JP5260900B2 - Liquid discharge head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid discharge head having suppressed driving deterioration. <P>SOLUTION: The liquid discharge head has a vibrating plate laminated on a flow path member having a plurality of liquid pressurizing rooms and a plurality of liquid ejecting holes communicating with the plurality of liquid pressurizing rooms so as to cover the plurality of liquid pressurizing rooms, the vibrating plate having a common electrode, a piezoelectric ceramic layer, and a plurality of driving electrodes thereon laminated in this order, wherein the plurality of driving electrodes are formed so as to face the plurality of liquid pressurizing rooms respectively, while a driving part disposed between the driving electrodes and the common electrode in the piezoelectric ceramic layer is polarized vertically to a principal plane of the piezoelectric layer, and further, a non-driving part not disposing between the driving electrodes and the common electrode in the piezoelectric layer which faces the liquid pressurizing rooms on seeing from the laminating direction is polarized slanting to the principal plane of the piezoelectric layer. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a liquid discharge head, and particularly can be suitably used for a liquid discharge apparatus for ejecting micro droplets or delivering a micro liquid or a print head mounted on an ink jet printer used for printing characters and images. The present invention relates to a liquid discharge head.

  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. The recording apparatus is widely used not only for commercially available small-sized printers but also for industrial applications such as the formation of electronic circuits, the production of color filters for liquid crystal displays, and the production of organic EL displays.

  In an ink jet recording apparatus, the ink jet head is moved in the main scanning direction, and the ink jet head is driven according to the recording information while moving the recording paper, the substrate, and the like in the sub scanning direction intersecting the main scanning direction. Thus, recording is performed by intermittently ejecting ink droplets from the nozzle openings of the inkjet head. For example, in the case of a small printer, characters and images are recorded on the surface of recording paper or the like. In the case of an industrial recording apparatus, an electronic circuit, a color filter for a liquid crystal display, a light emitting cell for an organic EL display, and the like are formed on the surface of a substrate or the like.

  In such an ink jet recording apparatus, a liquid ejecting apparatus for ejecting liquid is mounted as a print head. This type of print head includes a heater as a pressurizing means in an ink flow path filled with ink. The ink is heated by the heater to boil, and the ink is added by bubbles generated in the ink flow path. And a thermal head system that ejects ink droplets from the liquid ejection holes, and a part of the walls of the ink channel filled with ink is bent and displaced by a displacement element, and the ink in the ink channel is mechanically pressurized. A piezoelectric method for discharging ink droplets from a liquid discharge hole is generally known.

  An inkjet head used in an inkjet printer using a piezoelectric method has a structure in which an actuator 51 is provided on a flow path member 53 as shown in FIG. 5A (for example, Patent Document 1, 2). The flow path member 53 has a plurality of liquid pressurizing chambers 53 a partitioned by a plurality of partition walls 53 b, and the opening of the liquid pressurizing chamber 53 a is formed to be covered by the piezoelectric actuator 51.

  The piezoelectric actuator 51 includes a common electrode 54, a piezoelectric ceramic layer 55, and a drive electrode 56 stacked in this order on a vibration plate 52, and includes a drive electrode 56, a common electrode 54, and a piezoelectric ceramic layer 55 sandwiched therebetween. A plurality of displacement elements 57 are formed. The piezoelectric ceramic layer 55 sandwiched between the drive electrode 56 and the common electrode 54 is polarized perpendicular to the main surface of the piezoelectric ceramic layer 55.

  Further, as shown in FIG. 5B, the drive electrodes 56 are arranged in a matrix on the surface of the piezoelectric ceramic layer 55, and the drive electrodes 56 are arranged directly above the liquid pressurizing chamber 53a. A lead electrode 56b for connecting to an external wiring circuit (not shown) is connected to the drive electrode 56a. The common electrode 54 is also electrically connected to a common electrode connection portion 54a for connecting to an external wiring circuit.

  In the ink jet head as described above, a voltage is applied between the common electrode 54 and the predetermined drive electrode 56 to displace the piezoelectric ceramic layer 55 immediately below the drive electrode 56, so that the displacement region 57a corresponds to the corresponding liquid application. By changing the volume of the pressure chamber 53 a and pressurizing the ink in the liquid pressurizing chamber 53 a, ink droplets can be ejected from the liquid ejection port 58 opened on the bottom surface of the flow path member 53.

The driving electrode 56a has a smaller area than the liquid pressurizing chamber 53a when viewed from the stacking direction. In other words, the piezoelectric ceramic layer 55 has a polarized drive portion 55a directly below the drive electrode 56 and an inactive portion 55b that is not polarized so as to surround the drive portion 55a. Therefore, the displacement element 57 can obtain a large displacement due to the restraining portion 55c that is not displaced.
JP 11-34321 A Japanese Patent Laid-Open No. 11-34323

  However, in the liquid ejection head described in Patent Document 1 or 2, when a voltage is applied between the common electrode 54 and the drive electrode 56 to repeatedly drive the displacement element 57, external stress is applied to the non-drive portion 55b. Therefore, the included ferroelectric domain wall moves (domain switching), and the piezoelectric ceramic expands and contracts. When the number of times of driving becomes very large, the movement of the domain wall proceeds due to the stress between the driving unit 55a and the non-driving unit 55b generated by the expansion and contraction of the porcelain due to the inverse piezoelectric effect of the piezoelectric body itself, and the displacement element 57 However, there is a possibility that the problem of drive deterioration that the displacement amount is reduced occurs.

