JP2002254634A - Laminated piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the whole of piezoelectric actuator 20 from curving and deforming along through holes 32, 33 as a base point in a baking process. SOLUTION: Piezoelectric sheets 21b, 21d, 21f, 22 having patterns of respective electrodes 24 formed on the surface and piezoelectric sheets 21a, 21c, 21e, 21g having a pattern of a common electrode 25 formed on the surface are alternately laminated. On the topmost layer, an insulation sheet 23 with surface electrodes 30, 31 is laminated. Through holes 32, 33 are bored through each piezoelectric sheet 21a-21g, 22, 23 while suitably shifting respective sheets so that the sheets adjacent each other in the direction parallel with the pattern line direction of the respective electrodes 24 are not arranged in a line along the parallel direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric element used as a driving source in various devices such as an ink jet head.

[0002]

2. Description of the Related Art Conventionally, piezoelectric elements have been used as driving sources (piezoelectric actuators) for various devices by utilizing the characteristic of converting electric energy into mechanical displacement (strain) by the piezoelectric effect.

[0003] Among them, a laminated piezoelectric element for increasing the amount of displacement due to strain is provided with a conductive paste on the surface (one wide surface) of a piezoelectric sheet made of a ceramic material such as PZT (lead zirconate titanate). A pattern of an individual electrode or a common electrode is formed of a conductive material such as the above, and a plurality of piezoelectric sheets having the individual electrode and a plurality of piezoelectric sheets having the common electrode are alternately laminated. .

In order to electrically connect the individual electrodes and the common electrodes in this type of laminated piezoelectric element, a through hole communicating with the individual electrodes or the common electrodes adjacent to each other in the laminating direction is connected to each piezoelectric sheet. It is known that holes are provided and each through hole is filled with a conductive material.

FIGS. 12 to 14 show an example of a conventional laminated piezoelectric element (piezoelectric actuator 100). Here, FIG. 12 is an exploded perspective view of the piezoelectric actuator 100, FIG. 13 is a cross-sectional view taken along the line XIII-XIII of FIG. 12, and FIG.

A conventional piezoelectric actuator 100 includes piezoelectric sheets 103a, 103c, 1 having individual electrodes 101.
03e, 103g and piezoelectric sheets 103b, 103d, 103f, 103h having the common electrode 102 are alternately laminated, and one insulating sheet 106 is laminated on the uppermost layer of the laminated body.

The individual electrodes 101 are arranged in odd-numbered piezoelectric sheets 103a (103c, 103e,
g), the piezoelectric sheet 1 on both sides of the center line of the short side.
Patterns are formed in parallel with the short side edges of 03a (103c, 103e, 103g) and in rows in the long side direction.

The common electrode 102 is an even-numbered piezoelectric sheet 103b (103d, 103f, 103f) counted from the bottom.
h), the piezoelectric sheet 103b (103d, 103d,
103f, 103h) are formed in a substantially rectangular shape in plan view extending in the long side direction.

[0009] In each of the piezoelectric sheets 103a to 103h, a portion where the individual electrode 101 and the common electrode 102 overlap in the laminating direction is an active portion 107 which generates distortion due to a piezoelectric effect.

The even-numbered piezoelectric sheets 103b (10
3d, 103f, 103h), in the vicinity of the pair of short sides, lead portions 102a, 102a extending over substantially the entire length of the short side are formed integrally with the common electrode 102.

The even-numbered piezoelectric sheets 103b
On the surface of (103d, 103f, 103h) other than the active portion, dummy individual electrodes 104 are formed in a pattern corresponding to the individual electrodes 101, that is, at the same vertical position as the individual electrodes 101. I have.

On the other hand, the odd-numbered piezoelectric sheets 103a
A dummy common electrode 105 is formed on the surface of (103c, 103e, 103g) at a position (the same vertical position) corresponding to the lead portions 102a, 102a.

The insulating sheet 10 as the uppermost piezoelectric sheet
6 has a surface electrode 1 corresponding to the individual electrode 101.
08 and the surface electrode 109 with respect to the common electrode 102.
Are formed along a pair of long side edges of the insulating sheet 106.

All the other piezoelectric sheets 103b to 103h and 106 except the lowermost piezoelectric sheet 103a have the surface electrode 108 and the individual electrode 10 at the corresponding position.
A through hole 110 is formed so that the first and dummy individual electrodes 104 communicate with each other. Similarly, at least one surface electrode 109 and a lead portion 102a at a position corresponding to the surface electrode 109 communicate with each other.
A through hole 111 is also formed.

