JP2008290409A - Liquid discharge head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge head capable of reducing cracks generated at the time of polarization of a piezoelectric ceramic layer.
A diaphragm is laminated on a flow path member having a plurality of liquid pressurizing chambers and a plurality of liquid discharge holes communicating with the plurality of liquid pressurizing chambers so as to cover the plurality of liquid pressurizing chambers. In addition, a liquid discharge head in which a common electrode, a piezoelectric ceramic layer, and a plurality of individual electrodes are stacked in this order on the diaphragm, and a displacement element is formed by the common electrode, the piezoelectric ceramic layer, and the individual electrodes. In addition, each of the individual electrodes has a power supply pad formed outside the liquid pressurizing chamber in the vicinity of the individual electrode when viewed from the stacking direction, and an outer side of the individual electrode when viewed from the stacking direction is the liquid pressurizing. It connects from the site | part located inside a chamber through several connection wires.
[Selection] Figure 1

Description

  The present invention relates to a liquid discharge head, and more particularly to a liquid discharge head mounted on an ink jet printer used for recording characters and images.

  In recent years, with the spread of personal computers and the development of multimedia, the use of ink jet recording apparatuses as recording apparatuses that output information to recording media is rapidly expanding. Such an ink jet recording apparatus is equipped with a print head, and this type of print head includes a heater as a pressurizing unit in an ink flow path filled with ink, and heats the ink with the heater. A thermal head system that boils, pressurizes ink with bubbles generated in the ink flow path, and discharges it as ink droplets from the ink discharge hole, and a part of the wall of the ink flow path filled with ink is bent by a displacement element A piezoelectric method is generally known that displaces, pressurizes the ink in the ink flow path mechanically, and discharges the ink as ink droplets from the ink discharge holes.

  For example, as shown in the partial cross-sectional view of FIG. 4A and the partial top view of FIG. 4B, the print head used in the ink jet recording apparatus using the piezoelectric method has a plurality of grooves formed in the liquid pressurizing chamber 123a. And a structure in which a piezoelectric actuator 116 is joined to a flow path member 123 in which a partition wall 123b is formed as a wall for partitioning each liquid pressurizing chamber 123a is proposed (for example, Patent Documents). 1.).

  The piezoelectric actuator 116 has a common electrode 112 formed on one main surface of the piezoelectric ceramic layer 113 and a plurality of individual electrodes 114 formed on the other main surface, and the main electrode 112 of the piezoelectric ceramic layer 113 is formed. A plurality of displacement elements 115 each including an individual electrode 114, a piezoelectric ceramic layer 113, and a common electrode 112 are provided on the surface. The piezoelectric actuator 116 is joined to the flow path member 123 such that the individual electrode 114 is positioned immediately above the liquid pressurizing chamber 123 a that is an opening of the flow path member 123.

  Then, a voltage is applied between the common electrode 113 and the individual electrode 114 to bend the displacement element 115 to pressurize the ink in the liquid pressurizing chamber 123 a, and the liquid that opens at the bottom surface of the flow path member 123. An ink droplet is ejected from the ejection hole 128.

  Further, as shown in FIG. 4B, a print head is provided in which a large number of individual electrodes 114 are arranged on the piezoelectric ceramic layer 113 at an equal pitch and a large number of displacement elements 115 are provided. This makes it possible to increase the speed and accuracy of the ink jet printer. A power supply pad 118 for applying a voltage is connected to the individual electrode 114 via a connection line 117.

When viewed from the stacking direction, the individual electrode 114 has a smaller area than the liquid pressurizing chamber 113a. There is a polarized piezoelectric active part on the liquid pressurizing chamber 123a and a non-active part that is not polarized so as to surround the piezoelectric active part. Further, since the restraining part 116a is provided on the outside thereof, the displacement element 115 can be displaced greatly. Be able to.
JP 2004-114342 A

  However, in the liquid discharge head described in Patent Document 1, after the piezoelectric actuator 116 and the flow path member 123 are joined, when the piezoelectric ceramic layer 113 sandwiched between the individual electrode 114 and the common electrode 112 is polarized, When polarization occurs, piezoelectric strain is generated in the piezoelectric ceramic layer 113 sandwiched between the individual electrode 114 and the common electrode 112 or between the connection line 117 and the common electrode 112, and stress is generated between the piezoelectric ceramic layer 113 and the connection. There was a problem that a crack occurred near the line 117.

  The crack occurred in the portion where the connection line 117 and the liquid pressurizing chamber 123a overlap each other when viewed from the stacking direction. The connection line 117 is connected to the flow path member 123 and straddles the boundary between the restraining portion 116a where the piezoelectric actuator 116 is not deformed and the non-restraining portion 116b where the piezoelectric actuator 116 is deformed because it is joined to the flow path member 123. This is because when the piezoelectric strain is generated in the piezoelectric ceramic layer 113 below the connection line 117 of the unconstrained portion 116b, stress is concentrated near the boundary between the restrained portion 116a and the unconstrained portion 116b.

  When the thickness T1 of the piezoelectric actuator 116 is as small as about 100 μm or less, if the polarization is performed before the piezoelectric actuator 116 is joined to the flow path member 123, the piezoelectric actuator 116 is greatly warped. Due to this warpage, the piezoelectric actuator 116 is damaged, or it is difficult to bond the piezoelectric actuator 116 to the flow path member 123 without being damaged.

  Accordingly, an object of the present invention is to provide a liquid discharge head capable of reducing cracks generated during polarization of a piezoelectric ceramic layer.