  If drive deterioration occurs in the displacement element 57, the amount and speed of the liquid ejected from the liquid ejection head change, which causes a problem that an appropriate image cannot be recorded.

  An object of the present invention is to provide a liquid discharge head in which drive deterioration is suppressed.

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 discharge head in which a diaphragm is stacked and a common electrode, a piezoelectric ceramic layer, and a plurality of drive electrodes are stacked in this order on the diaphragm, wherein the plurality of drive electrodes are respectively placed in the plurality of liquid pressurizing chambers. Polarization only for polarization, which is formed so as to oppose and does not overlap the common electrode on the surface or inside of the piezoelectric ceramic layer facing the periphery of the liquid pressurizing chamber when viewed from the stacking direction. includes a use electrodes, wherein the driving portion sandwiched by said common electrode and the drive electrode of the piezoelectric ceramic layers is polarized perpendicularly to the main surface of the piezoelectric ceramic layer, further wherein when viewed from the lamination direction fluid Addition Wherein the non-driving portions that are not sandwiched between the common electrode and the drive electrode of the chamber opposite to the piezoelectric ceramic layer are polarized at an angle to the main surface of the piezoelectric ceramic layer.

  Further, it is preferable that the polarization electrode and the drive electrode are formed in the same layer, and the distance between them is equal to or less than the thickness of the piezoelectric ceramic layer.

  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 driving electrodes are stacked in this order on the diaphragm, wherein the plurality of driving electrodes are the plurality of liquid pressurizing chambers. And the driving part sandwiched between the driving electrode and the common electrode in the piezoelectric ceramic layer is polarized perpendicularly to the main surface of the piezoelectric ceramic layer, and is further laminated. Of the piezoelectric ceramic layer facing the liquid pressurizing chamber as viewed from the direction, a non-driving portion that is not sandwiched between the driving electrode and the common electrode is polarized obliquely with respect to the main surface of the piezoelectric ceramic layer. To be Ri, non-driving portion is inhibited from domain rotation by the stress occurs, change the displacement characteristics of the non-driving portion can be suppressed that the drive deterioration occurs.

  Further, when the electrode for polarization is provided on the surface or inside of the piezoelectric ceramic layer facing the periphery of the liquid pressurizing chamber when viewed from the stacking direction, it is not necessary to align the electrode with high accuracy during polarization, The non-driving part can be easily polarized in an oblique direction.

  In addition, when the polarization electrode and the common electrode do not overlap when viewed from the stacking direction, the charge does not concentrate on the overlapping portion of the polarization electrode and the common electrode facing each other at the time of polarization. The polarization of the non-driving part can be increased.

  Further, when the polarization electrode and the drive electrode are formed in the same layer and the distance between them is equal to or less than the thickness of the piezoelectric ceramic layer, the non-drive portion between the polarization electrode and the drive electrode The diagonal polarization can be made stronger.

  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 of a liquid discharge head according to the present embodiment, and FIG. 1B is a top view thereof. FIG. 1A is a cross-sectional view taken along line XX in FIG. As shown in FIGS. 1A and 1B, this liquid discharge head includes a plurality of liquid pressurizing chambers 3a and a plurality of liquid discharge holes 8 communicating with the plurality of liquid pressurizing chambers 3a. 3, the piezoelectric actuator 1 is laminated so as to cover the plurality of liquid pressurizing chambers 3 a. In the piezoelectric actuator 1, a common electrode 4, a piezoelectric ceramic layer 5, and a plurality of drive electrodes 6 are stacked on the diaphragm 2 in this order. The flow path member 3 is laminated on the diaphragm 2 side of the piezoelectric actuator 1. The plurality of drive electrodes 6 are directly above the plurality of liquid pressurizing chambers 3a. A plurality of drive electrodes 6 are arranged two-dimensionally and regularly (that is, in a matrix) on the surface of the piezoelectric ceramic layer 5.

  The piezoelectric actuator 1 is formed with a plurality of displacement elements 7 composed of a drive electrode 6, a common electrode 4, and a piezoelectric ceramic layer 5 a sandwiched between the drive electrode 6 and the common electrode 4. Thereby, when a voltage is applied between the drive electrode 6 and the common electrode 4, the piezoelectric ceramic layer 5 a at a portion sandwiched between the drive electrode 6 and the common electrode 4 to which the voltage is applied is displaced. Specifically, when a drive electrode is applied to the drive electrode 6, the displacement in the direction orthogonal to the stacking direction is suppressed by the diaphragm 2, so that the displacement element 7 bends in the stacking direction. That is, the piezoelectric actuator 1 is a unimorph type actuator.