Thereby, the through holes 110 and 111 are formed.
Each of the individual electrodes 101 is filled with a conductive material filled therein.
Are electrically connected to the surface electrode 108 at the corresponding position, and the common electrodes 102 are electrically connected to the surface electrode 109 at the corresponding position.

In this case, each of the piezoelectric sheets 103a to 103a-1
03h, 106, the through holes 110,
111 is a direction parallel to the arrangement direction of the patterns of the individual electrodes 101, in other words, the piezoelectric sheets 103a to 103a to 103d.
103h and 106 are arranged in a line along the long side direction (see FIG. 12).

The lowermost piezoelectric sheet 103a includes
The through holes 110 and 111 are not provided in order to prevent the piezoelectric actuator 100 from conducting to a driven body (for example, a cavity plate in an inkjet head) to which the piezoelectric actuator 100 is bonded and fixed.

[0018]

As shown in FIG. 13, each of the piezoelectric sheets 103a to 103h, 10h
6 are stacked, the through holes 110, 111
Are arranged in a line along the long side direction of each of the piezoelectric sheets 103a to 103h and 106 while communicating with each other in the stacking direction (vertical direction). In the longitudinal direction (each of the piezoelectric sheets 103a to 103h,
6 along the long side direction), and portions having weak strength were intermittently connected.

In addition, the rows in the stacking direction of the through holes 110 and 111 constituting the weak portions are all in the form of a bottomed cylinder due to the presence of the lowermost piezoelectric sheet 103a. Piezoelectric sheets 103a-1
When the laminate composed of the substrates 03h and 106 is fired, when the laminate (piezoelectric actuator 100) contracts, the laminate shown in FIG.
As shown in FIG. 4, the entire piezoelectric actuator 100 was warped and deformed into a V-shape with the through hole as a valley as viewed from the longitudinal end.

If such a sharp bend or a large warp occurs in the piezoelectric actuator 100, for example,
When the piezoelectric actuator 100 is used as a drive source of an ink-jet head, when the piezoelectric actuator 100 is bonded and fixed to the surface of the cavity plate with an adhesive, a gap is formed in a bent portion or the like, and ink leakage or the like is caused. There is a problem that a defect is caused.

Therefore, an object of the present invention is to provide a laminated piezoelectric element which solves the above-mentioned problems.

[0022]

According to the present invention, there is provided a laminated piezoelectric element comprising a plurality of piezoelectric sheets each having a pattern of individual electrodes formed on one wide surface and a plurality of piezoelectric sheets having a pattern of common electrodes formed on one wide surface. Alternately with the piezoelectric sheet of
The portion where the individual electrodes and the common electrodes overlap in the stacking direction constitutes an active portion, and the individual electrodes or the common electrodes adjacent to each other in the stacking direction are formed on the piezoelectric sheet via a conductive material. It is configured to provide a through hole for conduction.

In order to solve the above-mentioned technical problem, the invention according to claim 1 is the invention in which the through holes adjacent to each other in the direction parallel to the arrangement direction of the patterns of the individual electrodes in each of the piezoelectric sheets are arranged in the parallel direction. It is configured so as to be appropriately shifted so as not to be aligned in a line.

According to a second aspect of the present invention, in the multilayer piezoelectric element according to the first aspect, a portion other than the active portion on one wide surface of the piezoelectric sheet having the common electrode is provided.
A pattern of a dummy individual electrode is formed, and a through hole for conducting the individual electrodes adjacent to each other in the stacking direction is provided in a region where the individual electrode and the dummy individual electrode overlap as viewed from the stacking direction. ing.

The through holes at the respective dummy individual electrodes are appropriately shifted from the through holes adjacent in the parallel direction so as not to be aligned in a line in the parallel direction. Have been.

According to a third aspect of the present invention, in the multilayer piezoelectric element according to the first or second aspect, the surface electrode formed on one of the front and rear wide surfaces of the laminated body of the piezoelectric sheet, and the surface electrode corresponding thereto. The individual electrode or the common electrode is configured to conduct through a through-hole, and the through-hole at each of the surface electrodes is, with respect to the through-hole adjacent to the parallel direction, They are appropriately shifted so as not to be aligned in a line along the parallel direction.

According to a fourth aspect of the present invention, in the multilayer piezoelectric element according to any one of the first to third aspects, the through-holes adjacent to each other in the laminating direction are appropriately shifted so as not to communicate with each other. .