  The liquid discharge head of the present invention covers the plurality of liquid pressurization chambers on a flow path member having a plurality of liquid pressurization chambers and a plurality of liquid discharge holes communicating with the plurality of liquid pressurization chambers. A liquid in which a diaphragm is laminated, a common electrode, a piezoelectric ceramic layer, and a plurality of individual electrodes are laminated in this order on the diaphragm, and a displacement element is formed by the common electrode, the piezoelectric ceramic layer, and the individual electrode. In the discharge head, each of the individual electrodes has a power supply pad formed outside the liquid pressurizing chamber in the vicinity of the individual electrode as viewed from the stacking direction, and an outer side of the individual electrode viewed from the stacking direction. It is connected from the site | part located inside the said liquid pressurization chamber via the some connection line.

  Further, each of the liquid pressurizing chamber and the individual electrode is a substantially parallelogram when viewed from the stacking direction, and the plurality of connection lines are divided into two sides that form one vertex of the individual electrode. In addition, it is preferable that the outer side of the individual electrode and the outer side of the liquid pressurizing chamber at a portion to which the connection line is connected are parallel to each other.

  Moreover, it is preferable that the angle formed by the outer side of the liquid pressurizing chamber and both outer sides of the connection line is an obtuse angle or a right angle when viewed from the stacking direction.

  According to the liquid discharge head of the present invention, the plurality of liquid pressurization chambers are covered on the flow path member having the plurality of liquid pressurization chambers and the plurality of liquid discharge holes communicating with the plurality of liquid pressurization chambers. And a common electrode, a piezoelectric ceramic layer, and a plurality of individual electrodes are laminated in this order on the diaphragm, and a displacement element is formed by the common electrode, the piezoelectric ceramic layer, and the individual electrodes. Each of the individual electrodes is disposed on a power supply pad formed outside the liquid pressurizing chamber in the vicinity of the individual electrodes when viewed from the laminating direction. When the piezoelectric ceramic layer sandwiched between the individual electrode and the common electrode is polarized by being connected via a plurality of connection lines from the portion where the side is located inside the liquid pressurizing chamber, Sandwiched between connecting wire and common electrode Stress can be reduced caused by the piezoelectric strain of the piezoelectric ceramic layers. That is, for example, when a single connecting line is divided into two, the width of the connecting line can be made smaller than that of a single connecting line, and the stress generated at the outer side in the width direction of the connecting line can be reduced. can do.

  Further, each of the liquid pressurizing chamber and the individual electrode is a substantially parallelogram when viewed from the stacking direction, and the plurality of connection lines are divided into two sides that form one vertex of the individual electrode. And when the outer side of the individual electrode at the part to which the connection line is connected and the outer side of the liquid pressurizing chamber are parallel, first, the liquid pressurizing chamber and the individual electrode are If the liquid ejection elements are arranged in parallel, the liquid ejection elements can be densely arranged on the plane with high area efficiency. For example, when the liquid ejection head is used as the head of an ink jet printer, the distance between the liquid ejection elements is short. Recordable images. Furthermore, since the connection lines are connected to both sides of the apex of the liquid pressurizing chamber, the effective area where the piezoelectric strain is generated can be reduced, and as a result, crosstalk with the adjacent liquid pressurizing chamber is increased. Can be suppressed.

  Further, when viewed from the stacking direction, when the piezoelectric ceramic layer sandwiched between the outer side of the liquid pressurizing chamber and the outer side of the connection line is fixed on one side by the flow path member and the other side is polarized Since the piezoelectric ceramic layer sandwiched between the connection line and the common electrode is deformed, it is a portion where stress is particularly concentrated, but the outer side of the liquid pressurizing chamber and both outer sides of the connection line are formed. When the angles are both obtuse or right angle, the ratio of the piezoelectric ceramic layer that relaxes stress is larger than the piezoelectric ceramic layer that generates stress in this part, so the concentration of deformation stress can be relaxed and the ceramic layer is damaged. Can be suppressed.

  Hereinafter, an embodiment of a liquid discharge head of the present invention will be described in detail with reference to the drawings.

  FIG. 1A is a partial longitudinal sectional view showing a liquid discharge head of this embodiment, and FIG. 1B is a partial top view thereof.

  As shown in FIG. 1A, the liquid discharge head according to the present embodiment includes a flow path member having a plurality of liquid pressurizing chambers 23a and a plurality of liquid discharge holes 28 respectively communicating with the plurality of liquid pressurizing chambers 23a. A piezoelectric actuator 16 is stacked on the liquid pressure chamber 23 so as to cover the plurality of liquid pressurizing chambers 23a. In the piezoelectric actuator 16, a diaphragm 11, a common electrode 12, a piezoelectric ceramic layer 13, and a plurality of individual electrodes 14 are laminated in order from the side in contact with the flow path member 23. The common electrode 12, the piezoelectric ceramic layer 13, and the individual electrode 14 form one displacement element 15, and the number of the displacement elements 15 is provided in the individual electrode 14. Further, each individual electrode 14 is applied to a power supply pad 18 formed outside the liquid pressurizing chamber 23a in the vicinity of the individual electrode 14 as viewed from the stacking direction, and the outer side of the individual electrode 14 is liquid-pressed as viewed from the stacking direction. A plurality of connection lines 17 are connected from a portion located inside the chamber 23a.

  Here, the portion of the piezoelectric ceramic layer 13 bonded to the flow path member 23 is a restraining portion 16a that is not easily deformed even under stress, and the portion of the piezoelectric ceramic layer 13 that is not bonded to the flow path member 23 is The unconstrained portion 16b is deformable when subjected to stress.

  In the liquid discharge head according to the present invention, when the power supply pad 18 and the common electrode 12 are connected to an external control circuit or the like and a voltage is applied between them, the piezoelectric ceramic between the individual electrode 14 and the common electrode 12 is provided. When the layer 13 is displaced and the displacement element 15 is displaced, the volume of the liquid pressurizing chamber 23 a is changed, and thereby the liquid is ejected from the liquid ejection port 28.

