JP2005074722A - Ink jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording head exhibiting excellent ink ejection performance and reliability. <P>SOLUTION: In the ink jet head, a piezoelectric actuator 21 having a plurality of individual electrodes 23 arrange on the surface of a piezoelectric ceramic layer 22 is fixed onto a channel member 31 arranged with a plurality of ink channels 33 having an ink ejection opening 32 while arranging the positions of the ink channels 33 and the land part 23b of the individual electrodes 23. A driving IC 41 is mounted on the piezoelectric actuator 21 and the land part 23b is bonded to the driving IC 41 through a power supply electrode 51 formed of an anisotropic conductive resin film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording head used in an ink jet recording apparatus, and more particularly to an ink jet recording head having excellent ink ejection performance and reliability.

  In recent years, with the spread of personal computers and the development of multimedia, as a recording device that outputs information to a recording medium, it is equipped with a piezoelectric actuator that can easily increase the number of gradations and color and can keep running costs low. The use of inkjet recording devices is rapidly expanding.

  Such a recording apparatus is equipped with an ink jet recording head. As this ink jet recording head, for example, as shown in FIG. 7, a piezoelectric actuator 91 is laminated and adhered on a flow path member 81 in which a plurality of ink flow paths 83 having ink discharge ports 82 are arranged. The piezoelectric actuator 91 includes, for example, laminated piezoelectric ceramic layers 92 and 92, a common electrode 94 disposed between the piezoelectric ceramic layers 92, and a plurality of individual electrodes 93 arranged on the outermost surface of the piezoelectric ceramic layer 92. A plurality of piezoelectric elements are formed by the individual electrode 93, the piezoelectric ceramic layer 92 immediately below the individual electrode 93, and the common electrode 94.

  A flexible circuit board (FPC) 95 having a wiring pattern (not shown) corresponding to each individual electrode 93 is disposed above the piezoelectric actuator 91, and each output pin of the driving IC 96 is connected to the FPC 95. Each individual electrode 93 is connected. The wiring of the FPC 95 and each individual electrode 93 are connected by solder 97 or the like. In the ink jet recording head having such a configuration, when a voltage is applied between the desired individual electrode 93 and the common electrode 94, the piezoelectric ceramic layer 92 immediately below the individual electrode 93 to which the voltage is applied is displaced by a predetermined amount of displacement. A predetermined amount of ink is ejected from the ejection port 82.

  However, since a plurality of individual electrodes are usually arranged on the surface of the piezoelectric ceramic layer in the piezoelectric actuator used in the ink jet recording head, when the FPC wiring pattern is individually bonded to each individual electrode, the FPC These wirings must be arranged on the piezoelectric actuator with high density. In particular, as the degree of integration of the individual electrodes increases, the area of the individual electrodes must be reduced, which makes it difficult to individually bond the FPC wiring to each individual electrode. There is a problem that it cannot be integrated.

  Patent Documents 1 and 2 propose an ink jet recording head in which a driving IC is mounted on a piezoelectric actuator. In this ink jet recording head, the drive IC is mounted on the piezoelectric actuator, whereby each output pin of the drive IC is joined to each individual electrode without passing through the FPC. As a result, the FPC wiring is not arranged at high density on the piezoelectric actuator, and it can easily cope with a piezoelectric actuator in which individual electrodes are highly integrated.

However, in the inkjet recording heads described in Patent Documents 1 and 2, generally, a BGA type semiconductor package (BGA: ball grid array) or an LGA type semiconductor package (LGA: land grid array) is used for driving. Since the IC and the individual electrode are joined by solder or the like, the piezoelectric actuator is exposed to a high temperature at the time of joining. As a result, thermal stress is applied to the piezoelectric ceramic layer, residual stress is generated in the piezoelectric ceramic layer, the piezoelectric characteristics and reliability of the piezoelectric actuator are reduced, and the ink ejection performance and reliability of the inkjet recording head are reduced. There's a problem.
JP 2002-103602 A JP 2002-103609 A

  An object of the present invention is to provide an ink jet recording head having excellent ink ejection performance and reliability.

