JP4432567B2 - Inkjet head - Google Patents

Description

  The present invention relates to an inkjet head used in an inkjet recording apparatus that performs printing by ejecting ink onto a recording medium.

  Ink-jet heads distribute ink supplied from an ink tank to a manifold to a plurality of pressure chambers, and selectively apply pulsed pressure to the plurality of pressure chambers to eject ink from nozzles communicating with the pressure chambers. Is configured to do. As described above, as means for selectively applying pressure to a plurality of pressure chambers, for example, an inkjet head including a ceramic piezoelectric sheet disposed over a plurality of pressure chambers has been proposed (for example, Patent Document 1). reference).

  In this ink jet head, a plurality of piezoelectric sheets are arranged in a laminated manner over a plurality of pressure chambers arranged on a plane. Among the plurality of laminated piezoelectric sheets, the uppermost piezoelectric sheet is provided with a plurality of surface electrodes formed in an elongated shape in one direction and corresponding to a plurality of pressure chambers in a matrix, Between the plurality of piezoelectric sheets, there are provided an internal electrode connected to the surface electrode through a through hole, and a common electrode provided in common to the plurality of pressure chambers and held at the ground potential. A plurality of contact portions are respectively provided at one end portions of the plurality of surface electrodes, and the contact portions of the plurality of surface electrodes are all arranged in the same direction. On the upper surface of the uppermost piezoelectric sheet, a flexible printed circuit (FPC) including a signal line for supplying the drive signal to the contact portion is disposed. The FPC is soldered to a plurality of contact portions. Connected by attaching.

  When a driving signal is supplied to the contact portion of the surface electrode through the plurality of signal lines of the FPC, a voltage is applied between the surface electrode, the internal electrode, and the common electrode, and the piezoelectric sheet is distorted to generate pressure. The volume of the chamber changes, and ink is ejected from the nozzle communicating with the pressure chamber.

JP2003-165215A (5th page, FIG. 5)

  By the way, in recent years, attempts have been made to arrange a plurality of pressure chambers at higher density in order to satisfy both the demands for improvement in printing image quality and downsizing of the inkjet head. In this case, the surface electrodes and contact portions respectively corresponding to the plurality of pressure chambers are also arranged on the piezoelectric sheet with high density. However, when the contact portions are arranged with high density on the piezoelectric sheet as described above, an FPC in which a plurality of signal lines for supplying drive signals to the plurality of contact portions is necessary is required. There is a limit in wiring these signal lines to a single FPC with high density. In view of this, it is conceivable to arrange a plurality of FPCs, on which signal lines are wired at a relatively coarse density, partially overlapping on the piezoelectric sheet.

  However, in the inkjet head described in Patent Document 1, when the plurality of FPCs are arranged on the piezoelectric sheet in a partially overlapping state, the FPC overlaps with the non-overlapping part. In the vicinity of the boundary portion, the upper FPC is easily peeled off. In particular, since the contact portions are arranged with high density as described above, an external force in the direction of peeling the upper FPC is applied when the distance from the boundary portion of the contact portion close to the boundary portion is short. Sometimes, the electrical connection between the contact portion and the FPC may be disconnected.

  The object of the present invention is that when a plurality of FPCs are arranged on a piezoelectric sheet, the contact points between the FPCs and the contact points are also close to the boundary between the overlapping part and the non-overlapping part. It is an object of the present invention to provide an ink jet head with improved electrical connection reliability.

Means for Solving the Problems and Effects of the Invention

  An ink jet head according to a first aspect of the present invention includes a flow path unit in which a plurality of pressure chambers communicating with a nozzle for discharging ink are disposed adjacent to each other along a plane, and a surface of the flow path unit disposed from the nozzle. An actuator unit that changes the volume of the pressure chamber in order to eject ink, the actuator unit corresponding to each of the plurality of pressure chambers, and a piezoelectric sheet disposed across the plurality of pressure chambers. A plurality of individual electrodes provided on the piezoelectric sheet and having contact portions, and a plurality of signal lines connected to the contact portions of these individual electrodes to supply drive signals for changing the volumes of the plurality of pressure chambers. A plurality of flexible printed wiring boards, and the plurality of flexible printed wiring boards are arranged partially overlapping on the piezoelectric sheet. , At least in the individual electrode close to the boundary portion between the overlapping portion of the plurality of flexible printed wiring boards and the non-overlapping portion, the contact portion is at the end of the individual electrode on the side away from the boundary portion. It is provided.

  This ink jet head raises the pressure in the pressure chamber by changing the volume in the pressure chamber by the actuator unit, and ejects ink from nozzles communicating with the pressure chamber. Here, in the actuator unit, when a drive signal for changing the volume of the pressure chamber is selectively supplied from the signal line of the flexible printed wiring board (FPC) to the contact portion of the individual electrode, a voltage is applied to the individual electrode. When applied, distortion occurs in the piezoelectric sheet, and the volume of the pressure chamber changes due to the distortion of the piezoelectric sheet.

  Incidentally, a plurality of FPCs are disposed on the piezoelectric sheet so as to partially overlap each other. Therefore, the upper FPC is easily peeled in the vicinity of the boundary between the overlapping portion and the overlapping portion of the plurality of FPCs. Therefore, if the distance from the boundary portion of the contact portion close to the boundary portion is short, the electrical connection between the contact portion and the upper FPC is easily cut, and the reliability of the electrical connection is lowered. Therefore, in the individual electrode close to the boundary portion, the contact portion is provided at the end of the individual electrode on the side away from the boundary portion, thereby increasing the separation distance from the boundary portion of the contact portion close to the boundary portion. can do. And it becomes possible to connect the upper FPC and the contact portion at a position as far as possible from the boundary where the upper FPC is easily peeled off, and to improve the reliability of electrical connection at the contact portion. Can do.

  The ink jet head according to a second aspect of the present invention is the ink jet head according to the first aspect, wherein, in all the individual electrodes provided on the piezoelectric sheet, the contact portion is provided at an end of the individual electrode on the side away from the boundary portion. It is characterized by that. By configuring in this way, the contact part pattern of the individual electrode becomes the same in the region divided by the boundary part, and there is no part where the distance between the contact parts is locally short. It becomes easy and the short circuit between the contact points can be prevented as much as possible.

  According to a third aspect of the present invention, there is provided an ink jet head according to the first or second aspect, wherein a plurality of flexible printed wiring boards disposed on the piezoelectric sheet are supported between the plurality of individual electrodes on the piezoelectric sheet. Dummy contact portions are provided, and the dummy contact portions are densely provided in the vicinity of the boundary portion as compared with locations other than the boundary portion. According to the configuration of the first or second invention, since the distance between the two contact portions sandwiching the boundary portion increases, the FPC falls between the contact portions due to the FPC's own weight, an external force acting on the FPC, or the like. When the FPC is in close contact with the piezoelectric sheet, there is a possibility that the deformation of the piezoelectric sheet during ink ejection may be hindered. Therefore, by providing the dummy contact portions supporting the FPC close to the boundary portion, it is possible to reliably prevent the FPC from falling between the contact portions.