According to a fifth aspect of the present invention, in the multilayer piezoelectric element according to any one of the first to fourth aspects, a portion other than the active portion is provided on one wide surface of the piezoelectric sheet having the individual electrodes. The pattern of the dummy common electrode is formed, and a through hole for conducting the common electrodes adjacent to each other in the stacking direction is in an area where the common electrode and the dummy common electrode overlap as viewed from the stacking direction. In addition, they are appropriately shifted so as not to communicate with each other.

[0029]

According to the first aspect of the invention, the through holes adjacent to each other in the direction parallel to the arrangement direction of the patterns of the individual electrodes in each of the piezoelectric sheets are aligned in a line in the parallel direction. The through-holes are appropriately shifted so as not to overlap with each other, and by stacking such piezoelectric sheets, the through-holes are dispersed in a zigzag shape in plan view. In this case, since the stress generated by shrinkage due to firing is dispersed in the multilayer piezoelectric element, the through-hole of the multilayer piezoelectric element fired in a subsequent step is weak in strength when viewed from the parallel direction in the parallel direction. The amount of deformation of a V-shaped warp having a valley can be reduced.

Then, for example, in the case where the multilayer piezoelectric element is used as a driving source of an ink jet head,
When the multilayer piezoelectric element is bonded and fixed to the surface of the cavity plate, no gap (space) is generated between these bonded surfaces, so that it is possible to prevent defects such as ink leakage when the product is formed as an inkjet head.

The configurations according to the second and third aspects of the present invention embody the invention of the first aspect. When configured as in claim 2 or claim 3, even in the piezoelectric sheet having the common electrode and the piezoelectric sheet having the surface electrode, the through holes at the dummy individual electrode or the surface electrode have a The through-holes adjacent to each other in the parallel direction are appropriately shifted so as not to be aligned in a line along the parallel direction. The effect of reducing the amount of warpage of the laminated piezoelectric element after dispersion and firing in the subsequent step as viewed from the parallel direction can be reliably achieved.

According to a fourth aspect of the present invention, the through holes are not only displaced appropriately so as not to be aligned in a line along the parallel direction in each of the piezoelectric sheets, but also stacked. In this case, it is possible to reduce the amount of warpage of the laminated piezoelectric element after firing in the subsequent step as viewed from the parallel direction, since the elements are appropriately shifted so as not to communicate with each other in the direction. Therefore, the function and effect of claim 1 can be improved.

According to a fifth aspect of the present invention, in order to embody the configuration of the first aspect, the dummy common electrodes patterned on the piezoelectric sheet having the individual electrodes are appropriately shifted so as not to communicate in the laminating direction. Was done,
Also in this case, the effect of reducing the amount of deformation of the warpage can be reliably achieved.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will be described below with reference to the drawings (FIGS. 1 to 11) when applied to a piezoelectric ink jet head.

FIGS. 1 to 8 show a first embodiment of the present invention. As shown in FIGS. 1, 2 and 8, a flexible printed cable is provided on the upper surface (wide surface) of the plate type piezoelectric actuator 20 which is joined to the metal plate cavity plate 10 for connection with an external device. 40 are overlap-joined, and ink is ejected downward from a nozzle 54 opened on the lower surface side of the cavity plate 10.

As shown in FIGS. 3 and 4, the cavity plate 10 is laminated by bonding and joining five thin plates of a nozzle plate 43, two manifold plates 12, a spacer plate 13, and a base plate 14 by bonding. It has a structure. In the first embodiment, each of the plates 12, 13, 14 excluding the nozzle plate 43
Is made of 42% nickel alloy steel plate, and is 50 μm to 150 μm.
m.

In the nozzle plate 43, nozzles 54 for ejecting ink having a very small diameter are arranged in a staggered arrangement in two rows along the longitudinal direction of the nozzle plate 43. That is, a large number of nozzles 54 are formed in a staggered arrangement at intervals of a minute pitch P along two reference lines 43a and 43b parallel to the longitudinal direction of the nozzle plate 43.

The pressure chambers 16 (details will be described later) corresponding to the respective nozzles 54 and the active portions 35 (details described later) of the piezoelectric actuator 20 correspond to each plate 4.
3, 12, 13, and 14 are arranged at corresponding positions overlapping vertically in plan view. Each of the pressure chambers 16 is formed so as to extend in a direction intersecting (perpendicular to) the longitudinal direction of the nozzle plate 43, and the rows of the pressure chambers 16 are arranged along the longitudinal direction of the nozzle plate 43. .

