Patent Publication Number: US-2023136678-A1

Title: Head chip, liquid ejecting head, and liquid ejecting apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2022-023607, filed Feb. 18, 2022 and JP Application Serial Number 2021-179518, filed Nov. 2, 2021, the disclosures of which are hereby incorporated by reference herein in their entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a head chip, a liquid ejecting head, and a liquid ejecting apparatus. 
     2. Related Art 
     A liquid ejecting apparatus represented by a piezo type ink jet printer generally includes a pressure chamber communicating with a nozzle and a piezoelectric element that causes pressure fluctuation in the pressure chamber. Here, for example, as disclosed in JP-A-2020-104456, a plurality of pressure chambers and a plurality of piezoelectric elements may be provided for one nozzle. 
     The head unit described in JP-A-2020-104456 includes a first pressure chamber and a second pressure chamber communicating with one nozzle, a first piezoelectric element corresponding to the first pressure chamber, a second piezoelectric element corresponding to the second pressure chamber, and a wiring substrate coupled to a switch circuit. Here, each of the first piezoelectric element and the second piezoelectric element includes a first electrode, a second electrode, and a piezoelectric layer sandwiched between both electrodes. Further, the first electrodes of the first piezoelectric element and the second piezoelectric element are common electrodes coupled to a common power supply line. On the other hand, the second electrodes of the first piezoelectric element and the second piezoelectric element are individual electrodes. Individual driving signals are sent from the switch circuit to the second electrodes of each of the first piezoelectric element and the second piezoelectric element. 
     Incidentally, in the related art, for example, as disclosed in JP-A-2018-51844, the natural frequency of a vibration section by a piezoelectric element may be measured. In the method described in JP-A-2018-51844, a measuring instrument called an impedance analyzer is used to measure the natural frequency of the vibration section by a piezoelectric actuator based on the result of measuring the impedance when a specific Sin wave is input into the piezoelectric actuator. 
     In JP-A-2020-104456, separate driving signals are sent from the switch circuit to the piezoelectric elements corresponding to the two pressure chambers communicating with the common nozzle. Therefore, the number of switching elements increases, and as a result, there is a possibility that the wiring substrate on which the switch circuit is mounted becomes large, or the switch circuit is overheated. Therefore, it is conceivable to reduce the size of the wiring substrate and suppress the heat generation of the switch circuit by sending a common driving signal to the individual electrodes of the two piezoelectric elements corresponding to the common nozzle. 
     However, in JP-A-2020-104456, two piezoelectric elements corresponding to a common nozzle are coupled to the same common electrode, and a power supply line for supplying power to the common electrode is also shared. Therefore, in JP-A-2020-104456, when a configuration in which a common driving signal is sent to the individual electrodes of the two piezoelectric elements corresponding to the common nozzle is adopted, by using the method described in JP-A-2018-51844, it is not possible to measure the natural frequencies of the two vibration sections corresponding to a common nozzle separately. Therefore, in this case, it is not possible to determine whether or not there is a characteristic difference between the two vibration sections. Under the above circumstances, in a configuration in which a plurality of pressure chambers are provided for one nozzle, it is desired to reduce the size of the head chip and suppress heat generation, and to inspect the performance of each pressure chamber. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a head chip including: a first nozzle that ejects a liquid; a second nozzle that ejects a liquid; a first pressure chamber communicating with the first nozzle; a second pressure chamber communicating with the first nozzle; a third pressure chamber communicating with the second nozzle; a fourth pressure chamber communicating with the second nozzle; a first piezoelectric body that generates a pressure in the first pressure chamber; a second piezoelectric body that generates a pressure in the second pressure chamber; a third piezoelectric body that generates a pressure in the third pressure chamber; a fourth piezoelectric body that generates a pressure in the fourth pressure chamber; a first individual electrode coupled to the first piezoelectric body; a second individual electrode coupled to the second piezoelectric body; a third individual electrode coupled to the third piezoelectric body; a fourth individual electrode coupled to the fourth piezoelectric body; a first common electrode commonly coupled to the first piezoelectric body and the third piezoelectric body; and a second common electrode that is independent of the first common electrode and is commonly coupled to the second piezoelectric body and the fourth piezoelectric body. 
     According to another aspect of the present disclosure, there is provided a liquid ejecting head including: the above-described head chip; and a relay substrate coupled to the head chip. 
     According to still another aspect of the present disclosure, there is provided a liquid ejecting apparatus including: the above-described liquid ejecting head; and a wiring member coupled to the liquid ejecting head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view illustrating a liquid ejecting apparatus according to a first embodiment. 
         FIG.  2    is a block diagram of a head unit of the liquid ejecting apparatus according to the first embodiment. 
         FIG.  3    is an exploded perspective view of a liquid ejecting head according to the first embodiment. 
         FIG.  4    is a view for explaining an operation of a driving circuit. 
         FIG.  5    is a sectional view of a head chip according to the first embodiment. 
         FIG.  6    is a sectional view of a piezoelectric element. 
         FIG.  7    is a schematic plan view for explaining the piezoelectric element according to the first embodiment. 
         FIG.  8    is a schematic diagram for explaining a wiring substrate according to the first embodiment. 
         FIG.  9    is a schematic diagram for explaining the driving circuit according to the first embodiment. 
         FIG.  10    is a schematic diagram for explaining a relay substrate according to the first embodiment. 
         FIG.  11    is a diagram for explaining a performance inspection of the head chip. 
         FIG.  12    is a schematic plan view for explaining a piezoelectric element according to a second embodiment. 
         FIG.  13    is a schematic diagram for explaining a wiring substrate according to the second embodiment. 
         FIG.  14    is a schematic plan view for explaining a piezoelectric element according to a third embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, preferred embodiments according to the present disclosure will be described with reference to the attached drawings. In the drawings, the dimensions and scale of each part may appropriately differ from the actual ones, and some parts are schematically illustrated for ease of understanding. Further, the scope of the present disclosure is not limited to these aspects unless otherwise stated to limit the disclosure in the following description. 