  An ink jet head according to a fourth invention is characterized in that, in any one of the first to third inventions, the individual electrodes are formed in an elongated shape in a direction crossing an arrangement direction along the boundary portion. To do. Therefore, in the individual electrode close to the boundary portion, when the contact portion is provided at the end portion on the side away from the boundary portion, the separation distance from the boundary portion of the contact portion close to the boundary portion is further increased. The FPC and the contact portion can be connected at a position further away from the center.

  Embodiments of the present invention will be described. As shown in FIGS. 1 and 2, the inkjet head 1 of this embodiment includes a head main body 70 having a rectangular planar shape extending in the main scanning direction for ejecting ink onto a sheet, and the head main body 70. And a base block 71 in which two ink reservoirs 3 are formed, which are disposed above and are flow paths for ink supplied to the head main body 70.

  As shown in FIGS. 1 and 2, the head main body 70 includes a flow path unit 4 in which an ink flow path is formed, and a plurality of actuator units 21 bonded to the upper surface of the flow path unit 4. Both the flow path unit 4 and the actuator unit 21 are configured by laminating a plurality of thin plates and bonding them together. Further, the actuator unit 21 includes a flexible printed circuit (FPC) 50 having flexibility, and the FPC 50 is drawn from the actuator unit 21 to the left and right on the paper surface of FIG. Here, as will be described later, each FPC 50 is pulled out to the left and right with two FPCs (see FIGS. 8 and 15A and 15B) partially overlapping. The base block 71 is made of a metal material such as stainless steel. The ink reservoir 3 in the base block 71 is a substantially rectangular parallelepiped hollow region formed along the longitudinal direction (main scanning direction) of the base block 71.

  The lower surface 73 of the base block 71 protrudes downward from the periphery in the vicinity of the opening 3b. The base block 71 is in contact with the flow path unit 4 only in the vicinity 73 a of the opening 3 b of the lower surface 73. Therefore, a region other than the vicinity 73a of the opening 3b on the lower surface 73 of the base block 71 is separated from the head main body 70, and the actuator unit 21 is disposed in this separated portion.

  The base block 71 is bonded and fixed in a recess formed on the lower surface of the grip portion 72 a of the holder 72. The holder 72 includes a gripping portion 72a and a pair of flat projections 72b extending from the upper surface of the gripping portion 72a at a predetermined interval in a direction orthogonal thereto. Each FPC 50 is arranged along the surface of the protrusion 72b of the holder 72 via an elastic member 83 such as a sponge. And driver IC80 is installed on FPC50 arrange | positioned on the protrusion part 72b surface of the holder 72. FIG. As will be described later, the FPC 50 is electrically connected to the electrodes 34 and 35 of the actuator unit 21 by soldering so as to transmit the drive signal output from the driver IC 80 to the electrodes 34 and 35 (see FIGS. 9A and 9B). It is joined to.

  Since the heat sink 82 having a substantially rectangular parallelepiped shape is closely disposed on the outer surface of the driver IC 80, the heat generated in the driver IC 80 can be efficiently dissipated. A substrate 81 is disposed above the driver IC 80 and the heat sink 82 and outside the FPC 50. The upper surface of the heat sink 82 and the substrate 81 and the lower surface of the heat sink 82 and the FPC 50 are bonded by a seal member 84, respectively.

  FIG. 3 is a plan view of the head main body 70 shown in FIG. In FIG. 3, the ink reservoir 3 formed in the base block 71 is virtually drawn with a broken line. The two ink reservoirs 3 extend in parallel with each other at a predetermined interval along the longitudinal direction (main scanning direction) of the head main body 70. Each of the two ink reservoirs 3 has an opening 3a at one end, and is always filled with ink by communicating with an ink tank (not shown) through the opening 3a. A large number of openings 3b are provided in each ink reservoir 3 along the longitudinal direction of the head main body 70, and connect each ink reservoir 3 and the flow path unit 4 as described above. A large number of the openings 3 b are arranged close to each other along the longitudinal direction of the head body 70. A pair of openings 3b communicating with one ink reservoir 3 and a pair of openings 3b communicating with the other ink reservoir 3 are arranged in a staggered manner.

  In the region where the openings 3b are not arranged, a plurality of actuator units 21 having a trapezoidal planar shape in a pattern opposite to the pair of openings 3b (in the description of the flow path unit 4 below, the FPC 50 is mainly used). It is arranged in a zigzag pattern. The parallel opposing sides (upper side and lower side) of each actuator unit 21 are parallel to the longitudinal direction of the head body 70. Further, a part of the oblique sides of the adjacent actuator units 21 overlap in the width direction of the head main body 70.

  FIG. 4 is an enlarged view of a region surrounded by a one-dot chain line in FIG. As shown in FIG. 4, an opening 3b provided in each ink reservoir 3 communicates with a manifold 5 that is a common ink chamber, and the tip of each manifold 5 branches into two to form a sub-manifold 5a. Yes. Further, in plan view, two sub-manifolds 5a branched from the adjacent openings 3b extend from the two oblique sides of the actuator unit 21, respectively. That is, below the actuator unit 21, a total of four sub-manifolds 5 a that are separated from each other extend along the parallel opposing sides of the actuator unit 21.

  The lower surface of the flow path unit 4 facing the actuator unit 21 is an ink discharge area. A large number of nozzles 8 are arranged in a matrix on the surface of the ink discharge area, as will be described later. In order to simplify the drawing, only a few of the nozzles 8 are illustrated in FIG. 4, but they are actually arranged over the entire ink discharge region.

  FIG. 5 is an enlarged view of a region surrounded by a dashed line drawn in FIG. 4 and 5 show a state where a plurality of pressure chambers 10 in the flow path unit 4 are arranged in a matrix when viewed from a direction perpendicular to the ink ejection surface. Each pressure chamber 10 has a substantially rhombic planar shape with rounded corners, and the longer diagonal line is parallel to the width direction of the flow path unit 4. One end of each pressure chamber 10 communicates with the nozzle 8, and the other end communicates with the sub-manifold 5a serving as a common ink flow path via an aperture 12 (see FIG. 6). An individual electrode 35 similar to the pressure chamber 10 and having a slightly smaller planar shape than the pressure chamber 10 is formed on the actuator unit 21 at a position overlapping each pressure chamber 10 in plan view. FIG. 5 shows only some of the large number of individual electrodes 35 in order to simplify the drawing. 4 and 5, the pressure chambers 10 and the apertures 12 that are to be drawn with broken lines in the actuator unit 21 or the flow path unit 4 are drawn with solid lines for easy understanding of the drawings.

  In FIG. 5, the plurality of virtual rhombus regions 10x each accommodating the pressure chambers 10 (10a, 10b, 10c, 10d) are arranged in the arrangement direction A (the first direction so as not to overlap each other). Direction) and array direction B (second direction) are adjacently arranged in a matrix. The arrangement direction A is the longitudinal direction (main scanning direction) of the inkjet head 1, that is, the extending direction of the sub-manifold 5a, and is parallel to the shorter diagonal line of the rhombic region 10x. The arrangement direction B is an oblique side direction of the rhombus region 10x that forms an obtuse angle θ with the arrangement direction A. The pressure chamber 10 has a common center position with the corresponding rhombus region 10x, and the contour lines of both are separated from each other in plan view.