The upper manifold plate 12 facing the spacer plate 13 has a pair of manifold chambers 12a, 12a as ink passages. The lower manifold plate 12 facing the nozzle plate 43 has a pair of manifold chambers 12b, 12b. , Are formed so as to extend along both sides of the row of the nozzles 54. In this case, each of the manifold chambers 12a and 12b extends so as to overlap the row of the pressure chambers 16 in a plan view (see FIGS. 3 and 4).

The manifold chambers 12b, 12b of the lower manifold plate 12 are formed so as to be open only on the upper surface side of the lower manifold plate 12 (see FIG. 4). These manifold chambers 12a,
12b has a structure in which the upper manifold plate 12 is sealed by stacking the spacer plate 13 on the upper manifold plate 12.

The base plate 14 is provided with a large number of narrow pressure chambers 16 extending in a direction (short side direction) perpendicular to the center line along the long side direction. Longitudinal reference lines 14a, 1 parallel on both the left and right sides of the center line.
4b, the tip 16a of the pressure chamber 16 on the left side of the center line is located on the left longitudinal reference line 14a, and conversely, the tip 16 of the pressure chamber 16 on the right side of the center line.
a is located on the right longitudinal reference line 14b.
The tips 16a of the left and right pressure chambers 16 are arranged alternately. Therefore, the left and right pressure chambers 1
6 are alternately arranged so as to extend in the opposite direction to each other (see FIG. 4).

The distal end 16a of each of the pressure chambers 16 has a small-diameter through hole formed in a staggered arrangement on the spacer plate 13 and the two manifold plates 12 with respect to the staggered arrangement of the nozzles 54 in the nozzle plate 43. And 17. On the other hand, the other end 16 of each of the pressure chambers 16
b communicates with the manifold chambers 12a and 12b of the manifold plate 12 through through holes 18 formed on both right and left sides of the spacer plate 13.

As shown in FIG. 4, the other end 16b
Are formed so as to be open only on the lower surface side of the base plate 14. Also, the uppermost base plate 1
A filter 29 for removing dust in the ink supplied from an ink tank (not shown) above the supply holes 19a, 19a formed at one end of the nozzle 4 is stretched. Supply holes 19b, 19b are also formed in the spacer plate 13 at positions corresponding to the supply holes 19a, 19a formed in one end of the base plate 14.

As described above, the ink flowing from the ink tank (not shown) into the left and right manifold chambers 12a and 12b via the supply holes 19a and 19b in the base plate 14 and the spacer plate 13 is supplied to the manifold chambers 12a and 12b. From each pressure chamber 16 through each through hole 18, and then from each pressure chamber 16 through each through hole 17 to the nozzle 54 corresponding to each pressure chamber 16. (See FIGS. 3 and 4).

Next, the structure of the piezoelectric actuator 20 which is a laminated piezoelectric element according to the present invention will be described with reference to FIGS.

As shown in FIG. 5, the piezoelectric actuator 2
0 denotes eight piezoelectric sheets 21a, 21b, 21c, 21
d, 21e, 21f, 21g, 22 and one insulating sheet 23 are laminated. In the first embodiment, each of the piezoelectric sheets 21a to 21g and 22 and the insulating sheet 23 has a thickness of about 15 μm to 40 μm. The insulating sheet 23 is preferably manufactured using the same material as the other piezoelectric sheets in terms of manufacturing.

Similarly to the one described in Japanese Patent Application Laid-Open No. 4-341851, the short side of the lowermost piezoelectric sheet 22 and the odd-numbered piezoelectric sheets 21b, 21d, and 21f counted upward from the surface (wide surface). On both sides of the center line
Each of the piezoelectric sheets 22 and 21 has a narrow individual electrode 24.
Patterns are formed in parallel with the short side edges of b, 21d, and 21f, and in rows in the long side direction. The individual electrode 24
These patterns correspond to the locations of the respective pressure chambers 16 in the cavity plate 10. Each of the individual electrodes 2
The width dimension of 4 is set to be slightly smaller than the corresponding wide portion of the pressure chamber 16.

The even-numbered piezoelectric sheets 21a, 21 from the bottom
A common electrode 25 common to the plurality of pressure chambers 16 is formed on the surfaces (wide surfaces) of c, 21e, and 21g. In each of the piezoelectric sheets 21a to 21g, a portion where the individual electrode 24 and the common electrode 25 overlap in the stacking direction, that is, a portion where the individual electrode 24 and the common electrode 25 are sandwiched, is an active portion 35 that generates distortion due to a piezoelectric effect.

