Liquid discharge head, liquid discharge device, and liquid discharge method

Abstract

To improve the stability of liquid discharge by the liquid dispensing head. [Solution] The liquid discharge head includes a nozzle for discharging liquid, a pressure chamber communicating with the nozzle, a nozzle plate on which the nozzle is formed, and an actuator positioned on the nozzle plate which deforms the nozzle plate to discharge the liquid in the pressure chamber from the nozzle. When a drive voltage is applied to the actuator, a controlled flow is generated in the liquid in the pressure chamber.

Description

Technical Field

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[0001] The present invention relates to a liquid ejection head, a liquid ejection device, and a liquid ejection method.

Background Art

[0002] A liquid ejection head that ejects liquid from a nozzle by vibrating a nozzle plate on which the nozzle is formed is known.

[0003] For example, Patent Document 1 discloses a liquid ejection head having a nozzle plate having a diaphragm closing a pressure chamber and a nozzle communicating with the pressure chamber, and an actuator disposed on the nozzle plate for deforming the diaphragm.

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to improve the ejection stability of liquid by a liquid ejection head.

Means for Solving the Problems

[0005] A liquid ejection head according to an aspect of the present invention includes a nozzle that ejects liquid, a pressure chamber communicating with the nozzle, a nozzle plate on which the nozzle is formed, and an actuator disposed on the nozzle plate for deforming the nozzle plate to eject the liquid in the pressure chamber from the nozzle. When a drive voltage is applied to the actuator, a controlled flow is generated in the liquid in the pressure chamber.

Effects of the Invention

[0006] According to the present invention, the ejection stability of liquid by a liquid ejection head can be improved.

Brief Description of the Drawings

[0007] [Figure 1] It is a schematic perspective view of a liquid ejection head according to the first embodiment. [Figure 2] This is a schematic cross-sectional view of the line II-II in Figure 1. [Figure 3] This is a schematic cross-sectional view illustrating bubbles that remain in a pressure chamber. [Figure 4] This is a schematic cross-sectional view illustrating a liquid dispensing head of a conventional unimorph type piezoelectric system. [Figure 5] This is a schematic cross-sectional view showing a first example of controlled liquid flow in a liquid discharge head according to the first embodiment. [Figure 6] This is a schematic cross-sectional view showing how bubbles remaining in the pressure chamber of a liquid discharge head according to the first embodiment are moved to a position where they can be discharged by a controlled flow of liquid. [Figure 7] This figure shows the driving voltage during liquid discharge in the liquid discharge head according to the first embodiment. [Figure 8] This figure shows the drive voltage during micro-drive in the liquid discharge head according to the first embodiment. [Figure 9] This is a schematic cross-sectional view illustrating an experimental method for evaluating flow within a pressure chamber. [Figure 10] This figure shows the first example of simulation results for evaluating flow within a pressure chamber. [Figure 11] This is a schematic cross-sectional view showing the controlled liquid flow in a liquid discharge head according to a modification of the first embodiment. [Figure 12A] This figure shows a second example of simulation results for evaluating flow within a pressure chamber. [Figure 12B] This figure shows the expansion and contraction of the pressure chamber due to the vibration of the nozzle plate. [Figure 13] This is a schematic cross-sectional view showing a liquid dispensing head according to the second embodiment. [Figure 14] This is a schematic cross-sectional view showing a liquid dispensing head according to the third embodiment. [Figure 15] This is a schematic cross-sectional view showing bubbles remaining in the pressure chamber of a liquid discharge head according to the third embodiment. [Figure 16]It is a schematic cross-sectional view showing a state where bubbles staying in a pressure chamber in a liquid ejection head according to a third embodiment are moved to a position where they can be discharged by a controlled liquid flow. [Figure 17] It is a schematic cross-sectional view showing a first example of liquid agitation in a liquid ejection head according to a fourth embodiment. [Figure 18] It is a schematic cross-sectional view showing a second example of liquid agitation in a liquid ejection head according to a fourth embodiment. [Figure 19] It is a block diagram showing the hardware configuration of a control unit of a liquid ejection device according to a fifth embodiment. [Figure 20] It is a schematic side view showing a first example of the overall configuration of a liquid ejection device according to a fifth embodiment. [Figure 21] It is a schematic bottom view showing a head unit in a liquid ejection device according to a fifth embodiment. [Figure 22] It is a schematic top view showing a second example of the overall configuration of a liquid ejection device according to a fifth embodiment. [Figure 23] It is a schematic diagram showing the configuration around a liquid ejection unit in a liquid ejection device according to a second example. [Figure 24] It is a schematic top view showing a first example of a liquid ejection unit according to a sixth embodiment. [Figure 25] It is a schematic side view showing a second example of a liquid ejection unit according to a sixth embodiment.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In each of the drawings for explaining the embodiments of the present invention, for components such as members and components having the same function or shape, the same reference numerals are attached as much as possible for discrimination, and the description thereof will be omitted after being explained once.

[0009] In each drawing, orthogonal coordinates having an X-axis, a Y-axis, and a Z-axis are used as the direction representation. The X-axis, the Y-axis, and the Z-axis are substantially orthogonal to each other. The direction in which the arrow of the X-axis points is denoted as the +X direction or the +X side, and the direction opposite to the +X direction is denoted as the -X direction or the -X side. The direction in which the arrow of the Y-axis points is denoted as the +Y direction or the +Y side, and the direction opposite to the +Y direction is denoted as the -Y direction or the -Y side. The direction in which the arrow of the Z-axis points is denoted as the +Z direction or the +Z side, and the direction opposite to the +Z direction is denoted as the -Z direction or the -Z side. The liquid ejection head according to the embodiment is configured to eject liquid in the +Z direction.

[0010] However, the terms indicating the above specific directions and positions are merely used to facilitate understanding of the relative directions and positions in the referenced drawings. These terms do not limit the direction of the embodiment, and the orientation during use of the liquid ejection head according to the embodiment is arbitrary. Also, in this specification, "arrange" is not limited to the case of direct contact, and includes the case of arranging indirectly, for example, via other members.

[0011] [First Embodiment] <Configuration of the Liquid Ejection Head According to the First Embodiment> Referring to FIGS. 1 and 2, the configuration of the liquid ejection head according to the first embodiment of the present invention will be described. FIG. 1 is a schematic perspective view of a liquid ejection head 10 according to the first embodiment. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1.

[0012] As shown in FIGS. 1 and 2, the liquid ejection head 10 according to the present embodiment includes a nozzle 1 that ejects liquid, a pressure chamber 2 that communicates with the nozzle 1, and a nozzle plate 3 on which the nozzle 1 is formed. Further, the liquid ejection head 10 includes an actuator 4 that is disposed on the nozzle plate and causes the liquid in the pressure chamber 2 to be ejected from the nozzle 1 by deforming the nozzle plate 3. In the example shown in FIGS. 1 and 2, the liquid ejection head 10 includes a flow path substrate 100 in which a flow path through which the liquid flows is formed. The nozzle plate is a thin film-like member that is disposed on the +Z side of the flow path substrate 100, that is, the side from which the liquid is ejected from the liquid ejection head 10, and extends in the X direction and the Y direction.

[0013] In the examples shown in Figures 1 and 2, the liquid discharge head 10 has a plurality of nozzles 1 and a plurality of pressure chambers 2. The plurality of nozzles 1 are formed on the nozzle plate 3, arranged in the X and Y directions, respectively. The plurality of pressure chambers 2 are formed on the flow path substrate 100. The plurality of pressure chambers 2 are in communication with the plurality of nozzles 1, corresponding to the plurality of nozzles 1. The partition wall 5 is a wall that separates the plurality of pressure chambers 2, arranged in the X and Y directions, respectively.

[0014] In the example shown in Figure 2, the nozzle plate 3 includes a diaphragm 31, a protective film 32 positioned on the +Z side of the diaphragm 31, wiring 33 electrically connected to the actuator 4, and an interlayer insulating film 34 covering the actuator 4. The wiring 33, interlayer insulating film 34, and actuator 4 are positioned on the +Z side surface of the diaphragm 31 and inside the protective film 32. The protective film 32 protects the wiring 33, interlayer insulating film 34, and actuator 4 by covering them.

[0015] The nozzle plate 3 has an inner surface 35 facing the pressure chamber 2. The pressure chamber 2 is a space defined at least by the inner surface 51 of the partition wall 5 and the inner surface 35 of the nozzle plate 3. Each of the internal spaces of the multiple pressure chambers 2 is filled with liquid. Multiple actuators 4 are arranged corresponding to the multiple pressure chambers 2.

[0016] In the example shown in Figure 2, the actuator 4 includes a lower electrode 41, a piezoelectric film 42 positioned on the +Z side of the lower electrode 41, and an upper electrode 43 positioned on the +Z side of the piezoelectric film 42. In the example shown in Figure 2, the actuator 4 is a piezoelectric element including the piezoelectric film 42. The upper electrode 43 is connected to the wiring 33. A drive voltage is applied to the actuator 4 through the wiring 33 to drive the actuator 4. When the actuator 4 is driven, the nozzle plate 3 deforms. The deformation of the nozzle plate 3 changes the pressure in the pressure chamber 2. Due to the pressure change in the pressure chamber 2, liquid is discharged from the nozzle 1.