  The pressure chambers 10 adjacently arranged in a matrix in two directions of the arrangement direction A and the arrangement direction B are separated along the arrangement direction A by a distance corresponding to 37.5 dpi. Further, 16 pressure chambers 10 are arranged in the arrangement direction B in one ink ejection region. The pressure chambers at both ends in the arrangement direction B are dummy and do not contribute to ink ejection.

  The plurality of pressure chambers 10 arranged in a matrix form a plurality of pressure chamber rows along the arrangement direction A shown in FIG. The pressure chamber rows are the first pressure chamber row 11a and the second pressure chamber row according to the relative position with respect to the sub-manifold 5a when viewed from the direction (third direction) perpendicular to the paper surface of FIG. 11b, a third pressure chamber row 11c, and a fourth pressure chamber row 11d. These first to fourth pressure chamber rows 11a to 11d are periodically arranged in four rows in the order of 11c → 11d → 11a → 11b → 11c → 11d → ... → 11b from the upper side to the lower side of the actuator unit 21. Has been placed.

  In the pressure chambers 10a constituting the first pressure chamber row 11a and the pressure chambers 10b constituting the second pressure chamber row 11b, a direction (fourth direction) orthogonal to the arrangement direction A when viewed from the third direction. ), The nozzle 8 is unevenly distributed on the lower side of the drawing sheet of FIG. And the nozzle 8 is located in the lower end part of the corresponding rhombus area | region 10x. On the other hand, in the pressure chambers 10c constituting the third pressure chamber row 11c and the pressure chambers 10d constituting the fourth pressure chamber row 11d, the nozzle 8 is unevenly distributed on the upper side in FIG. 5 in the fourth direction. Yes. And the nozzle 8 is located in the upper end part of the corresponding rhombus area | region 10x, respectively. In the first and fourth pressure chamber rows 11a and 11d, when viewed from the third direction, more than half of the pressure chambers 10a and 10d overlap the sub-manifold 5a. In the second and third pressure chamber rows 11b and 11c, the entire region of the pressure chambers 10b and 10c does not overlap the sub-manifold 5a when viewed from the third direction. Therefore, for the pressure chambers 10 belonging to any pressure chamber row, the width of the sub-manifold 5a is formed as wide as possible while preventing the nozzle 8 communicating therewith from overlapping the sub-manifold 5a. Ink can be supplied smoothly.

  Next, the cross-sectional structure of the head body 70 will be further described with reference to FIGS. As shown in FIG. 6, each nozzle 8 communicates with the sub-manifold 5 a through the pressure chambers 10 (10 a, 10 b) and the aperture 12. In this manner, the individual ink flow paths 32 extending from the outlet of the sub-manifold 5 a to the nozzle 8 through the aperture 12 and the pressure chamber 10 are formed in the head main body 70 for each pressure chamber 10. The individual ink flow path 32 (hereinafter also referred to as a channel) corresponds to one recording element.

  As shown in FIG. 6, the pressure chamber 10 and the aperture 12 are provided at different depths in the stacking direction of the plurality of thin plates. As a result, as shown in FIG. 5, in the flow path unit 4 corresponding to the ink discharge area below the actuator unit 21, the aperture 12 communicating with one pressure chamber 10 is moved to a pressure chamber adjacent to the pressure chamber. 10 and can be arranged at the same position in plan view. As a result, the pressure chambers 10 are in close contact with each other and are arranged at high density, so that high-resolution image printing is realized by the inkjet head 1 having a relatively small occupation area.

  As shown in FIG. 7, the head main body 70 includes an actuator unit 21, a cavity plate 22, a base plate 23, an aperture plate 24, a supply plate 25, manifold plates 26, 27 and 28, a cover plate 29 and a nozzle plate 30 from above. It has a laminated structure in which a total of 10 sheet materials are laminated. Among these, the flow path unit 4 is composed of nine plates excluding the actuator unit 21.

  As will be described in detail later, the actuator unit 21 is formed by stacking five piezoelectric sheets 41 to 45 (see FIG. 9A) and arranging electrodes so that three of them are active layers when a voltage is applied. (Hereinafter simply referred to as a layer having an active layer), and the remaining two layers are inactive layers. The cavity plate 22 is a metal plate provided with a number of substantially rhombic openings corresponding to the pressure chambers 10. The base plate 23 is a metal plate provided with a communication hole between the pressure chamber 10 and the aperture 12 and a communication hole from the pressure chamber 10 to the nozzle 8 for one pressure chamber 10 of the cavity plate 22. The aperture plate 24 is provided with a communication hole from the pressure chamber 10 to the nozzle 8 in addition to the aperture 12 formed by two etching holes and a half-etching region connecting the two holes with respect to one pressure chamber 10 of the cavity plate 22. It is a metal plate. The supply plate 25 is a metal plate provided with a communication hole between the aperture 12 and the sub-manifold 5 a and a communication hole from the pressure chamber 10 to the nozzle 8 for one pressure chamber 10 of the cavity plate 22. The manifold plates 26, 27, and 28 are metal plates each provided with a communication hole from the pressure chamber 10 to the nozzle 8 for one pressure chamber 10 of the cavity plate 22 in addition to the sub-manifold 5 a. The cover plate 29 is a metal plate provided with a communication hole from the pressure chamber 10 to the nozzle 8 for one pressure chamber 10 of the cavity plate 22. The nozzle plate 30 is a metal plate in which the nozzles 8 are provided for one pressure chamber 10 of the cavity plate 22.

  These ten sheets 21 to 30 are stacked in alignment with each other so that the individual ink flow paths 32 as shown in FIG. 7 are formed. The individual ink flow path 32 first extends upward from the sub-manifold 5a, extends horizontally at the aperture 12, then further upwards, extends horizontally again at the pressure chamber 10, and then moves away from the aperture 12 for a while. Toward the nozzle 8 in a vertically downward direction.

Next, the actuator unit 21 and the driver IC 80 electrically connected to the actuator unit 21 will be described with reference to FIGS.
The actuator unit 21 is provided on the uppermost piezoelectric sheet 41 corresponding to the five piezoelectric sheets 41 to 45 disposed in a stacked manner over the plurality of pressure chambers 10 and the plurality of pressure chambers 10, and contacts. 2 having a plurality of individual electrodes 35 having a portion 91, and a plurality of signal lines for supplying drive signals for changing the volumes of the plurality of pressure chambers 10 to the contact portions 91 of the plurality of individual electrodes 35. Two FPCs 50 (50a, 50b) are connected. The actuator unit 21 deforms the piezoelectric sheets 41 to 45 by selectively supplying a drive signal from the driver IC 80 (see FIG. 2) to the plurality of contact portions 91 on the piezoelectric sheet 41 via the FPC 50. The volume of the pressure chamber 10 corresponding to the contact portion 91 supplied with the drive signal is changed.

  As shown in FIGS. 8, 9A, and 9B, the five piezoelectric sheets 41, 42, 43, 44, and 45 are formed to have the same thickness of about 15 μm. These piezoelectric sheets 41 to 45 are arranged so as to be stacked over a large number of pressure chambers 10 formed in one ink ejection region in the inkjet head 1, and form a continuous layered flat plate (continuous flat plate layer).

