LIQUID DISCHARGE HEAD AND METHOD FOR MANUFACTURING LIQUID DISCHARGE HEAD

Abstract

To provide a liquid discharge head capable of securing stable discharge characteristics, and a method for manufacturing the liquid discharge head.SOLUTION: A liquid discharge head includes an actuator, and a narrowed part. The actuator has a plurality of grooves constituting a plurality of pressure chambers and a plurality of dummy chambers, a plurality of side walls, and an electrode layer. The plurality of pressure chambers communicate with nozzles for discharging a liquid, and both sides thereof communicate with a communication chamber. The plurality of dummy chambers are arranged between the pressure chambers. The plurality of side walls are formed between the grooves. The electrode layer is formed in the inner wall of the pressure chamber. The narrowed part has a projection part composed of an electro-deposition coating material formed in the electrode layer, in at least a part of an opening communicating with the common chamber of the pressure chamber.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] In recent years, high productivity is required for inkjet heads, and high speed and an increase in droplet volume are issues. For example, a share-mode shared-wall type inkjet head is high-powered and suitable for ejecting high-viscosity ink and ejecting large droplets. In a share-mode shared-wall type inkjet head, the same driving column is shared by two pressure chambers, and so-called three-cycle driving is common, in which one-third of the multiple arranged chambers are simultaneously driven as pressure chambers. In addition, an independent driving head has been developed in which both sides of the driven pressure chamber are used as dummy pressure chambers and one pressure chamber is driven by two independent driving columns. For example, a structure has been developed in which many grooves are formed in a piezoelectric body, and the entrances and exits of every other groove are blocked, and the grooves whose entrances and exits are not blocked are used as pressure chambers and the blocked grooves are used as air chambers, and the independently driven structure is used.

[0003] In such inkjet heads, after an ink droplet is ejected, ink is replenished from the common liquid chamber to the pressure chamber. At this time, a phenomenon occurs in which the ink overshoots at the nozzle, causing the meniscus to swell. The smaller the fluid resistance of the flow path from the common liquid chamber to the nozzle, the larger the overshoot becomes, and unless this overshoot subsides, ejection cannot be performed with the meniscus in a stable state. Therefore, in order to increase the speed of an inkjet head, it is necessary to quickly converge the meniscus swell and ensure stable ejection characteristics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-94036 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 ensuring stable ejection characteristics, and a method for manufacturing the liquid ejection head. [Means for solving the problem]

[0006] A liquid ejection head according to one embodiment includes an actuator and a throttling portion. The actuator has a plurality of grooves constituting a plurality of pressure chambers and a plurality of dummy chambers, a plurality of side walls, and an electrode layer. The plurality of pressure chambers communicate with a nozzle that ejects liquid, and both sides communicate with a common chamber. The plurality of dummy chambers are disposed between the pressure chambers. A plurality of side walls are formed between the grooves. An electrode layer is formed on an inner wall of the pressure chamber. The throttling portion has a protrusion formed of an electrocoating paint formed on the electrode layer, at least in a portion of an opening of the pressure chamber that communicates with the common chamber. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing an inkjet head according to an embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing a configuration of a portion of an inkjet head according to an embodiment. [Diagram 3] FIG. 2 is an enlarged perspective view showing a configuration of a portion of the inkjet head. [Figure 4] FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. [Diagram 5] FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. [Figure 6] 3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. [Figure 7] 3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. [Figure 8] 3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. [Figure 9] FIG. 4 is an explanatory diagram of an inkjet head according to Test Example 1 and Test Example 2. [Figure 10] 13 is a graph showing the ejection speed of the inkjet head in Test Example 1. [Figure 11] 13 is a graph showing the ejection speed of an inkjet head according to Test Example 2. [Figure 12] 13 is a graph showing meniscus recovery characteristics of the inkjet heads according to Test Examples 1 and 2. [Figure 13] FIG. 13 is an explanatory diagram of an inkjet head of an end shooter according to Test Example 1 and Test Example 3. [Figure 14] 13 is a graph showing driving waveforms of the inkjet heads according to Test Examples 1 and 3. [Figure 15] 13 is a graph showing nozzle flow velocity vibration of the inkjet heads according to Test Examples 1 and 3. [Figure 16] 13 is a graph showing the ejection volume of the inkjet heads according to Test Examples 1 and 3. [Figure 17] 13 is a graph showing meniscus recovery characteristics of the inkjet heads according to Test Examples 1 and 3. [Figure 18] FIG. 1 is a schematic diagram showing an inkjet printer according to an embodiment. [Figure 19] 8A to 8C are explanatory diagrams of a method for manufacturing an inkjet head according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The configuration of the inkjet head 10, which is a liquid ejection head according to the first embodiment, will be described below with reference to FIGS. 1 to 5. FIG. 1 is a perspective view showing the inkjet head according to the first embodiment, and FIG. 2 is an exploded perspective view of a part of the inkjet head. FIG. 3 is an enlarged perspective view showing a part of the configuration of the inkjet head, and FIGS. 4 and 5 are enlarged cross-sectional views showing a part of the configuration of the inkjet head. FIGS. 6 to 8 are explanatory diagrams of a manufacturing process of the inkjet head. In the drawings, X, Y, and Z respectively indicate a first direction, a second direction, and a third direction which are perpendicular to each other. In this embodiment, the directions will be described based on the orientation in which the parallel direction of the nozzles 28 and pressure chambers 31 of the inkjet head 10 is along the X axis, the extension direction of the pressure chambers 31 is along the Y axis, and the ejection direction of the liquid is along the Z axis, but the present invention is not limited to this.

