Liquid ejection head and method of manufacturing the same

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 having a plurality of grooves constituting a plurality of pressure chambers and a plurality of dummy chambers arranged between the plurality of pressure chambers, and a side wall part formed between the plurality of grooves; a common chamber which is provided on both sides of the pressure chambers and communicates the pressure chambers; a cover part for separating the dummy chamber and the common chamber; and a wall part which contains a photosensitive resin, separates the grooves constituting the pressure chambers and at least a part between the wall part and the common chamber, and forms a diaphragm port which communicates the common chamber and the pressure chamber and has fluid resistance larger than the inside the pressure chamber in at least a part in the groove depth direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a liquid ejection head and a method for manufacturing a liquid ejection head. [Background technology]

[0002] In recent years, demands for higher productivity, higher speeds, and increased droplet volume have emerged for inkjet heads, which are liquid ejection heads. For example, shear-mode, shared-wall inkjet heads offer high power and are suitable for ejecting high-viscosity inks and large droplets. In shear-mode, shared-wall inkjet heads typically share the same drive column with two pressure chambers, driving one-third of the multiple chambers simultaneously as pressure chambers, a so-called three-cycle drive. Independent drive heads have also been developed, in which dummy pressure chambers are used on both sides of the driven pressure chamber, and each pressure chamber is driven by two independent drive columns. For example, a structure has been developed in which multiple grooves are formed in a piezoelectric material, with every other groove blocked, allowing the open grooves to function as pressure chambers and the blocked grooves to function as air chambers, allowing for independent drive.

[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 in the flow path from the common liquid chamber to the nozzle, the greater the overshoot. 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] Japanese Patent Application Laid-Open No. 2008-94036 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a liquid ejection head that can ensure 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 comprises an actuator member having a plurality of grooves that define a plurality of pressure chambers and a plurality of dummy chambers arranged between the pressure chambers, and a side wall portion formed between the plurality of grooves; a common chamber provided on both sides of the pressure chambers and communicating with the pressure chambers; a cover portion that separates the dummy chambers from the common chamber; and a wall portion that contains a photosensitive resin, separates at least a portion between the grooves that define the pressure chambers and the common chamber, and communicates with the common chamber and the pressure chamber in at least a portion in the depth direction of the groove, forming a throttle opening with greater fluid resistance than the pressure chamber. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing an inkjet head according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing a configuration of a portion of the inkjet head according to the embodiment. [Figure 3] FIG. 2 is an enlarged perspective view showing a part of the configuration of the inkjet head. [Figure 4] FIG. 2 is an enlarged cross-sectional view showing a part of the configuration of the inkjet head. [Figure 5] FIG. 2 is an enlarged cross-sectional view showing a part of the configuration of the inkjet head. [Figure 6] FIG. 2 is an enlarged cross-sectional view showing a part of the configuration of the inkjet head. [Figure 7] FIG. 2 is an enlarged cross-sectional view showing a part of the configuration of the inkjet head. [Figure 8] FIG. 2 is an enlarged cross-sectional view showing a part of the configuration of the inkjet head. [Figure 9]3A to 3C are explanatory diagrams illustrating a method for manufacturing the inkjet head. [Figure 10] FIG. 10 is an explanatory diagram of an inkjet head according to Test Example 1 and Test Example 2. [Figure 11] 10 is a graph showing the ejection speed of the inkjet head according to Test Example 1. [Figure 12] 10 is a graph showing the ejection speed of an inkjet head according to Test Example 2. [Figure 13] 10 is a graph showing meniscus recovery characteristics of inkjet heads according to Test Examples 1 and 2. [Figure 14] FIG. 10 is an explanatory diagram of an inkjet head of an end shooter according to Test Example 1 and Test Example 3. [Figure 15] 10 is a graph showing the driving waveforms of the inkjet heads according to Test Examples 1 and 3. [Figure 16] 10 is a graph showing nozzle flow velocity vibrations of inkjet heads according to Test Examples 1 and 3. [Figure 17] 10 is a graph showing the ejection volume of the inkjet heads according to Test Examples 1 and 3. [Figure 18] 10 is a graph showing meniscus recovery characteristics of inkjet heads according to Test Examples 1 and 3. [Figure 19] FIG. 1 is a schematic diagram showing an inkjet printer according to an embodiment. [Figure 20] FIG. 10 is an enlarged cross-sectional view showing a configuration of a portion of an inkjet head according to another embodiment. [Figure 21] FIG. 2 is an enlarged cross-sectional view showing a part of the configuration of the inkjet head. [Figure 22] FIG. 10 is an enlarged cross-sectional view showing a configuration of a portion of an inkjet head according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] The configuration of an inkjet head 10, which is a liquid ejection head according to a first embodiment, will be described below with reference to FIGS. 1 to 8. FIG. 1 is a perspective view of an inkjet head according to the first embodiment, and FIG. 2 is an exploded perspective view of a portion of the inkjet head. FIG. 3 is a perspective view showing an enlarged view of a portion of the inkjet head. FIGS. 4 to 8 are cross-sectional views showing an enlarged view of a portion of the inkjet head. FIG. 9 is an explanatory diagram of a manufacturing process for an inkjet head. In the drawings, X, Y, and Z represent a first direction, a second direction, and a third direction, which are orthogonal to one another. In this embodiment, the directions will be described based on an attitude in which the arrangement 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 liquid is along the Z axis, but the present invention is not limited to this.