In order to solve the above problems, an ink jet recording head of the present invention has the following configuration.
(1) A piezoelectric actuator in which a plurality of individual electrodes are arranged on the surface of the piezoelectric ceramic layer has a position of the ink flow path and the individual electrodes on a flow path member in which a plurality of ink flow paths having ink discharge ports are arranged. And an ink jet recording head in which a driving IC is mounted on the piezoelectric actuator, wherein the individual electrodes are joined to the driving IC through a conductive resin. head.
(2) The ink jet recording head according to (1), wherein the conductive resin is an anisotropic conductive resin.
(3) The inkjet recording head according to (2), wherein an anisotropic conductive resin film is laminated on a surface of the piezoelectric actuator, and the individual electrodes are bonded to the driving IC via the anisotropic conductive resin film. .
(4) The ink jet recording head according to (3), wherein the anisotropic conductive resin film is laminated in a region extending over the plurality of individual electrodes.
(5) The ink jet recording head according to (4), wherein the region extends over the plurality of individual electrodes arranged in at least one row.
(6) The ink jet recording head according to (4), wherein the region extends over all the individual electrodes.
(7) The individual electrode includes a drive unit that contributes to piezoelectric driving, and a drive voltage application land portion that extends from one end of the drive unit, and the anisotropic conductive resin film includes the drive unit. The ink jet recording head according to (6), wherein a hole corresponding to is provided with a hole.

  According to the ink jet recording head described in (1), since the individual electrode is joined to the driving IC via the conductive resin, when joining the individual electrode and the driving IC, it is as in soldering. In addition, the piezoelectric actuator is not exposed to high temperatures. As a result, it is possible to suppress the occurrence of residual stress in the piezoelectric ceramic layer, and it is possible to prevent the piezoelectric characteristics and reliability of the piezoelectric actuator from deteriorating, so that the ink jet recording head has excellent ink ejection performance and reliability. Can be obtained. Moreover, in this ink jet recording head, since the driving IC is mounted on the piezoelectric actuator, it can be easily highly integrated.

  As described in (2) above, when the conductive resin is an anisotropic conductive resin having high conductivity in the thickness direction and high insulation in the plane direction, the anisotropic conductive resin is adjacent to the plurality of adjacent conductive resins. Even if it is arranged across the individual electrodes, it does not conduct between the adjacent individual electrodes, but only between the opposing portions in the thickness direction, that is, between the individual electrodes and the output pin of the driving IC facing the individual electrodes. Conduction is achieved.

  In the ink jet recording head described in (3) above, the individual electrodes are bonded to the driving IC via the anisotropic conductive resin film laminated on the surface of the piezoelectric actuator. Since the anisotropic conductive resin film conducts only in the thickness direction as described above, the anisotropic conductive resin film may be laminated in a region extending over a plurality of individual electrodes as described in the above (4) and (5). As a result, it is not necessary to individually bond the power supply electrodes to the individual electrodes, and the electrodes can be electrically connected by a simple printing technique. Therefore, the cost can be reduced and the electrodes can be easily bonded. .

  In addition, as described in (6) above, when the anisotropic conductive resin film spans all the individual electrodes, the anisotropic conductive resin film is bonded to the individual electrodes in a large area. The driving IC can be firmly bonded. In addition, since the anisotropic conductive resin film is disposed so as to cover the surface of the piezoelectric ceramic layer, it is preferable to suppress the vibration of a portion where it is preferable not to vibrate, that is, the piezoelectric ceramic layer on which the individual electrode is not formed. Can do. Thereby, interference between adjacent piezoelectric elements can be reduced.