[0009] 1 to 5, the inkjet head 10 is a so-called side shooter type share mode share wall type inkjet head. The inkjet head 10 is a device for ejecting ink, and is mounted inside an inkjet printer, for example. For example, the inkjet head 10 is an independently driven inkjet head in which pressure chambers 31 and dummy chambers 32 are alternately arranged. The dummy chambers 32 are air chambers to which ink is not supplied, and do not include nozzles 28.

[0010] The inkjet head 10 includes an actuator base 11, a nozzle plate 12, and a frame 13. The actuator base 11 is an example of a substrate. An ink chamber 27 is formed inside the inkjet head 10 to which ink, which is an example of a liquid, is supplied.

[0011] Furthermore, the inkjet head 10 includes components such as a circuit board 17 that controls the inkjet head 10 and a manifold 18 that forms part of a path between the inkjet head 10 and an ink tank.

[0012] As shown in FIGS. 2 to 5, the actuator base 11 includes a substrate 21, a pair of actuators 22, and a throttle portion 240. The ... throttle portion 240 includes a throttle section 240a.

[0013] The substrate 21 is formed in a rectangular plate shape from ceramics such as alumina. The substrate 21 has a flat mounting surface. A pair of actuators 22 are bonded to the mounting surface of the substrate. A plurality of supply holes 25 and discharge holes 26 are formed in the substrate 21.

[0014] 2 and 3, a pattern wiring 211 is formed on the substrate 21 of the actuator base 11. The pattern wiring 211 is formed of, for example, a nickel thin film. The pattern wiring 211 has a common pattern and an individual pattern, and is configured in a predetermined pattern shape connected to the electrode layer 34 formed on the actuator 22.

[0015] The supply holes 25 are provided in the center of the substrate 21, between the pair of actuators 22, and aligned in the longitudinal direction of the actuators 22. The supply holes 25 communicate with the ink supply portion of the manifold 18. The supply holes 25 are connected to an ink tank via the ink supply portion. The supply holes 25 supply ink from the ink tank to the ink chambers 27.

[0016] The discharge holes 26 are arranged in two rows, sandwiching the supply holes 25 and the pair of actuators 22. The discharge holes 26 communicate with the ink discharge portion of the manifold 18. The discharge holes 26 are connected to the ink tank via the ink discharge portion. The discharge holes 26 discharge ink from the ink chambers 27 to the ink tank.

[0017] A pair of actuators 22 is bonded to the mounting surface of the substrate 21. The pair of actuators 22 are arranged in two rows on the substrate 21 with a supply hole 25 in between. Each actuator 22 is formed of two plate-shaped piezoelectric bodies made of, for example, lead zirconate titanate (PZT). The two piezoelectric bodies are bonded together so that their polarization directions are opposite to each other in the thickness direction. The actuators 22 are bonded to the mounting surface of the substrate 21 by, for example, a thermosetting epoxy adhesive. As shown in FIG. 2, the actuators 22 are arranged in parallel in the ink chamber 27 in correspondence with the two rows of nozzles 28. The actuators 22 divide the ink chamber 27 into a first common chamber 271 in which the supply hole 25 opens and two second common chambers 272 in which the discharge hole 26 opens.

[0018] The actuator 22 has a width in the short side direction that gradually increases from the top side toward the substrate side. The cross-sectional shape of the actuator 22 along the direction (short side direction) perpendicular to the longitudinal direction is formed into a trapezoid. The side surface portion 221 of the actuator 22 has an inclined surface that is inclined with respect to the second direction and the third direction. The top portion of the actuator 22 is bonded to the nozzle plate 12. The actuator 22 includes a plurality of pressure chambers 31 and a plurality of dummy chambers 32. The actuator 22 has a plurality of side wall portions 33, and has grooves between the side wall portions 33 that form the pressure chambers 31 and the dummy chambers 32. In other words, the side wall portions 33 are formed as drive elements between the grooves that form the pressure chambers 31 and the dummy chambers 32.

[0019] 1 to 5, the bottom surface of the groove and the main surface of the substrate 21 are connected by an inclined side surface 221. The pressure chambers 31 and the dummy chambers 32 are arranged alternately. The pressure chambers 31 and the dummy chambers 32 each extend in a direction intersecting the longitudinal direction of the actuator 22, and are arranged in parallel in a first direction (X-axis in the drawings) which is the longitudinal direction of the actuator 22. In this embodiment, for example, the groove 14 is configured so that its width dimension in the X direction is constant in the depth direction along the Z direction, and its cross section perpendicular to the Y direction which is the extension direction is configured to be rectangular.

[0020] The pressure chamber 31 and the dummy chamber 32 may have different shapes. The side wall portion 33 is formed between the pressure chamber 31 and the dummy chamber 32, and changes the volume of the pressure chamber 31 by deforming in response to a drive signal.

[0021] An electrode layer 34 is provided on each of the inner wall surfaces of the pressure chamber 31 and the dummy chamber 32 of the actuator base 11. The electrode layer 34 is formed of a conductive film such as a nickel thin film. The electrode layer 34 extends from the inner surface of the groove onto the substrate 21 and is connected to the pattern wiring 211. For example, the electrode layer 34 is formed on at least the side surface of the side wall portion 33, i.e., the side wall surface of the groove that constitutes the pressure chamber 31. The electrode layer 34 may be formed on the side surface and bottom surface of the pressure chamber 31, for example.