[0009] As shown in Figures 1 to 8, the inkjet head 10 is a so-called side-shooter, share-mode, share-wall inkjet head. The inkjet head 10 is a device for ejecting ink and is mounted inside, for example, an inkjet printer. For example, the inkjet head 10 is an independently driven inkjet head in which pressure chambers 31 and dummy chambers 32 are arranged alternately. The dummy chambers 32 are air chambers to which ink is not supplied and do not have 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 the path between the inkjet head 10 and an ink tank.

[0012] As shown in FIGS. 2 to 8, the actuator base 11 includes a substrate 21, an actuator 22 as a pair of actuator members, a cover portion 23, and a wall portion 24 having a throttle opening 242.

[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, 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 that is 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 the ink tank via the ink supply portion. The supply holes 25 supply ink from the ink tank to the ink chambers 27. The supply holes 25 may be slit-shaped and long in one direction.

[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 into the ink tank.

[0017] A pair of actuators 22 is bonded to the mounting surface of the substrate 21. The pair of actuators 22 is arranged in two rows on the substrate 21, sandwiching the supply hole 25 therebetween. Each actuator 22 is formed of two plate-shaped piezoelectric elements, for example, made of lead zirconate titanate (PZT). The two piezoelectric elements 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 with, for example, a thermosetting epoxy adhesive. As shown in FIG. 2, the actuators 22 are arranged parallel to each other in the ink chamber 27, corresponding to the two rows of nozzles 28. The actuators 22 divide the ink chamber 27 into a first common chamber 271 through which the supply hole 25 opens and two second common chambers 272 through which the discharge holes 26 open. Therefore, the common chambers 271 and 272 are formed on both sides of the actuator 22. That is, the pressure chamber 31 and the dummy chamber 32 are formed by grooves 14 formed over the entire length along the second direction, which is the short side direction of the actuator 22, and common chambers 271 and 272 are formed adjacent to each other at both ends in the second direction (Y direction in the figure), which is the short side direction of the actuator 22.

[0018] The width of the actuator 22 in the short-side direction gradually increases from the top side toward the substrate side. The cross-sectional shape of the actuator 22 along the direction perpendicular to the longitudinal direction (short-side direction) is formed into a trapezoid shape. 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. That is, the cross-section of the actuator 22 perpendicular to the second direction is configured to be trapezoidal. The top 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 sidewall portions 33, and grooves 14 that form the pressure chambers 31 and dummy chambers 32 are formed between the sidewall portions 33. In other words, the sidewall portions 33 are formed as drive elements between the grooves 14 that form the pressure chambers 31 and dummy chambers 32.

[0019] As shown in FIGS. 1 to 8 , the bottom surface of the groove 14 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 perpendicular to 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 such that its width 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 its extension direction, is rectangular. Note that the shape of the pressure chambers 31 and the shape of the dummy chambers 32 may be different. At the ends of the multiple grooves 14 that form the pressure chambers 31 and the dummy chambers 32 of the actuator 22, a wall portion 24 and a cover portion 23 are provided at communication portions with common chambers 271 and 272 provided adjacent to the pressure chambers 31 and the dummy chambers 32, respectively.

[0020] The side wall portion 33 is formed between the pressure chamber 31 and the dummy chamber 32, and deforms in response to a drive signal to change the volume of the pressure chamber 31. A wall portion 24 is provided at the end of the groove 14 that constitutes the pressure chamber 31 in the extension direction.

[0021] The multiple pressure chambers 31 communicate with multiple nozzles 28 of the nozzle plate 12 joined to the top of the side wall portion 33. Furthermore, both ends of the pressure chambers 31 in the second direction communicate with the ink chambers 27 via throttle ports 242. That is, one end opens to a first common chamber 271 of the ink chambers 27, and the other end opens to a second common chamber 272 of the ink chambers 27. For this reason, ink flows in from one end of the pressure chambers 31, and ink flows out from the other end.

[0022] The wall portion 24 partially separates the groove 14 that constitutes the pressure chamber 31 from the common chamber 272, and forms a throttle port 242 that connects the pressure chamber 31 to the first common chamber 271 and the second common chamber 272 in at least a portion of the depth direction of the groove 14. As an example, the wall portion 24 is formed on both ends in the second direction of the groove 14 that constitutes the pressure chamber 31.