[0017] The drive voltage applied to the actuator 4 may be generated by a drive circuit integrally formed with the liquid discharge head 10, or it may be generated by an externally connected device. When the drive circuit is integrally formed with the liquid discharge head 10, for example, the flow channel substrate 100 is formed by applying a MEMS (Micro Electro Mechanical Systems) process to an SOI (Silicon on Insulator) substrate. The drive circuit is composed of transistors, resistors, etc. formed on the flow channel substrate 100.

[0018] The partition wall 5 is made of silicon (Si) or the like. The nozzle plate 3 is made of silicon oxide (SiO2) or the like. The piezoelectric film 42 is made of scandium aluminum nitride (ScAlN) thin film or the like.

[0019] The protective film 32 is composed of benzocyclobutene (BCB) or the like. The protective film 32 may also be a liquid-repellent film. By making the protective film 32 a liquid-repellent film, the adhesion of liquid to the outer surface of the nozzle plate 3 can be suppressed, and the liquid discharged from the nozzle 1 can be prevented from being affected by the liquid adhering to the outer surface of the nozzle plate 3. If the solvent of the liquid is aqueous, perfluorodecyltrichlorosilane or perfluorooctyltrichlorosilane can be used as the material for the liquid-repellent film.

[0020] Wiring 33 is independently connected to the actuator 4 located in each of the multiple pressure chambers 2. The liquid discharge head 10 can individually drive the multiple actuators 4, to which the wiring 33 is connected, by applying a drive voltage to each actuator 4, thereby discharging liquid individually from the multiple nozzles 1.

[0021] <Removal of air bubbles in the liquid dispensing head 10> This section explains the effect of air bubbles present in the pressure chamber of the liquid discharge head on liquid discharge. In a liquid discharge head, air bubbles may form in the liquid filling the pressure chamber. These air bubbles absorb the pressure applied to the liquid in the pressure chamber by the actuator. This pressure absorption by the air bubbles can lead to non-discharge, where no liquid is discharged from the nozzle, or discharge defects where the volume, discharge speed, or discharge direction of the liquid discharged from the nozzle deviates from the specified values.

[0022] One known method for removing air bubbles from a pressure chamber is to purge the liquid inside the chamber by pressurizing or suctioning it, thereby forcibly expelling the air bubbles along with the liquid from the pressure chamber. Pressurizing the liquid inside the pressure chamber can be done, for example, by driving an actuator. Suctioning the liquid inside the pressure chamber can be done, for example, by using a suction pump located outside the liquid discharge head to draw the liquid from the pressure chamber through a nozzle.

[0023] However, within a pressure chamber, stagnation areas where liquid accumulates may occur, such as at the corners of the pressure chamber. Here, Figure 3 is a schematic cross-section illustrating bubbles 7 accumulating in the pressure chamber 2. The dashed line indicates a stagnation area 70 that occurs at the corner of the pressure chamber 2. Bubbles 7 represent bubbles present in the liquid within the stagnation area 70. The arrows represent the purge flow 60, which is generated by purging the liquid in the pressure chamber 2 by pressurizing or suctioning it. The direction in which the arrows representing the purge flow 60 point indicates the direction in which the liquid flows in the purge flow 60.

[0024] As shown in Figure 3, even when purging is performed, the purge flow 60 does not act on the liquid in the stagnant region 70. From another perspective, the purge flow 60 does not contribute to the movement of the liquid in the stagnant region 70. Therefore, the liquid in the stagnant region 70 and the bubbles 7 present in the liquid do not move within the pressure chamber 2 even when purging is performed, and are not discharged from the pressure chamber 2. The retention of bubbles 7 without being discharged from the pressure chamber 2 may result in non-discharge or discharge failure.

[0025] Figure 4 is a schematic cross-sectional view illustrating a conventional unimorph-type piezoelectric liquid discharge head 10X. In Figure 4, for the sake of clarity, components in the liquid discharge head 10X that have the same function as the liquid discharge head 10 according to this embodiment are indicated by adding "X" to the reference numeral of the component in the liquid discharge head 10.

[0026] In a liquid discharge head 10X, a method is known that uses acoustic waves 71 generated in the pressure chamber 2X by micro-driving to expel bubbles or prevent the liquid from drying out. Micro-driving refers to a driving method in which the liquid in the pressure chamber 2X is driven without the liquid being discharged from the nozzle 1X by applying a drive voltage to the actuator 4X that is smaller than the drive voltage used to discharge the liquid from the nozzle 1X. In micro-driving in the liquid discharge head 10X, the liquid in the pressure chamber 2X is micro-driven by acoustic waves 71 generated by vibrating the actuator 4X, which is located on the opposing wall 30 facing the inner surface 35X of the nozzle plate 3X.

[0027] However, in the liquid discharge head 10X, the acoustic waves 71 do not reach the liquid in the stagnant region 70 at the corners of the pressure chamber 2X, and therefore cannot move the liquid in the stagnant region 70. Consequently, the liquid discharge head 10X cannot move the bubbles 7 present in the stagnant region 70 to a position where they can be discharged by pressurization or suction, and therefore cannot discharge them. As a result of the bubbles 7 remaining without being discharged from the pressure chamber 2X, the liquid discharge head 10X may experience non-discharge or poor discharge.

[0028] In this embodiment, for example, in order to reduce the stagnant area 70 and discharge the bubbles 7 within the stagnant area 70, a drive voltage is applied to the actuator 4 located on the nozzle plate 3, thereby generating a controlled flow in the liquid within the pressure chamber 2. Here, Figure 5 is a schematic cross-sectional view showing a first example of the controlled liquid flow in the liquid discharge head 10. Figure 6 is a schematic cross-sectional view showing how bubbles stagnant in the pressure chamber 2 are moved to a dischargeable position by the controlled liquid flow in the liquid discharge head 10. The flow 6 represented by the arrow in Figure 5 represents a first example of the controlled liquid flow in the liquid discharge head 10. The direction in which the arrow representing the flow 6 points indicates the direction in which the liquid flows in the flow 6.

[0029] In the example shown in Figure 5, the liquid discharge head 10 generates a controlled flow 6. In the example shown in Figure 5, the controlled flow 6 includes a liquid flow 6a along the inner surface 35 of the nozzle plate 3. In another view, the controlled flow 6 includes a liquid flow 6a in the direction away from the nozzle 1. In yet another view, the controlled flow 6 includes a liquid flow 6a generated at a position closer to the inner surface 35 than the opposing surface 350 that faces the inner surface 35 in the pressure chamber 2. The opposing surface 350 is the surface of the opposing wall 30, which is positioned opposite the nozzle plate 3, that faces the inner surface 35.

[0030] The liquid flow 6a along the inner surface 35 of the nozzle plate 3, the liquid flow 6a away from the nozzle 1, or the liquid flow 6a at a position closer to the inner surface 35 than to the opposing surface 350 may be at least a part of the flow 6 generated by the application of a drive voltage to the actuator 4. Furthermore, "along the inner surface 35" means that the direction of the liquid flow 6 has an inclination of ±20 degrees or less with respect to the inner surface 35.

[0031] In the example shown in Figure 5, the liquid in the pressure chamber 2 flows along the inner surface 35 away from the nozzle 1 at a position closer to the inner surface 35 than to the opposing surface 350. Subsequently, the liquid in the pressure chamber 2 strikes the inner surface 51 of the partition wall 5 and flows along the inner surface 51 on the opposite side from where the nozzle 1 is located, i.e., the -Z side.

[0032] The flow 6 along the inner surface 35 away from the nozzle 1 also acts on the liquid in stagnant areas 70, such as the corners of the pressure chamber 2. From another perspective, the flow 6 contributes to the movement of the liquid in the stagnant areas 70. The liquid discharge head 10 causes the liquid in the stagnant areas 70 to flow through the controlled flow 6. As a result, as shown in Figure 6, the liquid discharge head 10 can move bubbles 7 present in the liquid of the stagnant areas 70, which are in positions where they cannot be discharged by pressurization or suction, to positions where they can be discharged by pressurization or suction. In Figure 6, the dashed lines represent bubbles 7 before they are moved. The solid lines represent bubbles 7a after they have been moved. "Positions where they can be discharged by pressurization or suction" means positions where the purge flow 60 contributes to the movement of bubbles 7, and where the liquid can be discharged by pressurization or suction.

[0033] The liquid discharge head 10 moves the bubbles 7 to a position where they can be discharged by pressurization or suction, thereby allowing the bubbles 7 to be discharged from the pressure chamber 2 through the nozzle 1 by pressurization or suction. The pressurization or suction pressure is preferably 50 kPa or less, with a maximum of about 100 kPa, from the viewpoint of creating many pass lines within the pressure chamber 2.