  Further, as described in (7) above, in the anisotropic conductive resin film, a hole is provided in a portion corresponding to the drive unit, thereby preventing the anisotropic conductive resin film from interfering with the piezoelectric drive of the drive unit. be able to. Thereby, excellent ink discharge performance can be obtained.

  Hereinafter, the ink jet recording head of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an ink jet recording head 11 according to an embodiment of the present invention, and FIG. 2 is a plan view showing a power feeding electrode 51 on a piezoelectric actuator 21 in the ink jet recording head 11.

  As shown in FIGS. 1 and 2, the inkjet recording head 11 includes a piezoelectric actuator 21 having a plurality of individual electrodes 23 arranged on the surface of a piezoelectric ceramic layer 22, and a plurality of ink flow paths 33 having ink discharge ports 32. The ink flow path 33 and the individual electrode 23 are mounted on the arranged flow path members 31 so that the driving IC 41 is mounted on the piezoelectric actuator 21.

  The piezoelectric actuator 21 includes stacked piezoelectric ceramic layers 22, 22, a common electrode 24 disposed between the piezoelectric ceramic layers 22, 22, and a plurality of individual electrodes 23 arranged on the surface of the piezoelectric ceramic layer 22. It is comprised by. The individual electrode 23 includes a driving unit 23a that contributes to piezoelectric driving and a land portion 23b for applying a driving voltage that extends from one end of the driving unit 23a. As a result, the piezoelectric actuator 21 is formed with a plurality of piezoelectric elements 27 by the drive portion 23 a of the individual electrode 23, the piezoelectric ceramic layer 22 immediately below the drive portion 23 a, and the common electrode 24.

  The land portion 23 b of the individual electrode 23 is connected to the driving IC 41 by the power feeding electrode 51. The common electrode 24 is a feeding electrode formed of an anisotropic conductive resin film via a via electrode 26 formed in the thickness direction in the piezoelectric ceramic layer 22 and an extraction electrode 25 formed on the surface of the piezoelectric ceramic layer 22. 51 and connected to the ground potential.

  A flexible circuit board (FPC) 61 is connected to the upper surface of the driving IC 41 by solder 71, and power is supplied to the driving IC 41 through the FPC 61.

  The power supply electrode 51 has a hole in a portion corresponding to the drive portion 23a, and is disposed so as to cover the surfaces of the piezoelectric ceramic layer 22 and the land portion 23b. That is, the power feeding electrode 51 is laminated on the surface of the piezoelectric actuator excluding the drive unit 23a, and is disposed in a region extending over all the land portions 23b. The power feeding electrode 51 is formed of an anisotropic conductive resin film having high conductivity in the thickness direction and high insulation in the plane direction.

  The anisotropic conductive resin constituting the power supply electrode 51 is obtained by dispersing conductive particles in a thermosetting resin such as an epoxy resin such as an acid anhydride curable type, a phenol curable type, or an amine curable type. As the conductive particles, for example, metal particles such as gold, silver and nickel, resin particles whose surfaces are plated with gold, and the like are used.

  The particle diameter of the conductive particles is generally about 3 to 15 μm, preferably about 5 to 10 μm. The compounding amount of the conductive particles in the thermosetting resin is preferably about 1 to 25% by mass.

  The thickness of the power supply electrode 51 is about 3 to 20 μm, preferably about 5 to 15 μm.

  Such a power supply electrode 51 is disposed between the land portion 23b of the individual electrode 23 and an output pin (not shown) of the driving IC 41, so that the land portion 23b and the drive opposite to the land portion 23b are driven. The output pin of the IC 41 can be electrically connected.

  Piezoelectric ceramics can be used as the piezoelectric ceramic layer 22 constituting the piezoelectric actuator 21. Specifically, for example, a Bi layered compound (layered perovskite compound), a tungsten bronze type compound, an Nb-based perovskite type compound (Nb) Nb acid alkaline compound (NAC) such as sodium oxide, Nb alkaline earth compound (NAEC) such as barium Nb), lead magnesium niobate (PMN), lead nickel niobate (PNN), Pb Examples thereof include substances containing perovskite type compounds such as lead zirconate titanate (PZT) and lead titanate.