  Here, in the piezoelectric actuator 1, it is important that the piezoelectric ceramic layer 5 b positioned between the adjacent displacement elements 7 is polarized in an oblique direction with respect to a direction perpendicular to the main surface of the piezoelectric ceramic layer 5. is there. Here, being polarized obliquely means not being in a non-polarized state and not being polarized parallel to a direction perpendicular to the main surface of the piezoelectric ceramic layer 5. That is, the oblique polarization here includes the case where the polarization is in a direction parallel to the main surface of the piezoelectric ceramic layer. Thereby, the drive deterioration of a displacement is suppressed. The reason for this is presumed as follows.

  That is, the piezoelectric ceramic layer 5 in the piezoelectric actuator 1 is divided into the following three parts. The portion of the piezoelectric ceramic layer 5a sandwiched between the drive electrode 6 and the common electrode 4 is an active portion that is polarized perpendicular to the main surface of the piezoelectric ceramic layer 5, and is referred to herein as the drive portion 5a. When a voltage is applied between the drive electrode 6 and the common electrode 4, the drive unit 5a changes its size due to piezoelectricity and is displaced. Next, the piezoelectric ceramic layer 5c joined to the flow path member 3 via the diaphragm 2 and the common electrode 4 is a restraining portion 5c and is a portion that is not displaced because it is fixed by the flow path member 3. There is a partial piezoelectric ceramic layer 5b in the liquid pressurizing chamber 3a that does not overlap the drive electrode 6 when viewed from the stacking direction. Here, the piezoelectric ceramic layer 5b is referred to as a non-driving portion 5b. The non-driving unit 5b has conventionally been an inactive unit that has not been subjected to polarization processing.

  Since the non-driving part 5b is not the restraint part 5c and is not fixed to the flow path member 3, it is displaced when the displacement element 7 is displaced. For this reason, in the conventional liquid ejection head in which the non-driving unit 5b is not polarized, the domain of the non-driving unit 5b may rotate due to the stress of the displacement when the number of displacements of the displacement element 7 increases.

  On the other hand, when the non-driving part 5b is polarized in a predetermined oblique direction, the crystal orientation (c-axis crystal orientation) of the non-driving part 5b is parallel to the main surface of the piezoelectric ceramic layer 5 (that is, the thickness of the diaphragm 2). Align in the direction close to (perpendicular to the direction). As a result, domain rotation of the non-driving unit 5b, which is a cause of a decrease in displacement at the time of driving, is suppressed, and driving deterioration of displacement can be suppressed even when unimorph vibration is repeated.

  When the piezoelectric actuator 1 is a unimorph actuator, the active portion 5a sandwiched between the common electrode 4 and the drive electrode 6 is polarized in the stacking direction.

The thickness T ₁ of the piezoelectric actuator 1 is 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less in terms of increasing the amount of displacement. Further, the lower limit value of the thickness T ₁ is 20 μm or more, preferably 25 μm or more, more preferably 30 μm or more in view of mechanical strength that does not cause damage during handling or operation.

  The same number of drive electrodes 6 as the liquid pressurizing chambers 3a are formed immediately above the liquid pressurizing chambers. The drive electrode connection portion 6a is connected to the drive electrode 6, and the drive electrode connection portion 6a is connected to an external wiring circuit (not shown) on the restraint portion 5c when viewed from the stacking direction. Moreover, the common electrode 4 and the common electrode connection part 4a are connected by a via electrode (not shown), and the common electrode connection part 4a is connected to an external wiring circuit (not shown). That is, when a voltage is applied between the common electrode connection portion 4a and any one of the drive electrode connection portions 6a from the external wiring circuit, the drive electrode 6 electrically connected to the drive electrode portion 6a to which the voltage is applied is included. The displaced displacement element 7 is displaced.

  The polarization electrode 9 is an electrode for obliquely polarizing the non-driving portion 5b described above. Polarization of the non-driving portion 5b can be performed by pressing an external electrode on the piezoelectric ceramic layer 5 from the outside during polarization. Therefore, the polarization electrode 9 is not always necessary. By forming 9, it is not necessary to align the external electrode with high precision during polarization, and the non-driving portion 5 b can be easily polarized in an oblique direction. As will be described later, since the degree of polarization in the oblique direction of the non-driving portion 5b varies depending on the distance between the polarization electrode 9 and the drive electrode 6, in order to increase the accuracy of polarization, the polarization electrode 9 is It is preferable to form.

  It is preferable that the polarization electrode 9 does not overlap the common electrode 4 when viewed from the stacking direction. If there is a portion overlapping the common electrode 4, the electric field tends to concentrate relatively on the portion, and thus it may be difficult to polarize the non-driving portion 5 b in an oblique direction. Since the polarization electrode 9 does not overlap the liquid pressurizing chamber when viewed from the stacking direction, the displacement of the vibration plate 2 and the piezoelectric ceramic layer 5 is not affected, so that no consideration is required when designing the liquid discharge head. Therefore, design becomes easy. When viewed from the stacking direction, the polarization electrode 9 overlaps the liquid pressurizing chamber, whereby the distance between the drive electrode 6 and the polarization electrode 9 can be reduced, and the non-drive portion 5b is polarized in the oblique direction. Can be strengthened.

  The thicknesses of the common electrode 4 and the common electrode connection portion 4a are 0.5 μm or more, preferably 1 μm or more. Thereby, the rigidity of the piezoelectric actuator 1 can be improved and the effect of suppressing warpage deformation can be enhanced. The thickness of the drive electrode 6 and the drive electrode connection portion 6a is 2 μm or less, preferably 1 μm or less, and the thickness of the common electrode connection portion 4a is 5 μm or more, preferably 10 μm or more.