     In the following description, for convenience, an X axis, a Y axis, and a Z axis that intersect each other are appropriately used. In the following, one direction along the X axis is an X1 direction, and the direction opposite to the X1 direction is an X2 direction. Similarly, the directions opposite to each other along the Y axis are a Y1 direction and a Y2 direction. In addition, the directions opposite to each other along the Z axis are a Z1 direction and a Z2 direction. In the following, viewing in the Z1 direction or the Z2 direction may be referred to as “plan view”. 
     Here, typically, the Z axis is a vertical axis, and the Z2 direction corresponds to a downward direction in the vertical direction. However, the Z axis does not have to be a vertical axis and may be inclined with respect to the vertical axis. In addition, the X axis, the Y axis, and the Z axis are typically orthogonal to each other, but are not limited thereto, and may intersect each other at an angle within the range of 80° or more and 100° or less, for example. 
     1. First Embodiment 
     1-1. Liquid Ejecting Apparatus 
       FIG.  1    is a schematic view illustrating a liquid ejecting apparatus  100  according to a first embodiment. The liquid ejecting apparatus  100  is an ink jet type printing apparatus that ejects ink, which is an example of a liquid, as droplets onto a medium M. The liquid ejecting apparatus  100  of the present embodiment is a so-called line type printing apparatus in which a plurality of nozzles for ejecting ink are distributed over the entire range in the width direction of the medium M. The medium M is typically a printing paper sheet. The medium M is not limited to a printing paper sheet, and may be a printing target of any material such as a resin film or cloth. 
     As illustrated in  FIG.  1   , the liquid ejecting apparatus  100  includes a liquid container  10 , a control unit  20 , a transport mechanism  30 , a plurality of head units  40 , and a circulation mechanism  50 . 
     The liquid container  10  stores ink. Specific examples of the liquid container  10  include a cartridge that is attachable to and detachable from the liquid ejecting apparatus  100 , a bag-like ink pack formed of a flexible film, an ink tank that can be refilled with ink, and the like. Any type of ink may be stored in the liquid container  10 . The ink in the liquid container  10  is transferred to a sub tank  51  by a pump  11  arranged between the liquid container  10  and the sub tank  51  to be described later. 
     The control unit  20  controls the operation of each element of the liquid ejecting apparatus  100 . The control unit  20  includes a processing circuit such as a central processing unit (CPU) or a field programmable gate array (FPGA), and a storage circuit such as a semiconductor memory. Various programs and various data are stored in the storage circuit. The processing circuit realizes various controls by executing the program and using the data as appropriate. 
     The transport mechanism  30  transports the medium M under the control of the control unit  20 . In the example illustrated in  FIG.  1   , the transport mechanism  30  transports the medium M in the Y1 direction. The transport mechanism  30  includes, for example, a long transport roller along the X axis and a motor that rotates the transport roller. In addition, the transport mechanism  30  is not limited to the configuration using a transport roller, and may be configured to use, for example, a drum or an endless belt that transports the medium M in a state of being attracted to the outer peripheral surface by an electrostatic force or the like. 
     Under the control of the control unit  20 , each of the plurality of head units  40  ejects ink supplied from the liquid container  10  via the circulation mechanism  50  from each of the plurality of nozzles onto the medium M. 
     In the example illustrated in  FIG.  1   , each of the plurality of head units  40  has a liquid ejecting head  41  and a drive module  42 . The plurality of liquid ejecting heads  41  constitute a line head arranged such that a plurality of nozzles are distributed over the entire range of the medium M in the direction of the X axis, and eject ink in the Z2 direction. The drive module  42  drives the liquid ejecting head  41  based on image information IP from the control unit  20 . The image information IP is information based on data indicating an image to be printed. In addition, the number of head units  40  is not limited to the example illustrated in  FIG.  1   , and is any number. 
     The circulation mechanism  50  is a mechanism for supplying ink to each head unit  40  and collecting the ink discharged from each head unit  40  for resupplying the ink to the head unit  40 . The circulation mechanism  50  includes, for example, the sub tank  51  for storing the ink supplied from the liquid container  10 , a supply flow path  53  for supplying the ink from the sub tank  51  to the head unit  40 , a collecting flow path  54  for collecting ink from the head unit to the sub tank, and a pump  52  for transferring ink to each of these flow paths. By the operation of the circulation mechanism  50  as described above, it is possible to suppress an increase in the viscosity of the ink and reduce the retention of air bubbles in the ink. 
     1-2. Head Unit 
       FIG.  2    is a block diagram of the head unit  40  of the liquid ejecting apparatus  100  according to the first embodiment. As described above, the head unit  40  has a liquid ejecting head  41  and a drive module  42 . The liquid ejecting head  41  and the drive module  42  are electrically coupled to each other via a wiring member  43 .  FIG.  3    is an exploded perspective view of the liquid ejecting head  41 . Note that  FIG.  3    also illustrates the wiring member  43 . 
     The wiring member  43  is a flexible member for electrically coupling the liquid ejecting head  41  and the drive module  42  to each other. Specifically, for example, the wiring member  43  is a flexible printed circuits (FPC) or a flexible flat cable (FFC). In addition, the configuration for electrically coupling the liquid ejecting head  41  and the drive module  42  to each other is not limited to the configuration using the wiring member  43 , and may be, for example, a configuration using a board to board (BtoB) connector or may be a configuration using both the BtoB connector and an FPC or FFC. 
     As illustrated in  FIG.  2   , the drive module  42  includes a control circuit  42   a , a power supply circuit  42   b , driving signal output circuits  42   c _ 1  to  42   c _m, and a conversion circuit  42   d . Note that m is a natural number of 2 or more, and corresponds to the number of head chips  41   a  (to be described later) mounted on the liquid ejecting head  41 . Further, in the following, each of the driving signal output circuits  42   c _ 1  to  42   c _m may be referred to as a driving signal output circuit  42   c . Further, in the following, the subscripts “_1” to “_m” are added to the codes of the elements corresponding to the driving signal output circuits  42   c _ 1  to  42   c _m. 