On the other hand, the pressure chamber 16 is
Are arranged in two rows along the long side direction, the common electrodes 25 are arranged so as to integrally cover the two rows of pressure chambers 16, 16.
Each of c, 21e, and 21g is formed in a substantially rectangular shape in a plan view extending in a long side direction at a central portion in a short side direction. In the vicinity of the pair of short sides of the even-numbered piezoelectric sheets 21a, 21c, 21e, 21g, lead portions 25a, 25a extending over substantially the entire length of the short side are integrally formed with the common electrode 25. .

The even-numbered piezoelectric sheets 21a,
On the surfaces of the surfaces 21c, 21e, and 21g other than the active portions 35 (the even-numbered piezoelectric sheets 21a, 21c,
21e and 21g, near the pair of long sides, where the common electrode 25 is not formed), a dummy individual electrode 26 having a width substantially equal to that of the individual electrode 24 and a short length is provided. It is formed in a pattern corresponding to the individual electrode 24, that is, at the same vertical position as the individual electrode 24. These dummy individual electrodes 24 are discarded pattern electrodes that do not contribute to the deformation action (distortion) of the piezoelectric actuator 20.
This is for reducing a change in a partial thickness when the insulating sheets 23a to 21g and the insulating sheet 23 are laminated.

The odd-numbered piezoelectric sheets 22, 21b,
21d, 21f of the drawer portions 25a, 2f
At a position corresponding to 5a (the same vertical position), a dummy common electrode 27 is formed as a discard pattern electrode.

The insulating sheet 23 as the uppermost piezoelectric sheet
The surface electrode 30 for the individual electrode 24
And the surface electrode 31 for the lead portion 25 a of the common electrode 25 are formed along a pair of long side edges of the insulating sheet 23.

Except for the lowermost piezoelectric sheet 22, all the other piezoelectric sheets 21a to 21g and the insulating sheet 23 have the surface electrode 30, the individual electrode 24 and the dummy individual electrode at the corresponding position. 26 are communicated with each other, and a through hole 32 is formed.

Similarly, each of the piezoelectric sheets 21a to 21a
At least one surface electrode 31 (the surface electrodes 31 at the four corners of the insulating sheet 23 in the first embodiment) and the lead portion 25a and the dummy common electrode 27 at the corresponding positions are provided on the 1g and the insulating sheet 23. Through holes 33 are formed so as to communicate with each other. Each of the through holes 32 and 33 is filled with a conductive material of the same material as the individual electrode 24 and the common electrode 25 (for example, an Ag-Pd-based conductive paste or the like).

As shown in FIGS. 5 and 6, in the first embodiment, the through-holes 32 and 33 in the piezoelectric sheets 21a to 21g and the insulating sheet 23 correspond to the piezoelectric sheets 21a to 21g and the insulating sheet 23, respectively. Long side direction (the individual electrode 24 (or the dummy individual electrode 26)
(In a direction parallel to the direction in which the patterns are arranged), the holes are appropriately shifted so as not to be aligned in a line.

That is, the through holes 32 and 33 in the insulating sheet 23 are appropriately dimensioned L1 and L2 in the direction from the long side to the short side of the insulating sheet 23 in order from one short side of the insulating sheet 23. The holes are provided at positions apart from each other by L3, L1,. And
Each of the piezoelectric sheets 21a to 21a below the insulating sheet 23
Each of the piezoelectric sheets 21a to 2 is also arranged such that the through holes 32 and 33 in 1g also correspond to (communicate with) the through holes 32 and 33 in the insulating sheet 23, respectively.
1 g of each of the piezoelectric sheets 21 in order from one short edge side.
a to 21 g, from the long side edge to the short side direction, dimensions L1, L
2, L3, L1,.

The arrangement of the through holes 32, 33 in the piezoelectric sheets 21a to 21g and the insulating sheet 23 is not limited to the above-mentioned pattern, but is limited to the through holes 32, 33 adjacent in the long side direction. Each other
What is necessary is just to displace it suitably so that it may not be aligned in a line along the long side direction.

The piezoelectric actuator 20 is manufactured by the following method.

That is, among the surfaces of a first material sheet (green sheet) having a size in which a plurality of piezoelectric sheets 21b (similarly, 21d, 21f, 22) in the piezoelectric actuator 20 are arranged in a matrix, A through hole 32 is formed in advance at a position where a plurality of individual electrodes 24 and a dummy common electrode 27 as a discarded pattern electrode are provided at a position to be the sheet 21b (21d, 21f).

Similarly, the piezoelectric sheets 21a (21c,
Of the second material sheet (green sheet) having a size obtained by arranging a plurality of piezoelectric sheets 21e and 21g) in a matrix.
e, 21g), a through-hole 33 is formed in advance at a position where the lead portions 25a of the plurality of common electrodes 25 and the dummy individual electrode 26 as a discarded pattern electrode are provided.