[0034] By discharging the bubbles 7 from the pressure chamber 2, non-discharge or poor discharge due to bubbles 7 is reduced. As a result, in this embodiment, the stability of liquid discharge by the liquid discharge head 10 can be improved. Note that the liquid discharge head 10 is not limited to the nozzle 1, and bubbles 7 can also be discharged from the inlet of the pressure chamber 2 located on the opposite side of the pressure chamber 2 from the nozzle 1.

[0035] In this embodiment, the flow 6 can move, for example, the bubbles 7 to the vicinity of the nozzle 1 or the inlet of the pressure chamber 2. This allows only the liquid near the nozzle 1 or the inlet of the pressure chamber 2 to be discharged by pressurization or suction, thereby discharging the bubbles 7 from the pressure chamber 2. As a result, in this embodiment, the amount of liquid discharged by pressurization or suction can be reduced, thereby reducing liquid consumption.

[0036] The effects of this embodiment are not limited to improving liquid discharge stability by expelling bubbles 7. For example, among the liquid in the pressure chamber 2, the liquid located near the nozzle 1 is exposed to the outside air and is therefore prone to drying and thickening. This thickening of the liquid can cause non-discharge or poor discharge. In this embodiment, the liquid in the pressure chamber 2 can be made to flow by generating a liquid flow 6. As a result, the liquid located near the nozzle 1 is continuously replaced, thereby reducing the thickening of the liquid in the pressure chamber 2. Consequently, non-discharge or poor discharge due to thickening of the liquid in the pressure chamber 2 can be reduced.

[0037] In this embodiment, from the viewpoint of reducing liquid stagnation in the pressure chamber 2 and suitably discharging bubbles 7, it is preferable that the controlled liquid flow 6 is a liquid flow along the inner surface 35 of the nozzle plate 3. Furthermore, from the viewpoint of the above, it is even more preferable that the controlled liquid flow 6 is a liquid flow along the inner surface 35 of the nozzle plate 3 away from the nozzle 1. Furthermore, from the viewpoint of the above, it is even more preferable that the controlled liquid flow 6 is a liquid flow along the inner surface 35 of the nozzle plate 3 away from the nozzle 1 at a position closer to the inner surface 35 of the nozzle plate 3 than to the opposing surface 350.

[0038] In this embodiment, the liquid discharge head 10 is capable of discharging a portion of the liquid in the pressure chamber 2 from the pressure chamber 2 by pressurization or suction. The liquid discharge head 10 generates a liquid flow 6, thereby moving bubbles 7 that are located in positions within the pressure chamber 2 that cannot be discharged by pressurization or suction to positions where they can be discharged by pressurization or suction. This allows bubbles 7 that are located in positions that cannot be discharged by pressurization or suction to be discharged from the pressure chamber 2 by pressurization or suction.

[0039] <Method for controlling liquid flow 6> Next, the method for controlling the liquid flow 6 in the liquid discharge head 10 will be described with reference to Figures 7 and 8. Figure 7 is a diagram showing the drive voltage W1 when liquid is discharged from the liquid discharge head 10. Figure 8 is a diagram showing the drive voltage W2 when the liquid discharge head 10 is driven slightly.

[0040] The liquid discharge head 10 generates a controlled flow 6 in the liquid within the pressure chamber 2 based on the drive voltage applied to the actuator 4. The greater the flow rate of the liquid within the pressure chamber 2, the greater the movement of liquid and bubbles within the pressure chamber 2, making it easier to discharge bubbles. On the other hand, if the applied drive voltage is too high, air may be drawn into the pressure chamber 2 from outside through the nozzle 1, and this drawn-in air may become bubbles, increasing the number of bubbles within the pressure chamber 2. Therefore, from the viewpoint of discharging bubbles and reducing bubbles, it is necessary to optimize the drive voltage applied to the actuator 4.

[0041] In this embodiment, the liquid flow 6 is controlled by at least one of the waveform, voltage value, and frequency of the drive voltage applied to the actuator 4. The drive voltage W1 during liquid discharge shown in Figure 7 will be explained as an example.

[0042] In the example shown in Figure 7, the drive voltage W1 includes a pulse waveform. The waveform of the drive voltage W1 is determined by the parameters of the pulse width ΔP1, the angle of the rising edge RS1, and the angle of the falling edge FL1 in the pulse waveform. Up to a predetermined pulse width, the longer the pulse width ΔP1, the greater the displacement of the nozzle plate 3 in response to the application of the drive voltage W1. After the displacement reaches its peak at the predetermined pulse width, the displacement of the nozzle plate 3 decreases as the pulse width ΔP1 increases.

[0043] The steeper the angle of the rising waveform RS1, the greater the displacement of the nozzle plate 3 in response to the application of the drive voltage W1. However, depending on the structure of the liquid discharge head 10, the steeper the angle of the rising waveform RS1, the smaller the displacement of the nozzle plate 3 in response to the application of the drive voltage W1 may be. Also, up to a predetermined rising angle, the steeper the angle of the rising waveform RS1, the greater the displacement of the nozzle plate 3, and beyond the predetermined rising angle, the steeper the angle, the smaller the displacement of the nozzle plate 3 may be. The relationship between the angle and the displacement of the nozzle plate 3 in the falling waveform FL1 is the same as the relationship between the angle and the displacement of the nozzle plate 3 in the rising waveform RS1.

[0044] The voltage value V1 of the drive voltage W1 has a simple proportional relationship with the displacement of the nozzle plate 3 in response to the application of the drive voltage W1. The higher the voltage value V1, the greater the displacement of the nozzle plate 3 in response to the application of the drive voltage W1. However, the voltage value V1 must be less than or equal to the breakdown voltage of the piezoelectric film 42 in the actuator 4.

[0045] Furthermore, depending on the timing of controlling the liquid flow 6, there are cases where liquid should not be discharged from the nozzle 1. In this case, a drive voltage W2 for fine driving, as shown in Figure 8, is applied to the liquid discharge head 10. The drive voltage W2, like the drive voltage W1, includes a pulse waveform. The waveform of the drive voltage W2 is determined using the pulse width ΔP2, the angle of the rising waveform RS2, and the angle of the falling waveform FL2 as parameters. The voltage value V2 of the drive voltage W2 is smaller than the voltage value V1 of the drive voltage W1. Because the voltage value V2 is small, the displacement of the nozzle plate 3 in response to the application of the drive voltage W2 is small, and the pressure applied to the liquid in the pressure chamber 2 is small, so that liquid is not discharged from the pressure chamber 2.

[0046] From another perspective, the liquid discharge head 10 can generate a liquid flow 6 when a drive voltage W2 is applied to the actuator 4 such that the drive voltage W2 is smaller than the drive voltage V1 that discharges liquid from the nozzle 1, and the drive voltage W2 that does not discharge liquid from the nozzle 1 is applied.

[0047] For example, the voltage value V2 at the drive voltage W2 is 70% or 50% of the voltage value V1 at the drive voltage W1. From the viewpoint of reducing power consumption, it is preferable that the voltage value V2 be 25% or more and 30% or less of the voltage value V1. When the drive voltage W2 is applied to the liquid discharge head 10, no liquid is discharged from the nozzle 1, and the liquid in the pressure chamber 2 vibrates.

[0048] Next, we will explain the frequency to which the drive voltage W1 is applied. There are two design philosophies for the frequency to which the drive voltage W1 is applied. The first design philosophy utilizes the superposition of waves in the flow 6 generated by the displacement of the nozzle plate 3. The higher the frequency of the drive voltage W1, and the more the waves that are repeatedly generated in response to the application of the drive voltage W1 overlap with each other, the greater the flow rate of the flow 6. Therefore, it is preferable to determine the maximum frequency in which the unit waveforms do not overlap, taking into account the waveform length of the unit waveform at the drive voltage W1. The second design philosophy is to generate the flow 6 by causing the pressure chamber 2 to resonate by setting the frequency of the applied drive voltage W1 to the resonant frequency of the pressure chamber 2. For example, if the resonant frequency of the pressure chamber 2 filled with liquid is 100 kHz, the frequency of the applied drive voltage W1 is set to 100 kHz, or the frequency at which the resonant vibration amplitude is maximized. This causes the entire liquid in the pressure chamber 2 to resonate, generating a flow 6 with a larger flow rate.

[0049] In both of the above design philosophies regarding the frequency to which the drive voltage W1 is applied, the waveform that maximizes the displacement of the nozzle plate 3 is defined as the unit waveform, and this unit waveform is applied repeatedly and continuously. For example, if the frequency is 2 kHz, the unit waveform of the drive voltage W1 is applied to the actuator 4 once every 500 μs. At least one of the two design philosophies is used depending on the shape and size of the pressure chamber 2.

[0050] In this embodiment, the liquid flow 6 is controlled by at least one of the waveform, voltage value, and frequency of the drive voltage W1 or drive voltage W2 applied to the actuator 4. This allows the drive voltage W1 or drive voltage W2 to be optimized according to the shape and size of the pressure chamber 2. In this embodiment, by optimizing the drive voltage W1 or drive voltage W2, bubbles can be effectively discharged and reduced.