     The power supply circuit  42   b  receives power from a commercial power source (not illustrated) and generates a power supply potential GVDD, a ground potential GND, a high potential side power supply potential VHV, and a low potential side power supply potential VDD. Each of these potentials is a constant potential. Specifically, for example, the power supply potential GVDD is approximately 7.5 V, the ground potential GND is approximately 0 V, the power supply potential VHV is approximately 42 V, and the power supply potential VDD is approximately 3.3 V. Each of these potentials is supplied to each of the driving signal output circuits  42   c _ 1  to  42   c _m. In addition, of these potentials, each of the ground potential GND, the power supply potential VHV, and the power supply potential VDD is supplied to the liquid ejecting head  41  via the wiring member  43  in addition to the driving signal output circuits  42   c _ 1  to  42   c _m. 
     The control circuit  42   a  is composed of, for example, a processing circuit such as a CPU or FPGA, and outputs various types of data and various signals based on the image information IP input from the control unit  20 . 
     Here, the control circuit  42   a  generates print data signals SI_ 1  to SI_m, a latch signal LAT, a change signal ch, and a clock signal SCK based on the image information IP. Each signal generated by this generation is input into the conversion circuit  42   d . Each of the print data signals SI_ 1  to SI_m is a digital signal for designating the type of operation of a piezoelectric element  400  to be described later. Specifically, each of the print data signals SI_ 1  to SI_m designates the type of operation of the piezoelectric element  400  by designating whether to supply driving signals COM_A and COM_B to the piezoelectric element  400 . The latch signal LAT and the change signal CH are used in combination with the print data signals SI_ 1  to SI_m, and define the drive timing of the piezoelectric element  400 . The timing of the pulses contained in these signals is defined based on the clock signal SCK. In addition, in the following, each of the print data signals SI_ 1  to SI_m may be referred to as a print data signal SI. Further, each of the driving signals COM_A and COM_B may be referred to as a driving signal COM. 
     The conversion circuit  42   d  generates a data signal DATA by converting the print data signals SI_ 1  to SI_m, the latch signal LAT, the change signal CH, and the clock signal SCK into a differential signal such as low voltage differential signaling (LVDS). The data signal DATA is input into the liquid ejecting head  41  via the wiring member  43 . In addition, the data signal DATA is not limited to LVDS, and may be, for example, a high-speed transfer type differential signal such as a low voltage positive emitter coupled logic (LVPECL) or a current mode logic (CML), or may be a signal having a part or all of the print data signals SI_ 1  to SI_m, the latch signal LAT, the change signal ch, and the clock signal SCK as a single end. 
     Further, the control circuit  42   a  generates driving data dA and dB. Each of the driving data dA and dB is input into each of the driving signal output circuits  42   c _ 1  to  42   c _m. 
     The driving signal output circuit  42   c  generates the driving signal COM_A based on the driving data dA and also generates the driving signal COM_B based on the driving data dB. The ground potential GND, the power supply potential VHV, and the power supply potential VDD are used for this generation. Here, for example, the driving signal output circuit  42   c  generates the driving signal COM_A by converting the driving data dA from a digital signal to an analog signal and then applying class D amplification to the analog signal. Similarly, the driving signal output circuit  42   c  generates the driving signal COM_B by converting the driving data dB from a digital signal to an analog signal and then applying class D amplification to the analog signal. Each of the driving signals COM_A and COM_B is input into the liquid ejecting head  41  via the wiring member  43 . 
     Further, the driving signal output circuit  42   c  generates an offset potential VBS in addition to the driving signals COM_A and COM_B. The power supply potential GVDD is used for this generation. The offset potential VBS is a constant potential. The specific potential of the offset potential VBS is not particularly limited, and may be, for example, a constant potential of approximately 5.5 V or 6 V, or may be a ground potential. The offset potential VBS is input into the liquid ejecting head  41  via the wiring member  43 . In addition, “constant potential” includes a case of being regarded as a constant potential when various fluctuations, such as potential fluctuations caused by the operation of peripheral circuits, potential fluctuations caused by circuit element variations, and potential fluctuations caused by the temperature characteristics of circuit elements, are taken into consideration. 
     The liquid ejecting head  41  has a restoration circuit  41   b  and head chips  41   a _ 1  to  41   a _m. As illustrated in  FIG.  3   , the liquid ejecting head  41  of the present embodiment has six head chips  41   a . In addition, in the following, each of the head chips  41   a _ 1  to  41   a _m may be referred to as a head chip  41   a.    
     The restoration circuit  41   b  restores the data signal DATA into a single-ended signal and separates the data signal into signals corresponding to the head chips  41   a _ 1  to  41   a _m. 
     Specifically, the restoration circuit  41   b  restores the data signal DATA to generate the print data signals SI_ 1  to SI_m, the latch signal LAT, the change signal ch, and the clock signal SCK. Further, the restoration circuit  41   b  separates the print data signals SI_ 1  to SI_m, the latch signal LAT, the change signal ch, and the clock signal SCK for each head chip  41   a . Each signal after this separation is input into each head chip  41   a . Here, the print data signals SI_ 1  to SI_m correspond to the head chips  41   a _ 1  to  41   a _m, respectively. 
     The above restoration circuit  41   b  is mounted on a relay substrate  440 . The relay substrate  440  is coupled to the drive module  42  via the wiring member  43 . In addition, the details of the relay substrate  440  will be described later with reference to  FIG.  10   . 
     Here, the driving signals COM_A, COM_B, the offset potential VBS, the ground potential GND, the power supply potential VHV, and the power supply potential VDD are supplied from the drive module  42  to each of the head chips  41   a _ 1  to  41   a _m via the relay substrate  440 . Further, as described above, the print data signal SI, the latch signal LAT, the change signal CH, and the clock signal SCK are input into each of the head chips  41   a _ 1  to  41   a _m from the restoration circuit  41   b.    