[0023] The wall portion 24 is made of a photosensitive resin or a material containing a photosensitive resin. For example, the wall portion 24 blocks the groove 14 that constitutes the pressure chamber 31 in the depth direction from the bottom of the groove 14 to a predetermined height that is lower than the height of the side wall portion 33, and a gap that becomes a throttle port 242 is formed on the nozzle plate 12 side of the wall portion 24.

[0024] The throttle port 242 is configured in a shape that narrows the opening of the communication port compared to the inside of the pressure chamber. As an example, the throttle port 242 is a communication port formed at the end of the pressure chamber 31 in the second direction, between the nozzle plate 12 and a wall portion 24 that closes the bottom side of the groove 14. The wall portion 24 may be formed on one side or the other side in the third direction, which is the depth direction of the groove 14 of the pressure chamber 31, or in an intermediate portion. The depth dimension of the throttle port 242 in the Z direction in the figure is configured to be smaller than the depth dimension in the third direction inside the pressure chamber 31, and therefore is configured to be smaller than the flow path cross-sectional area of the pressure chamber 31. In other words, the wall portion 24 partially blocks the communication ports at both ends of the pressure chamber 31 in the second direction, increasing the flow path resistance, and forming a throttle portion 240 configured to have greater fluid resistance than the inside of the pressure chamber 31.

[0025] For example, the wall portion 24 is formed by depositing a film of photosensitive resin and then exposing and developing it, or by depositing a film of photosensitive resin and then exposing, developing, and machining it. For example, the wall portion 24 is formed into a predetermined shape by applying photosensitive resin to the inlets on both sides of the pressure chamber 31, then hardening the target portions that will become the wall portion 24 by an exposure process using an exposure mask, and then developing the resin that will become the narrowed opening 242 by washing away the unexposed resin with a developer. Note that the cover portion 23 may be formed at the same time at this time. Alternatively, the wall portion 24 may be molded by hardening the photosensitive resin at predetermined locations of the communication openings on both sides of the pressure chamber 31, then removing portions of the photosensitive resin by machining such as dicing to form the narrowed opening 242.

[0026] If the fluid resistance of the throttle portion 240 is made too large, the supply of ink to the pressure chamber 31 after the ink droplet is ejected will be slow, hindering higher speeds. The rise of the meniscus will differ depending on the ink viscosity, ejection volume, drive frequency, etc. Therefore, the shape of the wall portion 24 and the dimensions and position of the throttle opening 242 of the throttle portion 240 are set to provide a flow path resistance that corresponds to the ink supply conditions and the characteristics of the rise of the meniscus.

[0027] One side of the dummy chamber 32 in the third direction is closed by the nozzle plate 12 joined to the top portion 222. In addition, both ends of the plurality of dummy chambers 32 in the second direction are closed by the cover portion 23, for example.

[0028] The cover portion 23 is made of a photosensitive resin or a material containing a photosensitive resin. The cover portion 23 closes the gap between the dummy chamber 32 and the common chambers 271, 272 at the end of the groove 14 that defines the dummy chamber 32. That is, the cover portion 23 is 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. Therefore, the dummy chamber 32 defines an air chamber into which ink does not flow.

[0029] 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. Note that the wall portion 24 and the cover portion 23 may be formed simultaneously using, for example, the same photosensitive resin material.

[0030] An electrode layer 34 is provided in each of the pressure chambers 31 and the dummy chambers 32 of the actuator base 11. The electrode layer 34 is formed, for example, from a nickel thin film. The electrode layer 34 extends from the inner surface of the groove 14 onto the substrate 21 and is connected to the pattern wiring 211. The electrode layer 34 is formed on the inner wall of the groove 14. For example, the electrode layer 34 is formed on the side surface and bottom surface of the side wall portion 33.

[0031] 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 has a plurality of nozzles 28 formed therein that penetrate the nozzle plate 12 in the thickness direction and eject liquid. The nozzle plate 12 is disposed opposite one side of the plurality of grooves 14 of the actuator 22 in the depth direction, and covers one side of the dummy chambers 32 and the pressure chambers 31.

[0032] The nozzles 28 are provided in the same number as the pressure chambers 31 and are arranged opposite each pressure chamber 31. The nozzles 28 are aligned along the first direction and arranged in two rows corresponding to the pair of actuators 22. Each nozzle 28 is configured in a cylindrical shape with its axis extending in the third direction. For example, the nozzles 28 may have a constant diameter or may have a shape that narrows toward the center or tip. The nozzles 28 are arranged opposite to the midpoints of the pressure chambers 31 formed in the pair of actuators 22 in the extension direction and are each connected to the pressure chambers 31. One nozzle 28 is arranged in the longitudinal center of each pressure chamber 31.

