Liquid discharge head

Abstract

To provide a liquid discharge head that can apply drive voltages for driving a plurality of piezoelectric actuators, to laminated piezoelectric body blocks in a comb-tooth shape in which the piezoelectric actuators are arranged.SOLUTION: A liquid discharge head according to an embodiment comprises a laminated piezoelectric body block, a pressure chamber, a substrate, a flexible substrate and wiring electrodes for the substrate. The laminated piezoelectric body block is formed in a comb tooth-shape in which a plurality of piezoelectric actuators and support pillars are alternately arranged. A portion of a bulkhead of the pressure chamber is joined to an end face of the piezoelectric actuator. The substrate is joined to a surface at the base end side of the laminated piezoelectric body block. The flexible substrate is connected to an outer periphery part of the substrate. The wiring electrode for the substrate is connected to an outer electrode of the piezoelectric actuator and also is connected to wiring of the flexible substrate, at the outer periphery part of the substrate, where an electrode width at a connection part between the substrate and the flexible substrate is set to be above a column width of the piezoelectric actuator.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] An embodiment of the present invention relates to a liquid ejection head. [Background technology]

[0002] Liquid ejection heads that supply a predetermined amount of liquid to a predetermined position are known. Liquid ejection heads are mounted on, for example, inkjet printers, 3D printers, and dispensing devices. Inkjet printers eject droplets of ink from an inkjet head to form an image or the like on the surface of a recording medium. 3D printers eject droplets of modeling material from a modeling material ejection head, harden the droplets, and form a three-dimensional object. Dispensing devices eject droplets of a sample and supply a predetermined amount to a plurality of containers, etc.

[0003] A liquid ejection head has a plurality of channels for ejecting liquid. Each channel is equipped with a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric actuator for changing the volume of the pressure chamber. The liquid ejection head selects a channel for ejecting liquid from among the plurality of channels, and applies a drive voltage to the piezoelectric actuator of the selected channel to eject the liquid. However, for example, if the piezoelectric actuators of the plurality of channels are integrally formed in a comb-shaped laminated piezoelectric block and a flexible substrate for applying the drive voltage is directly connected to the laminated piezoelectric block, the laminated piezoelectric block is likely to be damaged. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-208234 A [Patent Document 2] JP 2016-137589 A [Patent Document 3] JP 2011-5774 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a liquid ejection head capable of applying a drive voltage for driving each piezoelectric actuator to a comb-like laminated piezoelectric block in which a plurality of piezoelectric actuators are arranged. [Means for solving the problem]

[0006] A liquid ejection head according to an embodiment of the present invention comprises a laminated piezoelectric block, a pressure chamber, a substrate, a flexible substrate, and wiring electrodes of the substrate. The laminated piezoelectric block is comb-shaped with a plurality of piezoelectric actuators and pillars arranged alternately. The pressure chamber has a portion of a partition joined to an end face of the piezoelectric actuator. The substrate is joined to the surface of the base end side of the laminated piezoelectric block. The flexible substrate is connected to the outer periphery of the substrate. The wiring electrodes of the substrate are connected to the external electrodes of the piezoelectric actuator and are connected to the wiring of the flexible substrate at the outer periphery of the substrate, and the electrode width at the connection portion between the substrate and the flexible wiring plate is greater than or equal to the pillar width of the piezoelectric actuator. [Brief description of the drawings]

[0007] [Figure 1] 1 is an overall configuration diagram of an inkjet printer equipped with an inkjet head according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of the inkjet head. [Diagram 3] FIG. 2 is a partially enlarged cross-sectional view of a head portion of the inkjet head. [Figure 4] FIG. 2 is a partially enlarged cross-sectional view of a head portion of the inkjet head. [Diagram 5] FIG. 2 is a partially enlarged plan view of a head portion of the inkjet head. [Figure 6] 4 is a plan view of an actuator substrate of the head unit. FIG. [Figure 7] FIG. 2 is a partially enlarged plan view of the actuator substrate. [Figure 8]FIG. 2 is a partially enlarged perspective view of the actuator substrate. [Figure 9] FIG. 2 is a partially enlarged perspective view of the actuator substrate. [Figure 10] FIG. 2 is a partially enlarged perspective view of the actuator substrate. [Figure 11] 3A to 3C are diagrams illustrating an assembly process of the inkjet head. [Figure 12] FIG. 2 is an assembly diagram of the inkjet head. [Figure 13] FIG. 4 is a circuit diagram of a control system for the inkjet head. [Figure 14] 4 shows a driving waveform applied to the actuator of the inkjet head. [Figure 15] 5A to 5C are diagrams illustrating the operation of the actuator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a liquid ejection head according to an embodiment will be described in detail with reference to the accompanying drawings. In each drawing, the same components are given the same reference numerals. Also, in order to clarify the orientation of the components shown in each drawing, XYZ coordinates are described in each drawing.