     As illustrated in  FIG.  3   , the liquid ejecting head  41  includes a fixing plate  470 , the head chips  41   a _ 1  to  41   a _m, a holder  450 , a relay substrate  440 , and a flow path structure  460 , and these are laminated in this order. The laminated parts constituting these liquid ejecting heads  41  are fixed by fixing tools such as adhesives or screws (not illustrated). 
     The fixing plate  470  has six opening portions  471  penetrating the fixing plate  470  in the Z2 direction. Then, the six head chips  41   a  are fixed to the surface of the fixing plate  470  facing the Z1 direction such that a nozzle substrate  413  of the head chips  41   a  is exposed from each of the six opening portions  471 . 
     The holder  450  is positioned on the Z1 direction side of the head chip  41   a , and accommodates the head chip  41   a  between the holder  450  and the fixing plate  470 . Two introduction sections  451  and two lead-out sections  452  are provided on the surface of the holder  450  facing the Z1 direction. Each of the two introduction sections  451  communicates with a first supply flow path hole (not illustrated) formed on a surface of the holder  450  facing the Z2 direction via a holder supply path (not illustrated) formed inside the holder  450 . The first supply flow path hole is coupled to a supply port H 1  of the head chip  41   a  to be described later. Each of the two lead-out sections  452  communicates with a first discharge flow path hole (not illustrated) formed on a surface of the holder  450  facing the Z2 direction via a holder discharge path (not illustrated) formed inside the holder  450 . The first discharge flow path hole is coupled to a discharge port H 2  of the head chip  41   a  to be described later. Further, the holder  450  has six opening portions  453  penetrating along the Z1 direction. The wiring substrates  430  of each of the six head chips  41   a  are inserted into the six opening portions  453 . 
     The relay substrate  440  is positioned in the Z1 direction of the holder  450 . The relay substrate  440  has a connector  445  to which one end of the wiring member  43  for electrically coupling the drive module  42  and the liquid ejecting head  41  is coupled. Further, on the relay substrate  440 , four opening portions  447  and two notch sections  448  are formed. The wiring substrate  430  of the head chip  41   a _ 2  to the head chip  41   a _ 5  is inserted into the four opening portions  447 . The wiring substrates  430  of each of the head chip  41   a _ 2  to the head chip  41   a _ 5  inserted into the four opening portions  447  are electrically coupled to the relay substrate  440  by solder or the like. Further, the wiring substrate  430  of the head chip  41   a _ 1  passes through one of the notch sections  448 , and the wiring substrate  430  of the head chip  41   a _ 6  passes through the other one of the notch sections  448 . Then, the wiring substrate  430  included in each of the head chips  41   a _ 1  and  41   a _ 6 , through which each of the two notch sections  448  pass, is electrically coupled to the relay substrate  440  by solder or the like. 
     The flow path structure  460  has two introduction sections  461  and two lead-out sections  462  protruding in the Z1 direction on a surface facing the Z1 direction. Each of the two introduction sections  461  communicates with a second supply flow path hole (not illustrated) formed on a surface of the flow path structure  460  facing the Z2 direction via a flow path (not illustrated) formed inside the flow path structure  460 . The second supply flow path hole is coupled to the introduction section  451  of the holder  450 . The supply flow path  53  formed of, for example, a tube is coupled to the two introduction sections  461 . Further, each of the two lead-out sections  472  communicates with a second discharge flow path hole (not illustrated) formed on a surface of the flow path structure  460  facing the Z2 direction via a flow path (not illustrated) formed inside the flow path structure  460 . The second discharge flow path hole is coupled to the lead-out section  452  of the holder  450 . The collecting flow path  54  formed by, for example, a tube is coupled to the two lead-out sections  462 . 
     Furthermore, the flow path structure  460  is formed with a through-hole  463  that penetrates along the Z1 direction. The wiring member  43  electrically coupled to the relay substrate  440  is inserted through the through-hole  463 . In addition, a filter or the like may be provided inside the flow path structure  460  to capture foreign matter contained in the ink flowing through the flow path formed inside the flow path structure  460 . 
     Each of the head chips  41   a _ 1  to  41   a _m has driving circuits  410 _ 1  to  410 _ m  for driving the piezoelectric element  400  (piezoelectric body). Hereinafter, the driving circuit  410  will be described. The details of the head chip  41   a  will be described with reference to  FIGS.  5  to  8    to be described later. Further, in the following, each of the driving circuits  410 _ 1  to  410 _ m  may be referred to as a driving circuit  410 . 
     The driving circuit  410  has a plurality of switching elements  410   sw  that switch whether to supply each of the driving signals COM_A and COM_B to the piezoelectric element  400  based on the clock signal SCK, the print data signal SI, the change signal CH, and the latch signal LAT. Here, among the waveforms included in the driving signals COM_A and COM_B, the waveform actually supplied to the piezoelectric element  400  is a driving signal VOUT. Further, of the pair of electrodes of the piezoelectric element  400 , the driving signal VOUT is supplied to one electrode (an individual electrode  401  to be described later), and the offset potential VBS is supplied to the other electrode (a common electrode  403  to be described later). In addition, an example of the change signal CH, the latch signal LAT, and the driving signals COM_A and COM_B will be described later with reference to  FIG.  4   . 
     The above driving circuit  410  is mounted on the wiring substrate  430 . The wiring substrate  430  electrically couples the plurality of piezoelectric elements  400  and the relay substrate  440 . In addition, the details of the wiring substrate  430  will be described later with reference to  FIG.  8   . 
     As described above, the liquid ejecting apparatus  100  includes the liquid ejecting head  41  and the wiring member  43  coupled to the liquid ejecting head  41 . Here, as described above, the liquid ejecting head  41  includes at least one head chip  41   a  and the relay substrate  440  coupled to the head chip  41   a.    