  The flow path member 23 is obtained by a rolling method or the like, and the liquid discharge port 28 and the liquid pressurizing chamber 23a are provided by being processed into a predetermined shape by etching or the like. The flow path member 23 is made of, for example, at least one selected from the group consisting of an alloy mainly composed of Fe and Cr, an alloy mainly composed of Fe and Ni, and an alloy mainly composed of WC and TiC. It is desirable that it be formed. In particular, in applications where ink is ejected, it is desirable to be made of a material having excellent corrosion resistance against ink, and an alloy containing Fe and Cr as main components is more preferable.

  Moreover, the flow path member 23 can be produced by laminating thin plates having a thickness of about 30 to 100 μm, for example. Each thin plate has fine grooves and holes formed by methods such as etching and punching with a mold. By laminating a plurality of thin plates, the grooves and holes formed in each thin plate are liquid pressurized. The chamber 23a, the liquid discharge port 28, the liquid flow path (not shown), and the like can be combined.

  Examples of the material for the thin plate include a metal material such as a stainless steel plate, an aluminum plate, and a molybdenum plate, a semiconductor material such as silicon, or a ceramic material such as alumina and silicon carbide. It is preferable to use a metal material that is inexpensive and can be precisely processed.

  As shown in FIG. 1A, the piezoelectric actuator 16 includes a diaphragm 11, a common electrode 12, a piezoelectric ceramic layer 13 and individual electrodes 14, a connection line 17, and a power feeding pad 18. The common electrode 12, the piezoelectric ceramic layer 13 and the individual electrode 14, the connection line 17, and the power feeding pad 18 are laminated in this order.

  The common electrode 12, the individual electrode 14, and the power supply pad 18 constitute an electrode of the piezoelectric actuator 16, and the individual electrode 14 and the power supply pad 18 form a pair, and as shown in FIG. A plurality of surfaces are formed. As a result, a plurality of displacement elements 15 configured by sandwiching the piezoelectric ceramic layer 13 between the common electrode 12 and the individual electrode 14 are formed. Therefore, the piezoelectric actuator 16 has an asymmetric structure in the thickness direction.

  The thickness T1 of the piezoelectric actuator 16 is 100 μm or less, preferably 50 μm or less. Thereby, since a large displacement can be obtained, it is possible to realize high-efficiency driving at a low voltage. The lower limit value of the thickness T1 of the piezoelectric actuator 16 has a sufficient mechanical strength, and is 10 μm, preferably 20 μm, and more preferably 30 μm in order to prevent breakage during handling and operation. As described above, the piezoelectric actuator 16 having such a thin thickness and an asymmetric structure in the thickness direction may cause a problem when the piezoelectric ceramic layer 13 is polarized. The thickness T1 is the thickness of the portion including the piezoelectric ceramic layer 13, the common electrode 12, and the diaphragm 11. The thickness of the individual electrode 14 is not included in the thickness T1.

  If polarization is performed before the piezoelectric actuator 16 and the flow path member 23 are joined, the piezoelectric actuator 16 is greatly warped. Due to this warpage, the piezoelectric actuator 16 is damaged or difficult to be bonded to the flow path member 23 without being damaged. Therefore, when polarization is performed after joining the piezoelectric actuator and the flow path member, piezoelectric strain is generated in the piezoelectric ceramic layer 13 sandwiched between the individual electrode 14 and the common electrode 12 or the connection line 17 and the common electrode 12 when polarization is performed. There is a problem that a tensile stress is generated between the piezoelectric ceramic layer 13 and the surrounding piezoelectric ceramic layer 13 and a crack is generated in the piezoelectric actuator 16. Even the piezoelectric actuator 16 having such a configuration will be described later. As described above, by setting the connection line 17 in a predetermined state, cracks are unlikely to occur and the bonding reliability of the individual electrode 12 can be kept high.

  When a voltage is applied between the individual electrode 14 and the common electrode 12 via the power supply pad 18 and the connection line 17, the piezoelectric ceramic layer 13 at a portion sandwiched between the individual electrode 14 and the common electrode 12 to which the voltage is applied is displaced. To do. Specifically, the displacement of the piezoelectric ceramic layer 13 in the direction perpendicular to the stacking direction is suppressed by the vibration plate 11, so that the displacement element 15 bends in the stacking direction. As a result, the piezoelectric actuator 16 is driven as a unimorph type actuator.

  The piezoelectric actuator 16 is preferably driven under the condition that the ratio E / Ec between the electric field intensity E during driving and the electric field intensity Ec of the piezoelectric ceramic layer 13 is smaller than 1. Thereby, the piezoelectric actuator 16 can be stably driven for a long time. On the other hand, if the ratio E / Ec is greater than 1, the contribution of domain rotation increases, and the displacement is likely to deteriorate.

  The diaphragm 11 is preferably made of piezoelectric ceramics, and the piezoelectric ceramic layer 13 is preferably made of piezoelectric ceramics having substantially the same composition as the diaphragm 11. Here, the piezoelectric ceramic means a ceramic exhibiting piezoelectricity, for example, a Bi layered compound, a tungsten bronze structure material, a perovskite structure compound of an alkali Nb acid compound, lead zirconate titanate (PZT) or titanium containing Pb. Examples include perovskite structural compounds containing lead oxide (PT), barium titanate (BT), etc. Among these, lead zirconate titanate (PZT) and lead titanate (PT) containing Pb are electrodes (common). This is preferable in that the wettability with the electrode 12, the individual electrode 14, the connection line 17 and the power supply pad 18) is enhanced and the adhesion strength with the electrode is enhanced.