  As shown in FIG. 8, on the upper surface of the uppermost piezoelectric sheet 41, the individual electrodes 35 having a substantially rhombic planar shape are regularly arranged in a matrix. Further, as shown in FIG. 9A, an individual electrode 36 having the same shape as that of the individual electrode 35 is arranged between the two piezoelectric sheets 42 and 43 at a position overlapping with the individual electrodes 35 in the vertical direction. Yes. Here, as described above, since the piezoelectric sheets 41 to 45 are arranged as a continuous flat plate layer across a large number of pressure chambers 10, the individual electrodes 35 and 36 are formed at a high density by using, for example, a screen printing technique. It is possible to arrange in. Therefore, the pressure chambers 10 formed at positions corresponding to the individual electrodes 35 and 36 can be arranged with high density, and high-resolution images can be printed.

  In the present embodiment, the piezoelectric sheets 41 to 45 are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity. In FIG. 9A, the FPC 50 and the piezoelectric sheet 41 are drawn so as to be bonded to each other, but in actuality, they are bonded to each other at the main electrode portion 90 of each individual electrode 35. Not. This is to prevent the FPC 50 attached to the main electrode portion 90 from inhibiting the deformation of the piezoelectric sheets 41 to 45.

  As shown in FIGS. 8, 9 (a), and 10, the individual electrode 35 has a thickness of about 1 μm, and is formed at a position corresponding to the pressure chamber 10 on the upper surface of the piezoelectric sheet 41. The individual electrode 35 has a shape that is substantially similar to the pressure chamber 10 in plan view (see FIG. 5).

  Further, the individual electrode 35 has a main electrode portion 90 having a substantially rhombus shape in plan view, and a contact portion 91 (land portion) formed so as to protrude from an acute angle portion at one end of the main electrode portion 90. . A drive signal is supplied to the contact portion 91 via a signal line wired to the FPC 50 described later. As shown in FIGS. 5 and 9A, the main electrode portion 90 overlaps the pressure chamber 10 when viewed from the third direction perpendicular to the surface of the piezoelectric sheet 41, while the large contact portion 91. The portion does not overlap the pressure chamber 10 when viewed from the third direction. In FIG. 8, among the individual electrodes 35 on the piezoelectric sheet 41, the individual electrode 35 located on the outermost peripheral side is a dummy electrode in which the contact portion 91 is not provided.

  By the way, in the plurality (8 rows, 364) of individual electrodes 35 arranged in the upper half of the piezoelectric sheet 41 in FIG. 8, the contact portion 91 is provided at the upper end of the individual electrode 35 in FIG. 8. In the plural (eight rows 300 pieces) individual electrodes 35 arranged in the lower half of the piezoelectric sheet 41 in FIG. 8, the contact portion 91 is provided at the lower end of the individual electrode 35 in FIG. 8. ing. The reason for this will be explained later.

  As shown in FIG. 9A, an individual electrode 36 having a shape similar to that of the individual electrode 35 and having a thickness of about 2 μm is interposed between the piezoelectric sheet 42 and the piezoelectric sheet 43. On the other hand, no electrode is disposed between the piezoelectric sheet 44 adjacent below the piezoelectric sheet 43 and the piezoelectric sheet 45 adjacent below the piezoelectric sheet 43 and below the piezoelectric sheet 45.

  As shown in FIG. 9A, in the piezoelectric sheets 41 and 42, between the individual electrode 35 and the individual electrode 36, one end portion of the main electrode portion 90 of the individual electrode 35 (the end portion on the opposite side to the contact portion 91). ) Through holes 41a and 42a extending downward. The through holes 41a and 42a are filled with a conductive material (silver palladium or the like) 48 as shown in FIG. 9C, and the individual electrode 35 and the individual electrode 36 are connected to each other through the conductive material 48. Each pressure chamber 10 is connected.

  As shown in FIG. 8, in the present embodiment, grounding electrodes 38 are formed in the vicinity of the four corners of the upper surface of the piezoelectric sheet 41. The region of the upper surface of the piezoelectric sheet 41 where the individual electrode 35 is formed is surrounded by a virtual region partitioned by the four grounding electrodes 38.

  As shown in FIG. 9B, a common electrode 33 having a thickness of about 2 μm is provided between the uppermost piezoelectric sheet 41 of the actuator unit 21 and the lower piezoelectric sheet 42 below the ground electrode 38. Intervene. The common electrode 33 is composed of a single conductive sheet extending over almost the entire area of the piezoelectric sheets 41 to 45. Similarly, a common electrode 34 having a thickness similar to that of the common electrode 33 and having a thickness of about 2 μm is interposed between the piezoelectric sheet 43 positioned third from the top and the piezoelectric sheet 44 below the piezoelectric sheet 43.

As shown in FIG. 9 (b), through holes 41 b, 42 b, 43 b penetrating the piezoelectric sheets 41, 42, 43 are formed below the ground electrode 38. The through holes 41b, 42b, and 43b are filled with a conductive material (silver palladium or the like) 49 as shown in FIG. 9D, and the ground electrode 38 is connected to the common electrode 33 and the conductive material 49 through the conductive material 49. The common electrode 34 is connected.
The individual electrodes 35 and 36 and the common electrodes 33 and 34 described above are made of a metal material such as an Ag-Pd system.

  Here, a large number of common electrodes 33 and 34 may be formed for each pressure chamber 10 so that the projection region in the stacking direction includes the pressure chamber region, or each projection region may have a projection region. Many small pressure chambers 10 may be formed for each pressure chamber 10 so as to be included in the pressure chamber region, and it is not necessarily required to be a single conductive sheet extending over the entire surface of the piezoelectric sheet. However, at this time, it is necessary that the common electrodes are electrically connected so that the portions facing the pressure chamber 10 all have the same potential.

  As shown in FIGS. 8 and 10, a large number of dummy contact portions 39 are provided on the uppermost piezoelectric sheet 41 in addition to the individual electrodes 35 and the grounding electrode 38. These dummy contact portions 39 are provided between the individual electrodes 35 arranged in a matrix, support the FPC 50 disposed on the piezoelectric sheet 41, and the FPC 50 between the contact portions 91 of the individual electrodes 35. The depression prevents the deformation of the piezoelectric sheet 41 during ink ejection.

Next, the driver IC 80 and the FPC 50 (50a, 50b) will be described.
The driver IC 80 (drive device) is electrically connected to the substrate 81 (signal supply device) and the plurality of individual electrodes 35 via the FPC 50, and is used as a signal for driving the driver IC 80 supplied from the substrate 81. Based on this, by selectively applying a voltage (supplying a drive signal) to the plurality of individual electrodes 35, the volume of the pressure chamber 10 corresponding to the individual electrode 35 to which the voltage is applied is changed, and the pressure is increased. Ink is ejected from a nozzle 8 communicating with the chamber 10.

