JP7650783B2 - LIQUID DISCHARGE HEAD AND METHOD FOR MANUFACTURING LIQUID DISCHARGE HEAD - Google Patents

Description

Embodiments of the present invention relate to a liquid ejection head and a method for manufacturing a liquid ejection head.

In recent years, high productivity is required for inkjet heads, and high speed and increased 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 large droplets. In a share-mode shared-wall type inkjet head, the same drive column is shared by two pressure chambers, and so-called three-cycle drive is common, in which one-third of the multiple arranged chambers are simultaneously driven as pressure chambers. In addition, an independent drive 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 drive 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 independent drive is performed.

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 meniscus swells due to overshooting at the nozzle. 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 in a stable meniscus 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.

JP 2008-94036 A

The problem that this invention aims to solve is to provide a liquid ejection head and a method for manufacturing a liquid ejection head that can ensure stable ejection characteristics.

The 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 the inner wall of the pressure chamber. The throttling portion has a protrusion formed of an electrocoating paint formed on the electrode layer in at least a portion of an opening of the pressure chamber that communicates with the common chamber.

FIG. 1 is a perspective view showing an inkjet head according to an embodiment. FIG. 2 is an exploded perspective view showing a configuration of a portion of an inkjet head according to an embodiment. FIG. 2 is an enlarged perspective view showing a configuration of a portion of the inkjet head. FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. 3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. 3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. 3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. FIG. 4 is an explanatory diagram of an inkjet head according to Test Example 1 and Test Example 2. 13 is a graph showing the ejection speed of the inkjet head according to Test Example 1. 13 is a graph showing the ejection speed of an inkjet head according to Test Example 2. 13 is a graph showing meniscus recovery characteristics of the inkjet heads according to Test Examples 1 and 2. FIG. 11 is an explanatory diagram of an inkjet head of an end shooter according to Test Example 1 and Test Example 3. 13 is a graph showing driving waveforms of the inkjet head according to Test Example 1 and Test Example 3. 13 is a graph showing nozzle flow velocity vibration of the inkjet heads according to Test Examples 1 and 3. 13 is a graph showing the ejection volume of the inkjet heads according to Test Examples 1 and 3. 13 is a graph showing meniscus recovery characteristics of the inkjet heads according to Test Examples 1 and 3. FIG. 1 is a schematic diagram showing an inkjet printer according to an embodiment. 8A to 8C are explanatory diagrams of a method for manufacturing an inkjet head according to another embodiment.

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 the 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 that are perpendicular to each other. In this embodiment, the directions are 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.

As shown in Figures 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 arranged alternately. The dummy chambers 32 are air chambers to which ink is not supplied, and do not have nozzles 28.

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. Inside the inkjet head 10, an ink chamber 27 is formed to which ink, an example of a liquid, is supplied.

The inkjet head 10 further 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 the ink tank.

As shown in Figures 2 to 5, the actuator base 11 includes a substrate 21, a pair of actuators 22, and a restrictor portion 240.

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.

As shown in Figures 2 and 3, a pattern wiring 211 is formed on the substrate 21 of the actuator base 11. The pattern wiring 211 is formed, for example, from 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.

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 section of the manifold 18. The supply holes 25 are connected to an ink tank via the ink supply section. The supply holes 25 supply ink from the ink tank to the ink chambers 27.

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 section of the manifold 18. The discharge holes 26 are connected to the ink tank via the ink discharge section. The discharge holes 26 discharge the ink from the ink chamber 27 into the ink tank.

The pair of actuators 22 are attached to the mounting surface of the substrate 21. The pair of actuators 22 are arranged in two rows on the substrate 21 with the supply hole 25 in between. Each actuator 22 is formed of two plate-shaped piezoelectric bodies made of lead zirconate titanate (PZT), for example. 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 attached to the mounting surface of the substrate 21, for example, with a thermosetting epoxy adhesive. As shown in FIG. 2, the actuators 22 are arranged in parallel 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 in which the supply hole 25 opens, and two second common chambers 272 in which the discharge hole 26 opens.

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 perpendicular to the longitudinal direction (short side direction) is formed into a trapezoid shape. The side 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 of the actuator 22 is bonded to the nozzle plate 12. The actuator 22 has 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.

As shown in Figures 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 dummy chambers 32 are arranged alternately. The pressure chambers 31 and 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 figure), which is the longitudinal direction of the actuator 22. In this embodiment, for example, the width dimension of the groove 14 in the X direction is constant in the depth direction along the Z direction, and the cross section perpendicular to the Y direction, which is the extension direction, is rectangular.

The shape of the pressure chamber 31 and the shape of the dummy chamber 32 may be different. 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.

An electrode layer 34 is provided on 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.