[0009] As an example of an image forming apparatus equipped with a liquid ejection head according to an embodiment, an inkjet printer 10 that prints an image on a recording medium will be described. Fig. 1 shows a schematic configuration of the inkjet printer 10. Inside a housing 11, the inkjet printer 10 has a cassette 12 that stores a sheet S, which is an example of a recording medium, an upstream transport path 13 for the sheet S, a transport belt 14 that transports the sheet S taken out of the cassette 12, a plurality of inkjet heads 100-103 that eject ink droplets toward the sheet S on the transport belt 14, a downstream transport path 15 for the sheet S, an ejection tray 16, and a control board 17. An operation unit 18 that is a user interface is disposed on the upper side of the housing 11.

[0010] Image data to be printed on the sheet S is generated, for example, by a computer 200, which is an externally connected device. The image data generated by the computer 200 is sent to a control board 17 of the inkjet printer 10 via a cable 201 and connectors 202 and 203.

[0011] The pickup roller 204 supplies the sheets S one by one from the cassette 12 to the upstream conveying path 13. The upstream conveying path 13 is composed of a pair of feed rollers 131 and 132 and sheet guide plates 133 and 134. The sheet S is fed to the upper surface of the conveying belt 14 via the upstream conveying path 13. An arrow 104 in the figure indicates the conveying path of the sheet S from the cassette 12 to the conveying belt 14.

[0012] The conveyor belt 14 is a mesh-like endless belt with many through holes formed on its surface. Three rollers, a drive roller 141 and driven rollers 142 and 143, support the conveyor belt 14 so that it can rotate freely. A motor 205 rotates the conveyor belt 14 by rotating the drive roller 141. The motor 205 is an example of a drive device. In the figure, 105 indicates the rotation direction of the conveyor belt 14. A negative pressure container 206 is disposed on the back side of the conveyor belt 14. The negative pressure container 206 is connected to a fan 207 for reducing pressure. The fan 207 creates a negative pressure inside the negative pressure container 206 by forming an airflow, and adsorbs and holds the sheet S on the upper surface of the conveyor belt 14. In the figure, 106 indicates the flow of the airflow.

[0013] Inkjet heads 100-103, which are an example of liquid ejection heads, are arranged to face sheet S, which is attracted and held on conveyor belt 14, with a small gap of, for example, 1 mm between them. Each of inkjet heads 100-103 ejects ink droplets in the -Z direction toward sheet S, which is conveyed from the -Y direction to the Y direction. Inkjet heads 100-103 print images when sheet S passes below them. Each of inkjet heads 100-103 has the same structure except that they eject different colors of ink. The ink colors are, for example, cyan, magenta, yellow, and black.

[0014] The inkjet heads 100-103 are connected to ink tanks 315-318 and ink supply pressure adjusting devices 321-324 via ink flow paths 311-314, respectively. Each ink tank 315-318 is disposed above each inkjet head 100-103. During standby, each ink supply pressure adjusting device 321-324 adjusts the pressure inside each inkjet head 100-103 to a negative pressure, for example, -1.2 kPa, relative to atmospheric pressure so that ink does not leak from the nozzles 24 (see FIG. 2) of the inkjet heads 100-103. During image formation, ink from each ink tank 315-318 is supplied to each inkjet head 100-103 by the ink supply pressure adjusting devices 321-324.

[0015] After the image is formed, the sheet S is sent from the conveyor belt 14 to a downstream conveying path 15. The downstream conveying path 15 is composed of pairs of feed rollers 151, 152, 153, and 154, and sheet guide plates 155 and 156 that define the conveying path of the sheet S. The sheet S passes through the downstream conveying path 15 and is sent from a discharge port 157 to a discharge tray 16. An arrow 107 in the figure indicates the conveying path of the sheet S.

[0016] Next, a description will be given of the configuration of the inkjet heads 100 to 103. The inkjet head 100 will be described below with reference to Figures 2 to 10, but the inkjet heads 101 to 103 have the same structure as the inkjet head 100.