In addition, lead zirconate titanate compounds such as lead zirconate titanate (PZT), which is a crystal containing Pb as the A site constituent element and Zr and Ti as the B site constituent element, have a higher piezoelectric constant. preferable for obtaining a stable piezoelectric sintered body having a d ₃₁ (the piezoelectric actuator 16).

  In particular, it is preferable that the composition ratio of the A site and the B site of the piezoelectric ceramics (that is, the piezoelectric ceramic layer 13 and the diaphragm 11) such as a lead zirconate titanate compound is {A site / B site} ≦ 1.

The piezoelectric ceramic layer 13 and the diaphragm 11 preferably include at least one selected from Sr, Ba, Ni, Sb, Nb, Zn, Yb, and Te. Thereby, a more stable piezoelectric sintered body (piezoelectric actuator 16) can be obtained. As such a piezoelectric ceramic layer 13 and the diaphragm 11, for example, Pb (Zn _1/3 Sb _2/3 ) O ₃ and Pb (Ni _1/2 Te _1/2 ) O ₃ are dissolved as subcomponents. Can be illustrated.

  The piezoelectric ceramic layer 13 and the diaphragm 11 particularly preferably contain an alkaline earth element as an A site constituent element. As the alkaline earth element, Ba and Sr are preferable in that a high displacement can be obtained, and the inclusion of 0.02 to 0.08 mol of Ba and 0.02 to 0.12 mol of Sr is mainly a tetragonal crystal composition. It is advantageous to obtain a large displacement in the case of the composition of

Examples of such a piezoelectric ceramic layer 13 and the vibration plate 11, for example, _{Pb 1-x-y Sr x} B ay (Zn 1/3 Sb 2/3) a (Ni 1/2 Te 1/2) bZr 1-a _−b−c Ti _c O ₃ + α wt% Pb _1/2 NbO ₃ (0 ≦ x ≦ 0.14, 0 ≦ y ≦ 0.14, 0.05 ≦ a ≦ 0.1, 0.002 ≦ b ≦ 0.01, 0.44 ≦ c ≦ 0.50, α = 0.1 to 1.0) and the like.

  The piezoelectric ceramic layer 13 and the diaphragm 11 which are laminated piezoelectric ceramics preferably have an average crystal grain size of 2.5 μm or less. Thereby, substitution substitution solution of Ag to piezoelectric ceramics, such as PZT, can be controlled more effectively. In order to make the crystal grain size within the above range, for example, the composition ratio of the A site and the B site during the preparation of the PZT raw material may be set to 1 or less. The average crystal grain size can be determined by, for example, an intercept method by observing with a scanning electron microscope (SEM).

  The thickness T2 of the piezoelectric ceramic layer 13 is about 5 to 50 μm, preferably about 10 to 30 μm. Thereby, the displacement element 15 can show a high displacement. On the other hand, when the thickness is less than 5 μm, the mechanical strength is lowered, and there is a risk of breaking during handling and operation. When the thickness is more than 50 μm, the displacement may be lowered, which is not preferable. The thickness T3 of the diaphragm 11 is 5 to 50 μm, preferably about 10 to 30 μm.

  The common electrode 12 is not particularly limited as long as it has conductivity. For example, Au, Ag, Pd, Pt, Cu, Al, or an alloy thereof can be used. Specifically, for example, an Ag—Pd alloy can be exemplified. Moreover, the thickness of the common electrode 12 needs to be an extent which has electroconductivity and does not prevent a displacement, and is about 0.5-5 micrometers normally, Preferably it is 1-4 micrometers. Moreover, when producing by simultaneous baking, it is preferable that the common electrode 12 consists of a silver-palladium alloy containing 60 to 85 volume%, preferably 70 to 80 volume% of silver. Thereby, the diffusion amount of Ag can be reduced and the intragranular destruction can be suppressed.

  The individual electrode 14 and the connection line 17 are not particularly limited as long as they have conductivity similar to the common electrode 12 described above. For example, Au, Ag, Pd, Pt, Cu, Al, and alloys thereof Etc. can be used. And the thickness of the individual electrode 14 needs to be a grade which has electroconductivity and does not prevent a displacement, for example, about 0.1-2 micrometers, Preferably it is 0.1-0.5 micrometer, More preferably, it is 0.00. It should be 1 to 0.3 μm. The thickness of the connection line 17 is preferably 1 μm or more in order to suppress the occurrence of disconnection or the like, and when the piezoelectric actuator 16 is manufactured, a part where the connection line 17 is formed and a part where the connection line 17 is not formed Is preferably 5 μm or less in order to suppress deformation. A more preferable thickness is 1.5 to 3 μm.

  The power supply pad 18 is not particularly limited as long as it has conductivity similar to the common electrode 12 and the individual electrode 14 described above. For example, Au, Ag, Pd, Pt, Cu, Al, and alloys thereof Etc. can be used. Further, the height of the power supply pad 18 needs to be a level that is conductive and does not cause a problem in bonding, and is, for example, about 1 to 20 μm, preferably 5 to 15 μm.

  It is important that a plurality of connection lines 17 are connected between the individual electrodes 14 and the power supply pads 18. This is because, when the piezoelectric actuator 16 and the flow path member 23 are joined, the portion located at the boundary between the restraint portion 16a joined to the flow path member 23 and the non-restraint portion 16b not joined to the flow path member 23, that is, The stress at the time of polarization concentrates on the connection line 17 on the unconstrained portion 16b and the periphery thereof. In order to alleviate this stress concentration, it is effective to reduce the effective piezoelectric area in which piezoelectric distortion occurs during polarization by dividing the connection line 17 into a plurality of lines. And the width per connection line 17 is preferably 70 μm or less, and more preferably 50 μm or less. This is because when the width of the connection line 17 is reduced, the effective piezoelectric area is reduced, and the stress is reduced. In order to increase the connection reliability, the width of each connection line 17 is preferably 10 μm or more, more preferably 20 μm or more.