[0022] The pressure chambers 31 communicate with the nozzles 28 of the nozzle plate 12 joined to the top. Both ends of the pressure chambers 31 in the second direction communicate with the ink chambers 27. That is, one end opens into a first common chamber 271 of the ink chambers 27, and the other end opens into a second common chamber 272 of the ink chambers 27. Therefore, ink flows in from one end of the pressure chambers 31, and ink flows out from the other end. A throttle portion 240 having a throttle port 242 configured to have a larger fluid resistance than the inside of the pressure chambers 31 is formed at the communication port of the pressure chambers 31 with the ink chambers 27. As an example, in this embodiment, a throttle portion 240 is formed at each of the ends on both sides of the pressure chamber 31.

[0023] The constriction portion 240 is configured in a shape that narrows the opening that communicates with the ink chamber 27 of the pressure chamber 31. As an example, the constriction portion 240 has a protrusion portion 241 formed on at least one portion of the inner surface of the groove at the end portion in the second direction of the pressure chamber 31. The protrusion portion 241 is made of an electrodeposition paint formed on the electrode layer 34 inside the pressure chamber 31. As the electrodeposition paint that constitutes the protrusion portion 241, for example, a synthetic resin such as an epoxy-based, butadiene-based, or polyamide-based resin is used.

[0024] In this embodiment, protrusions 241 made of electrodeposition paint are formed on both side surfaces of the groove in the first direction. For example, the protrusions 241 on both side surfaces may be formed over the entire length in the third direction, which is the depth direction of the groove of the pressure chamber 31, or may be formed on a part in the third direction. For example, electrodeposition paint may be formed on the bottom surface of the groove in addition to both side surfaces, and the protrusions 241 on both sides may be continuous at the bottom of the groove. For example, the protrusions 241 on both side surfaces are each configured in a rectangular shape that is long in the third direction.

[0025] The grooves constituting the pressure chambers 31 are not completely covered by the protrusions 241, and between the pair of protrusions 241 on both sides, a throttle port 242 is formed that communicates the pressure chambers 31 with the first common chamber 271 and the second common chamber 272. The throttle port 242 has a slit shape extending in the third direction, which is the depth direction of the pressure chambers, and the opening width in the first direction is configured to be smaller than the width in the first direction inside the pressure chambers 31, and is therefore configured to be smaller than the flow path cross-sectional area of ​​the pressure chambers 31. In other words, the protrusions 241 partially block the communication ports at both ends in the second direction, forming throttle portions 240 in which the flow path resistance increases. For example, the throttle portion 240 is configured in a predetermined shape by forming an electrodeposited resist film 244 on the inner walls of the pressure chambers 31 and the dummy chambers 32, forming the electrodeposited resist film 244 in the resist regions other than the paint region by exposure and development, and then forming an electrodeposited paint film 243 in the paint region where the electrodeposited resist film 244 is not formed, and removing the electrodeposited resist film 244 by etching. For example, the electrodeposition resist film 244 is made of a photosensitive acrylic resin.

[0026] If the fluid resistance of the throttling portion 240 is too large, the supply of ink to the pressure chamber 31 after the ink droplet is ejected will be delayed, hindering high-speed operation. The rise of the meniscus will differ depending on the ink viscosity, ejection volume, drive frequency, etc. Therefore, the shape of the protrusion 241 and the dimensions and position of the throttle port 242 of the throttling portion 240 are each set so as to provide a flow path resistance according to the ink supply conditions and the characteristics of the rise of the meniscus. The throttling portions 240 on both sides may have different configurations.

[0027] One side of the dummy chamber 32 in the third direction is blocked by the nozzle plate 12 joined to the top. In addition, both ends of the multiple dummy chambers 32 in the second direction are blocked by the cover portion 23, for example. That is, the cover portions 23 are respectively disposed between the first common chamber 271 of the ink chamber 27 and the inlet of the dummy chamber 32, and between the outlet of the dummy chamber 32 and the second common chamber 272, and both ends of the dummy chamber 32 are separated from the ink chamber 27. For this reason, the dummy chamber 32 constitutes an air chamber into which ink does not flow.

[0028] For example, the cover portion 23 is formed by applying a photosensitive resin to both ends of the dummy chamber 32 and then curing the target portion.

[0029] The nozzle plate 12 is formed of, for example, a rectangular polyimide film. The nozzle plate 12 faces the mounting surface of the actuator base 11. The nozzle plate 12 is formed with a plurality of nozzles 28 that penetrate the nozzle plate 12 in the thickness direction.

[0030] The nozzles 28 are provided in the same number as the pressure chambers 31, and are arranged opposite the pressure chambers 31, respectively. The nozzles 28 are aligned along the first direction, and are arranged in two rows corresponding to the pair of actuators 22. Each nozzle 28 is configured in a cylindrical shape with an axis extending in the third direction. For example, the nozzles 28 may have a constant diameter, or may have a shape that narrows in diameter toward the center or tip. The nozzles 28 are arranged opposite to the midpoint of the pressure chambers 31 formed in the pair of actuators 22 in the extension direction, and each nozzle 28 communicates with the pressure chambers 31. The nozzles 28 are arranged at positions corresponding to between both ends of each pressure chamber 31, for example, one nozzle each at the center in the longitudinal direction.

[0031] The frame 13 is formed into a rectangular frame shape, for example, from a nickel alloy. The frame 13 is interposed between the mounting surface of the actuator base 11 and the nozzle plate 12. The frame 13 is bonded to both the mounting surface of the actuator base 11 and the nozzle plate 12. In other words, the nozzle plate 12 is attached to the actuator base 11 via the frame 13.