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

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 part of the inner surface of the groove at the end of the pressure chamber 31 in the second direction. The protrusion portion 241 is composed of an electrocoating paint formed on the electrode layer 34 inside the pressure chamber 31. As the electrocoating 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.

In this embodiment, protrusions 241 made of electrocoating paint are formed on both side surfaces of the groove in the first direction. For example, the protrusions 241 on both sides 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 of the groove in the third direction. For example, electrocoating 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 configured to be continuous at the bottom of the groove. For example, the protrusions 241 on both sides are configured in a rectangular shape that is long in the third direction.

The groove constituting the pressure chamber 31 is not completely covered by the protrusions 241, and between the pair of protrusions 241 on both sides, a throttle port 242 is formed that connects the pressure chamber 31 to 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 chamber, and its opening width in the first direction is configured to be smaller than the width in the first direction inside the pressure chamber 31, and is therefore configured to be smaller than the flow path cross-sectional area of the pressure chamber 31. In other words, the protrusions 241 partially block the communication ports at both ends in the second direction, forming a throttle portion 240 in which the flow path resistance increases. For example, the throttle portion 240 is configured to have a predetermined shape by forming an electrodeposited resist film 244 on the inner walls of the pressure chamber 31 and the dummy chamber 32, forming the electrodeposited resist film 244 in the resist area other than the paint area by exposure and development, and then forming an electrodeposited paint film 243 in the paint area where the electrodeposited resist film 244 is not formed, and removing the electrodeposited resist film 244 by etching. For example, a photosensitive acrylic resin is used as the electrodeposition resist film 244.

If the fluid resistance of the throttling section 240 is too large, the supply of ink to the pressure chamber 31 after the ink droplets are ejected will be slow, hindering high speeds. The meniscus rise will vary depending on the ink viscosity, ejection volume, drive frequency, etc. Therefore, the shape of the protrusion 241 and the dimensions and position of the throttling opening 242 of the throttling section 240 are each set to provide a flow path resistance according to the ink supply conditions and the characteristics of the meniscus rise. The throttling sections 240 on both sides may have different configurations.

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, cover portions 23 are respectively arranged 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 forms an air chamber into which ink does not flow.

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 area.

The nozzle plate 12 is formed, for example, from a rectangular film made of polyimide. 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, which penetrate the nozzle plate 12 in the thickness direction.

The nozzles 28 are provided in the same number as the pressure chambers 31, and are arranged opposite each of the pressure chambers 31. The nozzles 28 are arranged in two rows along the first direction, 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 toward the center or tip. The nozzles 28 are arranged opposite the midpoint of the extension direction of the pressure chambers 31 formed in the pair of actuators 22, and each 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 each in the longitudinal center.

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 adhered 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.

The manifold 18 is joined to the actuator base 11 on the side opposite the nozzle plate 12. Inside the manifold 18, an ink supply section, which is a flow path that communicates with the supply hole 25, and an ink discharge section, which is a flow path that communicates with the discharge hole 26, are formed.

The circuit board 17 is a film carrier package (FCP). The circuit board 17 has a flexible resin film 51 on which multiple wirings are formed, and an IC 52 connected to the multiple 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.

Inside 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 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 connected to a plurality of pressure chambers 31.

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 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.

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. This causes ink in the ink chamber 27 to flow into the pressure chamber 31.

When the volume of the pressure chamber 31 has 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. This pressurizes the ink in the pressure chamber 31, causing it to be ejected from the nozzle 28.

The manufacturing method of the inkjet head 10 will be described with reference to Figures 6 to 8. First, a piezoelectric member having multiple grooves is attached to a plate-shaped substrate 21 with 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 multiple sheets may be formed in advance and then divided to manufacture multiple actuator bases 11 of the predetermined shape.

Next, the electrode layer 34 and the pattern wiring 211 are formed on the inner surfaces of the grooves that form 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.

Next, as shown in Figures 6 to 8, a throttle portion 240 is formed at the end of the pressure chamber 31, which is a communication port having a flow resistance greater than the inside of the pressure chamber 31. For example, a method for forming the throttle portion 240 includes a resist film formation process Act1 in which an electrodeposited resist film 244 is formed in the 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.

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, an 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 in which the resist region in which 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 in which the diaphragm portion 240 is to be formed is exposed through the photomask 245, and the electrodeposited resist film 244 in the exposed portion is removed with a developer. That is, the electrodeposited resist film 244 in the resist region other than the portion in which the protrusion portion 241 is to be formed is hardened by the exposure process. The 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.

Then, after the electrodeposition resist film 244 is formed and shaped, an electrodeposition paint film 243 is formed and cured in the paint area where the electrodeposition resist film 244 is not formed, as paint film formation process Act3. 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 opening 242 can be formed. After that, the electrodeposition resist film 244 is removed by etching process Act4.