  The common electrode 4 and the common electrode connection portion 4a are preferably formed of the same material. For example, it is preferable to use a metal such as Au, Ag, Cu, Cr, Pd, or Pt, or an alloy containing at least one of these as a main component, and an Ag—Pd alloy, Furthermore, it is more preferable to add a small amount of the same material as the piezoelectric ceramic layer 5 (for example, a perovskite crystal structure type piezoelectric ceramic).

  As the via electrode and the common electrode connecting portion 4a, for example, a metal such as Au, Ag, Cu, Cr, Pd, Pt, or an alloy containing at least one of these as a main component can be used, preferably Au or A metal (or alloy) mainly composed of Ag is preferable.

  The drive electrode 6 and the drive electrode connection portion 6a are preferably formed of the same material. For example, it is preferable to use a metal such as Au, Ag, Cu, Cr, Pd, or Pt, or an alloy containing at least one of these as a main component, and high conductivity can be obtained even if the layer is thinned. In particular, it is preferable to use Au.

The piezoelectric ceramic layer 5 is composed of a ceramic exhibiting piezoelectricity, for example, a piezoelectric material having a perovskite crystal structure such as a lead zirconate titanate compound [PbZrTiO ₃ compound (PZT)], a lead titanate compound, a barium titanate compound, or the like. A layered compound, a tungsten bronze structure substance, or a perovskite structure compound of an Nb acid alkali compound can be preferably used.

Among those exemplified above, lead zirconate titanate (PZT) and lead titanate (PT) containing Pb enhance the wettability with the electrodes (common electrode 4, drive electrode 6) and increase the adhesion strength with the electrodes. It is suitable in terms of increasing. Furthermore, lead zirconate titanate-based 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 more absolute value. preferable for obtaining a stable piezoelectric sintered body having a high piezoelectric constant d ₃₁ (the piezoelectric actuator 1).

  In particular, it is preferable that the composition ratio of the A site and the B site of piezoelectric ceramics (that is, the piezoelectric ceramic layer 5 and the diaphragm 2) such as a lead zirconate titanate compound is {A site / B site} ≦ 1. As a result, the crystal form of the piezoelectric ceramic layer 5 becomes a tetragonal crystal. Therefore, when the piezoelectric ceramic layer 5b positioned between the displacement elements 7 adjacent to each other is polarized in a predetermined oblique direction, the piezoelectric ceramic of the non-driving part around the driving part The crystal orientation (c-axis crystal orientation) of the layer 5b may be aligned in the substrate surface direction (that is, the direction perpendicular to the thickness direction of the diaphragm 2).

  Various types of ceramics, metals, or composites thereof can be used for the diaphragm 2, but the diaphragm 2 is also capable of increasing the bonding strength with the piezoelectric ceramic layer 5 and reducing the thermal expansion coefficient difference. It is desirable to use substantially the same material as the piezoelectric ceramic layer 5. For example, piezoelectric materials such as PT and PZT, and ceramics such as alumina and aluminum nitride can be used. Among these, in order to reduce the difference in thermal expansion coefficient, it is preferable to use substantially the same material as the piezoelectric body used for the piezoelectric ceramic layer 5. In general, the diaphragm 2 can be obtained by firing simultaneously with the common electrode 4, the piezoelectric ceramic layer 5, and the like.

The piezoelectric ceramic layer 5 and the diaphragm 2 preferably include at least one of Sr, Ba, Ni, Sb, Nb, Zn, Yb, and Te. As a result, a more stable piezoelectric sintered body (piezoelectric actuator 1) can be obtained. As such a piezoelectric ceramic layer 5 and the diaphragm 2, 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.

  Moreover, it is desirable that the piezoelectric ceramic layer 5 and the diaphragm 2 further 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. This composition is advantageous in obtaining a large displacement.

Examples of such a piezoelectric ceramic layer 5 and the vibration plate 2, for example, _{Pb 1-x-y Sr x} Ba y (Zn 1/3 Sb 2/3) a (Ni 1/2 Te 1/2) b Zr 1- _ab-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 thickness of the piezoelectric ceramic layer 5 is preferably 30 μm or less in terms of voltage reduction, and preferably has a mechanical strength that does not break during handling or operation, and is preferably in the range of 10 to 20 μm. It is good. The thickness of the diaphragm 2 is 5 to 50 μm, preferably about 10 to 30 μm. Thereby, the piezoelectric actuator 1 can be made into a unimorph type.

  The piezoelectric ceramic layer 5 and the diaphragm 2 preferably have a c-axis lattice constant of 0.4085 nm to 0.4100 nm. In order to adjust the lattice constant of the c axis within the above range, for example, the Ag ratio of Ag / Pd of the common electrode 4 is set to 90% by volume or less, or the composition ratio of A site and B site at the time of PZT raw material preparation is 1 The following should be done.

