Patent Publication Number: US-11390074-B2

Title: Liquid ejection head and liquid ejection apparatus

Description:
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-161233, filed on Sep. 4, 2019, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a liquid ejection head and a liquid ejection apparatus. 
     BACKGROUND 
     Inkjet heads that eject liquid from nozzles are known. Inkjet heads are also sometimes referred to as a liquid ejection heads. Inkjet recording apparatuses in which such inkjet heads are mounted are also known. Inkjet recording apparatuses are examples of a liquid ejection apparatus. One liquid jet head is known that ejects a liquid by applying a drive voltage to an actuator. In such an liquid jet head (or inkjet head), when the driving voltage is high, the lifetime of the actuator(s) tends to decrease. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating aspects of an inkjet head according to an embodiment. 
         FIG. 2  is a plan view illustrating aspects of a flow path substrate. 
         FIG. 3  is a plan view illustrating aspects of an actuator and a surroundings thereof. 
         FIG. 4  is a cross-sectional view taken along line A-A in  FIG. 3 . 
         FIG. 5  is a schematic view illustrating aspects of an inkjet recording apparatus according to an embodiment. 
         FIG. 6  is a graph illustrating a waveform of a drive signal. 
         FIG. 7  is a graph illustrating a waveform of a pressure oscillation. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a liquid ejection head comprises a pressure chamber, an actuator configured to change a pressure of a liquid in the pressure chamber in accordance with a drive signal, and a drive circuit configured to supply the drive signal to the actuator to cause the liquid to be discharged via a nozzle fluidly connected to the pressure chamber. The drive signal comprises a first waveform and N second waveforms after the first waveform, where N is greater than or equal to one. The first waveform comprises a first change from a first voltage to a second voltage that reduces the pressure of the liquid in the pressure chamber; and a second change after the first change. The second change is from the second voltage to a third voltage that is between the first voltage and the second voltage and occurs after the first change by one half of a natural oscillation period of the liquid in the pressure chamber. The N second waveforms comprises a third change from the third voltage to the second voltage that reduces the pressure of the liquid in the pressure chamber and a fourth change after the third change. The fourth change is from the second voltage to the third voltage and occurs after the third change by a time period that is less than one half of the natural oscillation period of the liquid in the pressure chamber. 
     Hereinafter, an inkjet head according to an embodiment and an inkjet recording apparatus equipped with the inkjet head according to an embodiment will be described with reference to the drawings. Note, in general, the drawings are not to scale. In addition, for the sake of description, various aspects present in an implemented embodiment may be omitted from certain drawings. 
       FIG. 1  is a perspective view illustrating an appearance of an inkjet head  1  according to an embodiment. The inkjet head  1  comprises a flow path substrate  2 , an ink supply unit  3 , a flexible wiring substrate  4 , and a drive circuit  5 . Note that the inkjet head  1  is an example of a liquid eject head. 
     In the flow path substrate  2 , actuators  6  provided with nozzles  17  (shown in  FIG. 3 , which will be described later) for ejecting ink are arranged in an array shape. The respective nozzles  17  do not overlap with each other in the printing direction, and are arranged at equal intervals with respect to a direction perpendicular to the printing direction. Each actuator  6  is electrically connected to the drive circuit  5  via the flexible wiring substrate  4 . The drive circuit  5  is electrically connected to a control circuit that performs printing control. The flow path substrate  2  and the flexible wiring substrate  4  are joined and electrically connected to each other by an anisotropic conductive film (ACF). The flexible wiring substrate  4  and the drive circuit  5  are joined and electrically connected to each other as, for example, a Chip-on-Flex (COF). 
     The ink supply unit  3  is joined to the flow path substrate  2  by, for example, an epoxy-based adhesive. The ink supply unit  3  has an ink supply port for connecting to a tube or the like, and supplies an ink fed to the ink supply port to the flow path substrate  2 . The pressure of the ink supplied to the ink supply port is preferably about 1000 Pa (1 kPa) lower than the atmospheric pressure. The ink fed in from the ink supply port and fills the inside of a pressure chamber  18  and the nozzle  17  if the pressure of the ink in the pressure chamber  18  is maintained at a pressure that is about 1000 Pa lower than the atmospheric pressure while waiting for an ejection of the ink to occur. The ink supply unit  3  can be considered an example of a liquid supply apparatus that supplies ink to the pressure chamber  18 . 