[0051] In this embodiment, it is preferable that the nozzle plate 3 vibrates when a drive voltage is applied to the actuator 4. The vibration of the nozzle plate 3 makes it easier to generate a flow 6 with a desired flow rate, velocity, or flow direction.

[0052] In this embodiment, the actuator 4 is preferably a piezoelectric element. This simplifies the configuration of the liquid discharge head 10 while generating a controlled liquid flow 6. However, the actuator 4 is not limited to a piezoelectric element and may be an electrostatic actuator or a thermal actuator, etc.

[0053] In this embodiment, the liquid discharge head 10 can generate a liquid flow 6 by applying a drive voltage W2 to the actuator 4 such that the drive voltage W2 is smaller than the drive voltage V1 that discharges liquid from the nozzle 1, thereby preventing liquid from being discharged from the nozzle 1. For example, when the liquid discharge head 10 discharges liquid to form an image on a recording medium such as paper, if the liquid in the pressure chamber 2 is discharged to remove air bubbles during the image formation period, liquid other than the liquid forming the image may be applied to the recording medium, potentially contaminating it. The liquid discharge head 10 generates a liquid flow 6 by micro-driving, thereby generating a liquid flow 6 without actually discharging liquid. This allows the liquid discharge head 10 to move and remove air bubbles by the flow 6 during periods when the liquid discharge head 10 should not be discharging liquid.

[0054] <Evaluation method for Flow 6> The controlled liquid flow 6 in this embodiment can be evaluated by experiment or simulation. The method for evaluating the controlled flow 6 will be described with reference to Figures 9 and 10. Figure 9 is a schematic cross-sectional view showing an experimental method for evaluating the flow in a pressure chamber. Figure 10 is a diagram showing a first example of the simulation results for evaluating the flow in a pressure chamber.

[0055] In Figure 9, the opposing wall 30 is a component of the pressure chamber 2 and is positioned opposite the nozzle plate 3. The opposing wall 30 is made of a glass or resin material that is transparent to visible light. The optical microscope 200 is a microscope capable of capturing still images or videos that visualize the conditions inside the pressure chamber 2 through the opposing wall 30.

[0056] In the evaluation experiment of flow 6, a liquid containing particles of a size observable by the optical microscope 200 is filled into the pressure chamber 2. By capturing still images or videos of the particles inside the pressure chamber 2 with the optical microscope 200, the behavior of the particles inside the pressure chamber 2 can be visualized. Based on the visualized behavior of the particles, the flow velocity or flow direction of the liquid flow 6 is evaluated. If the opposing wall 30 is made up of silicon or the like, which does not transmit visible light, an infrared microscope may be used instead of the optical microscope 200.

[0057] The example shown in Figure 9 illustrates a configuration for capturing still or moving images of particles inside the pressure chamber 2 through the opposing wall 30. However, the configuration is not limited to this, and still or moving images of particles inside the pressure chamber 2 may be captured using an optical microscope 200 or an infrared microscope through the wall members on the +Y or -Y side that constitute the pressure chamber 2, in a direction perpendicular to the direction of liquid discharge.

[0058] A liquid containing fluorescently labeled microparticles may be filled into the pressure chamber 2, and still images or videos of the fluorescently labeled microparticles in the pressure chamber 2 may be captured using an optical microscope 200 or an infrared microscope. Based on the behavior of the visualized fluorescently labeled microparticles, the flow velocity or flow direction of the liquid flow 6 can be evaluated. In addition, if bubbles are generated in the pressure chamber 2, still images or videos of the bubbles in the pressure chamber 2 may be captured using an optical microscope 200 or an infrared microscope. Based on the behavior of the visualized bubbles, the flow velocity or flow direction of the liquid flow 6 can be evaluated.

[0059] On the other hand, in the simulation results for the first example shown in Figure 10, the flow of liquid in the pressure chamber 2 is displayed as a velocity vector when the waveform shown in Figure 7 is applied to actuator 4 at 200 kHz. The lengths of the multiple lines displayed in the pressure chamber 2 represent the liquid flow velocity, and the directions of the multiple lines represent the direction of liquid flow. In the first example shown in Figure 10, the liquid flow from nozzle 1 towards the wall surface of pressure chamber 2, for example, along the XZ plane, is visualized. In the region 15 around nozzle 1, which is closer to the inner surface 35 than the opposing surface 350, the liquid flow along the inner surface 35 of nozzle plate 3 away from nozzle 1 is visualized. This liquid flow moves the liquid and bubbles in the pressure chamber 2, and the bubbles can be discharged from nozzle 1 or the inlet of pressure chamber 2 located on the opposite side of nozzle 1.

[0060] As described above, the controlled liquid flow 6 in this embodiment can be evaluated by experiment or simulation. For example, it is possible to evaluate which region within the pressure chamber 2 of the liquid discharge head 10 the liquid is flowing in which direction and at what velocity.

[0061] <Modified form of the first embodiment> Next, a modified example of the liquid discharge head according to the first embodiment will be described. Note that names and reference numerals identical to those used in the previously described embodiments indicate the same or identical components or configurations, and detailed explanations will be omitted as appropriate. This also applies to the embodiments described later.

[0062] Figure 11 is a schematic cross-sectional view showing the controlled liquid flow 6a in a liquid discharge head 10a according to a modified example of the first embodiment.

[0063] The modified liquid discharge head 10a differs from the liquid discharge head 10 according to the first embodiment in that it generates a liquid flow 6 in which the liquid flow in the direction away from the nozzle 1 and the liquid flow in the direction towards the nozzle 1 switch.

[0064] In the example shown in Figure 11, flow 6a periodically switches between a liquid flow away from nozzle 1 and a liquid flow towards nozzle 1. From another perspective, in the liquid discharge head 10a, the liquid in pressure chamber 2 oscillates at a predetermined frequency. The frequency at which the liquid in pressure chamber 2 oscillates corresponds to the frequency of the drive voltage applied to actuator 4. For example, the frequency at which the liquid in pressure chamber 2 oscillates and the frequency of the drive voltage applied to actuator 4 are approximately the same.

[0065] For example, bubbles in the pressure chamber 2 may adhere to the wall of the pressure chamber 2 or the inner surface 35 of the nozzle plate 3, and become immobile. The liquid discharge head 10a generates a liquid flow 6 that switches between a liquid flow away from the nozzle 1 and a liquid flow towards the nozzle 1. Compared to a case where the liquid flows in only one direction, this increases the force that detaches bubbles adhering to the wall of the pressure chamber 2 or the inner surface 35 of the nozzle plate 3. As a result, bubbles adhering to the wall of the pressure chamber 2 or the inner surface 35 of the nozzle plate 3 become easier to detach from these surfaces. Consequently, the detached bubbles are more easily discharged from the pressure chamber 2.

[0066] Figure 12A shows a second example of the simulation results for evaluating the flow within pressure chamber 2. The calculation conditions for the simulation results shown in Figure 12A are the same as those for the simulation results shown in Figure 10. Furthermore, the simulation results shown in Figure 12A show a snapshot of the liquid flow state within pressure chamber 2 at a different time than the time shown in the simulation results in Figure 10. The interpretation of Figure 12A is the same as that of Figure 10 described above.

[0067] In the example shown in Figure 12A, the flow from pressure chamber 2 toward nozzle 1 is visualized. In other words, the simulation confirms that the liquid flow, which was flowing from nozzle 1 toward pressure chamber 2 in Figure 10, is now flowing from pressure chamber 2 toward nozzle 1 in Figure 12A. From another perspective, the simulation confirms that the liquid is oscillating within pressure chamber 2.

[0068] The liquid flow from nozzle 1 into pressure chamber 2 corresponds to a liquid flow away from nozzle 1. The liquid flow from pressure chamber 2 towards nozzle 1 corresponds to a liquid flow towards nozzle 1. Thus, the liquid discharge head 10 according to this embodiment can generate a liquid flow that switches between a liquid flow away from nozzle 1 and a liquid flow towards nozzle 1. From another viewpoint, the liquid discharge head 10 according to this embodiment can vibrate the liquid within pressure chamber 2.

[0069] The vibration of the liquid makes it easier for bubbles adhering to the wall of the pressure chamber 2 or the inner surface 35 of the nozzle plate 3 to detach. As a result, the detached bubbles are more easily discharged from the pressure chamber 2. In addition, bubbles are more easily discharged from both the nozzle 1 and the inlet of the pressure chamber 2.

[0070] In the liquid discharge head 10 according to this embodiment, the direction of flow within the pressure chamber 2 is switched regardless of the frequency of the drive voltage applied to the liquid discharge head 10. The phenomenon of the direction of flow within the pressure chamber 2 being switched is caused by the repeated expansion and contraction of the pressure chamber 2 due to the vibration of the nozzle plate 3. Now, with reference to Figure 12B, the phenomenon of the direction of flow within the pressure chamber 2 being switched will be explained. Figure 12B is a diagram showing the expansion and contraction of the pressure chamber 2 due to the vibration of the nozzle plate 3.