     1-3. Operation of Driving Circuit  410   
       FIG.  4    is a view for explaining an operation of the driving circuit  410 . As illustrated in  FIG.  4   , the latch signal LAT includes a pulse PlsL for defining a unit period Tu. In the example illustrated in  FIG.  4   , the unit period Tu is defined as a period from the rise of the pulse PlsL to the rise of the next pulse PlsL. The unit period Tu corresponds to a printing cycle in which dots are formed on the medium M by ink from nozzle N. That is, the unit period Tu corresponds to the control cycle of the driving circuit  410  to be described above. 
     The change signal CH includes the pulse PlsC for dividing the unit period Tu into a control period Tu 1  and a control period Tu 2 . The control period Tu 1  and the control period Tu 2  are arranged in this order over time. The control period Tu 1  is, for example, a period from the rise of the pulse PlsL to the rise of the first pulse PlsC. The control period Tu 2  is, for example, a period from the rise of the first pulse PlsC to the rise of the subsequent second pulse PlsC. In addition, in the example illustrated in  FIG.  4   , the control period Tu 1  and the control period Tu 2  have the same time length, but are not limited thereto, and the control period Tu 1  and the control period Tu 2  may have different time lengths. Further, the change signal CH may divide the unit period into three or more control periods. 
     The driving signal COM_A has a pulse PA 1  provided in the control period Tu 1  and a pulse PA 2  provided in the control period Tu 2 . The driving signal COM_B has a pulse PB 1  provided in the control period Tu 1  and a pulse PB 2  provided in the control period Tu 2 . 
     In the example illustrated in  FIG.  4   , each of the pulses PA 1 , PA 2 , and PB 2  is potential pulses for driving the piezoelectric element  400  such that the pressure fluctuation of the strength of ejecting ink from the nozzle N to be described later is generated in the pressure chambers Ca and Cb to be described later. On the other hand, the pulse PB 1  is a potential pulse for driving the piezoelectric element  400  such that a pressure fluctuation having a strength that does not eject ink from the nozzle N to be described later is generated in the pressure chambers Ca and Cb to be described later. In addition, the waveforms of the pulses PA 1 , PA 2 , PB 1 , and PB 2  are not limited to the example illustrated in  FIG.  4   , and are any waveforms. Further, the pulse PB 1  may be a potential pulse for driving the piezoelectric element  400  such that a pressure fluctuation having a strength that ejects ink from the nozzle N to be described later is generated in the pressure chambers Ca and Cb to be described later. 
     The above pulses PA 1 , PA 2 , PB 1 , and PB 2  are appropriately selected for each unit period Tu and used for the driving signal VOUT. As a result, the amount of ink ejected from the nozzle N can be adjusted, and the ink in the nozzle N can be slightly vibrated without ejecting the ink from the nozzle N. 
     1-4. Head Chip 
       FIG.  5    is a sectional view of the head chip  41   a  according to the first embodiment. In the following description, for convenience, in addition to the X axis, the Y axis, and the Z axis, a V axis and a W axis are appropriately used. Further, one direction along the V axis is the V1 direction, and the direction opposite to the V1 direction is a V2 direction. Similarly, the directions opposite to each other along the W axis are a W1 direction and a W2 direction. 
     Here, the V axis is an axis along a nozzle array direction DN, which is the arrangement direction of the plurality of nozzles N described later, and is an axis obtained by rotating the Y axis around the Z axis at a predetermined angle. The W axis is an axis obtained by rotating the X axis around the Z axis at the predetermined angle. Therefore, the V axis and the W axis are typically orthogonal to each other, but are not limited thereto, and may intersect each other at an angle within the range of 80° or more and 100° or less, for example. Further, the predetermined angle, that is, the angle formed by the V axis and the Y axis, or the angle formed by the W axis and the X axis is, for example, within the range of 40° or more and 60° or less. 
     As illustrated in  FIG.  5   , the head chip  41   a  includes a flow path substrate  411 , a pressure chamber substrate  412 , a nozzle substrate  413 , a vibration absorbing body  414 , a vibrating plate  415 , a cover  416 , a case  417 , a plurality of piezoelectric elements  400 , and a wiring substrate  430 . Here, the pressure chamber substrate  412  and the vibrating plate  415  constitute an actuator substrate  420  on which a plurality of piezoelectric elements  400  are mounted. 
     The flow path substrate  411  and the pressure chamber substrate  412  are laminated in the Z1 direction in this order, and form a plurality of individual flow paths P for supplying ink to the plurality of nozzles N. The plurality of individual flow paths P are arranged in a direction along the V axis. Each of the plurality of individual flow paths P communicates with different nozzles N, and has the pressure chamber Ca, the pressure chamber Cb, a nozzle flow path Nf, a supply flow path Ra 1 , a discharge flow path Ra 2 , a first vertical flow path Na 1 , and a second vertical flow path Na 2 . In the following, each of the pressure chambers Ca and Cb may be referred to as a pressure chamber C. 
     The vibrating plate  415 , the plurality of piezoelectric elements  400 , the covers  416  and  417 , and the wiring substrate  430  are installed in a region positioned in the Z1 direction with respect to the laminated body composed of the flow path substrate  411  and the pressure chamber substrate  412 . On the other hand, the nozzle substrate  413  and the vibration absorbing body  414  are installed in the region positioned in the Z2 direction with respect to the laminated body. Each element of the head chip  41   a  is generally a plate-shaped member elongated in the direction along the V axis, and is joined to each other by, for example, an adhesive. A plurality of nozzles N are provided on the nozzle substrate  413 . The plurality of nozzles N are arranged in a direction along the V axis (the nozzle array direction DN to be described later). Each of the plurality of nozzles N penetrates the nozzle substrate  413  and is a through-hole through which ink passes. 