     The drive circuit  5  applies an electric signal to the actuator  6 . The electric signal is also referred to as a drive signal. When the drive circuit  5  applies a drive signal to the actuator  6 , the actuator  6  changes the volume of (or otherwise pressure inside) the pressure chamber  18  inside the flow path substrate  2 . Accordingly, the ink in the pressure chamber  18  generates a pressure oscillation. Due to the pressure oscillation, the ink is ejected from the nozzle  17  provided in the actuator  6  in the normal direction of the surface of the flow path substrate  2 . Note that the inkjet head  1  can realize gradations in color (tone representation) by changing the number or size of ink droplets that land at a position corresponding to one pixel. The inkjet head  1  changes the amount of ink droplets that land on one pixel by changing the number of times the ink is ejected to form a particular pixel. As described above, the drive circuit  5  can be considered an example of an application unit that applies the drive signal to the actuator. 
       FIG. 2  is a plan view illustrating details of the flow path substrate  2 . In  FIG. 2 , the repeated portions having the same pattern are omitted. In the flow path substrate  2 , a number of actuators  6 , a plurality of individual electrodes  7 , a common electrode  8   a , a common electrode  8   b , and a large number of mounting pads  9  are formed. Note that both the common electrode  8   a  and the common electrode  8   b  may be more simply referred to as a common electrode  8  in certain contexts when it unnecessary to distinguish between the two. 
     The individual electrode  7  electrically connects each actuator  6  to a mounting pad  9 . The individual electrodes  7  are electrically independent of each other. The common electrode  8   b  is electrically connected to the mounting pads  9  on the end. The common electrode  8   a  branches from the common electrode  8   b  and is electrically connected to the plurality of actuators  6 . The common electrode  8   a  and the common electrode  8   b  are electrically shared by a plurality of actuators  6 . 
     The mounting pads  9  are electrically connected to the drive circuit  5  via a large number of wiring patterns formed on the flexible wiring substrate  4 . An anisotropic conductive film may be used as a connection between the mounting pads  9  and the flexible wiring substrate  4 . In addition, each mounting pad  9  may be connected to the drive circuit  5  by a method such as wire bonding or the like. 
       FIG. 3  is a plan view illustrating details of the actuator  6  and the surroundings thereof.  FIG. 4  is a cross-sectional view taken along the line A-A line in  FIG. 3 . The actuator  6  includes a common electrode  8   a , a vibration plate  10 , a lower electrode  11 , a piezoelectric body  12 , an upper electrode  13 , an insulating layer  14 , a protective layer  16 , and a nozzle  17 . Each lower electrode  11  is electrically connected to an individual electrode  7 . 
     The flow path substrate  2  is formed of, for example, a single-crystal silicon wafer having a thickness of 500 μm. The pressure chamber  18  is formed inside the flow path substrate  2 . The diameter of the pressure chamber  18  is, for example, 200 μm. The pressure chamber  18  is formed, for example, by drilling a hole using a dry etching technique from the lower surface of the flow path substrate  2 . 
     The vibration plate  10  is formed integrally with the flow path substrate  2  so as to cover the upper surface of the pressure chamber  18 . The vibration plate  10  is silicon dioxide formed by heating the flow path substrate  2  at a high temperature prior to formation of the pressure chamber  18 . The vibration plate  10  has a through-hole having a diameter greater than that of the nozzle  17 . The through-hole is aligned concentrically with the nozzle  17 . The thickness of the vibration plate  10  is, for example, 4 μm. 
     On the vibration plate  10 , the lower electrode  11 , the piezoelectric body  12 , and the upper electrode  13  are formed in a donut shape (annular shape) around the nozzle  17 . The inner diameter is 30 μm as an example. The outer shape is, for example, 140 μm. As an example, the lower electrode  11  and the upper electrode  13  are formed by depositing platinum or the like by a sputtering method or similar method. The piezoelectric body  12  is formed by depositing PZT (Pb(Zr,Ti)O 3 ) (lead zirconate titanate) or the like by a sputtering method, a sol-gel method, or the like. The thickness of the upper electrode  13  and the thickness of the lower electrode  11  are, for example, 0.1 μm to 0.2 μm. The thickness of the PZT is, for example, 2 μm. 
