JP2003211667A - Ink jet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the pressurizing force of ink in an ink chamber. <P>SOLUTION: An actuator section 7 for pressurizing an ink chamber 1 is formed of a multilayer piezoelectric element 12 comprising a plurality of piezoelectric ceramic layers 8a, 8b, 8c, substantially entire surface common electrodes 9a, 9b, 9c, piezoelectric ceramic layers 10a, 10b, 10c, and discrete electrodes 11a, 11b, 11c arranged to be positioned on respective ink chambers 1 laid in layer sequentially and integrated and then subjected to polarization in the thickness direction of the piezoelectric ceramic layers 8b, 8c, 10a, 10b, 10c interposed between the substantially entire surface common electrodes 9a, 9b, 9c, and the discrete electrodes 11a, 11b, 11c. The width W1 of the discrete electrode 11a closest to the ink chamber 1 is set in the range of 60-90% of the width L of the ink chamber 1, and at least one width W2, W3 of other discrete electrodes 11b, 11c is set wider than the width W1 of the discrete electrode 11a closest to the ink chamber 1 thus constituting an ink jet recording head 20. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head mounted on an ink jet recording apparatus used for printing characters and images. 2. Description of the Related Art In recent years, with the spread of personal computers and the development of multimedia, the use of ink jet recording devices as recording devices for outputting information to recording media has been rapidly expanding. [0003] Such an ink jet recording apparatus is equipped with an ink jet recording head (hereinafter referred to as a head), and a head as a pressurizing means is provided in an ink chamber filled with ink. A thermal jet method in which the ink is heated and boiled by a heater, the ink is pressurized by bubbles generated in the ink chamber, and ejected as ink droplets from the ink ejection holes, and a part of the wall of the ink chamber filled with ink. A piezoelectric method is generally known in which a piezoelectric element is bent and displaced by a piezoelectric element to mechanically pressurize ink in an ink chamber and discharge the ink as ink droplets from an ink discharge hole. Among them, as a piezoelectric type ink jet recording head 40, for example, as shown in FIG. 3, a flow path member 26 having a plurality of ink chambers 21 partitioned by a plurality of partition walls 22, and each ink chamber 21 And an actuator unit 27 for pressurizing the ink to be filled therein. The flow path member 26 is composed of a plate 25 having a plurality of slits arranged side by side, and a nozzle plate 24 having a plurality of ink discharge holes 23 and ink supply holes (not shown). A plurality of grooves are formed by bonding the respective ink ejection holes 23 and the ink supply holes with the respective slits of the plate-like body 25 in a state where they are aligned. The ink discharge hole 23 and the ink supply hole are opened. The actuator section 27 includes piezoelectric ceramic layers 28a, 28b, 28c and a substantially entire surface common electrode 29.
a, 29b, 29c, piezoelectric ceramic layers 30a, 30
b, 30c, and a plurality of individual electrodes 31a, 31b, 31c arranged so as to be located on the ink chambers 21, respectively, are laminated and integrated in this order, and the substantially entire common electrodes 29a, 29b, 29c and Individual electrodes 31a, 31
b, 31c and the piezoelectric ceramic layers 28b, 28
Each of c, 30a, 30b, and 30c is formed by a laminated piezoelectric element 32 that has been subjected to polarization processing in the thickness direction. The width of each of the individual electrodes 31a, 31b, and 31c is constant in the lamination direction, and the width of the ink chamber 21 is set. (See JP-A-3-274159). The ink jet recording head 4
In order to discharge the ink droplets by 0, the individual electrodes 31a, 31b, 31c of the multilayer piezoelectric element 32 and the substantially entire common electrodes 29a, 29b are filled with the ink into the ink chamber 21 from an ink supply hole (not shown). When an electric field is generated by applying a voltage between the piezoelectric ceramic layers 28b, 28c, 30a, 30b, and 30c, the piezoelectric ceramic layers 28b, 28c, 30a, 30b, and 30c on which the electric field acts tend to expand and contract in a direction perpendicular to the stacking direction. Since the electric field does not act on the lowermost piezoelectric ceramic layer 28a and does not vibrate, the actuator portion 27 on the ink chamber 21 generates bending vibration due to the restriction of the partition wall 22, and the ink in the ink chamber 21 is applied by the bending vibration. The ink droplet is ejected from the ink ejection hole 23 by pressing. As described above, the actuator using the laminated piezoelectric element 32 as the actuator section 27 has an advantage that a large bending vibration can be generated. However, in order to increase the vibration of the laminated piezoelectric element, the area of the electrodes arranged with the piezoelectric ceramic layer interposed therebetween is increased, and a large electric field is applied to the piezoelectric ceramic layer. The actuator section 27 is joined to the partition wall 22 and the width of the individual electrodes 31a, 31b and 31c is the same as the width of the ink chamber 21 as in the ink jet recording head 40 shown in FIG. If the degree is too small, there is a problem that a sufficiently large bending vibration cannot be generated. That is, the piezoelectric ceramic layers 28b, 28c, 30b, 30 located at positions distant from the joint with the partition wall 22.