  Further, even if an abnormality occurs in one of the connection lines 17, the connection line 17 is not disconnected due to a plurality of connections.

  It is important that the individual electrode 14 and the connection line 17 are connected at a portion located inside the liquid pressurizing chamber 23a of the individual electrode 14 when viewed from the stacking direction. By adopting such a structure, there is a portion where the individual electrode 14 is formed inside the liquid pressurizing chamber 23a when viewed from the stacking direction. That is, since the non-restraining portion 16b is formed around the individual electrode 14, the displacement of the liquid ejection element 15 can be increased. In order to further increase the displacement of the liquid ejection element 15, it is preferable to increase the proportion of the individual electrodes 14 positioned inside the liquid pressurizing chamber 23a. Specifically, the ratio of the length of the outer side of the individual electrode 14 in contact with the unconstrained portion 16b to the length of the outer side of the individual electrode 14 may be increased. The ratio is preferably 75% or more. In particular, it is preferable that all the individual electrodes 14 are formed inside the liquid pressurizing chamber 23a.

  Further, the liquid pressurizing chamber 23a and the individual electrode 14 are substantially parallelograms as viewed from the stacking direction, and the outer side of the individual electrode 14 and the outer side of the liquid pressurizing chamber 23a to which the connection line 17 is connected. The sides are preferably parallel. Thereby, the liquid ejection elements 15 can be densely arranged on the plane with high area efficiency. For example, when the liquid ejection head is used as the head of an ink jet printer, the distance between the liquid ejection elements 15 is short, so that a dense image is recorded. it can. At this time, forming the power supply pad 18 and the vicinity of the liquid pressurizing chamber 23a from the outer side of the liquid pressurizing chamber 23a in the vicinity of the size of the liquid pressurizing chamber 23a and shortening the length of the connecting line 17 can improve the area efficiency. It is preferable at the point which raises, and the point which improves the connection reliability of the connection line 17. FIG.

  In addition, as described above, the ratio of the outer side of the individual electrode 14 that is in contact with the piezoelectric ceramic layer 13 that is an inactive part and is a non-constrained part of the outer side of the individual electrode 14 is 75%. preferable. That is, it is preferable that three of the four outer sides of the individual electrode 14 are formed inside the liquid ejection element 23a.

  Furthermore, it is preferable that the plurality of connection lines 17 be divided and connected to two sides forming one vertex of the individual electrode 14. As a result, it is possible to reduce the effective area where the connection line 17 generates piezoelectric strain per side of the liquid pressurizing chamber 23a, and as a result, the crosstalk with the adjacent liquid pressurizing chamber 23a increases. Can be suppressed.

  Here, FIG. 2A, which is a partially enlarged top view of FIG. 1A, and FIG. 2 (2), which is a partially enlarged top view of a liquid ejection head according to another embodiment of the present invention, regarding the shape of the connection line 17. This will be described with reference to b).

  In FIG. 2A, the individual electrode 14 and the power supply pad 18 are connected by two connection lines 17, and a liquid pressurizing chamber 23 a and a liquid discharge port 28 are provided immediately below the individual electrode 16. Then, inside the liquid pressurizing chamber 23a, angles 17A and 17B formed by the outer side of the liquid pressurizing chamber 23a and the outer side of the connection line 87 are at right angles.

  In FIG. 2B, the individual electrode 94 and the power supply pad 98 are connected by two connection lines 97, and a liquid pressurizing chamber 93 a and a liquid discharge port 94 are provided immediately below the individual electrode 96. Although not shown, this liquid discharge head has the same cross-sectional structure as FIG. The angle 97A formed between the outer side of the liquid pressurizing chamber 94a and the outer side of the connection line 97 is about 150 degrees inside the liquid pressurizing chamber 94a, and the outer side of the liquid pressurizing chamber 94a and the outer side of the connection line 97. The angle 97B formed by is about 30 degrees.

  In the liquid discharge head shown in FIG. 2B, since there are a plurality of connection lines 97, the stress applied to the piezoelectric ceramic layer can be reduced, but the outer side of the liquid pressurizing chamber 94 a and the outer side of the connection line 97. Is an acute angle of about 30 degrees, so that one side is the restraining portion 16a joined and fixed by the flow path member, and the other side is connected to the connection line 97 and the common electrode (not shown) when polarized. When the piezoelectric ceramic layer sandwiched between the two layers is deformed, the deformation stress is concentrated at the acute angle portion, so that cracking of the piezoelectric ceramic layer is relatively likely to occur.

  On the other hand, in FIG. 2A, since the angles 17A and 17B formed by the outer side of the liquid pressurizing chamber 23a and the outer side of the connection line 17 are at right angles, the stress during polarization is less likely to concentrate. Further, the generation of cracks in the piezoelectric ceramic layer 13 can be suppressed.

  3A to 3I show a liquid discharge head according to another embodiment of the present invention. 3A to 3I are partial top views showing individual electrodes, connection lines, power supply pads, a liquid pressurizing chamber, and a liquid discharge port of one liquid discharge element, respectively. Although not shown, each liquid discharge head has the same cross-sectional structure as that shown in FIG.

  In each of the liquid ejection heads shown in FIGS. 3A to 3I, the individual electrodes and the connection lines are connected to each other at a site inside the liquid pressurizing chamber as viewed from the stacking direction. Thereby, since there is an unrestrained portion between the individual electrode and the outer side of the liquid pressurizing chamber, the displacement of each liquid ejection element can be increased. In addition, since the individual electrodes and the liquid pressurizing chambers are similar parallel, substantially parallelograms, and the corresponding sides are parallel, the liquid discharge elements are arranged on a plane in an area-efficient manner between the liquid discharge elements. The distance can be shortened.