     The pressure chamber substrate  412  is provided with the plurality of pressure chambers Ca and the plurality of pressure chambers Cb. The plurality of pressure chambers Ca are arranged in a direction along the V axis. The plurality of pressure chambers Cb are arranged in the direction along the V axis at positions in the W1 direction with respect to the plurality of pressure chambers Ca. Here, the pressure chambers Ca and Cb corresponding to the common nozzle N are arranged in a direction along the W axis, and the nozzle N is arranged between the pressure chamber Ca and the pressure chamber Cb corresponding to the common nozzle N when viewed in the Z2 direction which is the ejection direction of the ink from the nozzle N. Each of the pressure chamber Ca and the pressure chamber Cb penetrates the pressure chamber substrate  412  and is a gap between the flow path substrate  411  and the vibrating plate  415 . 
     The flow path substrate  411  is provided with spaces R 1   a  and R 2   a , the nozzle flow path Nf, the supply flow path Ra 1 , and the discharge flow path Ra 2 . 
     Each of the spaces R 1   a  and R 2   a  is a space that penetrates the flow path substrate  411  in the direction along the Z axis. Here, the space R 1   a  constitutes a part of a first common liquid chamber R 1 . Further, the space R 2   a  constitutes a part of a second common liquid chamber R 2 . The vibration absorbing body  414  that closes the opening by the spaces R 1   a  and R 2   a  is installed on the surface of the flow path substrate  411  facing the Z2 direction. 
     The vibration absorbing body  414  is a layered member made of an elastic material. The vibration absorbing body  414  forms a part of the wall surface of the first common liquid chamber R 1  and the second common liquid chamber R 2 , and absorbs the pressure fluctuation in the first common liquid chamber R 1  and the second common liquid chamber R 2 . 
     The nozzle flow path Nf is a space in which the pressure chamber Ca and the pressure chamber Cb communicate with each other. In the example illustrated in  FIG.  5   , the nozzle flow path Nf has a horizontal flow path Nf 1 , the first vertical flow path Na 1 , and the second vertical flow path Na 2 . The horizontal flow path Nf 1  is a space in the groove provided on the surface of the flow path substrate  411  facing the Z2 direction. Here, the nozzle substrate  413  constitutes a part of the wall surface of the horizontal flow path Nf 1 . Each of the first vertical flow path Na 1  and the second vertical flow path Na 2  is a space extending along the Z axis and penetrating the flow path substrate  411 . The first vertical flow path Na 1  allows the pressure chamber Ca to communicate with the horizontal flow path Nf 1  and guides the ink from the pressure chamber Ca to the horizontal flow path Nf 1 . On the other hand, the second vertical flow path Na 2  allows the pressure chamber Cb to communicate with the horizontal flow path Nf 1  and guides the ink from the horizontal flow path Nf 1  to the pressure chamber Cb. 
     Each of the supply flow path Ra 1  and the discharge flow path Ra 2  is a space extending along the Z axis and penetrating the flow path substrate  411 . The supply flow path Ra 1  allows the first common liquid chamber R 1  to communicate with the pressure chamber Ca, and supplies the ink from the first common liquid chamber R 1  to the pressure chamber Ca. Here, one end of the supply flow path Ra 1  is opened on the surface of the flow path substrate  411  facing the Z1 direction. On the other hand, the other end of the supply flow path Ra 1  is an upstream end of the individual flow path P and opens to the wall surface of the first common liquid chamber R 1  on the flow path substrate  411 . On the other hand, the discharge flow path Ra 2  allows the second common liquid chamber R 2  to communicate with the pressure chamber Cb, and discharges the ink from the pressure chamber Cb to the second common liquid chamber R 2 . Here, one end of the discharge flow path Ra 2  is opened on the surface of the flow path substrate  411  facing the Z1 direction. On the other hand, the other end of the discharge flow path Ra 2  is the downstream end of the individual flow path P, and opens to the wall surface of the second common liquid chamber R 2  on the flow path substrate  411 . 
     The vibrating plate  415  is a plate-shaped member that can elastically vibrate. The details of the vibrating plate  415  will be described later with reference to  FIG.  6   . 
     A plurality of piezoelectric elements  400  corresponding to different pressure chambers C are installed on the surface of the vibrating plate  415  facing the Z1 direction. The piezoelectric element  400  overlaps the corresponding pressure chamber C in plan view. When the driving signal VOUT is supplied, the piezoelectric element  400  vibrates the vibrating plate  415  with its own deformation. Along with this vibration, the pressure chamber C expands and contracts such that the pressure of the ink in the pressure chamber C fluctuates. 
     The case  417  is a case for storing ink. Spaces R 1   b  and R 2   b  are provided in the case  417 . The space R 1   b  and the above-described space R 1   a  form the first common liquid chamber R 1 . Further, the space R 2   b  and the above-described space R 2   a  form the second common liquid chamber R 2 . Further, the case  417  is provided with the supply port H 1  and the discharge port H 2 . The supply port H 1  is a conduit that communicates with the first common liquid chamber R 1  and is coupled to the supply flow path  53  of the circulation mechanism  50  described above via the holder  450  and the flow path of the flow path structure  460  described above. Therefore, the ink from the circulation mechanism  50  is supplied to the first common liquid chamber R 1  via the supply port H 1 . On the other hand, the discharge port H 2  is a conduit that communicates with the second common liquid chamber R 2  and is coupled to the collecting flow path  54  of the circulation mechanism  50  via the holder  450  and the flow path of the flow path structure  460  described above. Therefore, the ink in the second common liquid chamber R 2  is discharged to the circulation mechanism  50  via the discharge port H 2 . 
     The cover  416  is a plate-shaped member installed on the surface of the vibrating plate  415  facing the Z1 direction, protects a plurality of piezoelectric elements  400 , and reinforces the mechanical strength of the vibrating plate  415 . Here, a space for accommodating the plurality of piezoelectric elements  400  is formed between the cover  416  and the vibrating plate  415 . 
     The wiring substrate  430  is mounted on a surface of the vibrating plate  415  facing the Z1 direction, and is a flexible wiring substrate such as a flexible printed circuit (FPC) or a flexible flat cable (FFC). The driving circuit  410  described above is mounted on the wiring substrate  430 . 