[0071] In Figure 12B, the drive voltage W3 is the drive voltage applied to the liquid discharge head 10. The first pressure chamber state 2A and the second pressure chamber state 2B are cross-sectional views of the pressure chamber 2 near the nozzle 1 in the liquid discharge head 10, showing the state of the pressure chamber 2. The first pressure chamber state 2A shows the state in which the nozzle plate 3 vibrates and the pressure chamber 2 expands when the falling waveform FL3 of the drive voltage W3 is applied. The second pressure chamber state 2B shows the state in which the nozzle plate 3 vibrates and the pressure chamber 2 contracts when the rising waveform RS3 of the drive voltage W3 is applied.

[0072] Flow 6a1 is the flow of liquid Q away from nozzle 1 that occurs in the first pressure chamber state 2A. Flow 6a2 is the flow of liquid Q towards nozzle 1 that occurs in the second pressure chamber state 2B. For example, when a drive voltage W3 is applied to the liquid discharge head 10 at a predetermined frequency, the nozzle plate 3 vibrates, and the state of the pressure chamber 2 periodically switches between the first pressure chamber state 2A and the second pressure chamber state 2B with a period corresponding to the frequency.

[0073] As shown in Figure 12B, in the liquid discharge head 10, the pressure chamber 2 periodically expands and contracts due to the vibration of the nozzle plate 3. This allows the flow of liquid Q within the pressure chamber 2 to periodically switch between a flow 6a1 away from the nozzle 1 and a flow 6a2 towards the nozzle 1. In this modified example, the switching between the liquid flow away from the nozzle 1 and the liquid flow towards the nozzle 1 does not necessarily have to be periodic; it may be aperiodic.

[0074] [Second Embodiment] Figure 13 is a schematic cross-sectional view showing the liquid discharge head 10b according to the second embodiment. Figure 13 shows a cross-section of the liquid discharge head 10b corresponding to the line II-II in Figure 1.

[0075] The liquid discharge head 10b differs from the liquid discharge head 10 according to the first embodiment in that a fluid resistance portion 8 is formed on the opposing wall 30 that faces the nozzle plate 3 of the pressure chamber 2.

[0076] For example, in the liquid discharge head 10b, since the pressure chambers 2 are closely spaced together, the pressure generated by the actuator 4 during liquid discharge may propagate to adjacent pressure chambers 2, potentially affecting the liquid discharge characteristics from the nozzle 1 corresponding to the adjacent pressure chamber 2.

[0077] The fluid resistance section 8 has the function of reducing the influence on the liquid discharge characteristics from the nozzle 1 corresponding to the adjacent pressure chambers 2. For example, in a typical unimorph piezoelectric liquid discharge head, such as a liquid discharge head that discharges liquid by vibrating a surface facing the nozzle communication wall having a communication port that communicates with the nozzle in the pressure chamber, the actuator is located on the opposing wall of the nozzle plate. Therefore, it is difficult to add a fluid resistance section 8 or the like to the opposing wall. In this embodiment, since the actuator 4 is located on the nozzle plate 3, a fluid resistance section 8 or the like can be easily added to the opposing wall 30 that faces the nozzle plate 3.

[0078] [Third Embodiment] Figure 14 is a schematic cross-sectional view showing the liquid discharge head 10c according to the third embodiment. Figure 14 shows a cross-section of the liquid discharge head 10c corresponding to line II-II in Figure 1. However, compared to the cross-section of the liquid discharge head 10c along line II-II in Figure 1, the number of nozzles 1 and the number of pressure chambers 2 corresponding to nozzles 1 are doubled in Figure 14.

[0079] Figure 15 is a schematic cross-sectional view showing bubbles 7 remaining in the pressure chamber 2 of the liquid discharge head 10c. Figure 16 is a schematic cross-sectional view showing how bubbles remaining in the pressure chamber 2 of the liquid discharge head 10c are moved to a position where they can be discharged by a controlled flow of liquid.

[0080] The liquid discharge head 10c has a plurality of pressure chambers 2, a plurality of supply passages 81 through which liquid is supplied to the plurality of pressure chambers 2, and a plurality of discharge passages 82 through which liquid is discharged from the plurality of pressure chambers 2. The liquid discharge head 10c can circulate a portion of the liquid in the pressure chambers 2. These points differentiate it from the liquid discharge head 10 according to the first embodiment. The liquid discharge head 10c is a liquid circulation type liquid discharge head. A liquid circulation type liquid discharge head may also be called a flow-through head.

[0081] In the example shown in Figure 14, multiple supply passages 81 and multiple discharge passages 82 are formed in the opposing wall 30 facing the nozzle plate 3 and are paths through which liquid can flow. The supply passages 81 and discharge passages 82 are arranged alternately. The supply passages 81 and discharge passages 82 are separated by a flow path partition wall 83. Liquid supplied to the pressure chamber 2 through the supply passages 81 is discharged from the pressure chamber 2 through the discharge passages 82. By repeatedly supplying and discharging a portion of the liquid within the pressure chamber 2, a portion of the liquid in the pressure chamber 2 circulates.

[0082] The liquid discharge head 10c circulates the liquid in the pressure chamber 2, thereby removing air bubbles from the pressure chamber 2 and reducing the drying of the liquid in the pressure chamber 2 without discharging liquid from the nozzle 1. Since the liquid discharge head 10c does not discharge liquid to remove air bubbles, the air bubble removal process can be performed not only before and after the image formation job, but also during the image formation job.

[0083] As shown in Figure 15, even in a liquid circulation type liquid discharge head 10c, a stagnation region 70 may occur within the pressure chamber 2 where the liquid remains. Bubbles 7 present in the stagnation region 70 do not move due to the circulation of the liquid and are not discharged from the pressure chamber 2.

[0084] For example, a liquid discharge head configuration is known in which the length of the partition wall between the supply and discharge paths is increased in the direction in which the nozzle plate extends, for example, in the XY direction, in order to reduce the stagnant area. This configuration allows even the liquid located near the nozzle plate to be circulated, thereby reducing the stagnant area. However, such liquid discharge heads are difficult to manufacture, which can lead to a decrease in the yield of liquid discharge heads or an increase in the cost of liquid discharge heads.

[0085] In this embodiment, a liquid flow 6c is generated to reduce the stagnant area and discharge bubbles within the stagnant area, thereby moving bubbles 7 located in positions within the pressure chamber 2 that are not discharged by the circulation of the liquid to positions where they can be discharged by the circulation of the liquid.

[0086] The example shown in Figure 16 illustrates a case where bubble removal is always performed during the period when the liquid discharge head 10c is performing an image formation job. Performing bubble removal during the period when an image formation job is being performed may contaminate the recording medium with the liquid discharged for bubble removal. Therefore, it is preferable to perform bubble removal by micro-driving without discharging liquid. The voltage value of the drive voltage for micro-driving is set to 75% of the voltage value of the drive voltage for discharging liquid. Furthermore, in order to reduce power consumption, etc., it is preferable to set the voltage value of the drive voltage applied to the actuator 4 corresponding to the nozzle 1 that performs bubble removal to 50% or 25% or less of the voltage value of the drive voltage for discharging liquid.

[0087] In the example shown in Figure 16, the liquid discharge head 10c moves the bubbles to the area where the circulating flow 60c is generated without discharging liquid from the nozzle 1. In Figure 16, the dashed line shows the bubbles 7 before they are moved. The solid line shows the bubbles 7b after they have been moved. The bubbles 7b that have moved to the area where the circulating flow 60c is generated are discharged to the outside of the pressure chamber 2 through the discharge passage 82 by the circulating flow 60c.

[0088] Furthermore, for example, if bubble removal processing is performed during the period when the liquid discharge head 10c is performing an image formation job, nozzles other than the nozzle targeted for bubble removal processing are discharging for image formation. Therefore, it is necessary to identify the nozzle targeted for bubble removal processing. The following are some possible methods for identifying the nozzle targeted for bubble removal processing.

[0089] First, the liquid dispensing device having a liquid dispensing head 10c has a detection unit that detects pixel defects in the image formed on the recording medium. The liquid dispensing device detects pixel defects caused by bubble entrapment, etc., using the detection unit and identifies the nozzle that causes the pixel defects. The detection unit transmits information about the identified nozzle to the control unit of the liquid dispensing device. The control unit applies a drive voltage lower than the drive voltage value for liquid dispensing to the identified nozzle and performs bubble discharge processing by micro-driving. Furthermore, for pixels that were intended to be formed by the nozzle causing the pixel defects, the image processing assigns them to other nozzles. After a predetermined time has elapsed and the bubbles have been discharged, the nozzle after the bubble discharge processing is made available for image formation, and its use for image formation is resumed. At this time, the time required for the bubble discharge processing varies depending on the differential pressure of the liquid circulation in the pressure chamber 2 and the drive voltage applied to the actuator 4.