  As shown in FIG. 15, the FPC 50 (50a, 50b) electrically connects the substrate 81 and the driver IC 80, and electrically connects the driver IC 80 to the individual electrodes 35 and 36 and the common electrodes 33 and 34. 9 (a) and 9 (b), the individual electrode 35 and the grounding electrode 38 disposed on the upper surface of the uppermost piezoelectric sheet 41 are respectively electrically joined by soldering. Connection pads 55 and 60. Driver ICs 80 (80a, 80b) are mounted on the FPC 50, respectively, and a connection part 100 (100a, 100b) provided at an end opposite to the end connected to the individual electrode 35 is provided on the substrate 81. The driver IC 80 and the substrate 81 are electrically connected via the FPC 50 by being inserted into a connector portion (not shown).

  By the way, in this inkjet head 1 of this embodiment, since the several pressure chamber 10 is arrange | positioned at high density in the matrix form (refer FIG. 5), the contact part of the individual electrode 35 corresponding to the several pressure chamber 10 respectively. 91 is also arranged on the piezoelectric sheet 41 with high density. However, a plurality of signal lines (in this embodiment, 664 individual electrodes 35 are supplied to drive signals to a plurality of individual electrodes 35 arranged at high density in one FPC having a limited width, respectively. There is a limit to wiring corresponding 664 signal lines).

  Therefore, in the inkjet head 1 of the present embodiment, the plurality of individual electrodes 35 includes two individual electrode sets 101 and 102 (specifically, the upper eight rows in FIG. 8) configured by different numbers of individual electrodes. 364 individual electrode sets 101 and 300 individual electrode sets 102 in the lower eight rows), and these two individual electrode sets 101 and 102 are divided by two FPCs 50a and 50b. The two driver ICs 80a and 80b are electrically connected to each other. As shown in FIGS. 8, 10 and 15A and 15B, two FPCs 50a and 50b are arranged on the piezoelectric sheet 41 so as to partially overlap each other. Wiring from the driver ICs 80a and 80b to the contact portions 91 of the plurality of individual electrodes 35 is performed by the FPCs 50a and 50b.

  Here, the two driver ICs 80a and 80b connected to the two FPCs 50a and 50b supply drive signals to the individual electrode sets 101 and 102 each composed of a different number of individual electrodes 35. Nevertheless, it has the same structure and the same circuit configuration. The configuration of the driver IC 80 (80a, 80b) having the same specification will be described in detail below.

  As shown in FIG. 11, a plurality of types of waveform signals (FIRE) are input from the substrate 81 to the driver IC 80, and a drive signal is output to each individual electrode 35 based on the plurality of types of waveform signals. ing. As an example of the waveform signal, FIG. 12 shows eight types of waveform signals FIRE (0) to FIRE (7). Here, FIRE (0) is a non-ejection signal that does not eject ink from the nozzle 8. Further, the three types of waveform signals FIRE (1) to FIRE (3) are pulse train signals having different numbers of times of Hi, and the number of ink ejections from the nozzles 8 is varied in accordance with the number of times of Hi. FIRE (1) to FIRE (3) are waveform signals for ejecting small, medium, and large ink droplets, respectively. That is, ink drops are ejected once in the case of FIRE (1), twice in the case of FIRE (2), and three times in the case of FIRE (3). FIRE (4) to FIRE (6) are waveform signals that are selected when ejecting small, medium, and large ink balls when the temperature or other external fluctuations occur. In the waveform signals of FIRE (1) to FIRE (6), the relatively narrow pulse added at the end is for suppressing the vibration of the ink remaining in the pressure chamber 10 after the ink droplet is ejected. Stop pulse. Further, FIRE (7) is a waveform signal selected when the nozzle 8 is flushed. Then, the driver IC 80 selects any one of the eight types of waveform signals FIRE (0) to FIRE (7) for each channel, and the drive generated based on the selected waveform signal. A signal is supplied to the individual electrode 35 and ink is ejected from the nozzle 8.

  Further, as shown in FIG. 11, the driver IC 80 selects any one of the eight types of waveform signals FIRE (0) to FIRE (7) for each nozzle 8 (each channel). The 3-bit selection data SIN (x) (x is 0, 1 or 2) is serially input. Then, as shown in FIG. 13, three-bit selection data SIN (x) input to each channel is used to select from eight types of waveform signals FIRE (0) to FIRE (7) for that channel. Any one of the waveform signals is selected.

  The driver IC 80 includes shift registers 110 to 117 as serial-parallel converters that convert serially inputted 3-bit selection data SIN (x) into parallel, D-flip flops 120 to 127 as latch circuits, Multiplexers 130 to 137 for selecting any one of the eight types of waveform signals FIRE (0) to FIRE (7) based on selection data SIN (x) corresponding to a plurality of channels, and multiplexers 130 to Drive buffers 140 to 147 that output the waveform signal output from 137 to the plurality of individual electrodes 35 as drive signals of a predetermined voltage are provided.

  Here, as shown in FIG. 11, one driver IC 80 corresponds to a maximum of 49 (0 system) corresponding to each of the 8 individual electrode 35 columns constituting the individual electrode set 101, 102 shown in FIG. It is divided into 8 blocks (0 system to 7 system) each having ˜42 (7 system) output terminals. One driver IC 80 (80a) has 364 output terminals (total number of 0-system to 7-system output terminals), and constitutes 364 individual terminals constituting the upper electrode group 101 in the upper half of FIG. A drive signal can be output to each of the electrodes 35, but some output terminals are not connected to the individual electrodes 35 and are not connected, and the number of the individual electrodes 35 is less than 364. A set of configured individual electrodes (specifically, a set 101 of individual electrodes composed of 300 individual electrodes 35 in the lower half of FIG. 8, and a configuration composed of 304 individual electrodes 35). A drive signal can also be output to a set of individual electrodes by a driver IC 80 having the same configuration. Hereinafter, the internal configuration of the driver IC 80 will be described in more detail using a block (system 0) that can output drive signals to a maximum of 49 individual electrodes 35 among the eight blocks.

  As shown in FIG. 14, 3-bit selection data SIN (x) is serially input from the substrate 81 to the 0-system shift register 110 of the driver IC 80 in accordance with the rise of CLK, and is further connected to the output terminal of the driver IC 80. Two mode identification data modes (0) and mode (1) for identifying whether the number of individual electrodes 35 is 364, 304, or 300 are input. Then, mode 364, mode 304, and mode 300 are determined by these mode identification data modes (0) and mode (1).

  As shown in FIG. 14, when both the mode identification data mode (0) and mode (1) are Low, the mode 364 is Hi, the mode 304 and the mode 300 are Low, and the 364 individual electrodes 35 are connected. It becomes the corresponding mode. At this time, the selection data SIN (x) is set in all the shift registers through the path a → d → e → f in FIG.

  When the mode identification data mode (0) is Low and mode (1) is Hi, mode 304 is Hi, mode 364 and mode 300 are Low, and the mode corresponds to the state connected to 304 individual electrodes 35. At this time, only the data set in the shift register through the path b → d → e → g in FIG. 14 is valid as the selection data SIN (x). That is, since the data set through the paths a and f becomes invalid, OUT001 to 005 and OUT044 to 049 corresponding to the output are not connected.