     In the head chip  41   a  having the above configuration, the ink is transferred to the first common liquid chamber R 1 , the supply flow path Ra 1 , the pressure chamber Ca, the nozzle flow path Nf, the pressure chamber Cb, the discharge flow path Ra 2 , and the second common liquid chamber R 2  by the operation of the circulation mechanism  50  described above. In addition, the operation period or operation timing of the circulation mechanism  50  is any period or timing. 
     Further, the pressure of the pressure chamber Ca and the pressure chamber Cb is caused to fluctuate by simultaneously driving the piezoelectric element  400  corresponding to both the pressure chamber Ca and the pressure chamber Cb communicating with the common nozzle N by the driving signal VOUT from the driving circuit  410 , and the ink is ejected from the nozzle N as the pressure fluctuates. In  FIG.  5   , the flow of ink when the piezoelectric element  400  corresponding to both the pressure chamber Ca and the pressure chamber Cb is driven at the same time is indicated by a broken line arrow. 
     1-5. Piezoelectric Element and Actuator Substrate 
       FIG.  6    is a sectional view of the piezoelectric element  400 . As described above, the actuator substrate  420  includes the pressure chamber substrate  412  having the pressure chamber C and the vibrating plate  415 . The piezoelectric elements  400  are arranged for each pressure chamber C on the surface of the actuator substrate  420  facing the Z1 direction. The vibrating plate  415  is laminated on the pressure chamber substrate  412 . 
     Here, in the example illustrated in  FIG.  6   , the vibrating plate  415  has a first layer  415   a  and a second layer  415   b , and these are laminated in the Z1 direction in this order. The first layer  415   a  is, for example, an elastic film made of silicon oxide (SiO 2 ). The elastic film is formed, for example, by thermally oxidizing one surface of a silicon single crystal substrate. The second layer  415   b  is, for example, an insulating film made of zirconium oxide (ZrO 2 ). The insulating film is formed by, for example, forming a zirconium layer by a sputtering method and thermally oxidizing the layer. 
     In addition, the first layer  415   a  is not limited to silicon oxide, and may be made of, for example, another elastic material such as elemental silicon. The constituent material of the second layer  415   b  is not limited to zirconium oxide, and may be another insulating material such as silicon nitride. Further, another layer such as a metal oxide may be interposed between the first layer  415   a  and the second layer  415   b . Further, a part or all of the vibrating plate  415  may be integrally made of the same material as the pressure chamber substrate  412 . Further, the vibrating plate  415  may be composed of a layer of a single material. 
     In addition, the vibrating plate  415  or at least a part of the vibrating plate  415  (for example, the second layer  415   b ) may be integrally formed with the pressure chamber substrate  412 . That is, in the present specification, the case where “the vibrating plate  415  is laminated on the pressure chamber substrate  412 ” include not only a case where the vibrating plate  415  or a part of the vibrating plate  415  is laminated on the pressure chamber substrate  412  which is a material different from the vibrating plate  415  or a part of the vibrating plate  415  and is fixed to the pressure chamber substrate  412 , but also a case where the vibrating plate  415  or a part of the vibrating plate  415  is integrally made of the same material as the pressure chamber substrate  412 . 
     The piezoelectric element  400  has the individual electrode  401 , a piezoelectric body  402 , and the common electrode  403 , and these are laminated in the Z1 direction in this order. 
     It should be noted that another layer such as a layer for enhancing adhesion may be appropriately interposed between the layers of the piezoelectric element  400  or between the piezoelectric element  400  and the vibrating plate  415 . Further, a seed layer may be provided between the individual electrode  401  and the piezoelectric body  402 . The seed layer has a function of improving the orientation of the piezoelectric body  402  when forming the piezoelectric body  402 . The seed layer is made of, for example, titanium (Ti) or a composite oxide having a perovskite structure such as Pb(Fe,Ti)O 3 . 
     The individual electrode  401  is an individual electrode mounted on the actuator substrate  420  and arranged apart from each other for each piezoelectric element  400 . The driving signal VOUT is supplied to the individual electrode  401 . The individual electrode  401  has, for example, a first layer made of titanium (Ti), a second layer made of platinum (Pt), and a third layer made of iridium (Ir), and these are laminated in the Z1 direction in this order. The individual electrode  401  is formed by, for example, a known film forming technique such as a sputtering method, and a known processing technique using photolithography, etching, or the like. 
     Further, the configuration of the individual electrode  401  is not limited to the above-described example. For example, either the above-described second layer or third layer may be omitted, or a layer made of iridium may be further provided between the above-described first layer and second layer. Further, instead of the second layer and the third layer, or in addition to the second layer and the third layer, a layer made of an electrode material other than iridium and platinum may be used. Examples of the electrode material include metal materials such as aluminum (Al), nickel (Ni), gold (Au), and copper (Cu). Among these, one of these may be used alone, and two or more types may be used in combination in the form of a laminate or an alloy or the like. 
     The piezoelectric body  402  is arranged between the individual electrode  401  and the common electrode  403 . In the example illustrated in  FIG.  6   , the piezoelectric body  402  is individually provided for each piezoelectric element  400 . Further, the piezoelectric body  402  may be provided in common with the plurality of piezoelectric elements  400 . In this case, the piezoelectric body  402  forms a strip extending in the direction along the Y axis to be continuous over the plurality of piezoelectric elements  400 . 
     The piezoelectric body  402  is made of a piezoelectric material having a perovskite-type crystal structure represented by the general composition formula ABO 3 . Specific examples of the piezoelectric material include lead titanate (PbTiO 3 ), lead zirconate titanate (Pb(Zr,Ti)O 3 ), lead zirconate (PbZrO 3 ), lead lanthanum titanate ((Pb,La),TiO 3 ), lead lanthanum zirconate titanate ((Pb,La) (Zr,Ti)O 3 ), lead niobate zirconate titanate (Pb(Zr,Ti,Nb)O 3 ), and lead magnesium niobate zirconate titanate (Pb(Zr,Ti) (Mg,Nb)O 3 ). Among them, lead zirconate titanate is preferably used as a constituent material of the piezoelectric body  402 . The piezoelectric body  402  may contain a small amount of other elements such as impurities. 