[0090] Regarding the liquid circulation effect, some pressure chamber designs may result in a greater circulation effect as the pressure difference between the supply passage 81 and the discharge passage 82 increases, while others may have the opposite effect. It is also possible that the circulation effect is high until a certain pressure difference is reached, and then decreases beyond that point. In any case, a pressure difference of around 50 kPa or less is preferable. To suppress variations in liquid discharge velocity due to liquid circulation, a pressure of 30 kPa or less is preferable, and for even more precise suppression, a pressure of 10 kPa to 20 kPa is preferable.

[0091] Furthermore, the above example shows a system where a voltage is applied only to nozzles that cause pixel defects for micro-driving. However, from the viewpoint of reducing the load on the control unit, it is preferable to always apply a drive voltage for micro-driving to nozzles that are not assigned pixels.

[0092] Unlike the above, when performing bubble removal processing before or after the image formation job, that is, when liquid may be discharged from the nozzle, the drive voltage may be set to the same value as the voltage used to discharge the liquid, or it may be set to the same value as the drive voltage for micro-driving, similar to the bubble removal processing during the image formation job.

[0093] The bubble discharge process may be performed only on nozzles in which bubbles are trapped within the pressure chamber 2, as identified by the detection unit. Alternatively, the drive voltage may be applied to all pressure chambers 2 without identifying the pressure chamber 2 in which bubbles are trapped, and the bubble discharge process may be performed on all pressure chambers 2.

[0094] For example, in a liquid circulation type liquid discharge head, if the height of the pressure chamber in the liquid discharge head is reduced in order to expel air bubbles through liquid circulation, the manufacturing difficulty of the liquid discharge head may increase, and the yield of the liquid discharge head may decrease. As the yield decreases, the cost of the liquid discharge head may increase. Note that the height of the pressure chamber corresponds to the length of the pressure chamber in the Z direction.

[0095] In this embodiment, since the bubbles 7 can be moved by the controlled flow 6c, even if the height of the pressure chamber of the liquid discharge head 10c of the liquid circulation type is high, the bubbles can be moved into the liquid circulation path and discharged by the circulation of the liquid. This makes it possible to increase the height of the pressure chamber 2 of the liquid discharge head 10c of the liquid circulation type. For example, the height of the pressure chamber can be increased to about 1000 μm. As a result, the difficulty of manufacturing the liquid discharge head 10c is reduced, the yield of the liquid discharge head 10c is improved, and the cost of the liquid discharge head 10c is reduced.

[0096] [Fourth Embodiment] The liquid discharge head according to the fourth embodiment will be described with reference to Figures 17 and 18. Figure 17 is a schematic cross-sectional view showing a first example of liquid agitation in the liquid discharge head 10d according to the fourth embodiment. Figure 18 is a schematic cross-sectional view showing a second example of liquid agitation in the liquid discharge head 10d. In Figures 17 and 18, arrows representing the flow of liquids indicate parts of the first liquid A and the second liquid B.

[0097] The liquid discharge head 10d differs from the liquid discharge head 10c according to the third embodiment in that it agitates the liquid in the pressure chamber 2 by generating a liquid flow. The liquid discharge head 10d is a liquid discharge head that uses a liquid circulation method, similar to the liquid discharge head 10c according to the third embodiment.

[0098] In the first example shown in Figure 17, the pressure chamber 2 is connected to two supply paths, a first supply path 84 and a second supply path 85. The first liquid A is supplied into the pressure chamber 2 through the first supply path 84, and the second liquid B is supplied into the pressure chamber 2 through the second supply path 85. The first liquid A and the second liquid B are, for example, different types of liquids. After the first liquid A and the second liquid B are supplied into the pressure chamber 2, a drive voltage is applied to the actuator 4. When the actuator 4 is driven, the first liquid A and the second liquid B are stirred and mixed almost uniformly. After that, the liquid discharge head 10d discharges the liquid from the nozzle 1.

[0099] In the second example shown in Figure 18, two different liquids, a first liquid A and a second liquid B, are supplied to the pressure chamber 2 through the supply passage 81. The first liquid A and the second liquid B supplied to the pressure chamber 2 are agitated and mixed by a controlled liquid flow 6e.

[0100] The liquid dispensing head 10d is suitable for cases where it is desired to mix and dispense two different liquids, a first liquid A and a second liquid B. For example, the liquid dispensing head 10d is suitable for dispensing adhesives and the like, which are cured by mixing two types of liquids and causing a chemical reaction. However, the first liquid A and the second liquid B are not limited to those that make up an adhesive; they can be anything that exhibits an effect when stirred. Furthermore, by increasing the number of supply channels, three or more types of liquids may be stirred and mixed.

[0101] [Fifth Embodiment] Next, a liquid dispensing device according to the fifth embodiment will be described. The liquid dispensing device according to this embodiment is a device having at least one of the liquid dispensing heads 10 to 10d according to the first embodiment. Hereinafter, the liquid dispensing device according to this embodiment will be described assuming that it has the liquid dispensing head 10 according to the first embodiment.

[0102] Figure 19 is a block diagram showing the hardware configuration of the control unit 600 of the liquid dispensing device 540 according to the fifth embodiment.

[0103] The liquid dispensing device 540 includes a liquid dispensing head 10 and a head drive unit 20 that drives the liquid dispensing head 10. The head drive unit 20 generates a controlled flow in the liquid in the pressure chamber by applying a drive voltage to the actuator of the liquid dispensing head 10. In the example shown in Figure 19, the liquid dispensing device 540 is configured by interconnecting the head unit 550, a control unit 600, a transport drive unit 710, an operation display unit 720, and an input / output interface 730 via a bus line 740. The head unit 550 includes the liquid dispensing head 10. An example of the liquid dispensing device 540 and the head unit 550 will be described later with reference to Figures 20 and 21.

[0104] The head drive unit 20 generates a drive waveform that deforms each piezoelectric element, which is an electromechanical conversion element acting as an actuator in each nozzle row, in response to a control signal input from the control unit 600. When this drive waveform is input to each piezoelectric element of the liquid discharge head 10 in each nozzle row, the liquid in the pressure chamber 2 communicating with the nozzle 1 is pressurized and discharge energy is applied, causing the liquid to be discharged from the corresponding nozzle 1.

[0105] The control unit 600 includes a CPU (Central Processing Unit) 610, a storage unit 620, a RAM (Random Access Memory) 630, and a ROM (Read Only Memory) 640. The CPU 610 reads various control programs and setting data stored in the ROM 640, stores them in the RAM 630, executes them, and performs various calculations. The CPU 610 also controls the overall operation of the liquid dispensing device 540. The storage unit 620 stores image forming jobs and the like that input via the input / output interface 730. The transport drive unit 710 supplies drive signals to the transport motor based on control signals supplied from the control unit 600, and transports the recording medium at a predetermined speed and timing.

[0106] The operation display unit 720 includes a display device such as a liquid crystal display or an organic EL display, and an input device such as an operation key and a touch panel superimposed on the screen of the display device. The operation display unit 720 displays various information on the display device and supplies operation signals to the control unit 600 corresponding to user input operations on the input device. The input / output interface 730 mediates the transmission and reception of data between the external device 800 and the control unit 600. The bus line 740 is a path for transmitting and receiving signals between the control unit 600 and other components.

[0107] (First example of liquid dispensing device 540) Next, a first example of the liquid dispensing device 540 will be described with reference to Figures 20 and 21. Figure 20 is a schematic side view showing a first example of the overall configuration of the liquid dispensing device 540. For the sake of explanation, Figure 20 shows the inside of the liquid dispensing device 540 as a transparent view. Figure 21 is a schematic bottom view showing the head unit 550 in the liquid dispensing device 540.

[0108] The liquid dispensing device 540 according to the first example includes a loading means 501 for loading a continuous body 510, a guiding and transporting means 503 for guiding and transporting the continuous body 510, such as continuous paper or sheet material, loaded from the loading means 501 to a printing means 505, a printing means 505 for performing printing to form an image by dispensing liquid onto the continuous body 510, a drying means 507 for drying the continuous body 510, and an unloading means 509 for unloading the continuous body 510.

[0109] The continuous body 510 is fed out from the winding roller 511 of the loading means 501, guided and transported by the rollers of the loading means 501, the guiding and transporting means 503, the drying means 507, and the unloading means 509, and then wound up by the winding roller 591 of the unloading means 509.

[0110] In the printing means 505, the continuum 510 is transported on the transport guide member 559, facing the head unit 550 and the head unit 555. An image is formed by the liquid discharged from the head unit 550, and post-processing is performed with the processing liquid discharged from the head unit 555.

[0111] Here, the head unit 550 has, for example, four full-line head arrays 551A, 551B, 551C, and 551D (hereinafter referred to as "head array 551" when color is not distinguished) arranged from the upstream side in the transport direction.

[0112] Each head array 551 is a liquid dispensing means, and each dispenses black K, cyan C, magenta M, and yellow Y liquids to the conveyed continuum 510. However, the types and number of colors are not limited to these.

[0113] The head array 551 is, for example, an arrangement of liquid discharge heads 10 arranged in a staggered pattern on a base member 552, but is not limited to this.