As a result of the above, a protrusion 241 is formed by the electrochemical paint film 243 in the paint area at the entrance and exit of the pressure chamber 31, and a constriction portion 240 is formed between the protrusions 241 on both sides.

Then, the cover portion 23 is formed in a predetermined location 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 photosensitive resin and curing it. Note that the cover portion 23 may be formed before the narrowing portion 240 is formed.

Then, the actuator base 11 is assembled to the manifold 18, and the frame 13 is attached to one side of the substrate 21 of the actuator base 11 using a thermoplastic resin adhesive sheet.

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 gluing to the polished surfaces of the top of the side wall 33, the frame 13, and the protrusion 241. At this time, the nozzle 28 is positioned so that it faces the pressure chamber 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.

Below, an example of an inkjet printer 100 equipped with an inkjet head 10 will be described 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.

The inkjet printer 100 is a liquid ejection device that ejects liquid such as ink onto a recording medium, such as paper P, while transporting the recording medium, such as paper P, along a predetermined transport path A that runs from the medium supply unit 112 through the image forming unit 113 to the medium ejection unit 114, thereby forming an image on the paper P.

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

The media supply unit 112 is equipped with multiple paper feed cassettes and is configured to hold multiple stacks of paper P of various sizes.

The medium discharge unit 114 is equipped with a paper discharge tray configured to hold the paper P discharged from the discharge port.

The image forming unit 113 includes a support unit 117 that supports the paper P, and a number of head units 130 that are arranged opposite each other above the support unit 117.

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 number of belt rollers 120 that are provided on the back side of the conveyor belt 118.

During image formation, the support section 117 supports the paper P on the 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 rotating the belt roller 120.

The head unit 130 includes multiple 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.

In this embodiment, the inkjet head 10 has four colors, cyan, magenta, yellow, and black, and ink tanks 132 that contain ink of each color. The ink tanks 132 are connected to the inkjet head 10 by a connection flow path 133. The connection flow path 133 has 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.

The ink tank 132 is also connected to a negative pressure control device such as a pump (not shown). 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, causing the ink supplied to each nozzle 28 of the inkjet head 10 to form a meniscus of a predetermined shape.

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

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

Each of the multiple guide plate pairs 121 has a pair of plate members arranged opposite each other with the paper P being transported therebetween, and guides the paper P along the transport path A.

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 that detect the conveying status of the paper are placed at various points along the conveying path A.

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

In the inkjet printer 100 configured as described above, when the control unit 116 detects a print instruction by a user operating the operation input unit, for example, in the 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, thereby driving 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 the 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, 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 from the supply hole 25 to the first common chamber 271 of the ink chamber 27 through the ink supply part 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 the dummy chambers 32. This ink is discharged from the discharge hole 26 through the ink discharge part of the manifold 18 to the ink tank 132.

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 has a protrusion 241 made of electrocoating paint at the opening of the pressure chamber 31, and can easily form a throttling section 240 with a higher flow resistance than the inside of the pressure chamber 31, the first common chamber 271, and the second common chamber 272. The opening of the throttling section 240 that opens into the first common chamber 271 and the second common chamber 272, which are the common chambers of the pressure chamber 31, is 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, reducing the effect on the next droplet, and improving ejection stability.

Figure 9 shows test example 1 for an inkjet head 110 equipped with a diaphragm (throttle section 240), and test example 2 for an inkjet head 1010 without a diaphragm. Figure 10 shows the frequency characteristics of the inkjet head 110 equipped with a diaphragm according to test example 1, and Figure 11 shows the frequency characteristics of an inkjet head 1010 without a diaphragm 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.

Here, the inkjet head 110 in 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, are connected to a common chamber, and the nozzle 28 opens halfway in the extension direction of the pressure chamber 31.

As shown in FIG. 11, in the inkjet head 1010 according to the test example 2, 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 test example 2, 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 test example 2, 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 there is a large difference in the ejection speed, it takes time for the meniscus to settle, which causes a decrease in print quality, and therefore high-speed driving is not possible.

On the other hand, as shown in FIG. 10, in the inkjet head 110 having a throttle portion, the ejection speed tends to be flat for both 1 drop and 3 drops. This is because the fluid resistance between the nozzles increases from the common liquid, and the meniscus rises less.

FIG. 12 shows the results of a simulation of the meniscus returning in Test Example 1, in which a throttling is provided in the pressure chamber, and Test Example 2, in which a throttling is not provided. According to FIG. 12, in the case of low frequency, the meniscus state of the nozzle has a sufficient time between the ejection of an ink droplet and the ejection of the next droplet, and ejection can be performed in a stable state after waiting for the meniscus to return regardless of the presence or absence of a throttling. On the other hand, in the case of 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 returns. For this reason, in the case of the inkjet head 1010 without a throttling, the meniscus rises large after ejection, and the meniscus cannot return before the ejection of the next droplet, resulting in a decrease in the ejection speed. In contrast, when a throttling is provided, the meniscus rises 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 throttling between the pressure chamber 31 and the common chamber leads to improved ejection stability of the inkjet head 110.