  Next, the manufacturing method of the piezoelectric actuator 1 described above will be described in the case where lead zirconate titanate (PZT) is used as the piezoelectric ceramic. First, a lead zirconate titanate compound (for example, a powder having a purity of 99% and an average particle diameter of 1 μm or less), a lead titanate compound (for example, a powder having a purity of 99% and an average particle diameter of 1 μm or less), a barium titanate compound (for example, a purity of 99 %, A powder having an average particle diameter of 1 μm or less) is prepared as a main component, and these are mixed to prepare a slurry. A green sheet is produced using the obtained slurry. As a method for producing the green sheet, for example, a known tape forming method such as a doctor blade method or a roll coater can be employed.

  Next, among the produced green sheets, a conductive paste coating layer is formed on the main surface of the green sheet that becomes the diaphragm 2 after firing, and a metal pattern that becomes the common electrode 4 after firing is formed. Examples of the method for forming the metal pattern include a screen printing method, but other known methods can also be adopted.

  On the other hand, a via hole for filling a via conductor is formed in another green sheet that becomes the piezoelectric ceramic layer 5 after firing. As a method for drilling a via hole, for example, a known method such as punching or laser processing can be employed. The obtained via hole is filled with a desired via conductor. The via conductor may be filled into the via hole before firing or after firing. In other words, via conductors can be filled before firing and fired at the same time as the green sheet. However, before the via conductors are formed, they are fired, the via holes of the sintered body are filled with a conductor paste, and heat treatment is performed. A conductor can also be formed.

  Next, these green sheets are laminated and brought into close contact to obtain a laminated molded body. The laminated molded body is cut into a predetermined shape and then fired at about 900 to 1100 ° C. to produce a laminated piezoelectric body incorporating the common electrode 4 and the via electrode.

  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 drive electrode 6 and the polarization electrode 9 and heat-treated at about 600 to 850 ° C. Finally, a metal pattern to be the common electrode connection portion 4a and the drive electrode connection portion 6a is formed by a screen printing method or the like and heat-treated at about 600 to 850 ° C. Thereby, the piezoelectric actuator 1 before polarization can be obtained. The common electrode connection portion 4a, the drive electrode 6, the drive electrode connection portion 6a, and the polarization electrode 9 can be produced by a single heat treatment by a method such as using the same conductor paste.

  Next, the polarization method of the piezoelectric actuator 1 before polarization obtained above will be described in detail with reference to the drawings. 2A and 2B are partially enlarged longitudinal sectional views of the liquid discharge head according to the present embodiment shown in FIG. 1A, and are schematic explanatory views for explaining a polarization method of the piezoelectric actuator. is there. 2 (a) and 2 (b), the same or equivalent parts as those in FIG. 1 (a) described above are denoted by the same reference numerals, and description thereof is omitted. A in each figure shows a direction perpendicular to the main surface of the piezoelectric ceramic 5.

  In FIG. 2A, the non-driving unit 5b is polarized simultaneously with the polarization of the driving unit 5a. That is, the common electrode 4 and the polarization electrode 9 are set to the same potential, and a polarization voltage is applied to the drive electrode 6 with respect to them. As a result, the drive unit 5a is polarized in a direction perpendicular to the main surface of the piezoelectric ceramic 5 as in B, and at the same time, the non-drive unit 5b is in a direction perpendicular to the main surface of the piezoelectric ceramic 5 in C. Polarized at an angle.

  In FIG. 2B, first, the non-driving unit 5b is polarized. The common electrode 4 and the drive electrode 6 are set to the same potential, and a polarization voltage is applied to the polarization electrode 9 with respect to them. As a result, the non-driving portion 5b is polarized obliquely with respect to the direction perpendicular to the main surface of the piezoelectric ceramic 5 as indicated by D. Subsequently, a polarization voltage is applied to the drive electrode 6 with respect to the common electrode 4. Thereby, the drive part 5a is polarized in a direction perpendicular to the main surface of the piezoelectric ceramic 5 like B. At this time, it is preferable that the polarization electrode 9 is not connected to the outside but floated in potential.

  FIG. 2 (c) is obtained by changing the pattern of the common electrode 14 from FIGS. 2 (a) and 2 (b), and the polarization electrode 19 and the common electrode 14 are not overlapped when viewed from the stacking direction. . The pattern of the common electrode 14 is shown in FIG. Polarization electrode. The liquid discharge head shown in FIG. 2C can be polarized by either the polarization method shown in FIG. 2A or the polarization method shown in FIG.

  FIG. 2C shows a polarization method similar to that shown in FIG. That is, first, the non-driving unit 15b is polarized. The common electrode 14 and the drive electrode 16 are set to the same potential, and a polarization voltage is applied to the electrode 19 for polarization. Thereby, the non-driving portion 15b is polarized obliquely with respect to the direction perpendicular to the main surface of the piezoelectric ceramic 15 as shown by D. At this time, since the polarization electrode 19 and the common electrode 14 do not overlap each other when viewed from the stacking direction, the polarization D in the oblique direction can be performed more effectively. Subsequently, a polarization voltage is applied to the drive electrode 16 with respect to the common electrode 14. As a result, the drive unit 15 a is polarized in a direction perpendicular to the main surface of the piezoelectric ceramic 15 like B. At this time, it is preferable that the polarization electrode 19 is not connected to the outside but floated in potential.