  Further, when the mode identification data mode (0) is Hi and mode (1) is Low, mode300 is Hi, mode364 and mode304 are Low, and the mode corresponding to the state connected to 300 individual electrodes 35 Become. At this time, only the data set in the shift register through the path of c → e → f in FIG. 14 is valid as the selection data SIN (x). That is, since the data set through the paths a and d becomes invalid, OUT001 to 008 corresponding to the output are not connected.

  In this way, the mode 364, mode 304, and mode 300 identify whether the number of the individual electrodes 35 connected to the driver IC 80 is 364, 304, or 300, and the selection data serially input to the driver IC 80. Of the SIN (x), only the selection data SIN (x) for the connected individual electrode 35 is valid. In the other seven blocks (system 1 to system 7), the shift registers 121 to 127 are configured in the same manner as the system 0 shift register 120, so that the number of connected individual electrodes 35 is different. The drive signal can be output to the individual electrode 35 by the driver IC 80 having the same specification. In addition, by configuring the shift registers 120 to 127 in this way, it is not necessary to serially input dummy selection data to the unconnected output terminals to the driver IC 80, and transfer time for transferring dummy data is eliminated. It can be prevented from becoming long.

  In this embodiment, when the driver IC 80 is connected to the 364 individual electrode set 101 in the upper half of FIG. 8, the mode 364 becomes Hi, and the driver is set in the lower half 300 individual electrode set 102. When the IC 80 is connected, mode300 becomes Hi. In addition, when the upper-half individual electrode set 101 or the lower-half individual electrode set 102 is composed of 304 individual electrodes 35 and the driver IC 80 is connected to the set of individual electrodes 35. In this case, mode 304 can be set to Hi.

  As shown in FIGS. 11 and 14, the serially input 3-bit selection data SIN (x) is parallel-converted by the shift registers 110 to 117 and output to the D flip-flops 120 to 127. The D flip-flops 120 to 127 output parallel selection data to the multiplexers 130 to 137 in accordance with the rise of the strobe control signal STRB transferred from the substrate 81 (see FIG. 2).

The multiplexers 130 to 137 receive selection data corresponding to the plurality of individual electrodes 35 and eight types of waveform signals FIRE0 to FIRE7. Then, one corresponding waveform signal is selected from the eight types of waveform signals FIRE0 to FIRE7 based on the selection data (see FIG. 13), and the waveform signal Bx is output to the drive buffers 140 to 147.
The drive buffers 140 to 147 generate a drive signal OUTn (n is an integer from 001 to 364) of a predetermined voltage based on the waveform signals output from the multiplexers 130 to 137, and supply the drive signal OUTn to the individual electrodes 35.

  In this way, the specifications of the two driver ICs 80 (80a, 80b) connected to the two individual electrode sets 101, 102 each composed of different numbers (364 and 300) of individual electrodes 35 are exactly the same. Therefore, it is advantageous in terms of cost compared to the case where driver ICs having different specifications are provided for the two individual electrode sets 101 and 102, respectively. In addition, each of the two individual electrode sets 101 and 102 and each of the two driver ICs corresponding to the individual electrode sets 101 and 102 are electrically connected by one FPC 50a (50b). The connection relationship between the individual electrode sets 101 and 102 and the driver IC 80 is simplified, and the connection work of the driver IC 80 to the FPC 50 (50a, 50b) is facilitated.

Next, the two FPCs 50a and 50b will be described in detail.
As shown in FIGS. 9A and 9B, each FPC 50 includes a base film 51, conductor portions 53 and 54 provided on the lower surface of the base film 51, and a conductor portion 53 with respect to substantially the entire surface of the base film 51. , 54 and a cover film 52 provided so as to cover. The FPC 50 is disposed so that the cover film 52 is in contact with the upper surface of the uppermost piezoelectric sheet 41. The base film 51 and the cover film 52 are both sheet-like members having insulating properties.

  Further, as shown in FIGS. 15A and 15B, the two FPCs 50a and 50b have substrates on the ends opposite to the ends connected to the individual electrodes 35 (on the right side in FIG. 15), respectively. The connection part 100 (100a, 100b) connected to 81 is provided. Here, the connection width Wa of the connection portion of the FPC 50a and the connection width Wb of the connection portion of the FPC 50b are the same width, and the connection between the two FPCs 50a and 50b and the substrate 81 can be performed in the same manner. Connection work can be performed quickly.

  Here, as shown in FIG. 9A, a conductive connection pad 55 is provided on the lower surface of the base film 51 at a position corresponding to one end of the individual electrode 35. That is, the connection pad 55 is provided at a position corresponding to the contact portion 91 of the individual electrode 35. Accordingly, one connection pad 55 is provided for each individual electrode 35. Further, as shown in FIG. 9B, a conductive connection pad 60 is provided on the lower surface of the base film 51 at a position corresponding to the grounding electrode 38 formed in the vicinity of the outer edge of the upper surface of the actuator unit 21. Is provided.

  And in the part corresponding to the connection pad 55 and the connection pad 60 of the cover film 52, as shown to Fig.9 (a), (b), it is a little larger than the diameter of the connection pad 55 and the connection pad 60. Through holes 52a and 52b having a diameter are formed. Therefore, most portions of the lower surface of the base film 51 except for the connection pads 55 and the connection pads 60 at positions corresponding to the through holes 52 a and 52 b are covered with the cover film 52.

  Moreover, the conductor parts 53 and 54 arrange | positioned between the base film 51 and the cover film 52 are formed with the copper foil. A plurality of signal lines for connecting the plurality of connection pads 55 and the driver IC 80 are wired by the conductor portion 53. On the other hand, the conductor portion 54 is provided to ground the connection pad 60. Therefore, the conductor parts 53 and 54 are provided on the lower surface of the base film 51 so as to form a predetermined pattern. In FIGS. 15A and 15B, a plurality of signal lines are drawn only on portions of the two FPCs 50a and 50b that overlap with the piezoelectric sheet 41. In practice, however, a plurality of individual electrodes 35 are provided. A plurality of signal lines extend in parallel from the plurality of connection pads 55 respectively connected to the driver IC 80.

  As described above, when the FPC 50 having the connection pads 55 and 60 is arranged on the upper surface of the piezoelectric sheet 41 on which the individual electrode 35 and the ground electrode 38 are formed, the connection pad 55 and the individual electrode 35 are electrically connected. At the same time, the connection pad 60 and the ground electrode 38 are electrically connected. Therefore, the individual electrode 35 is electrically connected to the driver IC 80 via the connection pad 55 and the conductor portion 53, and the ground electrode 38 is grounded in a region (not shown) via the connection pad 60 and the conductor portion 54. The

  The plurality of individual electrodes 35 are connected to the driver IC 80 via individual conductor portions 53 that are independent of each other. The individual electrodes 35 and 36 are connected to each pressure chamber 10 via a conductive material 48 provided in through holes 41 a and 42 a formed in the piezoelectric sheets 41 and 42. Therefore, the potentials of the individual electrodes 35 and 36 can be controlled independently for each pressure chamber 10.

  Each of the grounding electrodes 38 is connected to the common electrode 33 via a conductive material 49 provided in a through hole 41 b formed in the piezoelectric sheet 41. The common electrodes 33 and 34 are connected via a conductive material 49 provided in through holes 42 b and 43 b formed in the piezoelectric sheets 42 and 43. Therefore, the common electrodes 33 and 34 connected to the grounding electrode 38 grounded via the connection pad 60 and the conductor portion 54 are kept at the same ground potential in the regions corresponding to all the pressure chambers 10.

