in which only the expansion / contraction mode was employed as the deformation mode of the piezoelectric element. However, the present invention is not limited to this, and the expansion / contraction mode, the unimorph mode, and The present invention is also applicable to a piezoelectric element in which the expansion mode and the bimorph mode are combined.

[0048]

According to the ink jet head driving device of the first aspect, the piezoelectric layers and the electrodes that are laminated are:
In addition to the piezoelectric layers and electrodes that contribute to the deformation due to the electrostriction effect, the dummy electrodes include the dummy piezoelectric layers and the dummy electrodes that do not contribute to the deformation due to the electrostriction effect. Even when a recess forming process such as a cutting process is performed, it is possible to reliably prevent the occurrence of electrode rupture that contributes to the deformation due to the electrostriction effect, and to reduce the occurrence of the piezoelectric deformation that contributes to the deformation due to the electrostriction effect. It is possible to reliably prevent the electrical characteristics of the deformed portion including the body layer and the electrode from deteriorating. As a result, the amount of deformation of each deformed portion of the piezoelectric element can be made uniform, and the speed and volume of the discharged droplet can be made uniform.

According to the ink jet head driving device of the present invention, the dummy piezoelectric layer is positioned at the uppermost layer and the lowermost layer so as to sandwich the piezoelectric layer contributing to the deformation due to the electrostrictive effect. And the dummy electrode layer is formed between the dummy piezoelectric layer and the piezoelectric layer contributing to the deformation due to the electrostriction effect, so that the piezoelectric layer contributing to the deformation due to the electrostriction effect is provided. In addition, the influence of the diffusion of the electrode and the electrode can be more reliably prevented, and the deterioration of the electrical characteristics of the deformed portion including the piezoelectric layer and the electrode due to the rupture of the electrode can be more reliably prevented. As a result, the amount of deformation of each deformed portion of the piezoelectric element can be made uniform, and the speed and volume of the discharged droplet can be made uniform.

According to the third aspect of the present invention, the piezoelectric layer is polarized in the laminating direction,
By applying a predetermined voltage to each of the electrodes,
Since an electric field parallel to the polarization direction is generated and the piezoelectric substance is deformed in the expansion and contraction mode by the electric field, the dummy piezoelectric layer and the dummy electrode can prevent the electrode from being thinned by diffusion as much as possible. Instead, since the deformation of the deformed portion can be compensated, the amount of deformation of each deformed portion of the piezoelectric element can be increased to improve the ink ejection performance.

According to the fourth aspect of the present invention, the thickness of the electrodes formed on the uppermost layer and the lowermost layer of the stacked piezoelectric layers is adjusted to the other piezoelectric layers. The thickness of the electrode is made larger than the thickness of the electrode, so that it is possible to reliably prevent the electrode from becoming thinner after the firing step, and to contribute to deformation due to the electrostriction effect even when a recess forming process such as a cutting process is performed. It is possible to reliably prevent the electrode from being broken. As a result, it is possible to reliably prevent a decrease in the electrical characteristics of the deformed portion including the piezoelectric layer and the electrode, which contributes to the deformation due to the electrostriction effect, and to make the deformation amount of each deformed portion of the piezoelectric element uniform, The speed and volume of the ejected droplets can be made uniform.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a laminate of a piezoelectric layer and an electrode layer before a firing step according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a completed state of the piezoelectric element according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a configuration of an ink jet head using the piezoelectric element of FIG.

FIG. 4 is a sectional view taken along line YY of FIG. 3;

FIG. 5 is a perspective view illustrating a configuration of a laminate of a piezoelectric layer and an electrode layer before a firing step according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a completed state of a piezoelectric element according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing a configuration of a conventional laminate of a piezoelectric layer and an electrode layer before a firing step.

FIG. 8 is a perspective view showing a completed state of a conventional piezoelectric element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element 5 ... Ink jet head 5a ... Cavity plate 16 ... Ink pressure chamber 19a, 19b, 19c, 19d, 19e, 19f, 1
9g ... electrode layers 20a, 20b, 20c, 20d, 20e, 20f, 2
0g, 20h: Electrode layer 30, 32: Dummy piezoelectric layer 31, 33: Dummy electrode layer

Claims (4)

[Claims] 1. A driving device for an ink-jet head for ejecting ink stored in an ink pressure chamber by applying a pressure change to the ink, the piezoelectric device comprising two or more piezoelectric layers; An electrode formed between the layers, wherein the piezoelectric layer and the electrode include a dummy piezoelectric layer and a dummy that do not contribute to the deformation due to the electrostriction effect, in addition to the piezoelectric layer and the electrode that contribute to the deformation due to the electrostriction effect. A driving device for an ink-jet head, comprising: 2. The dummy piezoelectric layer is provided at an uppermost position and a lowermost position so as to sandwich the piezoelectric layer contributing to deformation due to the electrostriction effect, and the dummy electrode layer is 2. The ink jet head driving device according to claim 1, wherein the driving device is formed between the dummy piezoelectric layer and a piezoelectric layer contributing to deformation due to the electrostriction effect. 3. The ink jet head according to claim 1, wherein the piezoelectric layer is polarized in a laminating direction, and is deformed in an expansion / contraction mode by an electric field parallel to the polarization direction. Drive. 4. A driving device for an ink jet head for discharging ink by applying pressure fluctuation to ink stored in an ink pressure chamber, comprising: a piezoelectric layer laminated in two or more layers; The thickness of the electrodes formed on the uppermost layer and the lowermost layer of the piezoelectric layer is larger than the thickness of the electrodes formed on the other piezoelectric layers. Driving device for an ink jet head.