c is a piezoelectric ceramic layer 30a that is hardly hindered by the partition wall 22 but is close to the joint with the partition wall 22.
Since the vibration is restricted by the partition wall 22, the bending vibration of the entire actuator section 27 is small. As a result, the force for pressurizing the ink in the ink chamber 21 is small, and the ejection speed of the ink droplets cannot be increased. In view of the above problems, the present invention has been made in view of the above problems, and has a flow path member having a plurality of ink chambers partitioned by a plurality of partition walls, and an actuator for pressurizing ink in each of the ink chambers. And an ink jet recording head comprising: a plurality of piezoelectric actuator layers, a substantially entire surface common electrode, a piezoelectric ceramic layer, and individual electrodes arranged so as to be positioned on each of the ink chambers. And a multilayer piezoelectric element that is polarized in the thickness direction of the piezoelectric ceramic layer between the substantially entire common electrode and the individual electrode, and the width of the individual electrode closest to the ink chamber is 60% to 90% of the width of the ink chamber, and at least one width of the other individual electrode is larger than the width of the individual electrode closest to the ink chamber. The feature is that it is made. Embodiments of the present invention will be described below. FIG. 1 is a partially broken perspective view showing an example of the ink jet recording head of the present invention. The ink jet recording head 20 (hereinafter referred to as the head 20) has a flow path member 6 having a plurality of ink chambers 1 partitioned by a plurality of partition walls 2, and each ink chamber 1
And an actuator section 7 for pressurizing the ink to be filled therein. The flow path member 6 includes a plate-like body 5 having a plurality of slits arranged in parallel and a nozzle plate 4 having a plurality of ink discharge holes 3 and ink supply holes (not shown). A plurality of grooves are formed by bonding, for example, by bonding in a state where each of the ink discharge holes 3 and the ink supply holes 3 and the slits of the plate 5 are aligned. At the same time, the ink discharge holes 3 and the ink supply holes are opened at the bottom of the groove. Here, the nozzle plate 4 constituting the flow path member 6
The material is not particularly limited, and resin, quartz, glass, silicon, metal, and ceramics can be used. Although FIG. 1 shows one plate material, a laminate in which two or more plate materials made of the above materials are bonded may be used. In this case, the plate material on the side of the ink chamber 1 is a comparative example. It is preferable to use quartz, glass, silicon, metal, or ceramics having high target rigidity, and to use, as the plate material on the ink ejection side, a resin that can easily form minute ink ejection holes 3. The material of the plate member 5 constituting the flow path member 6 is resin, quartz, glass,
Although silicon, metal, and ceramics can be used, in order to prevent the partition wall 2 from being deformed by the vibration of the actuator section 7, it is preferable that the partition wall 2 be formed of a material having appropriate rigidity, such as quartz, glass, silicon, metal, or the like.
It is preferable to use any one of ceramics. FIG. 1 shows an example in which the nozzle plate 4 and the plate-like body 5 are separately formed and bonded as the flow path member 6, but any one of resin, quartz, glass, silicon, metal, and ceramics is shown. It is also possible to use a flow path member in which a groove serving as the ink chamber 1 is formed in a kind of plate-like body, and an ink discharge hole 3 and an ink supply hole are formed in the bottom of the groove. On the other hand, the actuator section 7 includes the piezoelectric ceramic layers 8a, 8b, 8c, the substantially entire common electrodes 9a, 9b,
9c, piezoelectric ceramic layers 10a, 10b, 10c, individual electrodes 1 arranged so as to be located on each of the ink chambers 1
1a, 11b, and 11c are laminated in this order in three layers to be integrated, and the substantially entire common electrodes 9a, 9b, and 9c are formed.