  FIG. 3A shows the same liquid ejection head as that shown in FIG. 1A except that the polarization electrode 29 is formed on the surface of the piezoelectric ceramic 25 bonded to the diaphragm 22. FIG. 3A shows a polarization method. That is, first, the non-driving unit 25b is polarized. The common electrode 24 and the drive electrode 26 are set to the same potential, and a polarization voltage is applied to the electrode 29 for polarization. As a result, the non-driving portion 25b is polarized obliquely with respect to the direction perpendicular to the main surface of the piezoelectric ceramic 25 as in E. At this time, since the polarization electrode 29 and the common electrode 24 do not overlap each other when viewed from the stacking direction, the polarization E in the oblique direction can be performed more effectively. Subsequently, a polarization voltage is applied to the drive electrode 26 with respect to the common electrode 24. As a result, the drive unit 25 a is polarized in a direction perpendicular to the main surface of the piezoelectric ceramic 25 as shown by B. At this time, it is preferable that the polarization electrode 29 is not connected to the outside but floated in potential.

  FIG. 3B shows the same liquid ejection head as that shown in FIG. 1A except that the polarization electrode 39 is formed inside the piezoelectric ceramic 35. FIG. 3B shows a polarization method. That is, first, the non-driving part 35b is polarized. The common electrode 34 and the drive electrode 36 are set to the same potential, and a polarization voltage is applied to the polarization electrode 39 with respect to them. As a result, the non-driving portion 35b is polarized obliquely with respect to the direction perpendicular to the main surface of the piezoelectric ceramic 35, such as F. At this time, since the polarization electrode 39 and the common electrode 34 do not overlap each other when viewed from the stacking direction, the polarization F in the oblique direction can be performed more effectively. Subsequently, a polarization voltage is applied to the drive electrode 36 with respect to the common electrode 34. As a result, the drive unit 35a is polarized in a direction perpendicular to the main surface of the piezoelectric ceramic 35 as shown in FIG. At this time, the polarization electrode 39 is preferably connected to the outside without being connected to the outside.

  The above polarization conditions may be arbitrarily selected according to the composition and thickness of the piezoelectric actuators 1 and 11, and are not particularly limited. For example, a DC voltage of about 1 to 5 kv / mm is 1 Polarization may be performed by applying for about 30 minutes.

  The method of polarization in the oblique direction has been described above, but the method is not particularly limited to this.

  As shown in FIG. 1, this liquid discharge head is provided with a piezoelectric actuator 1 on a flow path member 3 and connected to a flexible wiring circuit (not shown) for connecting to the external circuit on the piezoelectric actuator 1. ing. In the flow path member 3, a plurality of liquid pressurizing chambers 3a are formed by the partition walls 3b, and an ink discharge port 8 communicates with each liquid pressurizing chamber 3a.

  The flow path member 3 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 3a, the ink discharge port 8, an ink 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. However, it is preferable to use a metal material that is inexpensive and can be precisely processed.

  Next, for example, an epoxy resin or the like is used so that the displacement element 7 and the liquid pressurizing chamber 3a are aligned, that is, the common electrode 4 and the drive electrode 6 are arranged directly above the liquid pressurizing chamber 3a. The piezoelectric actuator 1 and the flow path member 3 are joined. Further, a flexible wiring board (not shown) is provided for connecting to an external circuit with respect to the piezoelectric actuator 1, and individual terminals (not shown) constituting the flexible wiring board, the common electrode connection portion 4a. And the drive electrode connecting portion 6a.

  The liquid discharge head having the above-described configuration is a liquid discharge head in which the drive deterioration of the displacement is suppressed because the non-driving unit 5b can be prevented from being polarized by the reverse piezoelectric action due to the stress at the time of driving.

  The liquid discharge head can be driven using an inexpensive IC. 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. Furthermore, by mounting this liquid discharge head on a printer, for example, in a printer having an ink tank that supplies ink to this liquid discharge head and a recording paper transport mechanism for printing on recording paper, compared to conventional printers. High-speed and high-precision printing can be easily achieved.

  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 2 and the piezoelectric ceramic layer 5 are each configured as one layer has been described. However, the present invention is not limited to this, and the diaphragm 2 and the piezoelectric ceramic layer 5 are not limited thereto. The ceramic layer 5 may be composed of a plurality of layers. In this case, the thickness of the piezoelectric actuator 1 can be easily adjusted. Moreover, you may form wiring circuit layers, such as an electrode, inside.

  Further, as described above, the diaphragm 2 is preferably made of substantially the same material as the piezoelectric ceramic of the piezoelectric ceramic layer 5, but the piezoelectric ceramic compositions of the diaphragm 2 and the piezoelectric ceramic layer 5 are completely identical. The composition may be different as long as the effect of the present invention, that is, the liquid discharge head in which the variation in the liquid discharge amount is small and the drive deterioration of the displacement is suppressed can be obtained.

  Further, although the case where the flow path member 3 and the piezoelectric actuator 1 are laminated and bonded via the adhesive layer has been described, a liquid discharge head in which the flow path member and the piezoelectric actuator are integrally formed, that is, a flow path integrated piezoelectric actuator. (A flow path integrated porcelain) may be used.