  By the way, as shown in FIGS. 8, 15A and 15B, in the inkjet head 1, two FPCs 50a and 50b are disposed on the uppermost piezoelectric sheet 41 so as to partially overlap. Has been. The plurality of connection pads 55 of the FPC 50a located on the lower side of the two FPCs 50 are connected to the contact portions 91 of the plurality of individual electrodes 35 arranged on the upper side in FIG. On the other hand, the plurality of connection pads 55 of the FPC 50b located on the upper side are connected to the contact portions 91 of the plurality of individual electrodes 35 arranged on the lower side in FIG.

  However, when the two FPCs 50a and 50b are superposed on the piezoelectric sheet 41 in this way, the boundary portion 92 of the portion where the two FPCs 50a and 50b overlap and the portion where the two FPCs 50a and 50b do not overlap is formed. At a short distance across 92, the upper FPC 50b is forced to deform more than the thickness of the lower FPC 50a in order to avoid the lower FPC 50a, and the contact portion 91 of the individual electrode 35 and the corresponding FPC 50b The connection with the connection pad 55 is weak against the application of external force. For this reason, when an external force in the direction of peeling off the upper FPC 50b is applied, the connection pad 55 of the upper FPC 50b is separated from the contact portion 91, and connection failure is likely to occur.

  Therefore, as shown in FIGS. 8 and 10, on the piezoelectric sheet 41, the contact portions 91 of all the individual electrodes 35 are provided at the end of the individual electrode 35 on the side away from the boundary portion 92. That is, in the individual electrode set 101 arranged in the upper half of the piezoelectric sheet 41 in FIG. 8, the contact portion 91 is provided at the upper end of the individual electrode 35 in FIG. In the set of individual electrodes 102 arranged in the lower half of the sheet 41 in FIG. 8, the contact portion 91 is provided at the lower end of the individual electrode 35 in FIG. 8. With this configuration, as shown in FIG. 16, the distance L from the boundary portion 92 of the contact portion 91 close to the boundary portion 92 is increased, so that the upper FPC 50 b can be easily peeled off from the boundary portion 92. The FPC 50b and the contact portion 91 can be connected at positions as far as possible, and the reliability of the electrical connection can be improved.

  Further, in all the individual electrodes 35 on the piezoelectric sheet 41, the contact portion 91 is provided at the end of the individual electrode 35 on the side away from the boundary 92. Therefore, the direction of the contact portion 91 of the individual electrode 35 is the same in the two regions divided in the vertical direction in FIG. Therefore, there is no portion where the distance between the contact portions 91 is locally shortened, the pattern formation of the contact portions 91 is facilitated, and a short circuit between the contact portions 91 can be prevented as much as possible.

  As shown in FIGS. 8 and 10, the above-described dummy contact portions 39 are densely provided near the boundary portion 92 as compared with locations other than the boundary portion 92. Therefore, the FPC 50 can be prevented from falling by the densely provided dummy contact portions 91 in the vicinity of the boundary portion 92 where the distance between the contact portions 91 is long.

  In the inkjet head 1 according to the present embodiment, the piezoelectric sheets 41 to 43 are polarized in the thickness direction. Therefore, when the individual electrodes 35 and 36 are set to a potential different from that of the common electrodes 33 and 34 and a voltage is applied to the piezoelectric sheets 41 to 43 in the polarization direction, the portion to which the voltage is applied functions as an active layer. It stretches or contracts in the thickness direction, that is, the stacking direction, and as a result, it tends to contract or extend in the direction perpendicular to the stacking direction, that is, the plane direction, due to the piezoelectric lateral effect. On the other hand, the remaining two piezoelectric sheets 44 and 45 are inactive layers that do not have a region sandwiched between the individual electrodes 35 and 36 and the common electrodes 33 and 34, and therefore cannot be deformed spontaneously. That is, the actuator unit 21 includes three piezoelectric sheets 41 to 43 on the upper side (that is, apart from the pressure chamber 10) as the layers on which the active layer is formed and two lower sheets (that is, close to the pressure chamber 10). This is a so-called unimorph type configuration in which the piezoelectric sheets 44 and 45 are inactive layers.

  Therefore, when the driver IC 80 is controlled so that the electric field and the polarization are in the same direction and the individual electrodes 35 and 36 are set to a positive or negative predetermined potential, the individual electrodes 35 and 36 of the piezoelectric sheets 41 to 43 and the common electrode 33, The active layer sandwiched between 34 contracts in the plane direction, while the piezoelectric sheets 44 and 45 do not spontaneously contract. At this time, as shown in FIG. 9A, the lower surfaces of the piezoelectric sheets 41 to 45 are fixed to the upper surfaces of the partition walls that define the pressure chambers 10 formed in the cavity plate 22. As a result, the piezoelectric sheets 41 to 45 are deformed so as to be convex toward the pressure chamber 10 (unimorph deformation). Then, the volume of the pressure chamber 10 decreases, the ink pressure increases, and ink is ejected from the nozzles 8. Thereafter, when the potentials of the individual electrodes 35 and 36 are restored, the piezoelectric sheets 41 to 45 have the original flat plate shape, and the volume of the pressure chamber 10 is restored to the original volume, so that ink is sucked from the manifold 5 side.

  As another driving method, the individual electrodes 35 and 36 are previously set to a potential different from that of the common electrodes 33 and 34, and the individual electrodes 35 and 36 are temporarily set to the same potential as the common electrodes 33 and 34 every time there is a discharge request. Thereafter, the individual electrodes 35 and 36 can be set to a potential different from that of the common electrodes 33 and 34 again at a predetermined timing. In this case, at the timing when the individual electrodes 35 and 36 and the common electrodes 33 and 34 become the same potential, the piezoelectric sheets 41 to 45 return to the original shape, and the volume of the pressure chamber 10 is in the initial state (the potentials of both electrodes are The ink is sucked into the pressure chamber 10 from the manifold 5 side. After that, at the timing when the individual electrodes 35 and 36 are set to a potential different from that of the common electrodes 33 and 34 again, the piezoelectric sheets 41 to 45 are deformed so as to protrude toward the pressure chamber 10, and the volume of the pressure chamber 10 decreases to reduce the ink. The pressure rises and ink is ejected.

  If the direction of the electric field applied to the piezoelectric sheets 41 to 43 and the polarization direction are opposite, the piezoelectric sheets 41 to 43 sandwiched between the individual electrodes 35 and 36 and the common electrodes 33 and 34 are caused by the piezoelectric lateral effect. The active layer tends to extend in a direction perpendicular to the polarization direction. Accordingly, the piezoelectric sheets 41 to 45 are deformed so as to be concave toward the pressure chamber 10 based on the piezoelectric lateral effect. For this reason, the volume of the pressure chamber 10 increases and ink is sucked from the manifold 5 side. After that, when the potentials of the individual electrodes 35 and 36 are restored, the piezoelectric sheets 41 to 45 have the original flat plate shape, and the volume of the pressure chamber 10 is restored to the original volume, so that ink is ejected from the nozzle 8.