The piezoelectric ceramic layers 8b, 8c, 10a, 10b, and 10c between the electrodes and the individual electrodes 11a, 11b, and 11c are formed by a laminated piezoelectric element 12 that has been polarized in the thickness direction as indicated by an arrow in FIG. The width W1 of the individual electrode 11a closest to the ink chamber 1 is set to 6 times the width L of the ink chamber 1.
0% to 90%, and the other individual electrodes 11b, 1
The widths W2 and W3 of 1c are made to be gradually larger than the individual electrodes 11a closest to the ink chamber 1 (W1 <W2 <W3). In order to eject ink droplets from the head 20, an electric field is generated by applying a voltage between the individual electrodes 11a, 11b, 11c and the substantially entire common electrodes 9a, 9b, 9c. The portions of the piezoelectric ceramic layers 8b, 8c, 10a, 10b, and 10c where the electric field acts tend to expand and contract in a direction perpendicular to the stacking direction, whereas the piezoelectric ceramic layers 8a where the electric field does not act are inactive portions. Between the partition walls 2 (on the ink chamber 1) because they do not vibrate
Can be flexed and vibrated in the stacking direction. At this time, according to the head 20 of the present invention,
The width W1 of the individual electrode 11a closest to the ink chamber 2 is smaller than the width L of the ink chamber 1 and the other individual electrodes 11a
Since the widths W2 and W3 of b and 11c are larger than the width W1 of the individual electrode 11a closest to the ink chamber 2, the bending vibration of the actuator 7 on the ink chamber 1 can be increased. That is, since the ink chamber 1 side of the actuator section 7 is constrained by the partition 2, if the width W 1 of the individual electrode 11 a closest to the ink chamber 1 is approximated to the width L of the ink chamber 1, The electrode 11a and the substantially common electrode 9
The expansion and contraction of the piezoelectric ceramic layer 10a between
The individual electrodes 11 closest to the ink chamber 1 as in the present invention.
If the width W1 is smaller than the width L of the ink chamber 1 and the distance to the partition 2 is increased, the amount of expansion and contraction of the piezoelectric ceramic layer 10a between the individual electrode 11a and the substantially entire common electrode 9a is slightly reduced. The vibration can be suppressed from being restrained by the partition wall 2, and as a result, the piezoelectric ceramic layer 10a can be bent to increase the vibration. Further, since the other individual electrodes 11b and 11c are separated from the junction with the partition 2, the vibration of the piezoelectric ceramic layers 8b, 8c, 10b and 10c is hardly restricted by the partition 2, and the other individual electrodes 11b and 11c are not separated. Widths W2 and W3 of electrodes 11b and 11c
Is larger than the width W1 of the individual electrode 11a closest to the ink chamber 1, it is possible to generate a bending vibration corresponding to the magnitude of the electric field. As a result, as compared with the conventional head 40 shown in FIG. 3, the amount of deflection of the actuator section 7 on the ink chamber 1 can be increased, and the pressure of the ink in the ink chamber 1 can be increased to increase the ink pressure. The ejection speed of the droplet can be improved. However, the individual electrode 1 closest to the ink chamber 1
When the width W1 of 1a is less than 60% of the width L of the ink chamber 1, the vibration of the piezoelectric ceramic layer 10a between the individual electrode 11a and the substantially entire surface common electrode 9a is less likely to be restrained by the partition 2. Since the width W1 of the electrode 11a is too small, the amount of expansion and contraction of the piezoelectric ceramic layer 10a is too small, and as a result, the amount of deflection of the actuator section 7 on the ink chamber 1 cannot be increased. Conversely, the individual electrode 11 closest to the ink chamber 1
If the width W1 of a is larger than 90% of the width L of the ink chamber 1, the effect of reducing the width W1 of the individual electrode 11a cannot be obtained, and the amount of deflection of the actuator section 7 on the ink chamber 1 is sufficiently large. Can not do it. For this reason, the individual electrode 1 closest to the ink chamber 1
It is preferable that the width W1 of 1a is 60% to 90% of the width L of the ink chamber 1. The individual electrode 11a and the substantially entire common electrode 9
a of the piezoelectric ceramic layer 10a between the partition walls 2
In order not to be restricted, it is preferable to increase the distance to the partition 2 within a range where the amount of deflection of the actuator section 7 is not significantly reduced by increasing the thickness of the piezoelectric ceramic layer 8a. On the other hand, the individual electrode 11 closest to the ink chamber 1
It is better that the widths W2 and W3 of the individual electrodes 11b and 11c other than a are large. However, if the widths W2 and W3 are too large, they may come into contact with the adjacent individual electrodes 11b and 11c or the adjacent ink chambers 1b and 11c.