[0114] (Second example of liquid dispensing device 540) Next, a second example of the liquid dispensing device 540 will be described with reference to Figures 22 and 23. Figure 22 is a schematic top view showing the overall configuration of the second example of the liquid dispensing device 540. Figure 23 is a schematic side view showing the configuration around the liquid dispensing unit 440 in the liquid dispensing device according to the second example.

[0115] The liquid dispensing device 540 according to the second example is a serial type device, and the carriage 403 reciprocates in the main scanning direction by the main scanning movement mechanism 493. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, etc. The guide member 401 is stretched across the left and right side plates 491A and 491B and holds the carriage 403 in a movable position. The carriage 403 is then reciprocated in the main scanning direction by the main scanning motor 405 via a timing belt 408 stretched between a drive pulley 406 and a driven pulley 407.

[0116] The carriage 403 is equipped with a liquid discharge unit 440 that integrates a liquid discharge head 10 and a head tank 441. The liquid discharge head 10 of the liquid discharge unit 440 discharges liquids of various colors, such as yellow (Y), cyan (C), magenta (M), and black (K). The liquid discharge head 10 is also mounted with a nozzle row consisting of multiple nozzles arranged in a sub-scanning direction perpendicular to the main scanning direction, and with the discharge direction facing downwards.

[0117] A supply mechanism 494 for supplying liquid stored outside the liquid discharge head 10 to the liquid discharge head 10 supplies the head tank 441 with liquid stored in the liquid cartridge 450.

[0118] The supply mechanism 494 consists of a cartridge holder 451, which is a filling section for mounting the liquid cartridge 450, a tube 456, a liquid delivery unit 452 including a liquid delivery pump, and the like. The liquid cartridge 450 is detachably mounted in the cartridge holder 451. Liquid is delivered from the liquid cartridge 450 to the head tank 441 via the tube 456 by the liquid delivery unit 452.

[0119] This device includes a transport mechanism 495 for transporting paper 410. The transport mechanism 495 includes a transport belt 412, which is a transport means, and a sub-scanning motor 416 for driving the transport belt 412.

[0120] The conveyor belt 412 attracts the paper 410 and transports it to a position opposite the liquid discharge head 10. This conveyor belt 412 is an endless belt and is stretched between the conveyor roller 413 and the tension roller 414. Attraction can be performed by electrostatic attraction or air suction, etc.

[0121] Then, the conveyor belt 412 moves in a circular motion in the sub-scanning direction as the conveyor rollers 413 are rotationally driven by the sub-scanning motor 416 via the timing belt 417 and timing pulley 418.

[0122] Furthermore, a maintenance and recovery mechanism 420 for maintaining and recovering the liquid discharge head 10 is positioned on one side of the carriage 403 in the main scanning direction, next to the conveyor belt 412.

[0123] The maintenance and recovery mechanism 420 consists of, for example, a cap member 421 that caps the nozzle surface (the surface on which the nozzle is formed) of the liquid discharge head 10, a wiper member 422 that wipes the nozzle surface, and the like.

[0124] The main scanning movement mechanism 493, the supply mechanism 494, the maintenance and recovery mechanism 420, and the transport mechanism 495 are mounted on a housing that includes side plates 491A, 491B, and a back plate 491C.

[0125] In this configured device, the paper 410 is fed onto the transport belt 412 and picked up, and the paper 410 is transported in the sub-scanning direction by the circumferential movement of the transport belt 412.

[0126] Therefore, by moving the carriage 403 in the main scanning direction and driving the liquid ejection head 10 in accordance with the image signal, liquid is ejected onto the stationary paper 410 to form an image.

[0127] Thus, since the liquid dispensing device 540 according to the first and second examples is equipped with a liquid dispensing head 10, the stability of liquid dispensing is improved, and high-resolution images can be stably formed.

[0128] [Sixth Embodiment] Next, a liquid dispensing unit according to the sixth embodiment will be described with reference to Figures 24 and 25. Figure 24 is a schematic top view showing a first example of the liquid dispensing unit 440 according to the sixth embodiment. Figure 25 is a schematic side view showing a second example of the liquid dispensing unit 440 according to the sixth embodiment.

[0129] The liquid discharge unit 440, shown in Figure 24 as the first example, consists of a housing portion composed of side plates 491A, 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and a liquid discharge head 10, which are components of the liquid discharge device.

[0130] Furthermore, a liquid dispensing unit can also be configured by attaching, for example, the side plate 491B of the liquid dispensing unit 440 to at least one of the aforementioned maintenance and recovery mechanism 420 and supply mechanism 494.

[0131] The liquid discharge unit 440 in the second example shown in Figure 25 consists of a liquid discharge head 10 to which a flow path component 444 is attached, and a tube 456 connected to the flow path component 444.

[0132] The flow path component 444 is located inside the cover 442. A head tank 441 can be included instead of the flow path component 444. Furthermore, a connector 443 for electrical connection to the liquid discharge head 10 is provided on the upper part of the flow path component 444.

[0133] In this application, a liquid dispensing device is a device that includes a liquid dispensing head or a liquid dispensing unit and drives the liquid dispensing head to dispense liquid. A liquid dispensing device includes not only devices that can dispense liquid onto objects to which liquid can adhere, but also devices that dispense liquid into air or into liquid.

[0134] This liquid dispensing device may also include means for feeding, conveying, and dispensing paper onto materials to which liquid can adhere, as well as pre-treatment devices, post-treatment devices, and the like.

[0135] For example, liquid ejection devices include image forming machines, which eject ink to form images on paper, and three-dimensional molding machines, which eject molding liquid onto a powder layer formed in layers to create three-dimensional objects.

[0136] Furthermore, liquid dispensing devices are not limited to those that visualize meaningful images such as letters or figures through the dispensed liquid. For example, they also include devices that form patterns that do not have meaning in themselves, or devices that create three-dimensional images.

[0137] The term "materials to which liquid can adhere" above refers to materials to which liquid can adhere, at least temporarily, including materials that adhere and solidify, or materials that adhere and penetrate. Specific examples include recording media such as paper, recording paper, film, and cloth; electronic components such as electronic circuit boards and piezoelectric elements; powder layers; organ models; and inspection cells. Unless otherwise specified, it includes all materials to which liquid can adhere.

[0138] The materials referred to as "materials to which liquid can adhere" above include paper, thread, fibers, fabrics, leather, metal, plastic, glass, wood, ceramics, building materials such as wallpaper and flooring, and textiles for clothing, as long as liquid can adhere to them, even temporarily.

[0139] Furthermore, "liquid" also includes inks, processing solutions, DNA samples, resists, pattern materials, binders, molding fluids, or solutions and dispersions containing amino acids, proteins, calcium, etc. In addition, "liquid" may also be molten metal such as solder.

[0140] Furthermore, while a "liquid dispensing device" includes devices in which the liquid dispensing head and the object to which the liquid can adhere move relative to each other, it is not limited to this. Specific examples include serial-type devices in which the liquid dispensing head moves, and line-type devices in which the liquid dispensing head does not move.

[0141] Other liquid dispensing devices include processing liquid coating devices that dispense processing liquid onto the surface of paper for purposes such as modifying the paper surface, and injection granulation devices that granulate fine particles of raw materials by spraying a compositional liquid, in which raw materials are dispersed in a solution, through a nozzle.

[0142] A "liquid dispensing unit" is a collection of components related to liquid dispensing, in which functional parts and mechanisms are integrated with a liquid dispensing head. For example, a "liquid dispensing unit" may include a combination of a liquid dispensing head with at least one of the following components: a head tank, carriage, supply mechanism, maintenance and recovery mechanism, and main scanning and moving mechanism.

[0143] Here, integration includes, for example, cases where the liquid dispensing head and functional components or mechanisms are fixed to each other by fastening, bonding, engaging, etc., or where one is held movably relative to the other. Furthermore, the liquid dispensing head and functional components or mechanisms may be configured to be detachable from each other.

[0144] For example, some liquid dispensing units have a liquid dispensing head and head tank integrated into one unit. Others have a liquid dispensing head and head tank integrated into one unit, connected to each other by tubes or the like. In these liquid dispensing units, a unit including a filter can also be added between the head tank and the liquid dispensing head.

[0145] Additionally, some liquid dispensing units have an integrated liquid dispensing head and carriage.

[0146] Furthermore, some liquid dispensing units integrate the liquid dispensing head and the scanning mechanism by movably holding the liquid dispensing head in a guide member that constitutes part of the scanning mechanism. Other liquid dispensing units integrate the liquid dispensing head, carriage, and main scanning mechanism.

[0147] Furthermore, some liquid dispensing units integrate the liquid dispensing head, carriage, and maintenance / recovery mechanism by fixing a cap component, which is part of the maintenance / recovery mechanism, to a carriage to which the liquid dispensing head is attached.

[0148] Furthermore, some liquid discharge units have a head tank or a liquid discharge head to which flow path components are attached, to which a tube is connected, integrating the liquid discharge head and the supply mechanism.

[0149] The main scanning movement mechanism shall include the guide member alone. The supply mechanism shall also include the tube alone and the loading section alone.