[0033] The frame 13 is formed into a rectangular frame shape from, for example, 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.

[0034] The manifold 18 is joined to the actuator base 11 on the side 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.

[0035] 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.

[0036] An ink chamber 27 is formed inside the inkjet head 10 configured as described above and is 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 divided 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.

[0037] In the inkjet head 10 configured as described above, ink circulates between the ink tank and the ink chamber 27 through the supply hole, pressure chamber, and discharge hole. For example, in response to a signal input from the control unit of the inkjet printer, the drive IC 52 applies a drive 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 33 in a shear mode. The volume of the pressure chamber 31 is changed by deforming the side wall 33 formed between the pressure chamber 31 and the dummy chamber 32 in response to the drive signal.

[0038] 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, ink in the ink chamber 27 flows into the pressure chamber 31.

[0039] With the volume of the pressure chamber 31 increased, the IC 52 applies a drive voltage of 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. As a result, the ink in the pressure chamber 31 is pressurized and ejected from the nozzle 28.

[0040] The method for manufacturing the inkjet head 10 will now be described. First, a piezoelectric member having a plurality of grooves 14 formed therein is attached to a plate-shaped substrate 21 with adhesive or the like, and then the piezoelectric member is machined using a dicing saw, slicer, or the like to form an actuator base 11 having a predetermined outer shape. Note that a block-shaped base member having a thickness equivalent to that of multiple plates may be formed in advance and then divided to manufacture multiple actuator bases 11 having the predetermined shape.

[0041] Next, an electrode layer 34 and pattern wiring 211 are formed on the inner surfaces of the grooves 14 that form the pressure chambers 31 and dummy chambers 32 and on the surface of the substrate 21. As a result of the above, the electrode layer 34 and pattern wiring 211 are formed in predetermined locations on the surface of the actuator base 11. Next, as shown in Fig. 9, the wall portions 24 and cover portions 23 are simultaneously formed using a photosensitive resin. For example, the wall portions 24 and cover portions 23 are formed by a filling process in which a photosensitive resin material is filled into communication openings that are entrances and exits on both sides of the grooves 14 that form the dummy chambers 32 and pressure chambers 31, and the communication openings on both ends are sealed with a cover material 243 containing the photosensitive resin material, and a molding process in which the cover material 243 is molded into a predetermined shape.

[0042] As an example, a photosensitive resin material is filled into the communication openings on both sides of the grooves 14 that form the dummy chambers 32 and the pressure chambers 31 to form the cover material 243, and then an exposure mask having an exposure pattern that leaves uncured the portion that forms the opening that becomes the aperture 242 is placed over it, and exposure is performed to cure the cured portion, and a developing process is performed in which the uncured portion is washed away with a developer to form the predetermined shape. In this way, the cover material 243 made of photosensitive resin is molded into the predetermined shape, and the cover portion 23 and the wall portion 24 having the aperture 242 are formed.

[0043] Furthermore, for example, the filling process may involve applying a photosensitive resin material to both ends of the dummy chambers 32 and the pressure chambers 31 and filling them, hardening the filled photosensitive resin material by exposure and development processes to close the communication openings of the dummy chambers 32 and the pressure chambers 31 with a cover material 243 that is a wall of the photosensitive resin material, and then, as a molding process, using a dicer having a desired width to machine the cover material 243 to form the wall portion 24 and the narrowed opening 242. In other words, after forming the cover material 243 that closes the pressure chambers 31 and the cover portion 23 that closes the dummy chambers, the cover material 243 of the pressure chambers 31 may be machined to form the narrowed opening 242, thereby forming the wall portion 24.

[0044] Furthermore, 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 thermoplastic resin.

[0045] The assembled frame 13 and actuator 22 are then polished so that the surfaces of the tops 222 of the sidewalls 33 facing the nozzle plate 12 are flush with each other. The nozzle plate 12 is then attached by bonding to the polished surfaces of the tops 222 of the sidewalls 33 and the frame 13. At this time, the nozzles 28 are positioned so that they face the pressure chambers 31. Furthermore, as shown in FIG. 1, 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, thereby completing the inkjet head 10.

[0046] An example of an inkjet printer 100 equipped with an inkjet head 10 will be described below with reference to Fig. 19. 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.

[0047] 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 that runs from a medium supply section 112 through an image forming section 113 to a medium ejection section 114.

[0048] The housing 111 forms the outer shell of the inkjet printer 100. The housing 111 has an outlet at a predetermined location for discharging the paper P to the outside.

[0049] The medium supply unit 112 includes a plurality of paper feed cassettes, and is configured to be able to hold a stack of multiple sheets of paper P of various sizes.