[0032] The manifold 18 is joined to the side of the actuator base 11 opposite to the nozzle plate 12. Inside the manifold 18, an ink supply portion which is a flow path communicating with the supply hole 25 and an ink discharge portion which is a flow path communicating with the discharge hole 26 are formed.

[0033] The circuit board 17 is a film carrier package (FCP). The circuit board 17 has a flexible resin film 51 on which a plurality of wirings are formed, and an IC 52 connected to the plurality of wirings of the film 51. The IC 52 is electrically connected to the electrode layer 34 via the wirings of the film 51 and the pattern wiring 211.

[0034] In the inkjet head 10 configured as above, an ink chamber 27 is formed surrounded by the actuator base 11, the nozzle plate 12, and the frame 13. That is, the ink chamber 27 is formed between the actuator base 11 and the nozzle plate 12. For example, the ink chamber 27 is partitioned into three sections in the second direction by the two actuators 22, and has two second common chambers 272 as common chambers into which the discharge holes 26 open, and a first common chamber 271 as common chamber into which the supply hole 25 opens. The first common chamber 271 and the second common chamber 272 are in communication with a plurality of pressure chambers 31.

[0035] In the inkjet head 10 configured as above, ink circulates between the ink tank and the ink chamber 27 through the supply hole, the pressure chamber, and the discharge hole. For example, in response to a signal input from a control unit of the inkjet printer, the driving IC 52 applies a driving voltage to the electrode layer 34 of the pressure chamber 31 via the wiring of the film 51, thereby generating a potential difference between the electrode layer 34 of the pressure chamber 31 and the electrode layer 34 of the dummy chamber 32, thereby selectively deforming the side wall portion 33 in a shear mode. The volume of the pressure chamber 31 is changed by deforming the side wall portion 33 formed between the pressure chamber 31 and the dummy chamber 32 in response to the driving signal.

[0036] When the side wall portion 33 undergoes shear mode deformation, the volume of the pressure chamber 31 in which the electrode layer 34 is provided increases, and the pressure decreases. As a result, the ink in the ink chamber 27 flows into the pressure chamber 31.

[0037] With the volume of the pressure chamber 31 increased, the IC 52 applies a drive voltage of a reverse potential to the electrode layer 34 of the pressure chamber 31. This causes the side wall portion 33 to deform in a shear mode, reducing the volume of the pressure chamber 31 in which the electrode layer 34 is provided, and increasing the pressure. This causes the ink in the pressure chamber 31 to be pressurized and ejected from the nozzle 28.

[0038] A method for manufacturing the inkjet head 10 will be described with reference to Figures 6 to 8. First, a piezoelectric member having a plurality of grooves is attached to a plate-like substrate 21 with an adhesive or the like, and then machining is performed using a dicing saw, slicer, or the like to form an actuator base 11 having a predetermined outer shape. Note that, for example, a block-shaped base member having a thickness equivalent to that of multiple sheets may be formed in advance, and then divided to manufacture multiple actuator bases 11 of the predetermined shape.

[0039] Next, the electrode layer 34 and the pattern wiring 211 are formed on the inner surfaces of the grooves that define the pressure chambers 31 and the dummy chambers 32 and on the surface of the substrate 21. As a result, the electrode layer 34 and the pattern wiring 211 are formed in predetermined locations on the surface of the actuator base 11.

[0040] 6 to 8, a throttle portion 240 is formed at an end of the pressure chamber 31 as a communication port having a flow resistance greater than that of the inside of the pressure chamber 31. For example, a method of forming the throttle portion 240 includes a resist film formation process Act1 in which an electrodeposited resist film 244 is formed in a groove that constitutes the pressure chamber 31, a resist forming process Act2 in which the electrodeposited resist film 244 is formed by exposure and development, a paint film formation process Act3 in which an electrodeposited paint film 243 is formed in an area where the electrodeposited resist film 244 is not formed, and an etching process Act4 in which the electrodeposited resist film 244 is removed.

[0041] Specifically, in Act 1 shown in FIG. 6, an electrodeposited resist is applied to the inner wall of the pressure chamber 31 by electrochemical coating to form an electrodeposited resist film 244. At this time, the electrodeposited resist film 244 is formed on the surfaces of the sidewalls 33 on both sides constituting the groove and on the bottom surface of the groove. Subsequently, as a resist forming process Act 2, the electrodeposited resist film 244 is formed by exposure and development processes. In the resist forming process Act 2, a photomask 245 having an exposure pattern that hardens the resist region where the electrodeposited resist film 244 is to be formed is overlaid and exposed. The electrodeposited resist may be either negative or positive. When a positive electrodeposited resist is used, as shown in FIG. 8, the electrodeposited resist film 244 at the inlet and outlet of the pressure chamber 31 where the throttling portion 240 is to be formed is exposed through the photomask 245, and the electrodeposited resist film 244 of the exposed portion is removed with a developer. That is, the electrodeposited resist film 244 in the resist region other than the portion where the protrusion portion 241 is to be formed is hardened by the exposure process. At this time, conditions such as the exposure direction and exposure intensity are set appropriately. As an example, as shown by the arrow in Fig. 8, by setting the exposure direction in the depth direction of the pressure chamber 31, the protrusions 241 on both sides can be exposed and formed simultaneously. When using a negative electrodeposition resist, a photomask with an exposure pattern inverted from that of the photomask 245 is used. Fig. 8 shows the structure of the electrodeposition resist film 244 after exposure and development processing, and the exposure direction is indicated by an arrow.