Of these, a perovskite compound containing at least Pb is particularly preferable. For example, lead magnesium niobate (PMN), nickel niobate (PNN), lead zirconate titanate (PZT) containing Pb, lead titanate and the like are preferable. In particular, a crystal containing Pb as the A site constituent element and Zr and Ti as the B site constituent element is preferable. With such a composition, a piezoelectric ceramic layer having a high piezoelectric constant can be obtained. Among these, lead zirconate titanate and lead titanate are suitable for adding a large displacement. As an example of the perovskite crystal, PbZrTiO ₃ can be preferably used.

In addition, other oxides may be mixed in the piezoelectric ceramic, and as long as the properties are not adversely affected, other elements may be substituted at the A site and / or B site as subcomponents. Good. For example, it may be a solid solution of Pb (Zn _1/3 Sb _2/3 ) O ₃ and Pb (Ni _1/2 Te _1/2 ) O ₃ to which Zn, Sb, Ni and Te are added as subcomponents.

  The common electrode 24 may be any material as long as it has conductivity, and Au, Ag, Pd, Pt, Cu, Al, and alloys thereof can be used. Specifically, for example, an Ag—Pd alloy is used. It can be illustrated. The thickness of the common electrode 24 is required to be conductive and not to hinder displacement, and is generally about 0.5 to 5 μm, preferably 1 to 4 μm.

  The individual electrode 23 may be any one as long as it has conductivity, and Au, Ag, Pd, Pt, Cu, Al, or an alloy thereof can be used. The thickness of the individual electrode 23 must be conductive and not to prevent displacement, and is generally about 0.1 to 2 μm, preferably 0.1 to 0.5 μm.

  Next, a method for manufacturing the ink jet recording head 11 will be described. First, a required number of green sheets mainly composed of the above-mentioned piezoelectric ceramic raw material powder are produced. Next, through holes are formed in some of the green sheets. A green sheet in which the through hole is formed is filled with a conductor to be the via electrode 26 by screen printing. A common electrode pattern is formed on substantially the entire surface of the green sheet forming the common electrode by screen printing. Next, the green sheets are laminated so as to have the configuration shown in FIG. 1 to form a laminate.

  Next, the laminate is cut into a predetermined shape and then fired at about 900 to 1100 ° C. to form a piezoelectric actuator body. A conductive paste is printed on the surface of the piezoelectric actuator main body to form individual electrode patterns to be the drive portion 23a and the land portion 23b at predetermined positions, and heat treatment is performed at about 600 to 850 ° C. Thereby, the piezoelectric actuator 21 can be obtained.

  The flow path member 31 is obtained by a rolling method or the like, and the ink discharge holes 32 and the ink flow path 33 are provided by being processed into a predetermined shape by etching. The flow path member 31 is formed of Fe—Cr or Fe—Cr—Ni stainless steel, Fe—Ni, WC—TiC, etc., and Fe—Cr is particularly excellent in corrosion resistance to ink. preferable.

  The piezoelectric actuator 21 and the flow path member 31 can be laminated and bonded through an adhesive layer, for example. As the adhesive layer, a known layer can be used. However, in order not to affect the piezoelectric actuator 21 and the flow path member 31, an epoxy resin, phenol resin, polyphenylene ether having a thermosetting temperature of 130 to 250 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group of resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric actuator 21 and the flow path member 31 can be heat-bonded.