Further, on the surface of the third material sheet (green sheet) having a size in which a plurality of the insulating sheets 23 are arranged in a matrix,
Through holes 32 and 33 are formed at positions where a plurality of surface electrodes 30 and 31 are provided.

The piezoelectric sheets 22, 21b,
The individual electrodes 24 and the dummy common electrodes 27 are provided on the surfaces of the piezoelectric sheets 21a, 21c,
The common electrode 25 and the dummy individual electrode 26 are provided on the surface of the e and 21g, and the surface electrodes 30 and 31 are provided on the surface of the insulating sheet 23.
Are formed by screen printing using a conductive material such as an Ag-Pd-based conductive paste.

In this case, each of the through holes 32, 33
Penetrates through the upper and lower wide surfaces of the first to third material sheets, so that the conductive material infiltrates into the through holes 32 and 33, and passes through the through holes 32 and 33 to form the electrode portions. Through the sheets 24, 25, 26, 27, 30, 31, the upper and lower surfaces of the sheet become conductive. Next, the respective material sheets are dried and laminated, and then pressed in a laminating direction to be integrated into one laminated body and fired. After that, it is cut into a predetermined size.

As described above, in the plurality of piezoelectric sheets 22, 21a to 21g and the insulating sheet 23 stacked vertically, the individual electrodes 24 and the dummy
And the surface electrode 30 are electrically connected via the conductive material in the through hole 32, while the upper and lower pluralities of the common electrode 25, the dummy common electrode 27, and the surface electrode 31 are also electrically connected to each other through the conductive material in the through hole 33. (See FIG. 7).

As shown in FIGS. 1, 2 and 8, the lower surface of the piezoelectric actuator 20 (the cavity plate 10)
An adhesive sheet 41 made of an ink-impermeable synthetic resin material as an adhesive layer is attached in advance to the entire wide surface facing the pressure chamber 16 of the cavity plate 1.
0, the individual electrodes 24 in the piezoelectric actuator 20 are bonded and fixed so as to correspond to the respective pressure chambers 16 in the cavity plate 10.

The flexible printed cable 40 is overlaid and pressed on the upper surface of the piezoelectric actuator 20 so that various wiring patterns (not shown) of the flexible printed cable 40 are formed.
Are electrically connected to the surface electrodes 30 and 31.

The material of the adhesive layer such as the adhesive sheet 41 is at least ink impervious and
A film having an electrical insulating property, such as a polyamide-based hot-melt adhesive or a polyester-based hot-melt adhesive that is mainly composed of a polyamide resin based on nylon or dimer acid may be used. However, a polyolefin-based hot-melt adhesive may be applied to the lower surface of the piezoelectric actuator 20 and then bonded and fixed to the cavity plate 10. The thickness of the adhesive layer is about 1 μm.

Then, all the individual electrodes 24 and the common electrode 25
Between the electrodes 24 and 25 of the piezoelectric sheets 21a to 21g by applying a voltage higher than that during normal use.
Polarization processing is performed on the portion sandwiched therebetween.

In the above configuration, by applying a voltage between any of the individual electrodes 24 of the piezoelectric actuator 20 and the common electrode 25, the voltage of the piezoelectric sheets 21a to 21g is reduced. The portion corresponding to the applied individual electrode 24 causes distortion in the laminating direction due to the piezoelectricity, and the distortion reduces the internal volume of the pressure chamber 16 corresponding to each individual electrode 24, so that the pressure in the pressure chamber 16 is reduced. The ink is ejected from the nozzles 54 in the form of droplets, and predetermined printing is performed (see FIG. 8).

In the first embodiment, each of the piezoelectric sheets 21
The through holes 32 and 33 in the insulating sheets 23a and 21g are formed so as to be appropriately shifted so as not to be aligned in a line along the long side direction of the piezoelectric sheets 21a to 21g and the insulating sheet 23. In the vicinity of the pair of longitudinal side edges of the piezoelectric actuator 20,
The through holes 32 and 33 communicating from the uppermost layer to the lowermost layer in the stacking direction are formed in a zigzag shape in a plan view.

That is, since the rows in the laminating direction of the through holes 32 and 33, which are the starting points of the warpage, are formed in a zigzag manner in plan view, the stress caused by shrinkage due to firing is applied to the piezoelectric actuator 20. Can be dispersed. Therefore, it is possible to reduce the amount of deformation of the V-shaped warp having troughs at the locations of the through holes 32 and 33 which are weak in strength when viewed from the longitudinal ends of the piezoelectric actuator 20 after firing in the subsequent step.