     When a positive voltage is applied to the actuator  6  and an electric field is generated in the thickness direction of the piezoelectric body  12 , deformation of the d31 mode occurs in the piezoelectric body  12 . That is, the piezoelectric body  12  contracts in a direction perpendicular to its own thickness direction when a positive voltage is applied to the actuator  6 . Due to this contraction, compressive stress is generated in the vibration plate  10  and the protective layer  16 . At this time, since the Young&#39;s modulus of the vibration plate  10  is larger than that of the protective layer  16 , the compressive force generated in the vibration plate  10  exceeds that generated in the protective layer  16 . Thus, when a positive voltage is applied, the actuator  16  curves (bows) in the direction of the pressure chamber  18 . Thereby, the volume of the pressure chamber  18  is made smaller than is the case when no voltage is applied to the actuator  6 . That is, as the value of the voltage of the drive signal applied to the actuator  6  becomes larger, the volume of the pressure chamber  18  becomes smaller. 
     The insulating layer  14  is formed on an upper surface of the upper electrode  13 . A contact hole  15   a  and a contact hole  15   b  are formed in the insulating layer  14 . The contact hole  15   a  is a donut-shaped opening, and the upper electrode  13  and the common electrode  8  are electrically connected to each other via this opening. The contact hole  15   b  is a circular opening, and the lower electrode  11  and the individual electrode  7  are electrically connected to each other via this opening. The insulating layer  14  is, as an example, silicon dioxide film, for example formed by a TEOS (tetraethoxysilane) CVD (chemical vapor deposition) method. The thickness of the insulating layer  14  is 0.5 μm as an example. The insulating layer  14  prevents the common electrode  8  and the lower electrode  11  from coming into electrical contact with each other in the outer periphery of the piezoelectric body  12 . 
     On the upper surface of the insulating layer  14 , the individual electrodes  7 , the common electrode  8  and the mounting pads  9  are formed. The individual electrode  7  is connected to the lower electrode  11 , and the common electrode  8  is connected to the upper electrode  13  via the contact holes  15   b  and  15   a , respectively. In addition, in other examples, the individual electrode  7  may be connected to the upper electrode  13  and the common electrode  8  may be connected to the lower electrode  11 . The individual electrodes  7 , the common electrode  8 , and the mounting pads  9  are formed by forming gold film by a sputtering method as an example. The thickness of an individual electrode  7 , the common electrode  8 , and a mounting pad  9  is, for example, 0.1 μm to 0.5 μm. 
     The protective layer  16  is formed on the individual electrodes  7 , the common electrode  8  and the insulating layer  14 . As an example, the protective layer  16  is formed by depositing a photosensitive polyimide material by a spin coating method. The protective layer  16  has a thickness of 4 μm, for example. In the protective layer  16 , the nozzle  17  communicating with the pressure chamber  18  is open. 
     The nozzle  17  is formed by, for example, exposing and then developing the photosensitive polyimide material forming the protective layer  16  in a photolithographic technique. The diameter of the nozzle  17  is, for example, 20 μm. The length of the nozzle  17  is determined by the sum of the thickness of the vibration plate  10  and the thickness of the protection layer  16 . The length of the nozzle  17  is, for example, 8 μm. 
     Next, an inkjet recording apparatus  100  having an inkjet head  1  will be described.  FIG. 5  is a schematic diagram for describing an example of the inkjet recording apparatus  100 . The inkjet recording apparatus  100  can also be referred to as an inkjet printer. Note that the inkjet recording apparatus  100  may also or instead be a device such as a copying machine. The inkjet recording apparatus  100  is one example of a liquid ejection apparatus. 
     The inkjet recording apparatus  100  performs various types of processing for image formation while transporting recording sheets P (recording media), for example, past the inkjet head  1 . The inkjet recording apparatus  100  in this example comprises a housing  101 , a sheet feeding cassette  102 , a sheet discharge tray  103 , a holding roller (drum)  104 , a conveyance device  105 , a holding device  106 , an image forming apparatus  107 , a static elimination peeling device  108 , a reversing device  109 , and a cleaning device  110 . 
     The housing  101  contains the various components that make up the inkjet recording apparatus  100 . The sheet feeding cassette  102  is in the housing  101  and can accommodate a number of recording sheets P. The sheet discharge tray  103  is at the top of the housing  101 . The sheet discharge tray  103  is a destination of the recording sheet P after an image has been formed thereon by the inkjet recording apparatus  100 . 