[0017] As shown in FIG. 2, the inkjet head 100 includes a head unit 2, which is an example of a liquid ejection unit. The head unit 2 is connected to the ink supply pressure adjustment device 321 in FIG. 1 via an ink flow path 311. When ink is circulated and supplied, the ink supply path and discharge path are connected to the head unit 2. The nozzles 24 of each ejection channel that ejects ink are arranged along a first direction, for example, the X direction, of the nozzle plate 23. The nozzle density is set, for example, within a range of 150 to 1200 dpi. The nozzles 24 are arranged in two rows, row A on the Y direction side and row B on the -Y direction side. For example, when the number of ejection channels is 656, row A arranges nozzles 1 to 328 in order from the X direction to the -X direction, and row B arranges nozzles 1 to 328 in order from the -X direction to the X direction. However, the nozzles 24 may be arranged in one row or three or more rows. As described above, the sheet S is transported from the -Y direction to the Y direction, and the ink is ejected in the -Z direction toward the surface of the sheet S located below the nozzles 24.

[0018] The head unit 2 is connected to a flexible printed wiring board 21, which is an example of a flexible substrate. The flexible printed wiring board 21 is connected to a printed circuit board 22, which is an example of a relay board. Two sets of the flexible printed wiring board 21 and the printed circuit board 22, for example, for row A and row B, are symmetrically connected to the head unit 2.

[0019] The flexible printed wiring board 21 is a flexible printed wiring board using a synthetic resin film such as polyimide. The flexible printed wiring board 21 is equipped with a driving IC (Integrated Circuit) 3, which is a driver chip (hereinafter referred to as a driving IC). The printed circuit board 22 is a hard through-hole board in which glass fiber-reinforced epoxy resin layers and copper wiring layers are laminated in multiple layers. The driving IC 3, which serves as a control unit for the inkjet head 100, temporarily stores data sent via the printed circuit board 22 from the control board 17, which has a CPU as a control unit for the inkjet printer 10, and provides driving signals to each channel to eject ink at a predetermined timing.

[0020] 3 to 5 are partial cross-sectional views of the head unit 2. Fig. 4 is a cross-sectional view taken along CC in Fig. 3, and Fig. 5 is a cross-sectional view taken along DD in Fig. 3. The ejection channels in row A and the ejection channels in row B are arranged symmetrically back to back with respect to the center line in the X direction. Therefore, in the following description, there are some parts where only the ejection channels in row A are illustrated and described, but the ejection channels in row B are also arranged in the same manner.

[0021] The nozzle plate 23 is bonded to one surface of the pressure chamber substrate 4. The nozzle plate 23 is a rectangular plate made of, for example, a resin such as polyimide or a metal such as stainless steel. The diaphragm 5 is bonded to one surface of the pressure chamber substrate 4 opposite the nozzle plate 23. The diaphragm 5 has flexibility such that it deforms when an external force is applied. The diaphragm 5 is a thin plate made of, for example, a metal such as nickel or stainless steel. The material of the diaphragm 5 may be a material other than metal, such as a polyimide film.

[0022] The pressure chambers 42 are formed in a pressure chamber substrate 4. The pressure chambers 42 of each ejection channel are arranged at the position of each nozzle 24 and are connected to the nozzles 24, respectively. The pressure chamber substrate 4 is formed of a metal such as stainless steel. As an example, the pressure chambers 42 are formed by forming a rectangular opening penetrating in the second direction, for example, the Z direction, in the pressure chamber substrate 4 and closing the openings on both sides with the nozzle plate 23 and the vibration plate 5, respectively. In other words, the vibration plate 5 constitutes a part of the partition wall of the pressure chamber 42.

[0023] The pressure chambers 42 communicate with a guide flow path 43 having a narrowed portion, and further communicate with an ink supply manifold 45 via an ink supply port 44 which is an opening hole penetrating the vibration plate 5. The guide flow path 43 is formed in the shape of a groove in a third direction, for example, the Y direction, on one surface of the pressure chamber substrate 4 on the vibration plate 5 side for each pressure chamber 42. The nozzles 24, pressure chambers 42 and guide flow paths 43 are provided in each ejection channel. The ink supply port 44 is shared by the ejection channels of row A and row B which are back-to-back.

[0024] The ink supply manifold 45 is formed in a frame 46 joined to one surface of the diaphragm 5. The ink supply manifold 45 extends in the X direction, and communicates with the pressure chambers 42 of each channel via the ink supply ports 44 and the guide flow paths 43 of each channel. The ink supply manifold 45, which serves as a common ink chamber, communicates with the ink flow path 311 (see FIGS. 1 and 2). An ink port 48 and an ink port 49 are provided at both ends of the frame 46 in the X direction and the -X direction. The ink port 48 and the ink port 49 may be used to supply and discharge ink, respectively, when filling with ink (see FIG. 12).