As a result, when the piezoelectric actuator 20 is bonded and fixed to the surface of the cavity plate 10, no gap (space) is generated in the bonding surface between the piezoelectric actuator 20 and the cavity plate 10. In this way, it is possible to prevent defects such as ink leakage in a product state.

Further, when the piezoelectric actuator 20 and the cavity plate 10 are bonded to each other, the bonding pressure for pressing the piezoelectric actuator 20 and the cavity plate 10 can be reduced so that the wide surface (bonding surface) becomes flat. In addition, this can also solve the problem that the piezoelectric actuator 20 is broken by pressing the two.

FIGS. 9 to 11 show a second embodiment of the arrangement pattern of through holes. In the second embodiment,
Except for the lowermost piezoelectric sheet 22, all the other piezoelectric sheets 21a to 21g and the insulating sheet 23 electrically connect the surface electrode 30 to the individual electrode 24 and the dummy individual electrode 26 at the corresponding position. Through hole 32 'is formed.

Similarly, each of the piezoelectric sheets 21a to 21a
1g and the insulating sheet 23 include at least one surface electrode 31 (the surface electrodes 31 at the four corners of the insulating sheet 23 in the second embodiment), and the lead portion 25a and the dummy common electrode 27 at the corresponding positions. A through-hole 33 'is also provided for electrical conduction. These through holes 32 ′ and 33 ′ are also filled with the same material (for example, Ag-Pd-based conductive paste or the like) as the individual electrode 24 and the common electrode 25.

As shown in detail in FIG. 10, in the second embodiment, each through hole 3 in the insulating sheet 23 is formed.
The positions 2 'and 33' are spaced apart from the long side of the insulating sheet 23 in the short side direction by appropriate dimensions L1, L2, L3, L1,... In order from one short side of the insulating sheet 23. The insulating sheet 23
Each through hole 3 in the piezoelectric sheet 21a under the layer
The positions 2 'and 33' are spaced apart from the long side of the piezoelectric sheet 21a by appropriate dimensions L2, L3, L1, L2,... In the short side direction in order from one short side of the piezoelectric sheet 21a. The hole is appropriately shifted.

Each of the through holes 32 ', 3' in the piezoelectric sheet 21b one layer below the piezoelectric sheet 21a.
3 'is shifted from the long side of the piezoelectric sheet 21b in the direction of the short side as appropriate in the short side direction from the one short side of the piezoelectric sheet 21b to a position separated by a distance L3, L1, L2, L3,. Has been drilled. Remaining piezoelectric sheet 21c
Each of the through holes 32 'and 33' at ~ 21g is also formed in accordance with the pattern.

That is, the through holes 32 ', 3
Reference numeral 3 'denotes a long side direction of each of the piezoelectric sheets 21a to 21g and the insulating sheet 23 (a direction parallel to a pattern arrangement direction of the individual electrodes 24 (or the dummy individual electrodes 26)).
Not only are not properly aligned so as not to be aligned in a line along the line, but are also appropriately shifted so as not to communicate with adjacent ones in the laminating direction (see FIG. 11).

Here, the through holes 32 ′ and 3 for conducting the individual electrodes 24 adjacent to each other in the laminating direction are provided.
3 ′, the individual electrode 24, the dummy individual electrode 26, and the surface electrode 30
Are set so as to be located in a region where the common electrode 25 overlaps, and in a region where the lead portion 25a of the common electrode 25, the dummy common electrode 27 and the surface electrode 31 overlap.

The conductive material in each of the through holes 32 ′, 33 ′ comes into contact with the surface of the electrode in the piezoelectric sheet below by one layer, and the individual electrodes 24,
The dummy individual electrode 26 and the surface electrode 30 conduct with each other,
In addition, the lead portion 25a of the common electrode 25, the dummy common electrode 27, and the surface electrode 31 conduct with each other.

With the above configuration, each of the through holes 32 'and 33' is connected to each of the piezoelectric sheets 21a to 21 '.
g and the insulating sheet 23 are not only formed so as not to be aligned in a line along the long side direction, but are also formed so as to be shifted as appropriate so that adjacent ones in the laminating direction do not communicate with each other. Therefore, the stress generated by shrinkage due to firing can be further dispersed in the piezoelectric actuator 20 than in the case of the first embodiment.

Therefore, the amount of deformation of the piezoelectric actuator 20 after firing in the subsequent step can be made smaller than in the first embodiment, and the accuracy of the flatness of the piezoelectric actuator 20 is improved.