     The holding roller  104  has a frame of a cylindrical conductor and a thin insulating layer formed on a surface of the frame. The frame is grounded (ground connected). The holding roller  104  conveys a recording sheet P by rotating while holding the recording sheet P on the surface thereof. 
     The conveyance device  105  has a plurality of guides and a plurality of conveyance rollers disposed along a conveyance path of the recording sheet P. The conveyance roller can be driven by a motor to rotate. The conveyance device  105  conveys the recording sheet P from the sheet feeding cassette  102  to the holding roller  104  to carry the recording sheet P past the inkjet head(s)  1  and then on to the sheet discharge tray  103 . 
     The holding device  106  directs the recording sheet P fed from the sheet feeding cassette  102  by the conveyance device  105  onto the surface (outer peripheral surface) of the holding roller  104 . The holding device  106  charges the recording sheet P and causes the recording sheet P to be attracted to the holding roller  104  by electrostatic force once the recording sheet P is pressed against the holding roller  104 . 
     The image forming apparatus  107  forms an image on a recording sheet P while it is being held on a surface of the holding roller  104 . The image forming apparatus  107  in this example has a plurality of inkjet heads  1  facing the surface of the holding roller  104 . The inkjet heads  1  form an image on the surface of the recording sheet P by ejecting inks of four different colors (cyan, magenta, yellow, and black) onto the recording sheet P, for example. 
     The static elimination peeling device  108  detaches the recording sheet P from the holding roller  104  by removing static electricity from the recording sheet P after image formation. The static elimination peeling device  108  supplies charge to neutralize existing charges on the recording sheet P and inserts a wedge between the recording sheet P and the holding roller  104 . This causes the recording sheet P to peel off the holding roller  104 . The conveyance device  105  then conveys the recording sheet P that has been detached from the holding roller  104  to the sheet discharge tray  103  or the reversing device  109 . 
     The reversing device  109  reverses the front and back sides of the recording sheet P and feeds a reversed recording sheet P back onto the surface of the holding roller  104  again. The reversing device  109  inverts the recording sheet P by, for example, transporting the recording sheet P along a predetermined reversing path that causes the recording sheet P to reverse in the front-back direction. 
     The cleaning device  110  cleans the holding roller  104 . The cleaning device  110  is arranged downstream of the static elimination peeling device  108  in the direction of rotation of the holding roller  104 . The cleaning device  110  causes a cleaning member  110   a  to rub on the surface of the rotating holding roller  104  to clean the surface of the rotating holding roller  104 . 
     Hereinafter, an operation of the inkjet head  1  according to an embodiment will be described.  FIG. 6  is a graph illustrating a waveform of a drive signal applied to the actuator  6  by the drive circuit  5 .  FIG. 6  shows a drive waveform W 1  and a drive waveform W 12 . The drive waveform W 1  is one example of a waveform of the drive signal according to an embodiment. The drive waveform W 12  is an example of a waveform of the drive signal in the related art (comparative example). In the  FIG. 6 , the vertical axis represents the voltage, and the horizontal axis represents time. Note that the length of one graduation on the horizontal axis is equal to 1 acoustic length (AL). Here, 1 AL unit is equal to one half of the natural vibration period (that is, the period at the main acoustic resonance frequency) of the ink in the pressure chamber  18 . 
     The drive waveform W 1  include one waveform W 11 , (n−1) waveforms W 12 , and one waveform W 13 . Here, n represents the number of times which the ink is ejected in a sequence and is an integer greater than or equal to 1. Note that the drive waveform W 1  illustrated in  FIG. 6  is the drive waveform W 1  for a case where n is 3. 
     The waveform W 11  is a pulse waveform including a change C 1  and a change C 2 . The pulse width of the waveform W 11  is preferably equal to one acoustic length (1 AL unit). The pulse width of waveform W 11  is the time from the start of the change C 1  to the start of the change C 2 . When the pulse width of waveform W 1  is 1 AL, the ink ejection force of the ink is increased. Note that waveform W 11  can be considered an example of a first waveform. 