[0042] Then, after the electrodeposition resist film 244 is formed and shaped, in paint film formation process Act 3, an electrodeposition paint film 243 is formed and cured in the paint area where the electrodeposition resist film 244 is not formed. At this time, the thickness of the electrodeposition paint film 243 can be controlled by controlling the coating conditions such as voltage. Therefore, the coating conditions are adjusted so that the thickness is such that the desired narrowing port 242 can be formed. Thereafter, the electrodeposition resist film 244 is removed by etching process Act 4.

[0043] As a result of the above, a protrusion 241 is formed by the electrodeposition paint film 243 in the paint region at the entrance and exit of the pressure chamber 31, and a throttle portion 240 is formed between the protrusions 241 on both sides.

[0044] Next, the cover portion 23 is formed at a predetermined position to close both ends of the dummy chamber 32. For example, the cover portion 23 is formed by filling the groove that constitutes the dummy chamber 32 with a photosensitive resin and curing it. The cover portion 23 may be formed before the narrowing portion 240 is formed.

[0045] Then, the actuator base 11 is assembled to the manifold 18, and the frame 13 is attached to one surface of the substrate 21 of the actuator base 11 with an adhesive sheet made of a thermoplastic resin.

[0046] The assembled frame 13, the top of the side wall 33 of the actuator 22, and the surface of the protrusion 241 facing the nozzle plate 12 are polished to be flush with each other. The nozzle plate 12 is then attached by bonding to the polished surfaces of the top of the side wall 33, the frame 13, and the protrusion 241. At this time, the nozzles 28 are positioned to face the pressure chambers 31. Furthermore, the driving IC chip 52 and the circuit board 17 are connected to the pattern wiring 211 formed on the main surface of the substrate 21 via a flexible printed circuit board as shown in FIG. 1, thereby completing the inkjet head 10.

[0047] An example of an inkjet printer 100 including an inkjet head 10 will be described below with reference to Fig. 18. The inkjet printer 100 includes a housing 111, a medium supply unit 112, an image forming unit 113, a medium discharge unit 114, a conveying device 115, and a control unit 116.

[0048] The inkjet printer 100 is a liquid ejection device that performs an image formation process on a sheet of paper P by ejecting a liquid such as ink while transporting the sheet of paper P as a recording medium, which is the object of ejection, along a predetermined transport path A from a medium supply section 112 through an image forming section 113 to a medium ejection section 114.

[0049] The housing 111 constitutes the outer shell of the inkjet printer 100. A discharge port for discharging the paper P to the outside is provided at a predetermined location of the housing 111.

[0050] The medium supply unit 112 includes a plurality of paper feed cassettes, and is configured to be able to hold a plurality of sheets of paper P of various sizes in a stack.

[0051] The medium discharge unit 114 includes a paper discharge tray configured to be able to hold the paper P discharged from the discharge opening.

[0052] The image forming section 113 includes a support section 117 that supports the paper P, and a plurality of head units 130 that are disposed above the support section 117 so as to face the support section 117.

[0053] The support section 117 includes a conveyor belt 118 provided in a loop shape in a predetermined area where image formation is performed, a support plate 119 supporting the conveyor belt 118 from the back side, and a plurality of belt rollers 120 provided on the back side of the conveyor belt 118.

[0054] During image formation, the support section 117 supports the paper P on a holding surface, which is the upper surface of the conveyor belt 118, and conveys the paper P downstream by feeding the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120.

[0055] The head unit 130 includes a plurality of inkjet heads 10 (four colors), ink tanks 132 as liquid tanks mounted on each inkjet head 10, a connection flow path 133 connecting the inkjet heads 10 and the ink tanks 132, and a circulation pump 134 as a circulation unit. The head unit 130 is a circulation type head unit that constantly circulates liquid in the ink tanks 132, and the pressure chambers 31, dummy chambers 32, and ink chambers 27 built inside the inkjet heads 10.

[0056] In this embodiment, the inkjet heads 10 are provided with four colors, cyan, magenta, yellow, and black, and ink tanks 132 that respectively accommodate ink of each color. The ink tanks 132 are connected to the inkjet heads 10 by connection flow paths 133. The connection flow paths 133 include a supply flow path that is connected to a supply port of the inkjet head 10, and a recovery flow path that is connected to a discharge port of the inkjet head 10.

[0057] A negative pressure control device such as a pump (not shown) is connected to the ink tank 132. The negative pressure control device controls the negative pressure in the ink tank 132 in accordance with the head value between the inkjet head 10 and the ink tank 132, thereby causing the ink supplied to each nozzle 28 of the inkjet head 10 to form a meniscus of a predetermined shape.

[0058] The circulation pump 134 is a liquid sending pump constituted by, for example, a piezoelectric pump. The circulation pump 134 is provided in the supply flow path. The circulation pump 134 is connected to a drive circuit of the control unit 116 by wiring, and is configured to be controllable by a CPU (Central Processing Unit). The circulation pump 134 circulates the liquid in the circulation flow path including the inkjet head 10 and the ink tank 132.

[0059] The conveying device 115 conveys the paper P along a conveying path A that extends from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114. The conveying device 115 includes a plurality of guide plate pairs 121 and a plurality of conveying rollers 122 that are arranged along the conveying path A.

[0060] Each of the guide plate pairs 121 includes a pair of plate members disposed opposite each other with the paper P being transported therebetween, and guides the paper P along the transport path A.

[0061] The conveying rollers 122 are driven to rotate under the control of the control unit 116, thereby sending the paper P downstream along the conveying path A. Sensors for detecting the conveying status of the paper are disposed at various points along the conveying path A.