[0050] The medium discharge unit 114 includes a paper discharge tray configured to be able to hold the paper P discharged from the discharge port.

[0051] 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 and face each other.

[0052] The support section 117 includes a conveyor belt 118 that is looped in a predetermined area where image formation is performed, a support plate 119 that supports the conveyor belt 118 from the back side, and a plurality of belt rollers 120 that are provided on the back side of the conveyor belt 118.

[0053] During image formation, the support unit 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 moving the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120.

[0054] 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.

[0055] In this embodiment, the system includes inkjet heads 10 of four colors, cyan, magenta, yellow, and black, and ink tanks 132 that store 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 the supply port of the inkjet head 10, and a recovery flow path that is connected to the discharge port of the inkjet head 10.

[0056] 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 inside 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.

[0057] The circulation pump 134 is a liquid feed pump configured, for example, as 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.

[0058] The conveying device 115 conveys the paper P along a conveying path A that runs 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.

[0059] Each of the guide plate pairs 121 includes a pair of plate members arranged opposite each other with the paper P being conveyed therebetween, and guides the paper P along the conveying path A.

[0060] 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 arranged at various points along the conveying path A.

[0061] The control unit 116 includes a control circuit such as a CPU which is a controller, a ROM (Read Only Memory) which stores various programs, a RAM (Random Access Memory) which temporarily stores various variable data and image data, and an interface unit which inputs data from the outside and outputs data to the outside.

[0062] In the inkjet printer 100 configured as described above, when the control unit 116 detects a print instruction entered by a user operating the operation input unit via an interface, for example, 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, thereby driving the inkjet head 10. In a liquid ejection operation, the inkjet head 10 sends a drive signal to the IC in response to 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 eject ink from the nozzles 28, thereby forming an image on the paper P held on the transport belt 118. In addition, in a liquid ejection operation, the control unit 116 drives the circulation pump 134 to circulate liquid through a circulation flow path that passes through the ink tank 132 and the inkjet head 10. By the circulation operation, the ink in the ink tank 132 is supplied from the supply hole 25 to the first common chamber 271 of the ink chamber 27 through the ink supply portion of the manifold 18 by driving the circulation pump 134. This ink is supplied to the multiple pressure chambers 31 and 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 dummy chambers 32. This ink is discharged from the discharge hole 26 to the ink tank 132 through the ink discharge portion of the manifold 18.

[0063] The above-described embodiment can provide a liquid ejection head and a method for manufacturing a liquid ejection head that can ensure stable ejection characteristics. That is, in the inkjet head 10 according to the above embodiment, by providing the wall portion 24 in the pressure chamber 31, the inlet and outlet of the pressure chamber 31 have higher flow path resistance than the interior of the pressure chamber 31, the first common chamber 271, and the second common chamber 272. As a specific example, the openings that open to the first common chamber 271 and the second common chamber 272, which are common chambers of the pressure chamber 31, are smaller than the flow path cross-sectional area of the pressure chamber 31. This reduces the rise of the meniscus when liquid is ejected from the inkjet head 10. This speeds up the recovery of the meniscus, reducing its impact on the next droplet and improving ejection stability.

[0064] Figure 10 shows Test Example 1 of inkjet head 110 equipped with a restrictor (restriction portion 240) with the same flow path resistance as restrictor port 242, and Test Example 2 of inkjet head 1010 equipped with no restrictor. Figure 11 shows the frequency characteristics of inkjet head 110 equipped with a restrictor according to Test Example 1, and Figure 12 shows the frequency characteristics of inkjet head 1010 equipped with no restrictor as Comparative Example 2. Figures 11 and 12 each show the relationship between nozzle ejection speed and frequency for 1 drop and 3 drops, respectively.

[0065] The inkjet head 110 according to Test Example 1 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 midway in the extension direction of the pressure chamber 31.

[0066] As shown in FIG. 12, the inkjet head 1010 according to Test Example 2 has a flat ejection speed in the low-frequency range but tends to decrease as the frequency increases, resulting in a difference in ejection speed between the low-frequency range and the high-frequency range. For the inkjet head 1010 according to Test Example 2, the ejection speed is flat up to 25 kHz, but tends to decrease as the frequency increases above 25 kHz. For the inkjet head 1010 according to Test Example 2, the ejection speed is flat up to 15 kHz, but tends to decrease as the frequency increases above 15 kHz. Therefore, the impact position varies depending on the print pattern. Such a large difference in ejection speed makes it difficult to drive at high speeds because it takes time for the meniscus to settle, resulting in a decrease in print quality.

[0067] On the other hand, as shown in Figure 11, in the inkjet head 110 with a throttle portion, the ejection speed for both 1 drop and 3 drops tends to be flat. This is because the fluid resistance between the nozzles increases due to the common liquid, and the rise of the meniscus decreases.