[0025] The actuators 6 of each discharge channel are arranged at positions facing the pressure chambers 42 of each discharge channel across the vibration plate 5. The actuators 6 of each discharge channel have their -Z end faces bonded to the vibration plate 5 constituting a part of the partition of the pressure chambers 42, for example, by adhesive. The actuators 6, which are an example of a piezoelectric actuator, are laminated piezoelectric actuators formed by alternately laminating a piezoelectric body 61 such as a piezo element, a first internal electrode 62, and a second internal electrode 63 (see FIG. 3 in particular). The piezoelectric bodies 61 are arranged such that the polarization directions are opposite to each other in the Z direction, for example, and are deformed in the d33 mode. The piezoelectric bodies 61 are formed of a lead-containing piezoelectric material such as lead zirconate titanate (PZT) or a lead-free piezoelectric material such as sodium potassium niobate.

[0026] The first internal electrode 62 and the second internal electrode 63 are conductive films formed on the main surfaces of the piezoelectric body 61. The first internal electrode 62 and the second internal electrode 63 are formed of a conductive material that can be fired, such as silver palladium. In the case of row A, the first internal electrodes 62 of the actuators 6 are formed up to one side surface of the actuator 6 in the Y direction and connected to the individual electrodes 64, which are external electrodes formed on this side surface. The second internal electrodes 63 are formed up to the other side surface of the actuator 6 in the -Y direction and connected to the common electrode 65, which is an external electrode formed on this side surface. The dummy layer 68 is made of the same material as the piezoelectric body 61. However, the dummy layer 68 does not deform because no internal electrode is provided and no electric field is applied to it.

[0027] The side surface of the actuator 6 on which the individual electrode 64 is formed is inclined outward from the end surface connected to the diaphragm 5 toward the substrate 47. The inclination angle θ is, for example, 45 to 80 degrees. On the other hand, the side surface of the actuator 6 on which the common electrode 65 is formed is inclined at an angle larger than θ, or is not inclined and stands, for example, perpendicular to the surface of the substrate 47. The individual electrodes 64 and the common electrode 65 are formed by depositing, for example, Ni, Cr, Au, or the like.

[0028] As shown in Fig. 4, the pillars 60 are disposed between the actuators 6 of the discharge channels via grooves 69. The pillars 60 are disposed at positions corresponding to the partition walls 40 between the adjacent pressure chambers 42. The driving actuators 6 and the dummy actuators serving as the pillars 60 are formed collectively using a common piezoelectric body 61, a first internal electrode 62, a second internal electrode 63, an individual electrode 64, and a common electrode 65, and a groove 69 is formed to form a comb-like laminated piezoelectric body block 600. The dummy layer 68 located on the base end side of the actuators 6 serves as a base for connecting the actuators 6 and the pillars 60 that are alternately adjacent to each other.

[0029] The laminated piezoelectric block 600 is fixed to the substrate 47 by bonding an end face in the Z direction to the surface of the substrate 47. The bonding surface with the substrate 47 to which the laminated piezoelectric block 600 is fixed is the surface on the base end side of the laminated piezoelectric block 600. The substrate 47 is, for example, a ceramic substrate. The ceramic substrate is, for example, an alumina substrate. The laminated piezoelectric block 600 and the substrate 47 are bonded together, for example, with an adhesive. As will be described in detail below, the substrate 47 electrically connects wiring electrodes formed on the surface to external electrodes of the actuator 6. The bonded laminated piezoelectric block 600 and the substrate 47 constitute the actuator substrate 601.

[0030] 6 to 10 are plan and perspective views of the actuator substrate 601. As shown in Figs. 6 to 10, individual electrodes 64, which are external electrodes formed on one side of each actuator 6, are connected to individual wirings 66, which are wiring electrodes formed for each ejection channel on the surface of the substrate 47. In addition, common electrodes 65, which are external electrodes formed on the other side of each actuator 6, are commonly connected to a common wiring 67, which is a wiring electrode formed on the surface of the substrate 47 along the arrangement direction of the actuators 6. The common wiring 67 of the ejection channels of rows A and B is separated by a separation groove 602 formed in the center of the substrate 47 along the X direction.