Crosstalk. Therefore, the width W of the individual electrodes 11b and 11c
When W2 and W3 are made larger than the width L of the ink chamber 1, the amount of protrusion is preferably suppressed to 30% or less of the width M of the partition wall 2, and more preferably 10% or less. In FIG. 1, among the three individual electrodes 11a, 11b and 11c located on the ink chamber 1, the width W1 of the individual electrode 11a closest to the ink chamber 1 is the smallest.
In addition, an example has been shown in which the width L of the ink chamber 1 is made smaller and the widths of the other individual electrodes 11b and 11c become larger in order of W2 and W3. However, the present invention is not limited to such a structure. For example, as shown in FIG. 2A, the width W1 of the individual electrode 11a closest to the ink chamber 1 is
And the width W2 of the next individual electrode 11b is made equal to the width W1 of the individual electrode 11a.
The width W3 of the individual electrode 11c farthest from the ink chamber 1 is
The width W1 of the individual electrode 11a closest to the ink chamber 1 is set to be larger than the width W1 of the individual electrode 11a closest to the ink chamber 1, as shown in FIG.
0% to 90%, the next individual electrode 11b and the ink chamber 1
The widths W2 and W3 of the individual electrodes 11c farthest away from each other are made larger than the width W1 of the individual electrodes 11a closest to the ink chamber 1, and as shown in FIG. Width W1 is 60% of width L of ink chamber 1
To 90%, the next individual electrode 11b is made larger than the width W1 of the individual electrode 11a closest to the ink chamber 1, and
The width W1 of the individual electrode 11a closest to the ink chamber 1, such as the width W3 of the individual electrode 11c farthest from the ink chamber 1 is larger than the width W1 of the individual electrode 11a and smaller than the width W2 of the individual electrode 11b. 60% -9 of width L of 1
0% and at least one of the widths W2 and W3 of the other individual electrodes 11b and 11c may be larger than the width W1 of the individual electrode 11a closest to the ink chamber 1. However, the piezoelectric ceramic layers 8b, 8c, 1
Since the vibrations of Oa, 10b, and 10c are more restricted by the partition wall 2 as they are closer to the joint with the partition wall 2, the individual electrode 1 closest to the ink chamber 1 is preferably provided as shown in FIG.
The width W1 of 1a is set to be 60% to 90% of the width L of the ink chamber 1, and the other individual electrodes 11b and 11c are preferably arranged so as to gradually increase as the distance from the individual electrode 11a increases. In the embodiment, the number of the individual electrodes 11a, 11b, 11c forming the laminated piezoelectric element 12 is set to three, but may be two or four or more. However, considering the cost and the increase in the size of the head 20, it is preferable to set the number of layers to about eight. Next, a method of manufacturing the ink jet recording head 20 according to the present invention will be described. First, in order to manufacture the flow path member 6, a plate 5 having a plurality of slits and a nozzle plate 4 having a plurality of ink discharge holes 3 and ink supply holes are prepared. Next, after aligning the slit of the plate member 5 with the ink discharge hole 3 and the ink supply hole of the nozzle plate 4, the plate member 5 and the nozzle plate 4 are joined by, for example, bonding. A groove formed by closing one of the slits with the nozzle plate 4 is defined as an ink chamber 1, a wall partitioning each groove is defined as a partition 2, and an ink discharge hole 3 and an ink supply hole are opened at the bottom of the groove. The flow path member 6 is manufactured. When the plate 5 and the nozzle plate 4 are made of ceramics, the unfired plate 5 and the unfired nozzle plate 4 are aligned and bonded, and then fired to integrate them. Alternatively, the flow path member 6 can be formed. On the other hand, to manufacture the actuator section 7, the unfired piezoelectric ceramic layers 8a, 8b, 8c, the substantially entire common electrodes 9a, 9b, 9c, the unfired piezoelectric ceramic layers 10a, 10b, 10c, the individual electrodes 11a, 11b,
11c are sequentially laminated in this order, and the widths W1, W of the individual electrodes 11a, 11b, 11c are respectively set.