[0062] The control unit 116 includes a control circuit such as a CPU which serves as a controller, a ROM (Read Only Memory) which stores various programs, a RAM (Random Access Memory) which temporarily stores various variable data, image data, etc., and an interface unit which inputs data from the outside and outputs data to the outside.

[0063] In the inkjet printer 100 configured as above, when the control unit 116 detects a print instruction by a user operating the operation input unit, for example, via an interface, the control unit 116 drives the transport device 115 to transport the paper P and outputs a print signal to the head unit 130 at a predetermined timing to drive the inkjet head 10. As a discharge operation, the inkjet head 10 sends a drive signal to the IC by an image signal corresponding to image data, applies a drive voltage to the electrode layer 34 of the pressure chamber 31 via wiring, and selectively drives the side wall portion 33 of the actuator 22 to discharge ink from the nozzle 28, thereby forming an image on the paper P held on the transport belt 118. As a liquid discharge operation, the control unit 116 drives the circulation pump 134 to circulate the liquid in a circulation flow path passing through the ink tank 132 and the inkjet head 10. By the circulation operation, the ink in the ink tank 132 is supplied through the ink supply portion of the manifold 18 and from the supply hole 25 to the first common chamber 271 of the ink chamber 27 by driving the circulation pump 134. This ink is supplied to the multiple pressure chambers 31 and the multiple dummy chambers 32 of the pair of actuators 22. The ink flows into the second common chamber 272 of the ink chamber 27 through the pressure chambers 31 and the dummy chambers 32. This ink is discharged from the discharge hole 26 through the ink discharge portion of the manifold 18 to the ink tank 132.

[0064] According to the above-mentioned embodiment, an inkjet head with high frequency characteristics can be provided. That is, the inkjet head 10 according to the above-mentioned embodiment is provided with a protrusion 241 made of electrocoating paint at the opening of the pressure chamber 31, and the throttling section 240 having a larger flow resistance than the inside of the pressure chamber 31, the first common chamber 271, and the second common chamber 272 can be easily formed. The throttling section 240 has an opening that opens to the first common chamber 271 and the second common chamber 272, which are the common chambers of the pressure chamber 31, smaller than the flow cross-sectional area of ​​the pressure chamber 31. Therefore, the meniscus does not rise as much when liquid is ejected from the inkjet head 10. Therefore, the meniscus returns quickly, the effect on the next droplet can be reduced, and ejection stability can be improved.

[0065] Fig. 9 shows Test Example 1 of inkjet head 110 equipped with a throttling portion 240, and Test Example 2 of inkjet head 1010 equipped with no throttling portion. Fig. 10 shows the frequency characteristics of inkjet head 110 equipped with a throttling portion according to Test Example 1, and Fig. 11 shows the frequency characteristics of inkjet head 1010 equipped with no throttling portion as Comparative Example 2. Figs. 11 and 12 each show the relationship between nozzle discharge speed and frequency for 1 drop and 3 drops, respectively.

[0066] The inkjet head 110 in the first test example is a side shooter type in which both sides in the second direction, which is the extension direction of the pressure chamber 31, communicate with a common chamber, and the nozzle 28 opens halfway in the extension direction of the pressure chamber 31.

[0067] As shown in FIG. 11, in the inkjet head 1010 according to the second test example, the ejection speed is flat in the low frequency region, but the ejection speed tends to decrease as the frequency increases, and there is a difference in the ejection speed between the low frequency region and the high frequency region. In the inkjet head 1010 according to the second test example, the ejection speed is flat up to 25 kHz, but the ejection speed tends to decrease as the frequency increases above 25 kHz. In addition, in the inkjet head 1010 according to the second test example, the ejection speed is flat up to 15 kHz, but the ejection speed tends to decrease as the frequency increases above 15 kHz. Therefore, the landing position is shifted depending on the printing pattern. If the difference in the ejection speed is large, it takes time for the meniscus to settle, which causes a decrease in print quality, and therefore high-speed driving is not possible.

[0068] On the other hand, in the inkjet head 110 having a throttle portion, the ejection speed tends to be flat for both 1 drop and 3 drops as shown in Fig. 10. This is because the fluid resistance between the nozzles increases from the common liquid, and the rise of the meniscus becomes smaller.

[0069] FIG. 12 shows the results of a simulation of meniscus recovery in Test Example 1, in which a throttle is provided in the pressure chamber, and Test Example 2, in which a throttle is not provided. According to FIG. 12, in the case of low frequency, the meniscus state of the nozzle has a sufficient time from when an ink droplet is discharged until the next droplet is discharged, and discharge is possible in a stable state after waiting for the meniscus to recover, regardless of whether a throttle is provided. On the other hand, in the case of high frequency, the time from when a dot (ink droplet) is discharged until the next droplet is discharged is short, so that the discharge of the next droplet begins before the meniscus recovers. For this reason, in the case of the inkjet head 1010 without a throttle, the meniscus rises large after discharge, and the meniscus cannot recover before the next droplet is discharged, and the discharge speed decreases. In contrast, when a throttle is provided, the rise of the meniscus is small, so the meniscus returns quickly and the impact on the next droplet can be reduced. Therefore, from these simulation results, it can be said that providing a throttle between the pressure chamber 31 and the common chamber leads to improved discharge stability of the inkjet head 110.

[0070] FIG. 13 is an explanatory diagram of a side shooter type inkjet head 110 as test example 1, and a share mode shared wall end shooter type inkjet head 2010 as test example 3, in which an ink inlet / outlet is formed at one end and a nozzle is formed at the other end.