[0031] The individual wiring 66 is drawn from the laminated piezoelectric block 600 to the edge of the substrate 47 for each ejection channel. Row A is drawn in a straight line in the Y direction, and row B is drawn in a straight line in the -Y direction. The edge of the substrate 47 becomes the connection portion 603 with the flexible printed wiring board 21. Since the support 60 is not driven, the individual wiring 66 is formed at a position corresponding to the actuator 6. Since the individual wiring 66 is not provided on the support 60, the pitch of the individual wiring 66 on the surface of the substrate 47 becomes twice as large as the pitch of the groove 69, and there is more space on the surface of the substrate 47. By utilizing this space, the individual wiring 66 is provided with a widened portion 604, so that the wiring width of the individual wiring 66 is widened to more than the column width of the actuator 6 in the X direction. It is preferable to provide the widened portion 604 closer to the laminated piezoelectric block 600, but it is sufficient that the widened portion 604 is widened to more than the column width of the actuator 6 at least at the connection portion 603. It is preferable that the individual wirings 66 are formed at the same pitch as the pitch of the actuators 6 in the X direction, so that the center line of the individual wirings 66 is aligned with the center of the width of the actuator 6 in the X direction.

[0032] The common wiring 67 is formed, for example, in a straight line along the X direction, which is the arrangement direction of the actuators 6 and the supports 60. To prevent current concentration during driving, the common wiring 67 has a wiring width wider than that of the individual wirings 66. Both ends are drawn out to the edges of the substrate 47. The drawing direction is the same as that of the individual wirings 66. In other words, the common wiring 67 is formed in the shape of this character when viewed in a plane, and the individual wirings 66 of each channel are arranged in parallel in the area inside the shape of the common wiring 67.

[0033] The flexible printed wiring board 21 is superimposed on the surface of the connection portion 603 of the substrate 47 and joined thereto. As a result, as shown in FIG. 7, each individual wiring 27 of the flexible printed wiring board 21 is electrically connected to each individual wiring 66 of the substrate 47. Similarly, the common wiring 28 of the flexible printed wiring board 21 is electrically connected to the common wiring 67 of the substrate 47. The substrate 47 and the flexible printed wiring board 21 are fixed to each other by, for example, ACF (Anisotropic Conductive Film), ACP (Anisotropic Conductive Paste), NCF (Non-Conductive Film), NCP (Non-Conductive Paste), etc., and are anisotropically conductively connected in the thickness direction. NCF is ACF from which conductive particles have been removed, and is an insulator in itself, but the individual wiring 27 and the individual wiring 66, and the common wiring 28 and the common wiring 67 are brought into contact with each other and thermally cured to provide electrical continuity in the thickness direction. Alternatively, they may be fixed to each other by solder or the like.

[0034] Here, the pillar width La in the X direction of the actuator 6, the width Sa of the groove 69, the wiring electrode width Lb of the individual wiring 66 of the substrate 47 and the space Sb which is the distance between the electrodes, and the wiring width Lf of the individual wiring 27 of the flexible printed wiring board 21 and the space Sf which is the distance between the electrodes have the following relationships with the pitch P of the ejection channels. Pitch P = 2 (La + Sa) = Lb + Sb = Lf + Sf Sb≧Lb>La Sf≧Lf>La

[0035] For example, when the pitch P is 169 μm, an example of La, Sa, Lb, Sb, Lf, Sf, and d is as follows. La=50 μm, Sa=34.5 μm, Lb=60μm, Sb=109μm, Lf=84μm, Sf=85μm, d=10μm

[0036] That is, since the actuators 6 and the supports 60 are alternately arranged, P=2(Sa+La). In the above example, La is 50 μm, which is narrower than half the pitch P. Since the individual wiring 66 of the supports 60 is not required on the substrate 47, the wiring electrode width Lb of the individual wiring 66 can be widened while maintaining the necessary space Sb on the substrate 47. This can be realized, for example, by the pattern shape of the exposure mask in the manufacturing process described later. In the above example, the widening portion 604 of d=10 μm widens La=50 μm to Lb=60 μm. By widening the wiring electrode width Lb of the individual wiring 66 on the substrate 47, the connection resistance is reduced, the ink ejection efficiency between the ejection channels is improved, and the connection reliability with the individual wiring 27 of the flexible printed wiring board 21 is improved. It is possible to further widen the wiring electrode width Lb of the individual wiring 66, but in order to further widen the wiring electrode width Lb, the distance d of the widening portion 604 needs to be increased. For example, in the case of inkjet printer 10 in FIG. 1, there is a demand for the distance between inkjet heads 100 to 103 in the Y direction to be as narrow as possible, and the dimension of inkjet head 100 in the Y direction is desired to be kept as small as possible, so Lb=60 μm.