Figure 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.

Figures 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. Figure 14 shows the drive waveform, Figure 15 shows the nozzle flow velocity vibration, Figure 16 shows the ejection volume, and Figure 17 shows the meniscus return characteristics.

The inkjet head 2010 in the test example 3 was an end shooter type in which one end in the second direction, which is the extension direction of the pressure chamber 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 that flows from one side in the second direction toward the nozzle 28.

The inkjet head 2010 of the end shooter type supplying from one side as Test Example 3 and the inkjet head 110 of the side shooter type supplying from both sides as Test Example 1 have the lowest drive voltage when the ejection volume, nozzle flow velocity vibration, and meniscus return characteristics are aligned, so it can be said that the side shooter type configuration with 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.

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 are facilitated.

In addition, in the inkjet head 10 according to the above embodiment, a partial restriction is formed in the communication port that serves as the entrance and exit 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.

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

In the above embodiment, the throttling 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 throttling 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 it may be a shape in which the area on the bottom side of the pressure chamber 31 is partially filled with photosensitive resin. For example, the throttling 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 oval. In addition, the throttling portions 240 on both sides may have different configurations. For example, the throttling 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 throttling portion 240 cheaply and easily.

In addition, 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 the above. For example, on the side of the actuator, a restrictor portion 240 such as the cover portion 23 that closes the dummy chamber 32 and 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.

In the above embodiment, an example is shown in which an actuator 22 having multiple grooves is arranged on the main surface portion of the substrate 21, but this is not limited to the above. For example, the actuator may be provided on the end surface of the 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.

In the above embodiment, the actuator base 11 is provided with a laminated piezoelectric body made of a piezoelectric member 131 on a substrate 21, but this is not limited to the above. For example, the actuator base 11 may be formed only from a 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, 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.

In the above embodiment, as an example, a circulation type inkjet head is illustrated 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, but this 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 located in the center of the pressure chamber 31. Even in this case, by providing a throttling 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. Also, the throttling sections 240 formed at both ends may have different configurations.

In the above embodiment, the throttle section 240 is formed at both ends of the pressure chamber 31 in the extension direction, but this is not limited to the above. The throttle section 240 may be formed only on one side of the inlets and outlets on both sides where the pressure chamber 31 communicates with the common chambers 271, 272 at both ends. For example, the throttle section 240 may be formed at one end such that the fluid resistance is higher than inside the pressure chamber 31, and the other end may be configured to have the same fluid resistance as inside 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.

In the above example, the exposure direction of the electrochemical resist film 244 when forming the throttling portion 240 is set in the depth direction of the pressure chamber 31, but this is not limited to this. 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 in turn. FIG. 19 shows the configuration of the electrochemical 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 area on one side of the inner wall of the groove, the resist area on the other side may be hardened by exposing it from a direction inclined to the opposite side.

In addition, 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.

In addition, 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.

At least one of the embodiments described above can provide a liquid ejection head and a method for manufacturing a liquid ejection head that can ensure stable ejection characteristics.

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 embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

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...housing, 112...medium supply section, 113...image forming section, 114...medium discharge section, 11 5...conveyor device, 116...controller, 117...support section, 118...conveyor belt, 119...support plate, 120...belt roller, 121...pair of guide plates, 122...conveyor roller, 130...head unit, 132...ink tank, 133...connecting flow path, 134...circulation pump, 211...pattern wiring, 221...side portion, 222...top, 240...throttling portion, 241...projection portion, 242...throttling port, 243...electrodeposition paint film, 244...electrodeposition resist film, 271...first common chamber, 27...ink chamber, 272...second common chamber.

Claims (5)

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: The liquid ejection head according to claim 1, wherein the constriction portion has a protrusion formed on the side wall at the end of the pressure chamber that narrows the opening of the pressure chamber, and is configured to have a larger fluid resistance than the inside of the pressure chamber. a nozzle plate having a plurality of nozzles that are in communication with the pressure chambers and that 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. A method for manufacturing a liquid ejection head, comprising: an actuator having a plurality of grooves that are arranged in a first direction, communicated with nozzles that eject liquid and communicate with a common chamber on both sides, and that form a plurality of dummy chambers arranged between the pressure chambers; a plurality of side walls formed between the grooves; and an electrode layer formed on the inner wall of the pressure chambers, the method comprising forming an electrodeposition paint film on at least a portion of an opening of the pressure chamber that communicates with the common chamber, thereby forming a throttle portion that communicates with the common chamber and the pressure chambers and has a higher fluid resistance than the inside of the pressure chamber. 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 .