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

  A liquid discharge head having a cross section shown in FIG. 2C and a structure of each internal layer shown in FIGS. 3A to 3C was manufactured. The schematic structure of the cross section is the same as that shown in FIG.

First, the piezoelectric actuator 11 is manufactured. A slurry of piezoelectric material was prepared by mixing lead zirconate titanate (PbZrTiO ₃ ) powder having a purity of 99% or more and an average particle size of 0.5 μm together with a binder and an organic solvent. Using this slurry, a green sheet having a thickness of 30 μm was prepared by a roll coater method. This green sheet becomes the vibration plate 12 and the piezoelectric ceramic layer 15 after firing.

  Separately, a conductor paste containing Ag—Pd alloy powder was prepared. Among the obtained green sheets, conductive paste was printed on the surface of the green sheet to be the vibration plate 12 by screen printing to form metal patterns to be the common electrodes 14.

  Next, via holes were punched out at predetermined positions on another green sheet to be the piezoelectric ceramic layer 15 to form via holes. Then, a green sheet to be the piezoelectric ceramic layer 15 is laminated on the green sheet to be the diaphragm 12 and heated and pressed to form a base laminate, and this base laminate is cut to form a laminate, and degreasing. After the treatment, firing was performed in an oxygen atmosphere at 1000 ° C. for 2 hours to produce a piezoelectric actuator body.

  Next, a metal paste mainly composed of Au is screen-printed on the surface of one piezoelectric ceramic layer 15 side of the piezoelectric actuator body and baked at 750 ° C., so that the drive electrode 16, the drive electrode connection portion 16 a, and the polarization A working electrode 19 was formed. Furthermore, after filling a via hole with a metal paste containing Ag as a main component to form a via electrode, the same conductor paste is screen-printed and baked at 600 ° C. to produce a common electrode connection portion 14a. The piezoelectric actuator 11 was obtained. Here, the thickness of the piezoelectric ceramic layer 15 is 25 μm, and the distance between the polarization electrode 19 and the drive electrode 16 is 20 μm. The plurality of displacement elements in the piezoelectric actuator 11 are arranged in a matrix on the main surface of the diaphragm.

  Next, the piezoelectric actuator 11 was joined to the flow path member 13 with an epoxy adhesive to obtain the liquid discharge head shown in FIG.

  The piezoelectric actuator 11 of the liquid discharge head obtained above was polarized by the method described below. First, the common electrode 14 and the drive electrode 16 were set to the same potential, and a polarization voltage was applied to the polarization electrode 19 to polarize the non-drive portion 15b in an oblique direction. The outline of polarization is in a state D in FIG. Next, after performing the polarization process, the drive unit 15 a was polarized perpendicularly to the main surface of the piezoelectric ceramic layer 15 by applying a polarization voltage between the common electrode 14 and the drive electrode 16. The outline of the polarization is in the state C in FIG. For each polarization condition, a DC voltage of 4 kv / mm was applied for 10 minutes.

  About the liquid discharge head (sample No. 1) obtained above, the crystal orientation degree of the non-driving portion 15b of the piezoelectric ceramic layer 15 before and after polarization was evaluated in the following direction.

  The substrate surface direction is measured by a local X-ray diffractometer, and is a direction perpendicular to the main surface of the piezoelectric ceramic layer 15 based on the diffraction peak intensity ratio of the (002) and (200) planes of PZT (that is, the diaphragm before firing). The c-axis orientation degree was calculated and obtained. Further, the degree of crystal orientation of the PZT substrate (that is, the diaphragm after firing) of the driving unit 15a and the non-driving unit 15b in the piezoelectric ceramic layer was determined by the following formula a. Next, the degree of crystal orientation of the non-driving portion 15b was evaluated by the above method. As a result, the degree of crystal orientation of the non-driving part 15b before polarization was 58%, and the degree of crystal orientation of the non-driving part 15b after polarization was 25%. As the degree of crystal orientation is smaller, the crystal orientation (c-axis crystal orientation) of the piezoelectric ceramic layer of the non-driving unit 15b is aligned with the substrate surface direction (that is, the direction perpendicular to the main surface of the piezoelectric ceramic layer 15). Means that. The measurement site of the non-driving unit 15b includes a central portion of the thickness of the piezoelectric ceramic layer in the thickness direction, and an outer side of the liquid pressurizing chamber 13a and a central portion of the driving electrode 16 when viewed from the stacking direction in the horizontal direction. did.

c-axis orientation (%) = I (002) / [I (002) + I (200) × 100] Formula a
However, I (002) is the X-ray diffraction peak intensity of the PZT (002) plane, and I (200) is the X-ray diffraction peak intensity of the PZT (200) plane.

  The displacement amount of the piezoelectric actuator 11 in this liquid discharge head was evaluated by the following method. The results are shown in Table 1.

  In addition to the X-ray diffraction described above, the domain polarization direction may be measured for each domain using a piezoelectric response microscope or the like. In this way, not only the angle of the domain but also the direction can be measured.