[0068] FIG. 13 also shows the results of a simulation of meniscus recovery for Test Example 1, in which a pressure chamber is provided with a throttle, and Test Example 2, in which a throttle is not provided. As shown in FIG. 13, when the nozzle meniscus is low-frequency, there is sufficient time between the ejection of an ink droplet and the ejection of the next droplet, allowing stable ejection after waiting for the meniscus to recover, regardless of whether a throttle is provided. On the other hand, when the nozzle is high-frequency, the time between the ejection of a dot (ink droplet) and the ejection of the next droplet is short, so the ejection of the next droplet begins before the meniscus recovers. Therefore, in the inkjet head 1010 without a throttle, the meniscus rises significantly after ejection, preventing it from recovering in time for the next droplet to be ejected, resulting in a slower ejection speed. In contrast, when a throttle is provided, the meniscus rises less, allowing the meniscus to recover more quickly, reducing the impact on the next droplet. Therefore, these simulation results suggest that providing a throttle between the pressure chamber 31 and the common chamber improves the ejection stability of the inkjet head 110.

[0069] FIG. 14 is an explanatory diagram of a side shooter type inkjet head 110 as test example 1 and a shared mode shared wall end shooter type inkjet head 2010 as test example 3, in which an ink inlet / outlet port is formed at one end and a nozzle at the other end.

[0070] 15 to 18 are graphs comparing the simulation characteristics when a throttle is provided in the end-shooter inkjet head 2010 of Test Example 3 and the side-shooter inkjet head 110 of Test Example 1. Fig. 15 shows the drive waveform, Fig. 16 shows the nozzle flow velocity vibration, Fig. 17 shows the ejection volume, and Fig. 18 shows the meniscus recovery characteristics.

[0071] 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, communicates with the common chamber, the other end is closed, and a nozzle opens at the end of the flow path. In other words, the inkjet head 2010 forms a flow path in which ink flows from one side in the second direction toward the nozzle 28.

[0072] In the case of the end-shooter inkjet head 2010 supplying ink from one side as Test Example 3 and the side-shooter inkjet head 110 supplying ink from both sides as Test Example 1, the side-shooter inkjet head with supplying ink from both sides has the lowest drive voltage when the ejection volume, nozzle flow velocity oscillation, and meniscus recovery characteristics are all the same, so it can be said that the side-shooter inkjet head with supplying ink from both sides is superior in terms of drive efficiency to the single-side inkjet head. In other words, the so-called side-shooter 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 inkjet head 2010.

[0073] In general, in a shear-mode, shared-wall inkjet head, the pressure chamber is typically formed as a fine groove in a piezoelectric material using a diamond cutter, making it difficult to reduce the cross-section of a portion of the pressure chamber. However, according to the above-described embodiment, the groove 14 of the actuator 22 is filled with a photosensitive resin and the throttle portion 240 is formed by patterning using an exposure process or machining. This allows for relatively flexible selection of the hole shape through exposure and development, making it easy to freely design the fluid resistance of the throttle. Furthermore, in the above-described embodiment, a shallow slit is formed by partially cutting the end of the photosensitive resin-containing cover material 243 opposite the bottom of the groove 14 in the depth direction. This facilitates better processing accuracy than, for example, a deep, narrow slit extending to the bottom of the groove. Furthermore, since the resin surface exposed to ink is minimal, burrs are reduced and chemical effects of ink are suppressed. Furthermore, in the above-described embodiment, the side surface 221 of the actuator 22 forms an inclined surface, which reduces restrictions on the exposure direction and facilitates exposure and development. Furthermore, by using machining in combination, finer patterning can be achieved with high precision.

[0074] Furthermore, in the inkjet head 10 according to the above embodiment, a restriction is formed partially at the communication port which serves as the entrance and exit of the pressure chamber 31, making it 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.

[0075] 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.

[0076] In the above embodiment, the throttle opening 242 is formed by removing a portion of the photosensitive resin material formed in the pressure chamber 31 on the nozzle plate side, and the width of the groove 14 is constant in the depth direction. However, this is not limiting. For example, as shown in FIGS. 19 and 20 , the throttle opening 242 may be formed by removing a portion of the side wall 33 when removing the photosensitive resin cover material 243. For example, in the inkjet head 10 shown in FIGS. 19 to 21 , when the photosensitive resin material is removed by processing, a portion of the side wall 33 constituting the side of the groove 14 is simultaneously removed, thereby increasing the width of the pressure chambers 31 in the nozzle plate 12-side region, which is the direction in which the pressure chambers 31 are aligned. In this embodiment, the width of the pressure chambers 31 on the nozzle plate 12 side is increased over the entire length of the pressure chambers 31 in the extension direction. This configuration facilitates processing of the throttle opening 242. Furthermore, the diameter of the nozzle 28 can be increased, improving design flexibility. In another embodiment, as shown in FIG. 21, the width of the pressure chamber 31 may be uniform in the depth direction, and the width of the throttle port 242 may be larger than the width of the pressure chamber 31.