The present invention is not limited to the above embodiment, but can be embodied in various forms. For example, the piezoelectric actuator 2
Although the piezoelectric sheet 22 is adopted as the lowermost layer of 0, another insulating material may be used as long as it transmits distortion of the piezoelectric sheet of another layer to the pressure chamber. Also, the uppermost insulating sheet 2
For 3, another insulating material may be used. In this case, it is desirable to suppress the distortion of the piezoelectric sheet that protrudes upward (the side opposite to the cavity plate 10).

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a piezoelectric inkjet head according to a first embodiment.

FIG. 2 is an enlarged perspective view showing one end of a piezoelectric actuator and a cavity plate.

FIG. 3 is an exploded perspective view of a cavity plate.

FIG. 4 is a partially enlarged perspective view of a cavity plate.

FIG. 5 is an exploded perspective view of the piezoelectric actuator.

FIG. 6 is a partially enlarged exploded perspective view of the piezoelectric actuator.

7 is a sectional side view taken along line VII-VII of FIG. 6;

FIG. 8 is an enlarged sectional view showing a state in which a flexible printed cable, a cavity plate, and a piezoelectric actuator are stacked.

FIG. 9 is an exploded perspective view of a piezoelectric actuator according to a second embodiment.

FIG. 10 is a partially enlarged exploded perspective view of a piezoelectric actuator.

FIG. 11 is a side sectional view taken along the line XI-XI of FIG. 10;

FIG. 12 is an exploded perspective view of a conventional piezoelectric actuator.

13 is a side sectional view taken along the line XIII-XIII of FIG.

FIG. 14 is an explanatory diagram of a modified state of FIG. 13;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cavity plate 12 Manifold plate 13 Spacer plate 14 Base plate 16 Pressure chamber 20 Piezoelectric actuator 21a-21g, 22 Piezoelectric sheet 23 Insulating sheet 24 Individual electrode 25 Common electrode 25a Leader 26 Dummy individual electrode 27 Dummy common electrode 30, 31 Surface electrode 32 , 33, 32 ', 33' Through hole 40 Flexible printed cable 43 Nozzle plate 54 Nozzle

Claims (5)

[Claims] 1. A plurality of piezoelectric sheets each having a pattern of an individual electrode formed on one wide surface and a plurality of piezoelectric sheets having a pattern of a common electrode formed on one wide surface are alternately laminated to each of the individual sheets. A portion where an electrode and each of the common electrodes overlap in the laminating direction forms an active portion, and in each of the piezoelectric sheets, the individual electrodes or the common electrodes adjacent to each other in the laminating direction are electrically connected via a conductive material. In the laminated piezoelectric element in which the through-holes are provided, in each of the piezoelectric sheets, the through-holes adjacent to each other in a direction parallel to the arrangement direction of the pattern of the individual electrodes are arranged in a line along the parallel direction. A laminated piezoelectric element, which is appropriately shifted so as not to be aligned. 2. A pattern of a dummy individual electrode is formed on a portion of one wide surface of the piezoelectric sheet having the common electrode other than the active portion, so that individual electrodes adjacent in the laminating direction are electrically connected to each other. Are disposed in a region where the individual electrode and the dummy individual electrode overlap each other when viewed from the laminating direction.
2. The device according to claim 1, wherein the through holes are arranged so as not to be aligned in a line along the parallel direction with respect to the through holes adjacent to the parallel direction.
3. The laminated piezoelectric element according to item 1. 3. A method in which a surface electrode formed on one of the front and back wide surfaces of the laminated body of the piezoelectric sheet and the corresponding individual electrode or the common electrode are electrically connected through a through hole. The through-holes at the positions of the surface electrodes are appropriately shifted from the through-holes adjacent to the parallel direction so as not to be aligned in a line along the parallel direction. 3. The method according to claim 1, wherein
3. The laminated piezoelectric element according to item 1. 4. The multi-layer piezoelectric element according to claim 1, wherein the through-holes adjacent in the laminating direction are appropriately shifted so as not to communicate with each other. 5. A pattern of a dummy common electrode is formed on a portion of the one wide surface of the piezoelectric sheet having the individual electrode other than the active portion, so as to conduct common electrodes adjacent in the laminating direction. Wherein the through-holes are located in a region where the common electrode and the dummy common electrode overlap when viewed from the laminating direction, and are arranged so as to be appropriately shifted so as not to communicate with each other. 5. The multilayer piezoelectric element according to any one of 4.