  A displacement amount was measured with a laser Doppler vibrometer when a DC voltage of 25 V was applied between the common electrode and the drive electrode, and driving was performed with a sin waveform having a frequency of 10 kHz at room temperature. The displacement reduction rate (%) was calculated by applying the displacement amount at each driving frequency to the formula: [1- (displacement amount at each driving frequency / displacement amount at the initial driving)] × 100. The displacement amount at the initial stage of driving means a displacement amount in 6 cycles of driving.

  Subsequently, sample No. 1 was prepared in the same manner as in Example 1 except that the common electrode was formed as a solid pattern. 2 liquid ejection heads were produced. The crystal orientation degree of the non-driving part before polarization of the piezoelectric actuator of this liquid discharge head was 58%, and the crystal orientation degree of the non-driving part after polarization was 42%.

  Further, sample No. 1 was formed in the same manner as in Example 1 except that the common electrode was formed in a solid pattern and the distance between the polarization electrode and the drive electrode was 30 μm. 3 liquid ejection heads were produced. The crystal orientation degree of the non-driving part before polarization of the piezoelectric actuator of this liquid discharge head was 58%, and the crystal orientation degree of the non-driving part after polarization was 45%.

  Next, as Comparative Example 1, Sample No. 4 liquid discharge heads were produced. This liquid discharge head was manufactured in the same manner as in Example 1 except that the non-driving portion 15b of the piezoelectric ceramic layer 15 was not polarized in a predetermined oblique direction. With respect to this liquid discharge head, the crystal orientation of the non-driving portion 15b of the piezoelectric ceramic layer 15 before and after polarization was evaluated in the same manner as in Example 1. As a result, the crystal orientation of the non-driving portion 15b before polarization was 58%. The degree of crystal orientation of the non-driving part 15b after polarization was 58%.

The displacement amount of the piezoelectric actuator in this liquid discharge head was evaluated in the same manner as in Example 1. The results are shown in Table 1.

As is apparent from Table 1, the sample No. In the liquid discharge heads 1 to 3, the drive deterioration was suppressed, and the displacement drop after 10 ¹¹ times drive was 3% or less. On the other hand, driving deterioration of 20% or more occurred in the sample N0.4 in which the non-driving portion was not obliquely polarized. Sample No. Sample No. 3 than The displacement deterioration of the liquid discharge head 2 is small. This is because the polarization in the oblique direction of the non-driving portion is increased because the distance between the polarization electrode and the driving electrode is shorter than the thickness of the piezoelectric ceramic layer. And sample no. Sample no. The displacement deterioration of one liquid discharge head is less. This is because the polarization in the oblique direction of the non-driving portion is further increased because there is no common electrode facing the polarization electrode.

(A) is a schematic sectional drawing which shows the liquid discharge head concerning one Embodiment of this invention, (b) is the top view. It is a schematic explanatory drawing for demonstrating the polarization method of the liquid discharge head concerning one Embodiment of this invention. 4A and 4B are schematic top views of each layer of a liquid discharge head according to another embodiment of the present invention, in which FIG. 5A is a piezoelectric ceramic layer, FIG. 5B is a diaphragm, and FIG. It is a schematic explanatory drawing for demonstrating the polarization method of the liquid discharge head concerning another one Embodiment of this invention.

It is a graph which shows the relationship between the displacement fall rate in an Example, and the frequency | count of a drive.
(A) is a schematic sectional drawing which shows the conventional liquid discharge head, (b) is the upper surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11, 21, 31 ... Piezoelectric actuator 2, 12, 22, 32 ... Diaphragm 3, 13, 22, 33 ... Flow path member 3a, 13a ... Liquid pressurization chamber 3b, 13b ... partition 4, 14, 24, 34 ... common electrode 4a, 14a ... common electrode connection 5, 15, 25, 35 ... piezoelectric ceramic layer 5a, 15a, 25a, 35a ... drive Part (piezoelectric ceramic layer)
5b, 15b, 25b, 35b ... non-driving part (piezoelectric ceramic layer)
5c, 15c, 25c, 35c ... restraining part (piezoelectric ceramic layer)
6, 16, 26, 36 ... drive electrode 6a, 16a ... drive electrode connecting portion 7, 7a, 17, 17a ... displacement element 8 ... liquid discharge port 9, 19, 29, 39 ...・ Polarization electrode

Claims (2)

A vibration plate 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. A liquid discharge head in which a common electrode, a piezoelectric ceramic layer, and a plurality of drive electrodes are laminated in this order on a plate, wherein the plurality of drive electrodes are formed to face the plurality of liquid pressurizing chambers, respectively. A piezoelectric electrode for polarization only that does not overlap with the common electrode on the surface or inside of the piezoelectric ceramic layer facing the periphery of the liquid pressurizing chamber when viewed from the stacking direction , The driving portion sandwiched between the driving electrode and the common electrode in the layer is polarized perpendicularly to the main surface of the piezoelectric ceramic layer, and further, the piezoelectric facing the liquid pressurizing chamber when viewed from the stacking direction. Sera A liquid discharge head characterized in that the non-driving portions that are not sandwiched between the common electrode and the drive electrode is polarized at an angle to the main surface of the piezoelectric ceramic layers of the click layer. The liquid discharge head according to claim 1, wherein the polarization electrode and the drive electrode are formed in the same layer, and a distance between them is equal to or less than a thickness of the piezoelectric ceramic layer.

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