[0071] 14 to 17 are diagrams comparing the simulation characteristics when a throttle is provided in the end-shooter type inkjet head 2010 of Test Example 3 and the side-shooter type inkjet head 110 of Test Example 1. Fig. 14 shows the drive waveform, Fig. 15 shows the nozzle flow velocity vibration, Fig. 16 shows the ejection volume, and Fig. 17 shows the meniscus return characteristics.

[0072] The inkjet head 2010 according to Test Example 3 was an end shooter type in which one end in the second direction, which is the extension direction of the pressure chambers 31, communicated with the common chamber, the other end was closed, and a nozzle opened at the end of the flow path. In other words, the inkjet head 2010 forms a flow path through which ink flows from one side in the second direction toward the nozzle 28.

[0073] In the case of the end-shooter type inkjet head 2010 supplying from one side as Test Example 3 and the side-shooter type inkjet head 110 supplying from both sides as Test Example 1, the drive voltage when the ejection volume, nozzle flow velocity vibration, and meniscus return characteristics are aligned is the lowest for the side-shooter type configuration with double-sided supply, so it can be said that the double-sided supply is superior to the single-sided supply in terms of drive efficiency. In other words, the so-called side-shooter type inkjet head 110, which has a nozzle in the center of the pressure chamber and ink inlets and outlets at both ends, has better ejection efficiency than the end-shooter type inkjet head 2010.

[0074] In addition, in general, in a share mode shared wall type inkjet head, for example, since the pressure chamber is composed of a fine groove formed in a piezoelectric body by a diamond cutter, it is difficult to reduce the cross section of a part of the pressure chamber. However, according to the above embodiment, the throttle portion 240 can be formed by forming an electrodeposition resist film on the groove of the actuator 22, patterning it by exposure processing, and forming an electrodeposition paint, and the throttle portion 240 can be formed inexpensively and easily with fewer steps. Furthermore, since the thickness and shape of the protrusion portion 241 can be relatively freely selected by exposure and development, it is also easy to freely design the fluid resistance of the throttle. For example, since the film thickness can be controlled by voltage, the throttle width of the throttle portion can be easily controlled. In addition, by forming the protrusion portion with electrodeposition paint, higher heat resistance and corrosion resistance can be ensured compared to, for example, forming the protrusion portion with electrodeposition resist. In the above embodiment, the side surface 221 of the actuator 22 forms an inclined surface, so that there are fewer restrictions on the exposure direction, and exposure and development processes become easier.

[0075] Furthermore, in the inkjet head 10 according to the above embodiment, a restriction is formed partially in the communication port serving as the inlet and outlet of the pressure chamber 31, so it is easier to ensure the volume of the pressure chamber 31 than if the pressure chamber 31 were narrowed overall. Therefore, there are fewer restrictions on the size of the nozzle and droplets compared to a configuration in which the pressure chamber is narrowed overall, making it easier to maintain ejection performance.

[0076] The present invention is not limited to the above-described embodiment, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention.

[0077] In the above embodiment, the throttle portion 240 that increases the flow resistance has a pair of protrusions 241 formed on the wall surface of the side wall portion 33 on both sides of the pressure chamber 31, but the shape of the throttle portion 240 is not limited to this. For example, it may be a protrusion formed on a part of the bottom side of the pressure chamber 31 or on a part of the nozzle plate 12 side, or a shape in which the area on the bottom side of the pressure chamber 31 is partially filled with a photosensitive resin. For example, the throttle port 242 is a slit shape extending in the third direction, which is the depth direction of the pressure chamber, but it may extend in other directions or may have other shapes including a circle or an ellipse. In addition, the throttle portions 240 on both sides may have different configurations. For example, the throttle portion 240 is formed by the protrusions 241 formed by the electrodeposition paint film 243 at at least one communication port of the pressure chamber 31, both sides of which communicate with the common chambers 271 and 272, thereby improving the discharge performance and providing the effect of being able to form the throttle portion 240 cheaply and easily.

[0078] Also, the cover portion 23 and the protrusion portion 241 are formed inside the grooves that form the pressure chamber 31 and the dummy chamber 32 and are shaped to fill part of the grooves, but this is not limited to this. For example, on the side surface of the actuator, a restricting portion 240 such as the cover portion 23 that closes the dummy chamber 32 or the protrusion portion 241 that partially closes the communication port of the pressure chamber 31 may be formed outside the grooves that form the pressure chamber 31 and the dummy chamber 32.

[0079] In the above embodiment, an example was shown in which actuator 22 having a plurality of grooves was disposed on the main surface portion of substrate 21, but this is not limited to the above. For example, the actuator may be provided on an end surface of substrate 21. Furthermore, the number of nozzle rows is not limited to that in the above embodiment, and a configuration having one row, or three or more rows may be used.

[0080] In the above embodiment, the actuator base 11 is provided with a laminated piezoelectric body made of the piezoelectric member 131 on the substrate 21, but the present invention is not limited to this. For example, the actuator base 11 may be formed only with the piezoelectric member without using a substrate. Also, instead of using two piezoelectric members, one piezoelectric member may be used. The dummy chamber 32 may be connected to the first common chamber 271 and the second common chamber 272, which are common chambers. The supply side and the discharge side may be reversed, or may be configured to be switchable.