In each of the liquid discharge heads of FIGS. 3A to 3H, the individual electrodes are formed inside the liquid pressurizing chamber as viewed from the stacking direction. Thereby, the displacement of each liquid ejection element can be further increased. In FIG. 5A, there are three connection lines, the line width of the connection lines can be further narrowed, and the stress during polarization can be further reduced.

  3 (a), (b), (e), (h), and (i), each of the individual electrode and the liquid pressurizing chamber is an approximately parallelogram having one acute angle, and the power supply pad is not attached. By arranging in a direction extending from the center of gravity of the substantially parallelogram to the direction of the acute angle vertex of the substantially parallelogram, the liquid ejecting element is more aligned in a direction perpendicular to the line connecting the acute angle vertices of the substantially parallelogram. It can be formed at a short distance.

  3 (c), (e) to (f), (i), the angle formed between the outer side of the liquid pressurizing chamber and both outer sides of the connection line inside the liquid pressurizing chamber as viewed from the stacking direction. Since both are perpendicular or obtuse, the stress can be further reduced. In FIG. 3 (h), the stress concentration is alleviated because the angle between the outer side of the liquid pressurizing chamber and the outer side of the connection line is an obtuse angle inside the liquid pressurizing chamber as viewed from the stacking direction. However, since the line width of the connection line of the unconstrained portion is increased in order to make both angles obtuse, the generated stress itself is increasing. In order to reduce the overall stress applied to the unconstrained portion, it is necessary to reduce the line width of the connection line and to make both the outer sides of the liquid pressurizing chamber and the outer sides of the connection line at right angles. More preferred.

  Next, the manufacturing method of the piezoelectric actuator 16 described above will be described in the case where lead zirconate titanate (PZT) is used as the piezoelectric ceramic. First, a raw material powder mainly composed of piezoelectric ceramics such as a lead zirconate titanate compound (for example, a powder having a purity of 99% and an average particle diameter of 1 μm or less) is prepared, and a slurry is prepared using the raw material powder. A green sheet is produced using the same. As a method for producing the green sheet, for example, a well-known tape forming method such as a doctor blade method or a roll coater can be employed.

  Next, a metal pattern that becomes the common electrode 12 after firing is formed on the main surface of the green sheet that becomes the diaphragm 11 after firing among the produced green sheets. Examples of the method for forming the metal pattern include a screen printing method, but other known methods can also be adopted.

  Next, these green sheets are laminated to form a laminated body, and this laminated body is pressed and adhered under a pressure of 10 to 100 MPa to obtain a laminated molded body. In the pressure contact, the pressure contact is performed in a state where a piezoelectric ceramic having substantially the same composition as the green sheet and a constraining sheet made of an organic composition are arranged on both surfaces or one surface of the laminate. Is preferred. Thus, the effect of reducing the curvature of a laminated body can be expected by suppressing the shrinkage of the outer green sheet with the restraint sheet.

Next, after cutting the laminated molded body into a predetermined shape, the binder is removed at about 500 ° C. and fired at about 900 to 1100 ° C. to produce a laminated piezoelectric body incorporating the common electrode 12. The green density before sintering is preferably 4.5 g / cm ² or more. As a result, firing at a lower temperature is possible, and when the green density is further increased, the evaporation of Pb can be suppressed.

  A conductive paste is printed on the surface of the laminated piezoelectric material by a method such as a screen printing method to form a metal pattern to be the individual electrode 14 and heat-treated at about 600 to 850 ° C. Further, after that, a metal pattern serving as a power feeding pad is formed by aligning with the individual electrode 14 and heat-treated at about 500 to 800 ° C. Thereby, the piezoelectric actuator 16 before polarization can be obtained. In addition, when sintering the individual electrode 14 and the electric power feeding pad 18 simultaneously, you may select the common electrode material sintered at the same temperature.

  As shown in FIG. 1A, the displacement element 15 and the liquid pressurizing chamber 23a are aligned with each other, that is, the common electrode 12 and the individual electrode 14 are arranged immediately above the liquid pressurizing chamber 23a. The piezoelectric actuator 16 and the flow path member 23 are joined to each other. Specifically, in the liquid discharge head, a plurality of liquid pressurizing chambers 23a are arranged in parallel, and the pre-polarization described above is provided on the flow path member 23 in which the partition walls 16b are formed as walls that partition the liquid pressurizing chambers 23a. The piezoelectric actuator 16 is joined. The bonding is performed so that the vibration plate 11 is in contact with the space of the liquid pressurizing chamber 23a. More specifically, the individual electrodes 14 of the displacement element 15 correspond to the liquid pressurizing chambers 23a. Be joined.

  Here, when the piezoelectric actuator 16 is joined to the surface of the flow path member 23, it is preferable that compressive stress is applied to the piezoelectric actuator 16 and the piezoelectric ceramic layer 13 of the piezoelectric actuator 16 is polarized in this state. Specifically, the joining includes a heating step and a cooling step. In the cooling step, a compressive stress is applied to the piezoelectric actuator 16, and the piezoelectric ceramic layer 13 of the piezoelectric actuator 16 is polarized in this state.

  The joining can be laminated and bonded through an adhesive layer, for example. As the adhesive layer, a well-known layer can be used, but it does not affect the piezoelectric actuator 16 and the flow path member 23, and an epoxy resin, phenol resin, polyphenylene ether having a thermosetting temperature of 100 to 250 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group consisting of resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric actuator 16 and the flow path member 23 can be heated and bonded (that is, a heating step), and when returning from the bonding temperature to room temperature (that is, cooling). In the step), compressive stress is applied to the piezoelectric actuator 16.