     The change C 1  is a change from voltage V 1  to voltage V 2 . The drive waveform W 1  maintains the voltage V 1  in the standby state before the change C 1 . The V 2  is a voltage lower than the voltage V 1 . The voltage V 2  is preferably 0V, but may be a slightly negative value, that is, have a polarity opposite to the voltage V 1 . However, if the negative value is too large, the polarization direction of the piezoelectric body  12  can be reversed with respect to the standby state, and the desired operation cannot be obtained. Therefore, the voltage V 2  is preferably 0V. Due to the change C 1 , the volume of the pressure chamber  18  expands. As a result, the pressure of the ink in the pressure chamber  18  decreases. 
     The change C 2  is a change from the voltage V 2  to the voltage V 3 . The voltage V 3  is a voltage between the voltage V 1  and the voltage V 2 . That is, the voltage V 3  is a voltage that is smaller than the voltage V 1  and larger than the voltage V 2 . The voltage V 3  is preferably a voltage that is one-half of the voltage V 1 . The change C 2  causes the volume of the pressure chamber  18  to contract. As a result, the pressure of the ink in the pressure chamber  18  increases, and the ink is ejected from the nozzle  17 . 
     The waveform W 12  is a pulse waveform that after the waveform W 11 . The waveform W 12  includes a change C 3  and a change C 4 . The pulse width of the waveform W 12  is shorter than 1 AL. The pulse width of the waveform W 12  is a time from the start of the change C 3  to the start of the change C 4 . Note that the pulse width of the waveform W 22  in the drive waveform W 2 , which is the comparative example, is 1 AL. That is, the pulse width of the waveform W 12  is shorter than the pulse width in the conventional waveform. Further, when the pulse width of the waveform W 12  is shorter than 1 AL, the voltage V 3  can be made larger than that in the related art while maintaining the ejection force. If the voltage V 3  can be increased, the voltage V 1  can be reduced while maintaining the ejection force. That is, by setting the pulse width of the waveform W 12  to be shorter than 1 AL, the voltage V 1  can be made smaller than that in the conventional art. Note that when the voltage V 3  is too low, it is necessary to increase the voltage V 1 , and when the voltage V 3  is too high, a residual vibration increases. Therefore, it is preferable that the voltage V 3  is about one-half of the voltage V 1 . Note that the waveform W 12  is one example of a second waveform. The change C 3  is a change from the voltage V 3  to the voltage V 2 . The change C 3  expands the volume of the pressure chamber  18 . As a result, the pressure of the ink in the pressure chamber  18  decreases. 
     The change C 4  is a change from the voltage V 2  to the voltage V 3 . The change C 4  causes the volume of the pressure chamber  18  to contract. As a result, the pressure of the ink in the pressure chamber  18  increases, and the ink ejects from the nozzle  17 . 
     The time t 1  from the middle point between the start of the change C 1  and the start of the change C 2  to the middle point between the start of the change C 3  in the first waveform W 12  and the start of the change C 4  is preferably 2AL in terms of the ejection power. In addition, the voltage of the drive waveform W 1  from the end of the change C 2  to the start of the change C 3  is the voltage V 3 . The time t 2  from the middle point between the start of the change C 3  in the (m−1)-th waveform W 12  and the start of the change C 4  to the middle between the start of the change C 3  in the m-th waveform W 12  and the start of the change C 4  is preferably 2AL. Note that here m is an arbitrary integer equal to or greater than 2 and equal to or less than n. The voltage of the drive waveform W 1  from the end of the change C 4  in the (m−1)-th waveform W 12  to the start of the change C 2  in the m-th waveform W 12  is voltage V 3 . 
     The waveform W 13  is a pulse waveform for cancelling the residual vibration. That is, the waveform W 13  is one example of a cancellation pulse for reducing the residual vibration. 
     The waveform W 13  is applied after the last ejection waveform. Note that the last ejection waveform is the (n−1)-th waveform W 12  when n is equal to or greater than 2. If n is 1, then last ejection waveform will be the waveform W 11 . Note that the pulse width of the waveform W 13  is set to be a width such that the residual vibration can be canceled. The drive waveform W 1  includes a change C 5  between the last ejection waveform and the waveform W 13 . The voltage of the drive waveform W 1  from the end of the change of the last ejection waveform (the change C 2  or the change C 4  depending on the value of n) to the start of the change C 5  is voltage V 3 . The change C 5  is a change from the voltage V 3  to the voltage V 1 . The change C 5  causes the volume of the pressure chamber  18  to contract. As a result, the pressure of the ink in the pressure chamber  18  increases. 