[0081] In the above embodiment, as an example, a circulation type inkjet head in which one side of the pressure chamber 31 is the supply side and the other side is the discharge side, and the first common chamber fluid flows in from one side of the pressure chamber and flows out from the other side is illustrated, but the present invention is not limited to this. For example, a non-circulation type may be used. Also, for example, the common chambers on both sides of the pressure chamber 31 may be the supply side, and the first common chamber fluid flows in from both sides. That is, the first common chamber may be configured so that the fluid flows in from both sides of the pressure chamber 31 and flows out from the nozzle 28 disposed in the center of the pressure chamber 31. Even in this case, the fluid resistance can be increased and the discharge efficiency can be improved by providing the throttle portion 240 at the communication port that serves as the inlet on both sides of the pressure chamber 31. Also, the throttle portion 240 formed at each end may have a different configuration.

[0082] In the above embodiment, the throttle portion 240 is formed at both ends of the pressure chamber 31 in the extension direction, but the present invention is not limited to this, and the throttle portion 240 may be formed only at one of the inlets and outlets at both ends where the pressure chamber 31 communicates with the common chambers 271, 272 at both ends. For example, the throttle portion 240 having a higher fluid resistance than the inside of the pressure chamber 31 may be formed at the end on one side, and the end on the other side may be configured to have the same fluid resistance as the inside of the pressure chamber 31, for example, the same cross-sectional area of ​​the communication port as the cross-sectional area of ​​the inside of the pressure chamber 31.

[0083] In the above example, the exposure direction of the electrodeposited resist film 244 when forming the narrowed portion 240 is set in the depth direction of the pressure chamber 31, but this is not limited thereto. For example, as another embodiment, as shown by the arrow in FIG. 19, the exposure direction may be set in a direction inclined with respect to the depth direction of the pressure chamber 31, and exposure processing may be performed sequentially on one inner surface and the other inner surface of both sides of the pressure chamber 31, and each side may be hardened sequentially. FIG. 19 shows the configuration of the electrodeposited resist film 244 after exposure and development processing, and the exposure direction is indicated by an arrow. That is, as shown by the arrow in FIG. 19, after hardening the resist region on one side of the inner wall of the groove, the resist region on the other side may be hardened by exposing it from a direction inclined to the opposite side.

[0084] Furthermore, for example, the liquid to be ejected is not limited to ink for printing, but may be, for example, a device that ejects liquid containing conductive particles for forming a wiring pattern on a printed wiring board.

[0085] In addition, in the above embodiment, the inkjet head is used in a liquid ejection device such as an inkjet printer, but the present invention is not limited to this and can also be used in, for example, 3D printers, industrial manufacturing machines, and medical applications, enabling reduction in size, weight, and cost.

[0086] According to at least one of the embodiments described above, it is possible to provide a liquid ejection head capable of ensuring stable ejection characteristics, and a method for manufacturing a liquid ejection head.

[0087] Although several other embodiments of the present invention have been described, these embodiments 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]

[0088] 10...inkjet head, 11...actuator base, 12...nozzle plate, 13...frame, 17...circuit board, 18...manifold, 21...substrate, 22...actuator, 24...cover member (wall portion), 25...supply hole, 26...discharge hole, 27...ink chamber, 31...pressure chamber, 32...dummy chamber, 33...side wall portion, 34...electrode layer, 51...film, 52...driving IC chip, 100...inkjet printer, 111...casing, 112...medium supply section, 113...image forming section, 114...medium discharge section, 11 5...conveying device, 116...control section, 117...support section, 118...conveying belt, 119...support plate, 120...belt roller, 121...pair of guide plates, 122...conveying roller, 130...head unit, 132...ink tank, 133...connecting flow path, 134...circulation pump, 211...pattern wiring, 221...side section, 222...top, 240...throttling section, 241...protrusion, 242...throttling port, 243...electrodeposited paint film, 244...electrodeposited resist film, 271...first common chamber, 27...ink chamber, 272...second common chamber.

Claims

1. an actuator having a plurality of pressure chambers, each of which communicates with a nozzle that ejects liquid and communicates with a common chamber on both sides, and a plurality of grooves that define a plurality of dummy chambers disposed between the pressure chambers, a plurality of side walls formed between the grooves, and an electrode layer formed on an inner wall of the pressure chamber; a restricting portion having a protrusion formed by an electrodeposition paint formed on the electrode layer in at least a part of an opening of the pressure chamber communicating with the common chamber; A liquid ejection head comprising:

2. The liquid ejection head according to claim 1 , wherein the throttle portion has a protrusion formed on the side wall at an end of the pressure chamber to narrow the opening of the pressure chamber, and is configured to have a larger fluid resistance than the inside of the pressure chamber.

3. a nozzle plate having a plurality of nozzles that communicate with the pressure chambers and are disposed at positions corresponding to both ends of the pressure chambers; The liquid ejection head according to claim 1 , wherein the protrusions are provided at both ends of the pressure chambers.

4. A method for manufacturing a liquid ejection head, comprising: an actuator having a plurality of grooves which are arranged in a first direction, the plurality of pressure chambers communicating with nozzles which eject liquid and which communicate with a common chamber on both sides, and a plurality of dummy chambers arranged between the plurality of pressure chambers; a plurality of side walls formed between the plurality of grooves; and an electrode layer formed on an inner wall of the pressure chambers, the actuator comprising: forming an electrocoating paint film on at least a portion of an opening which communicates with the common chamber of the pressure chambers, thereby forming a throttle portion which communicates with the common chamber and the pressure chambers and has a higher fluid resistance than the inside of the pressure chambers.

5. Before forming the electrodeposition paint film, an electrodeposition resist film is formed in a resist region different from a paint region in which the electrodeposition paint film is to be formed; After forming the electrodeposition paint film, the electrodeposition resist film is removed. The method for manufacturing a liquid ejection head according to claim 4 .

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