[0077] In the above embodiment, as an example, the first common chamber 271 is arranged on one side of the pressure chamber 31, the second common chamber 272 is arranged on the other side, and the fluid flows in from one side of the pressure chamber and out from the other side. However, the present invention is not limited to this. For example, the common chambers on both sides of the pressure chamber 31 may be configured as supply sides, and the fluid may flow in from both sides. That is, the fluid may flow in from both sides of the pressure chamber 31 and out from the nozzle 28 arranged in the center of the pressure chamber 31. Even in this case, by providing a throttle at the inlet portion on both sides of the pressure chamber 31, the fluid resistance can be increased and the ejection efficiency can be improved.

[0078] Furthermore, in the above embodiment, an example has been shown in which the throttle portion 240 is formed at both ends in the extension direction of the pressure chamber 31, but this is not limited to this, and the throttle portion 240 may be formed only on one side of the two inlets and outlets at which the pressure chamber 31 communicates with the common chambers 271, 272 at both ends. For example, a configuration may be possible in which the throttle portion 240 is formed at one end so that the fluid resistance is higher than inside the pressure chamber 31, and the other end has the same fluid resistance as inside the pressure chamber 31, for example, the cross-sectional area of the communication port is the same as the cross-sectional area of the inside of the pressure chamber 31.

[0079] Furthermore, in the above embodiment, the throttle portion 240 that increases the flow path resistance has a configuration including a wall portion 24 formed on the groove bottom side of the pressure chamber 31, but the shape of the throttle portion 240 is not limited to this. For example, it may be a wall member formed in a midway portion of the pressure chamber 31 in the depth direction, or in a portion on the nozzle plate 12 side, or it may be a shape in which the region of the pressure chamber 31 on the nozzle plate 12 side is partially filled with photosensitive resin. For example, the throttle port 242 has been shown to be rectangular in shape to follow the shape of the groove 14, but it may also have other shapes, including circular or oval.

[0080] Furthermore, the cover portion 23 and the wall portion 24 are formed inside the grooves 14 that form the pressure chambers 31 and the dummy chambers 32 and have a shape that fills part of the grooves 14, but this is not limited to this. For example, on the side surface of the actuator 22, a photosensitive resin may be disposed outside the grooves 14 that form the pressure chambers 31 and the dummy chambers 32 to form the cover portion 23 that closes the dummy chambers 32, or the wall portion 24 that has a throttle port 242 that partially closes the communication port of the pressure chamber 31 and partially communicates with it.

[0081] In the above embodiment, an example was shown in which the actuator 22 having a plurality of grooves 14 was arranged on the main surface portion of the substrate 21, but this is not limited to this. For example, a configuration in which the actuator is provided on the end surface of the substrate 21 may also be used. Furthermore, the number of nozzle rows is not limited to that in the above embodiment, and a configuration in which one row, or three or more rows are provided may also be used.

[0082] In the above embodiment, the actuator base 11 is provided with a laminated piezoelectric element made of the piezoelectric member 131 on the substrate 21, but this is not limiting. 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, a single piezoelectric member may be used. The dummy chamber 32 may be connected to the common chambers, namely the first common chamber 271 and the second common chamber 272. The supply side and the discharge side may be reversed, or may be configured to be switchable.

[0083] In the above embodiment, a circulation-type inkjet head is illustrated as an example in which one side of the pressure chamber 31 is the supply side and the other side is the discharge side, and fluid flows in from one side of the pressure chamber and out from the other side. However, the present invention is not limited to this. For example, a non-circulation-type inkjet head may be used. For example, by configuring the discharge hole 26 to be closed during printing, the inkjet head can be used as a non-circulation, double-sided supply type. Furthermore, for example, a common chamber on either side of the pressure chamber 31 may be the supply side, and fluid may flow in from both sides. That is, a configuration may be possible in which 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, by providing a throttle section 240 at the communication port that serves as the inlet on both sides of the pressure chamber 31, the fluid resistance can be increased and the ejection efficiency can be improved.

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

[0085] Furthermore, in the above embodiment, the inkjet head is used in a liquid ejection device such as an inkjet printer, but the invention is not limited to this and can also be used in, for example, 3D printers, industrial manufacturing machines, and medical applications, allowing for reductions 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 and a method for manufacturing a liquid ejection head that can ensure stable ejection characteristics.