[0037] In flexible printed wiring board 21, the wiring width of individual wiring 27 is further increased to, for example, Lf=84 μm and Sf=85 μm. That is, the wiring width (line) and the distance between wirings (space) on flexible printed wiring board 21 are approximately 1:1. The wiring width Lf of individual wiring 27 of flexible printed wiring board 21 is 24 μm larger than the wiring electrode width Lb of individual wiring 66 of substrate 47. When flexible printed wiring board 21 and substrate 47 are overlapped and connected, it is aimed that the center lines of individual wiring 27 and individual wiring 66 coincide with each other, but when NCF, ACF, or the like is sandwiched between them for thermocompression bonding, flexible printed wiring board 21 thermally expands and manufacturing errors occur in the connection position, so that the center lines often do not coincide accurately. However, in the above example, the wiring width Lf of the individual wiring 27 of the flexible printed wiring board 21 is 24 μm larger than the wiring electrode width Lb of the individual wiring 66 of the substrate 47, so even if the center lines are misaligned by a maximum of ±12 μm, Lb will not go beyond the range of La. Therefore, even if the center lines are misaligned by ±12 μm, the connection resistance between the individual wiring 27 of the flexible printed wiring board 21 and the individual wiring 66 of the substrate 47 will not change. This makes it possible to make the ink ejection characteristics uniform between the ejection channels, and to suppress unevenness in print density. Moreover, since the distance (space) between the wiring electrodes on the substrate 47 does not fall below half the pitch P, connection reliability can be ensured.

[0038] As an example, the comb-like laminated piezoelectric block 600 in which the actuators 6 and the supports 60 are arranged alternately is manufactured as follows. First, a first internal electrode 62 and a second internal electrode 63 are formed on the main surfaces of a long piezoelectric body 61 processed into a thin plate, and the piezoelectric bodies 61 are laminated and fired to be integrated. Then, this rectangular block is bonded to the surface of the substrate 47, for example, with an adhesive. After that, a conductive film is formed on the surfaces of this rectangular block and the substrate 47, for example, by plating.

[0039] After that, grooves 69 are formed in the rectangular block by, for example, machining, and the actuators 6 and the support columns 60 are separated. The conductive film formed by plating the entire surface will later function as the individual electrodes 64 and common electrodes 65 of the actuators 6, and the individual wiring 66 and common wiring 67 of the substrate 47, but at this point, they are all short-circuited. Therefore, for example, liquid resist is applied to the rectangular block with the grooves 69 formed therein, the resist is exposed through a mask, and the conductive film is selectively etched to form the individual electrodes 64 and individual wiring 66 of each ejection channel as shown in FIG. 8. Note that the selective etching also includes removal of the conductive film on the end face of the actuator 6 that connects to the vibration plate 5. It may be removed by polishing to make the height of the end face uniform. The individual electrodes 64 and the individual wiring 66 have different heights in the -Z direction, but the side of the actuator 6 is inclined, which makes exposure easier. Note that if the exposure height differs, there is a problem that it is difficult to achieve precision in the wiring width, but the wiring electrode width Lb is permissible with a width of Sb≧Lb>La, which has the effect of making exposure easier. In this method, the individual electrodes 64 and the individual wiring 66 can be integrally formed with the same conductive film, but they may also be formed separately. Also, the individual wiring 66 of the pillars 60 is not necessary, but the conductive film on the side of the pillars 60 that corresponds to the individual electrodes 64 may be left unetched.

[0040] On the other hand, the common electrode side is not patterned like the individual electrodes side, so that the side surfaces of the adjacent actuators 6 and the support columns 60 and the substrate 47 are in a state where a conductive film is formed by plating on the entire surface as shown in FIG. 9. That is, the common electrode 65 and the common wiring 67 are integrally formed with the same conductive film. The portions of the common wiring 67 that are drawn out to the edge portions of the substrate 47 at both ends are formed at the same time as patterning the individual wiring 66. Also, the separation grooves 602 that separate the common wiring 67 of row A and the common wiring 67 of row B may be formed at the same time as patterning the individual wiring 66. Since the common electrode side is not selectively etched, it is preferable to make the inclination of the side surface of the actuator 6 steeper than the individual electrode 64 side or not to incline it, thereby suppressing the need for unnecessary space and making the head width narrow and compact.

[0041] That is, the laminated piezoelectric block 600 has a trapezoidal shape with one side inclined and the other side vertical, in a rectangular state before being bonded to the substrate 47, or at least before the grooves 69 are formed. At this time, it is preferable to polish the upper end surface in the -Z direction to a uniform height for the next bonding process with the vibration plate 5. In this way, when the grooves 69 are formed in the rectangular block, it can be separated into the trapezoid actuator 6 and the support 60, which are uniform in height with respect to the surface of the substrate 47.