     The waveform W 13  includes a change C 6  and a change C 7 . Note that the voltage of the drive waveform V 1  from the end of the change C 5  to the start of the change C 6  is voltage V 1 . The change C 6  is a change from the voltage V 1  to the voltage V 3 . The change C 6  expands the volume of the pressure chamber  18 . As a result, the pressure of the ink in the pressure chamber  18  decreases. The change C 7  is a change from the voltage V 3  to the voltage V 1 . The change C 5  causes the volume of the pressure chamber  18  to contract. As a result, the pressure of the ink in the pressure chamber  18  increases. 
     Note that the time t 3  from the middle point between the start of the first change in the last ejected waveform and the start of the second change in the last ejected waveform to the middle point between the start of the change C 6  and the start of the change C 7  in the waveform W 13  is preferably 3 AL. Note that the first change included in the last ejection waveform is the change C 1  when n is 1, and the second change included in the last ejection waveform is the change C 2  when n is 1. The first change included in the last ejection waveform is the change C 3  when n is 2 or more, and the second change included in the last ejection waveform is the change C 4  when n is 2 or more. 
       FIG. 7  is a graph illustrating a waveform of the pressure oscillation of the ink in the pressure chamber  18 , the pressure oscillation is being generated in accordance with the drive signal.  FIG. 7  shows a pressure waveform PW 1  and a pressure waveform PW 2 . The pressure waveform PW 1  is one example of a waveform of the pressure oscillation of the ink in the pressure chamber  18  when the drive waveform W 1  is applied. The pressure waveform PW 2  is one example of a waveform of the pressure oscillation of the ink in the pressure chamber  18  when the drive waveform W 2  is applied. In the graph in  FIG. 7 , the vertical axis represents the pressure (in arbitrary units), and the horizontal axis represents time. Note that the length of one graduation on the horizontal axis is 1 AL. 
     As shown in  FIG. 7 , for the pressure waveform PW 1  and the pressure waveform PW 2 , the amplitudes are approximately equal to each other. Therefore, it can be seen that the ink can be ejected with the same ejection force when the drive waveform W 1  is applied to the actuator  6  as when the drive waveform W 2  is applied. 
     As shown in  FIG. 7 , it can be seen that the residual vibration is sufficiently canceled by the waveform W 13  (see  FIG. 6 ) in the pressure waveform PW 1 . 
     The above-described embodiments may also be modified in various ways. The inkjet recording apparatus  100  of an embodiment is an inkjet printer that forms a two dimensional image by ejecting ink onto the recording sheet P. However, the inkjet recording apparatus  100  according to the present disclosure is not limited thereto. The inkjet recording apparatus  100  may be, for example, a 3D printer, an industrial manufacturing machine, a medical machine, or the like. In the case where the inkjet recording apparatus  100  is a 3D printer, an industrial manufacturing machine, or a medical machine, the inkjet recording apparatus  100  may form a three dimensional object by ejecting a material and/or a binder for solidifying a material from the inkjet head rather than simple ink. 
     The inkjet recording apparatus  100  of the example embodiment includes four inkjet heads  1 , and the color of ink used by each inkjet head  1  is cyan, magenta, yellow, or black. However, the number of inkjet heads  1  included in the inkjet recording apparatus  100  is not limited to four and the number of inkjet heads  1  may be any number of one or more. Further, the color, the characteristics, and the like of the ink used by each inkjet head  1  are not limited. For example, the inkjet head  1  can eject transparent glossy ink, ink that develops color when irradiated with light (e.g., infrared rays, ultraviolet rays) or the like, or other special inks. In some examples, the inkjet head  1  may eject a liquid other than ink, such as in dispensing of liquids in a medical research apparatus. Note that the liquid ejected by the inkjet head  1  may be a liquid solution or a suspension. Examples of a liquid other than ink that can be ejected by inkjet head  1  include a liquid including conductive particles for forming a wiring pattern of a printed wiring board, a binder material for applications such as an artificial tissue or an organ growth, a binder material such as an adhesive, a wax, a liquid resin, or the like for 3D printing applications. 
     In addition to the above-described embodiments, the inkjet head  1  may have a structure in which a vibration plate (diaphragm or the like) is deformed by piezoelectricity to eject ink, or a structure in which ink is ejected from a nozzle by using heat energy, such as generated by a local heater. In these cases, the diaphragm, the heater, or the like may be referred to as actuators that change the pressure of the ink in the pressure chamber. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.