[0087] Although several 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 embodied 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 within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. The following is a description equivalent to the invention described in the claims of the original application. (1) An actuator having a plurality of side walls that define a plurality of pressure chambers and a plurality of dummy chambers disposed between the plurality of pressure chambers; a common chamber provided on both sides of the pressure chamber and communicating with the pressure chamber; a cover portion separating the dummy chamber and the common chamber; a wall portion including a photosensitive resin, separating at least a portion of the groove constituting the pressure chamber from the common chamber, communicating at least a portion of the groove in a depth direction with the common chamber and the pressure chamber, and forming a throttle port having a larger fluid resistance than the pressure chamber; A side shooter type liquid ejection head comprising: (2) a nozzle plate disposed opposite one side of the plurality of grooves of the actuator in a depth direction, covering one side of the dummy chambers and the pressure chambers, and having a plurality of nozzles that eject liquid at positions opposite the pressure chambers; The liquid ejection head described in (1), wherein the orifice is formed on the nozzle plate side of the wall portion, and the depth dimension of the groove of the orifice is smaller than the depth dimension of the groove in the pressure chamber. (3) The liquid ejection head according to (1) or (2), wherein the width of the region of the throttle port and the pressure chamber on the nozzle plate side is greater than the width of the region of the pressure chamber on the bottom side. (4) a side surface of an actuator having a plurality of pressure chambers communicating with nozzles that eject liquid, a plurality of grooves that form a plurality of dummy chambers arranged between the plurality of pressure chambers, and a plurality of sidewall portions formed between the pressure chambers and the grooves that form the dummy chambers; supplying a cover material containing a photosensitive resin to a communication portion with a common chamber provided adjacent to an end portion of the plurality of grooves constituting the pressure chamber; A method for manufacturing a liquid ejection head, comprising removing a portion of the cover material at the end of the pressure chamber, thereby forming a throttle opening that connects the pressure chamber and the common chamber in at least a portion of the depth direction of the groove and has a higher fluid resistance than the pressure chamber. (5) The method for manufacturing a liquid ejection head according to (4), wherein the throttle opening is formed to be larger than the width of the groove by removing a part of the cover material and a part of the side wall at the end of the pressure chamber. [Explanation of symbols]

[0088] 10...inkjet head, 11...actuator base, 12...nozzle plate, 13...frame, 17...circuit board, 18...manifold, 21...substrate, 22...actuator, 23...cover portion, 24...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, 81...ink supply portion, 82...ink discharge portion, 100...inkjet printer, 111...casing, 112...medium supply portion, 1 13...image forming unit, 114...medium discharge unit, 115...conveying device, 116...control unit, 117...support unit, 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 portion, 222...top portion, 240...throttling portion, 242...throttling port, 243...cover material, 271...first common chamber, 27...ink chamber, 272...second common chamber.

Claims

1. an actuator having a plurality of sidewall portions that define a plurality of pressure chambers and a plurality of dummy chambers disposed between the plurality of pressure chambers; a common chamber provided on both sides of the pressure chamber and communicating with the pressure chamber; a cover portion separating the dummy chamber and the common chamber; a wall portion including a photosensitive resin, separating at least a portion of the groove constituting the pressure chamber from the common chamber, communicating at least a portion of the groove in a depth direction with the common chamber and the pressure chamber, and forming a throttle port having a larger fluid resistance than the pressure chamber; A side shooter type liquid ejection head comprising:

2. a nozzle plate disposed opposite one side of the groove of the actuator in a depth direction, covering one side of the dummy chamber and the pressure chamber, and having a plurality of nozzles that eject liquid at positions opposite the pressure chambers; 2. The liquid ejection head according to claim 1, wherein the throttle port is formed on the nozzle plate side of the wall portion, and the dimension of the throttle port in the depth direction of the groove is smaller than the dimension of the groove in the pressure chamber in the depth direction.

3. The liquid ejection head according to claim 2 , wherein a width of the region of the throttle port and the pressure chamber on the nozzle plate side is greater than a width of a region of the pressure chamber on the bottom side.

4. a side surface of an actuator having a plurality of pressure chambers communicating with nozzles that eject liquid, a plurality of grooves that form a plurality of dummy chambers arranged between the plurality of pressure chambers, and a plurality of sidewall portions formed between the pressure chambers and the grooves that form the dummy chambers; supplying a cover material containing a photosensitive resin to a communication portion with a common chamber provided adjacent to an end portion of the plurality of grooves constituting the pressure chamber; A method for manufacturing a liquid ejection head, comprising removing a portion of the cover material at the end of the pressure chamber, thereby forming a throttle opening that connects the pressure chamber and the common chamber in at least a portion of the depth direction of the groove and has a higher fluid resistance than the pressure chamber.

5. The method for manufacturing a liquid ejection head according to claim 4 , wherein the throttle opening is formed to be larger than the groove in the width direction by removing a part of the cover material and a part of the side wall at the end of the pressure chamber.

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