According to the inkjet head 1 described above, the following effects can be obtained.
Since the two driver ICs 80 connected to the two individual electrode sets 101 and 102 formed of different numbers of individual electrodes 35 can have the same specification, the two individual electrode sets 101 and 102 are On the other hand, it is advantageous in terms of cost compared to the case where driver ICs having different specifications are provided.

  Since the wiring members that electrically connect the two individual electrode sets 101 and 102 and the two driver ICs 80 corresponding to the two individual electrode sets 101 and 102 are configured by the flexible FPC 50, Two FPCs 50a and 50b can be partially overlapped on the actuator unit 21 to increase the degree of freedom in arranging the FPC 50 and the driver IC 80.

  Since the contact portions 91 of all the individual electrodes 35 arranged on the piezoelectric sheet 41 are provided at the end of the individual electrode 35 on the side away from the boundary portion 92, the contact portions 91 that are close to the boundary portion 92. The separation distance from the boundary portion 92 increases. Accordingly, the FPC 50b and the contact portion 91 can be connected at a position as far as possible from the boundary portion 92 where the upper FPC 50b is easily peeled off, and the reliability of the electrical connection can be improved. Further, since the direction of the contact portion 91 of the individual electrode 35 is the same in the two regions divided in the vertical direction in FIG. 8 with the boundary portion 92 as a boundary, there is a portion where the distance between the contact portions 91 is locally shortened. Thus, the pattern formation of the contact portions 91 is facilitated, and a short circuit between the contact portions 91 can be prevented as much as possible.

  Since the individual electrode 35 is formed in an elongated shape in a direction intersecting with the arrangement direction (first direction) along the boundary portion 92, the contact portion 91 is connected to the boundary portion in the individual electrode 35 close to the boundary portion 92. When provided at the end portion on the side away from 92, the separation distance from the boundary portion 92 is further increased, so that the FPC 50 and the contact portion 91 can be connected at a position further away from the boundary portion 92. .

  Since the dummy contact portions 39 are densely provided in the vicinity of the boundary portion 92 as compared to locations other than the boundary portion 92, the dummy contact portions 39 are densely arranged in the vicinity of the boundary portion 92 where the distance between the contact portions 91 is separated. It is possible to surely prevent the FPC 50 from dropping due to the provided dummy contact portion 39 and inhibiting the deformation of the piezoelectric sheets 41 to 45.

Next, modified embodiments in which various modifications are made to the embodiment will be described.
1] The method of connecting the plurality of individual electrodes 35 of one actuator unit 21 to the driver IC 80 is not limited to that of the above-described embodiment. For example, the plurality of individual electrodes 35 include a plurality of individual sets of three or more sets. Three or more identical driver ICs 80 corresponding to a plurality of groups of three or more groups may be provided by being divided into groups of electrodes. Then, three or more FPCs 50 may be arranged on the piezoelectric sheet 41 so as to overlap each other. Further, a plurality of identical driver ICs 80 may be connected to a plurality of individual electrodes 35 by one FPC 50, and conversely, one driver IC 80 is connected to a plurality of individual electrodes 35 by a plurality of FPCs 50. Also good.

  2] The contact portion 91 is provided at the end of the individual electrode 35 on the side away from the boundary portion 92 only for the individual electrode 35 close to the boundary portion 92 where the plurality of FPCs 50 overlap and not overlap. You may comprise as follows.

  3] In the above embodiment, the common electrodes 33 and 34 are grounded. However, the common electrode is not necessarily grounded, and the actuator unit can be operated in the same manner as in the present embodiment. A drive signal different from the drive signal supplied to the individual electrode may be supplied to the common electrode.

  4] The material of the piezoelectric sheet or electrode is not limited to the above-described material, but may be changed to other known materials. Moreover, you may change suitably the planar shape, cross-sectional shape, arrangement | positioning form, etc. of a pressure chamber and an electrode. Further, the number of piezoelectric sheets including the active layer and the number of piezoelectric sheets not including the active layer can be appropriately changed. The layer thicknesses of the piezoelectric sheet including the active layer and the piezoelectric sheet not including the active layer may be the same or different. Moreover, you may use insulating sheets other than a piezoelectric sheet as an inactive layer.

1 is a perspective view of an inkjet head according to an embodiment of the present invention. It is the II-II sectional view taken on the line of FIG. It is a top view of a head body. It is an enlarged view of the area | region enclosed with the dashed-dotted line of FIG. It is an enlarged view of the area | region enclosed with the dashed-dotted line of FIG. FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. It is a partial exploded perspective view of a head body. It is a top view of an actuator unit. It is sectional drawing of the individual electrode periphery of an actuator unit. FIG. 6 is a cross-sectional view around the grounding electrode of the actuator unit. FIG. 10 is an enlarged view inside the round frame of FIG. FIG. 10 is an enlarged view in a round frame of FIG. It is the elements on larger scale near the boundary part of FIG. It is a block diagram of a driver IC. It is a figure which shows eight types of waveform signals. It is a figure which shows the correspondence of selection data and a waveform signal. It is a block diagram of a part (0 system) of a driver IC. It is a figure which shows a flexible printed wiring board (FPC), (a) is a top view of lower FPC, (b) is a top view of upper FPC. It is the sectional view on the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 4 Flow path unit 10 Pressure chamber 21 Actuator unit 35 Individual electrode 39 Dummy contact part 41-45 Piezoelectric sheet 50 FPC
91 Contact point 92 Boundary part

Claims (4)

A plurality of pressure chambers communicating with nozzles for ejecting ink are arranged adjacent to each other along a plane, and the pressure chambers are disposed on the surface of the channel unit to eject ink from the nozzles. An actuator unit that changes the volume of
The actuator unit includes a piezoelectric sheet disposed over the plurality of pressure chambers, a plurality of individual electrodes provided on the piezoelectric sheet corresponding to the plurality of pressure chambers and having contact portions, and the individual electrodes. A plurality of flexible printed wiring boards provided with a plurality of signal lines that are connected to the contact portion and supply a drive signal for changing the volume of the plurality of pressure chambers,
The plurality of flexible printed wiring boards are disposed so as to partially overlap each other on the piezoelectric sheet, and are at least individually adjacent to a boundary portion between the overlapping portion and the non-overlapping portion of the plurality of flexible printed wiring boards. The ink jet head according to claim 1, wherein the contact portion is provided at an end of the individual electrode on the side away from the boundary portion.   2. The inkjet head according to claim 1, wherein, in all the individual electrodes provided on the piezoelectric sheet, the contact portion is provided at an end of the individual electrode on the side away from the boundary portion.   On the piezoelectric sheet, a plurality of dummy contact portions for supporting a flexible printed wiring board disposed on the piezoelectric sheet are provided between the plurality of individual electrodes, and the dummy contact portions are other than the boundary portions. The ink jet head according to claim 1, wherein the ink jet head is densely provided near the boundary portion as compared with a portion.   The inkjet head according to claim 1, wherein the individual electrodes are formed in an elongated shape in a direction intersecting with the arrangement direction along the boundary portion.

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