2, W3, the width W1 of the individual electrode 11a closest to the ink chamber 1 is 60% to 90% of the width L of the ink chamber 1, and at least one width W2, W of the other individual electrodes 11b, 11c.
3 is larger than the width W1 of the individual electrode 11a. Thereafter, after firing the laminate, the common electrodes 9a, 9b, 9c and the individual electrodes 11a, 11b, 1
1c and the piezoelectric ceramic layers 8b, 8c, 10a, 1
It is manufactured by performing a polarization process on 0b and 10c. The piezoelectric ceramic layers 8a, 8b, 8
As materials for forming c, 10a, 10b, and 10c,
Piezoelectric ceramics containing lead zirconate titanate (PZT), lead magnesium niobate (PMN-based), lead nickel niobate (PNN-based), or the like as a main component can be used. The material for forming the substantially entire common electrodes 9a, 9b, 9c and the individual electrodes 11a, 11b, 11c includes piezoelectric ceramic layers 8a, 8b, 8c, 10a, 10c.
Any material that can withstand the baking temperatures b and 10c may be used. For example, a conductor containing at least one of Ag, Pd, Pt, Rh, Au, and Ni may be used. After the individual electrodes 11a, 11b, and 11c of the obtained actuator section 7 are positioned on the ink chamber 1 and the individual electrodes 11a are positioned so as to be closest to the ink chamber 1, the actuator section 7 It can be obtained by bonding the flow path member 6 with an adhesive or the like. Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and may be improved or changed without departing from the gist of the present invention. Absent. Here, the individual electrodes 11 of the actuator section 7 provided in the ink jet recording head 20 shown in FIG. 1 will be described.
a, 11b, 11c have different widths W1, W2, W3,
An experiment was conducted to check the ejection performance of ink droplets. The actuator section 7 forms a plurality of green sheets by forming a slurry containing lead zirconate titanate into a sheet by a roll coater method, and then punches the green sheets into a rectangular shape using a mold. A plurality of rectangular sheets were prepared. Next, on one main surface of the three rectangular sheets, an electrode paste for forming the substantially whole common electrodes 9a, 9b, 9c is printed over substantially the entire surface, and each individual electrode 11a is printed on the other main surface. , 11b and 11c were printed. At this time, the widths W1, W2, W3 of the individual electrodes 11a, 11b, 11c are made different depending on the sample.
A paste containing Ag-Pd was used as the electrode paste. Then, a rectangular sheet having the electrode paste printed thereon and a rectangular sheet having no electrode paste printed thereon were sequentially laminated to produce a laminate having a structure as shown in Table 1. In Table 1, the first layer is the individual electrode 11a arranged closest to the ink chamber 1 and the second layer is the individual electrode 11b arranged close to the ink chamber 1 next to the individual electrode 11a. The three layers indicate the individual electrodes 11c arranged at positions farthest from the ink chamber 1. Thereafter, the obtained laminate is heated to 1000 ° C.
After firing at a temperature of 1200 ° C., the common electrode 9a,
9b, 9c and the individual electrodes 11a, 11b, 11c, a voltage is applied between the piezoelectric ceramic layers 8a, 8c.
The actuator section 7 was fabricated by subjecting b, 8c, 10a, 10b, and 10c to polarization processing. Note that each of the piezoelectric ceramic layers 8a, 8
b, 8c, 10a, 10b, 10c have a thickness of 15 μm,
Substantially entire surface common electrode layers 9a, 9b, 9c and individual electrodes 11
a, 11b, and 11c have thicknesses in the range of 2 to 5;
It was set to be μm. On the other hand, the flow path member 6 manufactures the plate-like body 5 by forming a slit which becomes the ink chamber 1 in a thin stainless steel plate by an etching method, and forms the ink ejection hole 3 and the ink in another thin stainless steel plate. A nozzle plate 4 was manufactured by piercing a supply hole (not shown) by an etching method. Then, the slit of the plate member 5 and the ink ejection hole 3 of the nozzle plate 4 are formed.