  Next, a method for joining the land portion 23b and the output pin of the driving IC 41 will be described. First, an anisotropic conductive resin paste (ACP) mainly composed of the above-mentioned thermosetting resin and conductive particles (Anisotropic Conductive Paste: ACP) is applied to the piezoelectric ceramic layer 22 in which the individual electrodes 23 are arranged by means such as screen printing. Apply to the surface. At this time, the anisotropic conductive resin paste is not applied to the surface of the drive unit 23a. Further, instead of the anisotropic conductive resin paste, an anisotropic conductive resin film (ACF) in which a portion corresponding to the drive unit 23a is cut out may be used. This anisotropic conductive resin film has thermosetting resin and conductive particles as main components and is previously formed into a film shape.

  Next, the output pins of the drive IC 41 are brought into contact with the anisotropic conductive resin paste or the anisotropic conductive resin film so that each output pin of the drive IC 41 faces the corresponding land portion 23b. Then, while pressing the driving IC 41 toward the piezoelectric ceramic layer 22 with a pressing tool, the driving IC 41 is heated at a curing temperature corresponding to the anisotropic conductive resin to be used to cure the resin.

  Specifically, for example, when an epoxy resin is used as the anisotropic conductive resin material, the curing temperature may be heat-cured at a low temperature of about 80 to 150 ° C. Thereby, since the piezoelectric actuator 21 is not exposed to a high temperature as in the case of soldering, it is possible to suppress the residual stress from being generated in the piezoelectric ceramic layer 22, and the piezoelectric characteristics and reliability of the piezoelectric actuator 21. Can be prevented from decreasing.

  Further, as described above, by heating and curing while pressing in the thickness direction of the anisotropic conductive resin paste or anisotropic conductive resin film, the power feeding electrode 51 in which conductive particles are present in a high density in the thickness direction is obtained. Can be obtained. The power supply electrode 51 thus obtained has high conductivity in the thickness direction and high insulation in the plane direction.

  Finally, by connecting the FPC 61 to the upper surface of the driving IC 41 with the solder 71, the ink jet recording head 11 having excellent ink ejection performance and reliability can be obtained.

  In the inkjet recording head 11 having such a configuration, the plurality of individual electrodes 23 are independently connected to the output pins of the driving IC 41, and the common electrode 24 is connected to the ground potential. When a voltage is applied between the common electrode 24 and the desired individual electrode 23, the piezoelectric ceramic layer 22 immediately below the drive unit 23 a of the individual electrode 23 to which the voltage is applied is displaced, and the inside of the ink flow path 33. Ink is pressurized, and ink droplets are ejected from the ink ejection holes 32.

<Other embodiments>
FIG. 3 is a schematic cross-sectional view showing an inkjet recording head 12 according to another embodiment of the present invention. As in the ink jet recording head 12 shown in FIG. 3, in the present invention, the FPC 61 that supplies power to the driving IC 41 may be fixed on the flow path member 31 and connected to the lower surface of the driving IC 41 by solder 71. Good. Others are the same as those of the ink jet recording head shown in FIGS.

  4 and 5 are schematic sectional views showing ink jet recording heads 13 and 14 according to still another embodiment of the present invention. As shown in FIGS. 4 and 5, in these ink jet recording heads 13 and 14, a driving IC 42 is mounted on a circuit board 43, and each terminal (not shown) of the circuit board 43 is connected via a power supply electrode 51. Are joined to the land portion 23 b of the individual electrode 23. Output pins (not shown) of the driving IC 42 and terminals of the circuit board are connected by electrical wiring inside the circuit board 43. Further, the circuit board 43 in the ink jet recording head 13 shown in FIG. 4 is provided with a land electrode 44 to which each terminal of the circuit board 43 is connected, and each terminal is connected to the power supply electrode 51 through the land electrode 44. It is connected to the.

  The circuit board 43 has a function of adjusting the pitch between the land portion 23 b of the individual electrode 23 and the output pin of the driving IC 42. That is, even if the pitch of the land portions 23b is changed, the pitch of the terminals of the circuit board 43 need only be changed without changing the pitch of the driving IC 42 in order to cope with the change. Thereby, productivity can be improved and cost reduction can be achieved. Others are the same as those of the ink jet recording head shown in FIGS.