Here, it is preferable that the thermal expansion coefficient of the flow path member 23 is larger than the thermal expansion coefficient of the piezoelectric actuator 16. Thus, when the piezoelectric actuator 16 is bonded to the surface of the flow path member 23, the piezoelectric actuator 16 can be brought into a state where compressive stress is applied when the temperature returns from the bonding temperature to room temperature. Specifically, the thermal expansion coefficient of the flow path member 23 is 6 × 10 ^{−6 to} 17 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the piezoelectric actuator 16 is 6 × 10 ⁻⁶ to 8 × 10 ⁻⁶ / The thermal expansion coefficient of the flow path member 23 is preferably larger than the thermal expansion coefficient of the piezoelectric actuator 16 within this range. The thermal expansion coefficient can be set to a predetermined value by adjusting the compositions of the piezoelectric actuator 16 and the flow path member 23. The thermal expansion coefficient is a value obtained by measuring in accordance with JIS R1618.

  Next, in this state, that is, when the joining is completed and the piezoelectric actuator 16 is fixed to the flow path member 23 and a compressive stress is applied to the piezoelectric actuator 16, a polarization voltage is applied between the individual electrode 14 and the common electrode 12. The liquid discharge head according to the present embodiment can be obtained by applying and polarizing the piezoelectric ceramic layer 13. The polarization condition may be arbitrarily selected according to the composition and thickness of the piezoelectric actuator 16, and is not particularly limited. For example, a direct current voltage of about 0.5 to 5 kV / mm is 1 Polarization may be performed by applying for about 10 minutes.

  When a voltage is applied between the individual electrode 14 and the common electrode 12 from a drive circuit (not shown), the ink in the liquid pressurizing chamber 23a corresponding to the displaced displacement element 15 is pressurized and applied, and the piezoelectric actuator By oscillating 16, ink in the liquid pressurizing chamber 23 a is ejected as ink droplets from the liquid ejection hole 18 opened in the bottom surface of the flow path member 23. Since this liquid discharge head is excellent in displacement characteristics, the feature of high-speed and high-precision discharge is obtained. As a result, a liquid discharge head suitable for high-speed printing can be provided. Further, by mounting the liquid discharge head of the present invention on a printer, for example, in a printer including an ink tank that supplies ink to the liquid discharge head and a recording paper transport mechanism for printing on recording paper, High-speed and high-precision printing can be easily achieved as compared with the prior art.

  As mentioned above, although one Embodiment of this invention was shown, it cannot be overemphasized that this invention is applicable to what was changed and improved in the range which does not deviate from the summary of this invention, without being limited to Embodiment mentioned above. For example, in the above-described embodiment, the case where the diaphragm 11 and the piezoelectric ceramic layer 13 are each constituted by one layer has been described. However, the present invention is not limited to this, and the diaphragm 11 and the piezoelectric ceramic layer 13 are piezoelectric. At least one of the ceramic layers 13 may be composed of a plurality of layers. In this case, the thickness of the piezoelectric actuator 16 can be easily adjusted. Moreover, you may form wiring circuit layers, such as an electrode, inside.

  The diaphragm 11 is preferably made of substantially the same material as the piezoelectric ceramics of the piezoelectric ceramic layer 13, but the piezoelectric ceramic compositions of the diaphragm 11 and the piezoelectric ceramic layer 13 do not have to be completely identical, and the present invention. In other words, the composition of the piezoelectric actuator 16 may be different within a range in which cracks are unlikely to occur in the piezoelectric actuator 16 and the occurrence of disconnection between the individual electrode 14 and the power supply pad 18 can be reduced.

  After joining the piezoelectric actuator 16 to the surface of the flow path member 23, the thermal expansion coefficient of the flow path member 23 is made larger than the thermal expansion coefficient of the piezoelectric actuator 16 as a method of applying a compressive stress to the piezoelectric actuator 16. The method for setting the predetermined state has been described, but the predetermined state may be set by adjusting the thermal expansion coefficient and the curing temperature of the adhesive used for bonding.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to a following example.

  First, a piezoelectric ceramic powder containing lead zirconate titanate having a purity of 99% or more was prepared as a raw material. Next, butyl methacrylate as an aqueous binder, polycarboxylic acid ammonium salt as a dispersant, and isopropyl alcohol and pure water as a solvent were added to the powder and mixed to obtain a slurry. This slurry was applied in a sheet shape on a carrier film by a roll coater method to produce a green sheet. This green sheet was used for both the piezoelectric ceramic layer and the diaphragm.

  Subsequently, the common electrode paste containing Ag—Pd alloy powder was printed on the surface of the green sheet for the diaphragm with a thickness of 5 μm, and then dried to form the common electrode 12. Further, a green sheet for a piezoelectric ceramic layer was laminated on a green sheet for a diaphragm with the surface on which the common electrode 12 was printed facing upward, and was pressed to obtain a laminate.

  The laminate is degreased at 500 ° C. in the atmosphere, and then sintered at 1000 ° C. in an atmosphere of 99% oxygen or more for 5 hours to be sintered, and the laminate composed of the piezoelectric ceramic layer 13, the diaphragm 11, and the common electrode 13. A sintered body was obtained. Next, the individual electrodes 14 and the connection lines 17 shown in FIG. 1B (the enlarged view is FIG. 2A) were formed on the surface of the piezoelectric ceramic layer 13. The line width of the connectivity 17 was 50 μm. The individual electrode 14 and the connection line 17 are formed by applying Au paste by screen printing and then baking it in the atmosphere at 700 ° C. Then, the power supply pad 18 is aligned so as to be connected to the connection line 17, and the screen Ag paste was applied by printing. This was baked in the atmosphere of 600 ° C. Finally, the lead wire was connected to the power supply pad 18 with solder to obtain the piezoelectric actuator 16.