After the alignment with the ink supply holes is performed, the two are bonded with an epoxy adhesive, the grooves formed by the slits and the nozzle plate 4 are used as the ink chambers 1, and the walls separating the grooves are formed by the partition walls 2. Was manufactured. The width L of the ink chamber 1 is 0.5 mm, and the length of the ink chamber 1 is 0.7 m.
m. Thereafter, the manufactured actuator section 7 and the flow path member 6 were aligned, and then bonded with an epoxy adhesive to obtain an experimental inkjet recording head 20. After the ink is filled in the ink chamber 1 of the obtained experimental ink jet recording head 20,
Substantially all common electrodes 9a, 9b, 9c of the actuator section 7
The actuator unit 7 was driven by applying a voltage of 20 V between the and the individual electrodes 11a, 11b, and 11c at a frequency of 20 KHz, and the ejection speed of ink droplets ejected from the ink ejection holes 3 was measured and evaluated. However, the measurement of the ejection speed of the ink droplet was obtained by performing image processing on the obtained image using a camera having a high-speed strobe photographing device. The results are as shown in Table 1. [Table 1] As a result, as can be seen from Table 1, the width W1 of the individual electrode 11a closest to the ink chamber 1 is set to 60% to 90% of the width L of the ink chamber 1, and the other individual electrodes 11b, 1
1c at least one width W2, W3
The ejection speed of the ink droplets can be increased by making the width W1 of the individual electrode 11a closest to the above. As described above, according to the present invention, a flow path member having a plurality of ink chambers partitioned by a plurality of partition walls and an actuator section for pressurizing ink in each of the ink chambers are provided. In an inkjet recording head,
The actuator section is formed by sequentially stacking and integrating a plurality of piezoelectric ceramic layers, a substantially entire surface common electrode, a piezoelectric ceramic layer, and individual electrodes arranged so as to be positioned on the respective ink chambers. The width of the individual electrode closest to the ink chamber is set to 60% to 90% of the width of the ink chamber, while being formed by a laminated piezoelectric element which is polarized in the thickness direction of the piezoelectric ceramic layer between the electrode and the electrode. By making the width of at least one of the other individual electrodes larger than the width of the individual electrode closest to the ink chamber,
Since the vibration of the actuator unit can be suppressed from being restrained by the partition wall, a larger vibration can be obtained,
Since the pressure of the ink in the ink chamber can be increased, the ejection speed of the ink droplets can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway perspective view showing an example of an ink jet recording head of the present invention. FIGS. 2A to 2C are partially enlarged cross-sectional views each showing an arrangement state of individual electrodes of an actuator unit which is another example of the ink jet recording head of the present invention. FIG. 3 is a partially broken perspective view showing an example of a conventional ink jet recording head. DESCRIPTION OF SYMBOLS 1, 21 Ink chamber 2, 22 Partition wall 3, 23 Ink ejection hole 4, 24 Nozzle plate 5, 25 Plate body 6, 26 Flow path member 7, 27 Actuator section 8a, 8, 8c, 28a, 28b, 28c, piezoelectric ceramic layers 9a, 9b, 9c, 29a, 29b, 29c Substantially entire common electrodes 10a, 10b, 10c, 30a, 30b, 30c Piezoelectric ceramic layers 11a, 11b, 11c, 31a, 31b, 31c Individual electrodes 12 , 32 Multilayer piezoelectric element 20, 40 Ink jet recording head

Claims (1)

1. An ink jet recording head comprising: a flow path member having a plurality of ink chambers partitioned by a plurality of partition walls; and an actuator section for pressurizing ink in each of the ink chambers. The unit is formed by sequentially stacking a plurality of layers of a piezoelectric ceramic layer, a substantially entire surface common electrode, a piezoelectric ceramic layer, and individual electrodes arranged so as to be positioned on each of the ink chambers, and is integrated with the substantially entire surface common electrode. It is composed of a laminated piezoelectric element which has been subjected to a polarization treatment in the thickness direction of a piezoelectric ceramic layer between the electrode and the electrode, and the width of the individual electrode closest to the ink chamber is 60% of the width of the ink chamber.
90%, and at least one other electrode has a width larger than the width of the individual electrode closest to the ink chamber.