  FIG. 6 is a schematic cross-sectional view showing an arrangement state of the power feeding electrodes 52 in the ink jet recording head 15 according to still another embodiment of the present invention. In this figure, the description of the driving IC and the FPC is omitted for convenience of explanation. As shown in FIG. 6, in the ink jet recording head 15, the long power supply electrode 52 is stacked in a region extending linearly over the land portions 23 b of the plurality of individual electrodes 23 arranged in the same row. Others are the same as those of the ink jet recording head shown in FIGS.

  According to the ink jet recording head of the present invention as described above, since the driving IC is mounted on the piezoelectric actuator, it is not necessary to join the FPC wiring pattern to each individual electrode, and the FPC wiring is on the piezoelectric actuator. Are not arranged with high density. Thereby, an ink jet recording head equipped with a highly integrated piezoelectric actuator can be easily obtained. Further, since the driving IC is directly joined to the individual electrode without using the FPC for the connection between the driving IC and the individual electrode, the driving reliability can be improved.

  In addition, since the individual electrode is joined to the driving IC via a conductive resin, the piezoelectric actuator may be exposed to a high temperature as in solder joining when the individual electrode and the driving IC are joined. Absent. As a result, it is possible to suppress the occurrence of residual stress in the piezoelectric ceramic layer, and it is possible to prevent the piezoelectric characteristics and reliability of the piezoelectric actuator from deteriorating, so that the ink jet recording head has excellent ink ejection performance and reliability. Can be obtained.

1 is a schematic cross-sectional view showing an ink jet recording head according to an embodiment of the present invention. It is a top view which shows the electrode for electric power feeding on the piezoelectric actuator in the inkjet recording head concerning one Embodiment of this invention. It is a schematic sectional drawing which shows the inkjet recording head concerning other embodiment of this invention. It is a schematic sectional drawing which shows the inkjet recording head concerning other embodiment of this invention. It is a schematic sectional drawing which shows the inkjet recording head concerning other embodiment of this invention. It is a schematic sectional drawing which shows the inkjet recording head concerning other embodiment of this invention. It is a schematic sectional drawing which shows the conventional inkjet recording head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 12, 13, 14, 15 Inkjet recording head 21 Piezoelectric actuator 22 Piezoelectric ceramic layer 23 Individual electrode 23a Drive part 23b Land part 24 Common electrode 31 Flow path member 32 Ink discharge port 33 Ink flow path 41 Driving IC
51,52 Power feeding electrode (anisotropic conductive resin film)

Claims (7)

A piezoelectric actuator having a plurality of individual electrodes arranged on the surface of the piezoelectric ceramic layer has a position where the ink flow path and the individual electrode are aligned on a flow path member having a plurality of ink flow paths having ink discharge ports. An ink jet recording head mounted and a driving IC mounted on the piezoelectric actuator,
An ink jet head, wherein the individual electrodes are joined to the driving IC via a conductive resin.   The ink jet recording head according to claim 1, wherein the conductive resin is an anisotropic conductive resin.   3. The ink jet recording head according to claim 2, wherein an anisotropic conductive resin film is laminated on the surface of the piezoelectric actuator, and the individual electrodes are bonded to the driving IC via the anisotropic conductive resin film.   The ink jet recording head according to claim 3, wherein the anisotropic conductive resin film is laminated in a region extending over the plurality of individual electrodes.   The inkjet recording head according to claim 4, wherein the region extends over the plurality of individual electrodes arranged in at least one row.   The inkjet recording head according to claim 4, wherein the region extends over all the individual electrodes. The individual electrode includes a driving unit that contributes to piezoelectric driving, and a driving voltage application land portion that extends from one end of the driving unit, and the anisotropic conductive resin film corresponds to the driving unit. The ink jet recording head according to claim 6, wherein the portion has a hole.

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