[0042] Thereafter, a polarization voltage is applied to the actuators 6 via the individual wiring 66 and the common wiring 67, thereby polarizing the piezoelectric body 61 of each actuator 6. Polarization is performed by connecting a polarization power source capable of applying a voltage higher than that of the drive voltage power source to the individual wiring 66 and the common wiring 67. Alternatively, as shown in Fig. 10, the polarization wiring may be formed in advance on the substrate 47, and after polarization, the polarization wiring may be cut together with the substrate 47 at the position indicated by the two-dot dashed line. Alternatively, polarization may be performed via the drive IC 3 after the flexible printed wiring board 21, the drive IC 3, and the printed circuit board 22 are connected.

[0043] The actuator substrate 601 thus produced as the first structure is bonded, for example by adhesive, to the flow path block as the second structure formed by bonding the nozzle plate 23, the pressure chamber substrate 4, the vibration plate 5, the frame 46, etc., as shown in Fig. 11. The inkjet head 100 shown in Fig. 12 is completed by further connecting the flexible printed wiring board 21 and the printed circuit board 22. The flexible printed wiring board 21 is bendable, so it is usually mounted by bending it as shown in Fig. 2. A power source for drive control signals and drive voltage is supplied to the printed circuit board 22, which is the relay board, via a connection cable 220.

[0044] Next, the operation of the inkjet head 100 will be described. Fig. 13 is a circuit diagram of the control system of the inkjet head 100. As shown in Fig. 13, the actuators 6 of each ejection channel (#1ch, #2ch, ... #nch) connect their individual electrodes 64 to the output terminals of the drive driver D (i.e., the drive circuit) of the drive IC 3 via individual wirings 66, 27. Furthermore, the actuators 6 connect their common electrodes 65 to a common potential via common wirings 67, 28. The common potential is, for example, ground (GND).

[0045] The driving IC 3 is connected to a power source 7 for driving voltage V1 and a power source 70 for driving voltage V2 to be applied to the actuator 6. The power sources 7 and 70 have their positive terminals connected to the driving IC 3 and their negative terminals connected to ground (GND). The driving IC 3 is connected to a signal line for print data sent from a control board 17 (see FIG. 1) which is the control unit of the inkjet printer 10. The print data is an example of a drive control signal supplied via a connection cable 220.

[0046] Next, the ink ejection operation will be described with reference to Figures 14 and 15. Each driving driver D of the driving IC 3 applies a driving waveform to the individual electrode 64 of each actuator 6 using driving voltages V1, V2 and ground (GND). Voltage V1 is, for example, 20V. Voltage V2 is, for example, 10V. Ground (GND) is, for example, 0V. Which actuator 6 is driven is based on, for example, print data. Figure 14 shows an example of the driving waveform applied to the actuator 6.

[0047] As shown in FIG. 14, when the actuator 6 is driven with a ground potential applied to the common electrode 65, a voltage V2 is applied to the individual electrode 64 to put it into a standby state. When the voltage V2 is applied, an electric field is applied in the direction of the polarization axis of the piezoelectric body 61, and as shown in FIG. 15(a), the actuator 6 expands in the stacking direction (Z direction), and the volume of the pressure chamber 42 is reduced. This is performed prior to the timing of ink ejection. Thereafter, by first lowering the potential of the individual electrode 64 to ground (GND) at the ink ejection timing (time t1 in FIG. 14), the expanded actuator 6 returns to its original state, that is, contracts relatively, as shown in FIG. 15(b), and the volume of the pressure chamber 42 expands relatively. Ink flows into the pressure chamber 42 through the guide flow path 43 by the amount of expansion of the volume of the pressure chamber 42.

[0048] Then, for example, after the lapse of 1 / 2 the pressure vibration period of the head unit 2, when a voltage V2 is applied to the individual electrode 64 at time t2 in FIG. 14, the actuator 6 expands in the stacking direction (Z direction) as shown in FIG. 15(c), and the volume of the pressure chamber 42 is relatively reduced, causing an ink droplet R to be ejected from the nozzle 24. Then, for example, after the lapse of 1 / 2 the pressure vibration period of the head unit 2, a voltage V1 is applied to the individual electrode 64 at time t3 in FIG. 14, and the voltage is returned to V2 at time t4 after a predetermined time. The volume of the pressure chamber 42 is reduced and restored by the expansion (FIG. 15(d)) and return (FIG. 15(a)) of the actuator 6 at that time, and the residual vibration is damped by this operation. In this way, the volume of the pressure chamber 42 changes in accordance with the longitudinal vibration of the actuator 6 in the stacking direction, and ink can be ejected.