  The piezoelectric actuator 16 obtained above was joined to the flow path member 23. The flow path member 23 is formed by joining thin stainless steel plates in which fine grooves and holes are formed by etching, and communicates with a plurality of liquid pressurizing chambers 23a and liquid pressurizing chambers 23a partitioned by a partition wall 23b. The plurality of liquid discharge holes 28 are provided. The joining was performed such that the displacement element 15 was disposed immediately above the liquid pressurizing chamber 23a, and a liquid discharge head was obtained. The stainless steel thin plates and the piezoelectric actuator 16 and the flow path member 23 were joined using an epoxy resin adhesive having a thermosetting temperature of 150 ° C. As a result, a compressive stress is applied to the piezoelectric actuator 16.

  After joining with the flow path member 23, a DC voltage of 3 kV / mm is applied in a state where compressive stress is applied to the piezoelectric actuator 16 (the thermal expansion coefficient of the flow path member 23 is larger than the thermal expansion coefficient of the piezoelectric actuator 16). The piezoelectric ceramic layer 13 was polarized by applying for 5 minutes.

  In the same manner as in the above example, a liquid discharge head in which the shapes of the individual electrodes, connection lines, and power supply pads were as shown in FIGS. 2B and 4B was manufactured and polarized. Note that the line width of the connection line 97 of the liquid discharge head shown in FIG. 2B is 50 μm, and the line width of the connection line 117 of the liquid discharge head shown in FIG. 4B is 100 μm.

  The presence or absence of cracks in the piezoelectric ceramic layer and the diaphragm directly above 100 liquid pressurizing chambers of each liquid discharge head was observed and evaluated with a 100 × optical microscope.

  The occurrence of cracks is 0 in the liquid discharge head shown in FIG. 2A, 2 in the liquid discharge head shown in FIG. 2B, and 2 in the shape of individual electrodes, connection lines, and power supply pads. In the liquid discharge head shown in FIG.

  In the liquid discharge head shown in FIG. 2A and FIG. 2B within the scope of the present invention, the line width of each connection line can be narrowed by using a plurality of connection lines. It was possible to reduce the generated stress and reduce the occurrence of cracks.

  In particular, in the liquid discharge head shown in FIG. 2A, the angle formed between the outer side of the liquid pressurizing chamber and the outer side of the connection line is not an acute angle when viewed from the stacking direction. Since the stress applied to the piezoelectric ceramic layer and the diaphragm at the corner formed by the side and the outer side of the connecting line can be reduced, the generation of cracks is eliminated.

  On the other hand, in the liquid ejection head shown in FIG. 4B outside the scope of the present invention, the line width is widened and cracks are frequently generated in order to ensure connection reliability.

(A) is a partial longitudinal cross-sectional view which shows the liquid discharge head of one Embodiment of this invention, (b) is the partial top view. (A) is a partially enlarged top view of the liquid ejection head of FIG. 1, and (b) is a partially enlarged top view showing a liquid ejection head of another embodiment of the present invention. (A)-(h) is a partial top view which shows the liquid discharge head of other embodiment of this invention. (A) is the fragmentary longitudinal cross-section which shows the conventional liquid discharge head, (b) is the partial top view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 111 ... Diaphragm 12, 112 ... Common electrode 13, 113 ... Piezoelectric ceramic layer 14, 96, 114 ... Individual electrode 15, 115 ... Displacement element 16, 116 ... Piezoelectric Actuators 16a, 116a ... restraining portions 16b, 116b ... restraining portions 17, 97, 117 ... connecting lines 17A, 97A ... angle formed by the outer side of the liquid pressurizing chamber and the outer sides of the connecting lines 17B 97B ... An angle formed by the outer side of the liquid pressurizing chamber and the outer side of the connecting line 18, 98, 118 ... Power supply pad 23, 113 ... Flow path member 23a, 93a, 123a ... Pressure chambers 23b, 123b ... partition walls 28, 94, 128 ... liquid ejection holes T1 ... thickness of piezoelectric actuator T2 ... thickness of piezoelectric ceramic layer T3 ... thickness of diaphragm

Claims (3)

On the flow path member having a plurality of liquid pressurizing chambers and a plurality of liquid discharge holes communicating with the plurality of liquid pressurizing chambers, a vibration plate is laminated so as to cover the plurality of liquid pressurizing chambers, A liquid discharge head in which a common electrode, a piezoelectric ceramic layer, and a plurality of individual electrodes are laminated in this order on a vibration plate, and a displacement element is formed by the common electrode, the piezoelectric ceramic layer, and the individual electrodes. Each of the electrodes is a power supply pad formed outside the liquid pressurizing chamber when viewed from the stacking direction in the vicinity of the individual electrode, and an outer side of the individual electrode is positioned inside the liquid pressurizing chamber when viewed from the stacking direction. A liquid ejecting head, wherein the liquid ejecting head is connected from a position thereof via a plurality of connecting lines. Each of the liquid pressurizing chamber and the individual electrode has a substantially parallelogram shape when viewed from the stacking direction, and the plurality of connection lines are divided and connected to two sides forming one vertex of the individual electrode. The liquid discharge head according to claim 1, wherein an outer side of the individual electrode at a portion to which the connection line is connected and an outer side of the liquid pressurizing chamber are parallel to each other. 3. The liquid ejection head according to claim 1, wherein an angle formed between an outer side of the liquid pressurizing chamber and both outer sides of the connection line is an obtuse angle or a right angle when viewed from the stacking direction.

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