[0150] Furthermore, the "liquid discharge head" is not limited to any particular pressure generating means. For example, in addition to the piezoelectric actuator described in the above embodiment (which may use a multilayer piezoelectric element), a thermal actuator using an electrothermal conversion element such as a heating resistor, or an electrostatic actuator consisting of a diaphragm and a counter electrode may also be used.

[0151] Furthermore, in the terminology used in this application, image formation, recording, printing, copying, printing, and shaping are all considered synonymous.

[0152] It should be noted that the present invention is not limited to the embodiments shown above. Within the scope of the present invention, each element of the above embodiments can be changed, added to, or modified in ways that would be easily conceivable to those skilled in the art. Furthermore, two or more embodiments described above can be combined as appropriate.

[0153] Examples of the present invention are as follows: <1> A liquid discharge head comprises a nozzle for discharging liquid, a pressure chamber communicating with the nozzle, a nozzle plate on which the nozzle is formed, and an actuator positioned on the nozzle plate which deforms the nozzle plate to discharge the liquid in the pressure chamber from the nozzle, wherein a drive voltage is applied to the actuator to generate a controlled flow in the liquid in the pressure chamber. <2> The nozzle plate has an inner surface facing the pressure chamber, and the controlled flow includes the flow of the liquid along the inner surface. <1> This is the liquid dispensing head described above. <3> The controlled flow includes the flow of the liquid in a direction away from the nozzle. <2> This is the liquid dispensing head described above. <4> The controlled flow includes the flow of the liquid generated at a position closer to the inner surface than the opposing surface in the pressure chamber that is opposite to the inner surface. <2> or the above <3> This is the liquid dispensing head described above. <5> The flow of the liquid is controlled by at least one of the waveform, voltage value, and frequency of the drive voltage applied to the actuator. <1> from the above <4> It is a liquid dispensing head as described in one of the following. <6> The drive voltage, which is smaller than the drive voltage that causes the liquid to be discharged from the nozzle, is applied to the actuator, thereby generating the flow of the liquid. <1> from the above <5> It is a liquid dispensing head as described in one of the following. <7> The actuator is a piezoelectric element, <1> from the above <6> This is the liquid dispensing head described above. <8> The liquid flow is generated in which the liquid flow is switched between a flow away from the nozzle and a flow towards the nozzle. <1> from the above <7> It is a liquid dispensing head as described in one of the following. <9> The nozzle plate vibrates when a drive voltage is applied to the actuator. <1> from the above <8> It is a liquid dispensing head as described in one of the following. <10> The system allows a portion of the liquid in the pressure chamber to be discharged from the pressure chamber by pressurization or suction, and by generating a flow of the liquid, it moves bubbles that are located in the pressure chamber that cannot be discharged by pressurization or suction to a location where they can be discharged by pressurization or suction. <1> from the above <9> It is a liquid dispensing head as described in one of the following. <11> The device comprises a plurality of pressure chambers, a plurality of supply passages through which the liquid is supplied to the plurality of pressure chambers, and a plurality of discharge passages through which the liquid is discharged from the plurality of pressure chambers, and is capable of circulating a portion of the liquid in the pressure chambers, and by generating the flow of the liquid, it moves bubbles that are located in positions within the pressure chambers that are not discharged by the circulation of the liquid to positions that can be discharged by the circulation of the liquid, <1> from the above <10> It is a liquid dispensing head as described in one of the following. <12> By generating the flow of the liquid, the liquid in the pressure chamber is stirred. <11> This is the liquid dispensing head described above. <13> The aforementioned <1> from the above <12> A liquid discharge device comprising a liquid discharge head as described in any one of the above, and a head drive unit for driving the liquid discharge head, wherein the head drive unit generates a controlled flow in the liquid in the pressure chamber by applying a drive voltage to the actuator. <14> A liquid discharge method using a liquid discharge device having a liquid discharge head comprising a nozzle for discharging liquid, a pressure chamber communicating with the nozzle, a nozzle plate on which the nozzle is formed, and an actuator disposed on the nozzle plate that deforms the nozzle plate to discharge the liquid in the pressure chamber from the nozzle, wherein the liquid discharge device drives the liquid discharge head with a head drive unit, and the head drive unit applies a drive voltage to the actuator to generate a controlled flow in the liquid in the pressure chamber. [Explanation of Symbols]

[0154] 1 nozzle 2. Pressure chamber 2A First pressure chamber conditions 2B Second pressure chamber conditions 3 Nozzle Plate 4 Actuators 5 Bulkhead 6, 6a, 6c, 6e flow 7, 7a, 7b bubbles 8 Fluid resistance section 10, 10a, 10b, 10c, 10d Liquid dispensing heads 15 areas 20 Head drive unit 30 Opposing wall 31 Vibration plate 32 Protective film 33 Wiring 34 Interlayer insulating film 35 Inner self 41 Lower electrode 42 Piezoelectric film 43 Upper electrode 51 Inner surface 60 Purge Flow 60°C circulating flow 70 Retention area 81 Supply route 82 Exhaust channel 83 Flow channel partition 84 1st supply route 85 2nd supply route 100 flow channel substrates 200 Optical Microscopes 350 Opposing surfaces 540 Liquid discharge device 550 Head Unit 600 Control Unit 610 CPU 620 Storage section 630 RAM 640 ROM 710 Conveyor drive unit 720 Operation display section 730 Input / Output Interface 740 Bus Line 800 External device A 1st liquid B Second liquid V1, V2 voltage values W1, W2, W3 drive voltage ΔP1 pulse width FL1, FL2, FL3 Falling edge waveforms RS1, RS2, RS3 rising edge waveforms [Prior art documents] [Patent Documents]

[0155] [Patent Document 1] Japanese Patent Publication No. 2014-172323

Claims

1. A nozzle for dispensing liquid, A pressure chamber communicating with the nozzle, The nozzle plate on which the nozzle is formed, The nozzle plate is positioned and includes an actuator that deforms the nozzle plate to discharge the liquid in the pressure chamber from the nozzle, A liquid discharge head that generates a controlled flow in the liquid within the pressure chamber when a drive voltage is applied to the actuator.

2. The nozzle plate has an inner surface facing the pressure chamber, The liquid dispensing head according to claim 1, wherein the controlled flow includes the flow of the liquid along the inner surface.

3. The liquid dispensing head according to claim 2, wherein the controlled flow includes the flow of the liquid in a direction away from the nozzle.

4. The liquid discharge head according to claim 2, wherein the controlled flow includes the flow of the liquid generated at a position closer to the inner surface than the opposing surface in the pressure chamber that is opposite to the inner surface.

5. The liquid discharge head according to claim 1, wherein the flow of the liquid is controlled by at least one of the waveform, voltage value, and frequency of the drive voltage applied to the actuator.

6. The liquid discharge head according to claim 1, wherein the liquid flow is generated by applying a drive voltage to the actuator that is smaller in voltage value than the drive voltage that discharges the liquid from the nozzle, and does not discharge the liquid from the nozzle.

7. The liquid dispensing head according to claim 1, wherein the actuator is a piezoelectric element.

8. The liquid discharge head according to claim 1, which generates a liquid flow in which the liquid flow in the direction away from the nozzle and the liquid flow in the direction towards the nozzle are switched.

9. The liquid discharge head according to claim 1, wherein the nozzle plate vibrates when a drive voltage is applied to the actuator.

10. A portion of the liquid in the pressure chamber can be discharged from the pressure chamber by pressurization or suction. The liquid discharge head according to claim 1, which generates the flow of the liquid, thereby moving bubbles located in the pressure chamber that cannot be discharged by pressurization or suction to a position where they can be discharged by pressurization or suction.

11. Multiple pressure chambers, Multiple supply paths through which the liquid is supplied to multiple pressure chambers, It has a plurality of discharge passages from which the liquid is discharged from a plurality of pressure chambers, A portion of the liquid in the pressure chamber can be circulated. The liquid discharge head according to claim 1, wherein by generating the flow of the liquid, bubbles located in the pressure chamber that are not discharged by the circulation of the liquid are moved to a position where they can be discharged by the circulation of the liquid.

12. The liquid discharge head according to claim 11, which generates the flow of the liquid to agitate the liquid in the pressure chamber.

13. A liquid dispensing head according to any one of claims 1 to 12, It has a head drive unit that drives the liquid discharge head, The head drive unit is a liquid discharge device that generates the controlled flow in the liquid in the pressure chamber by applying the drive voltage to the actuator.

14. A nozzle for dispensing liquid, A pressure chamber communicating with the nozzle, The nozzle plate on which the nozzle is formed, A liquid discharge method using a liquid discharge device having a liquid discharge head having an actuator disposed on the nozzle plate and which deforms the nozzle plate to discharge the liquid in the pressure chamber from the nozzle, wherein the liquid discharge device is The head drive unit drives the liquid discharge head, The head drive unit generates a controlled flow in the liquid within the pressure chamber by applying a drive voltage to the actuator, thereby providing a liquid discharge method.

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