[0049] As described above, according to the above-mentioned embodiment, it is possible to provide an inkjet head 100 capable of applying a drive voltage to drive each actuator 6 to a comb-like laminated piezoelectric block 600 in which a plurality of actuators 6 and supports 60 are arranged alternately.

[0050] In the above embodiment, the inkjet head 100 of the inkjet printer 10 has been described as an example of a liquid ejection head, but the liquid ejection head may be a modeling material ejection head of a 3D printer or a sample ejection head of a dispensing device.

[0051] That is, a liquid ejection head according to a preferred embodiment of the present invention can be expressed as follows. (1) a comb-like laminated piezoelectric block in which a plurality of piezoelectric actuators and supports are arranged alternately; a pressure chamber in which a part of a partition wall is joined to an end surface of the piezoelectric actuator; a substrate bonded to a surface of the base end side of the laminated piezoelectric block; A flexible substrate connected to the outer periphery of the substrate; a wiring electrode formed on the substrate, connected to an external electrode of the piezoelectric actuator and connected to the wiring of the flexible substrate at the outer periphery of the substrate, the electrode width at the connection portion between the substrate and the flexible wiring plate being greater than or equal to the pillar width of the piezoelectric actuator. (2) The wiring width of the flexible substrate is larger than the electrode width of the wiring electrodes at the connection portions, and the pitch of the wiring electrodes and the pitch of the wiring of the flexible substrate are equal at the connection portions. (3) The substrate and the flexible substrate are connected at the connection portion by an anisotropic conductive film (ACF). (4) Of the external electrodes of the piezoelectric actuator, individual electrodes for applying a drive voltage are formed on the side surface of the piezoelectric actuator, and this side surface is inclined outwardly from the end surface toward the substrate. (5) Of the external electrodes of the piezoelectric actuator, a common electrode that applies a common potential to a plurality of the piezoelectric actuators is formed on a side surface of the piezoelectric actuator, and the inclination of this side surface is greater (i.e., steeper) than the inclination of the individual electrodes. (6) The individual electrodes of the piezoelectric actuators and the wiring electrodes of the substrate connected to the individual electrodes and connected to the wiring of the flexible substrate at the outer periphery of the substrate are formed of an integral conductive film. (7) The common electrode of the piezoelectric actuator and the wiring electrodes of the substrate, which are connected to the common electrode and connected to the wiring of the flexible substrate at the outer periphery of the substrate, are formed from an integral conductive film.

[0052] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0053] 10. Inkjet Printer 100~103 Inkjet head 2 Head section 24 Nozzles 3. Driver IC 47 Substrate 6 Actuators 60 pillars 64 individual electrodes 65 Common electrode 66 Individual wiring 67 Common Wiring 600 Laminated Piezoelectric Block 604 Widening section

Claims

1. a comb-like laminated piezoelectric block in which a plurality of piezoelectric actuators and supports are alternately arranged; a pressure chamber in which a part of a partition wall is joined to an end surface of the piezoelectric actuator; a substrate bonded to a surface of the base end side of the laminated piezoelectric block; A flexible substrate connected to the outer periphery of the substrate; a wiring electrode of the substrate which is connected to an external electrode of the piezoelectric actuator and is connected to the wiring of the flexible substrate at the outer periphery of the substrate, and the electrode width at the connection portion between the substrate and the flexible wiring plate is greater than or equal to the pillar width of the piezoelectric actuator.

2. a wiring width of the flexible substrate is larger than an electrode width of the wiring electrode at the connection portion; 2. The liquid ejection head according to claim 1, wherein the pitch of the wiring electrodes and the pitch of the wiring of the flexible substrate are equal at the connection portion.

3. 3. The liquid ejection head according to claim 1, wherein the substrate and the flexible substrate are connected at the connection portion by an anisotropic conductive film (ACF).

4. The liquid ejection head according to claim 1, characterized in that, among the external electrodes of the piezoelectric actuator, individual electrodes for applying a driving voltage are formed on a side surface of the piezoelectric actuator, and this side surface is inclined outward from the end face toward the substrate.

5. A liquid ejection head as described in claim 4, characterized in that among the external electrodes of the piezoelectric actuator, a common electrode which applies a common potential to a plurality of the piezoelectric actuators is formed on a side surface of the piezoelectric actuator, and the inclination of this side surface is greater than the inclination of the individual electrodes.

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