     The piezoelectric body  402  is formed by forming a precursor layer of the piezoelectric body by, for example, a liquid phase method such as a sol-gel method or a metal organic decomposition (MOD) method, and firing and crystallizing the precursor layer. Here, the piezoelectric body  402  may be composed of a single layer, but when it is composed of a plurality of layers, there is an advantage that the characteristics of the piezoelectric body  402  can be easily improved even when the thickness of the piezoelectric body  402  is increased. 
     The common electrode  403  is a band-shaped common electrode extending in the direction along the Y axis to be continuous over the plurality of piezoelectric elements  400 . The offset potential VBS is applied to the common electrode  403 . Here, as will be described later with reference to  FIG.  7   , the common electrode  403  is independent of the piezoelectric element  400  corresponding to the pressure chamber Ca and the piezoelectric element  400  corresponding to the pressure chamber Cb. 
     The common electrode  403  is made of, for example, a metal such as iridium (Ir), titanium (Ti), platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), or copper (Cu), or an alloy containing these metals or a conductive oxide. The common electrode  403  is formed by, for example, a known film forming technique such as a sputtering method, and a known processing technique using photolithography, etching, or the like. In addition, the common electrode  403  may be composed of a plurality of layers. 
       FIG.  7    is a schematic plan view for explaining the piezoelectric element  400  according to the first embodiment. In  FIG.  7   , n nozzles N are illustrated as nozzles N_ 1  to N_n, the pressure chambers Ca corresponding to the nozzles N_ 1  to N_n are illustrated as pressure chambers Ca_ 1  to Ca_n, and the pressure chambers Cb corresponding to the nozzles N_ 1  to N_n are illustrated as pressure chambers Cb_ 1  to Cb_n. n is a natural number of 2 or more, and is not particularly limited, but is, for example, in the range of 200 or more and 600 or less. Here, the nozzles N_ 1  to N_n are arranged in the nozzle array direction DN along the V axis, and form a nozzle array LN. Further, in  FIG.  7   , a plurality of individual electrodes  401 , a plurality of common electrodes  403 , and a plurality of piezoelectric bodies  402  arranged on the actuator substrate  420  are illustrated. 
     As illustrated in  FIG.  7   , the head chip  41   a  has individual electrodes  401 _A 1  to  401 _An, individual electrodes  401 _B 1  to  401 _Bn, piezoelectric bodies  402 _A 1  to  402 _An, piezoelectric bodies  402 _B 1  to  402 _Bn, a first common electrode  403 _A, and a second common electrode  403 _B. 
     The individual electrodes  401 _A 1  to  401 _An are individual electrodes  401  corresponding to the pressure chambers Ca_ 1  to Ca_n, respectively. Similarly, the individual electrodes  401 _B 1  to  401 _Bn are individual electrodes  401  corresponding to the pressure chambers Cb_ 1  to Cb_n, respectively. 
     In the present embodiment, the individual electrodes  401 _A 1  to  401 _An and the individual electrodes  401 _B 1  to  401 _Bn are independent on the actuator substrate  420 . Here, each of the individual electrodes  401 _A 1  to  401 _An has a terminal section  401   a  for coupling with the wiring substrate  430 . Each of the individual electrodes  401 _B 1  to  401 _Bn has a terminal section  401   b  for coupling with the wiring substrate  430 . The terminal sections  401   a  and  401   b  are arranged in the nozzle array direction DN. In the example illustrated in  FIG.  7   , each of the nozzles N_ 1  to N_n is arranged between the corresponding terminal section  401   a  and the terminal section  401   b  in plan view. 
     The piezoelectric bodies  402 _A 1  to  402 _An are piezoelectric bodies  402  corresponding to the pressure chambers Ca_ 1  to Ca_n, respectively. Therefore, the corresponding individual electrodes  401 _A 1  to  401 _An are coupled to the piezoelectric bodies  402 _A 1  to  402 _An. Similarly, the piezoelectric bodies  402 _B 1  to  402 _Bn are piezoelectric bodies  402  corresponding to the pressure chambers Cb_ 1  to Cb_n, respectively. Therefore, the corresponding individual electrodes  401 _B 1  to  401 _Bn are coupled to the piezoelectric bodies  402 _B 1  to  402 _Bn. 
     The first common electrode  403 _A is the common electrode  403  corresponding to the pressure chambers Ca_ 1  to Ca_n. Therefore, the first common electrode  403 _A is commonly coupled to the piezoelectric bodies  402 _A 1  to  402 _An. Here, the piezoelectric bodies  402 _A 1  to  402 _An are located between the individual electrodes  401 _A 1  to  401 _An and the first common electrode  403 _A. Similarly, the second common electrode  403 _B is the common electrode  403  corresponding to the pressure chambers Cb_ 1  to Cb_n. Therefore, the second common electrode  403 _B is commonly coupled to the piezoelectric bodies  402 _B 1  to  402 _Bn. Here, the piezoelectric bodies  402 _B 1  to  402 _Bn are located between the individual electrodes  401 _B 1  to  401 _Bn and the second common electrode  403 _B. 
     The first common electrode  403 _A and the second common electrode  403 _B are independent on the actuator substrate  420 . That is, the first common electrode  403 _A and the second common electrode  403 _B are arranged on the actuator substrate  420  at intervals from each other. 
     Here, the first common electrode  403 _A has two terminal sections  403   a _A for coupling with the wiring substrate  430 . The two terminal sections  403   a _A are arranged at or near both ends of the first common electrode  403 _A in the nozzle array direction DN, and are arranged in the nozzle array direction DN on the same straight line as the plurality of terminal sections  401   a  and the plurality of terminal sections  401   b  described above. 
     Similarly, the second common electrode  403 _B has two terminal sections  403   a _B for coupling with the wiring substrate  430 . The two terminal sections  403   a _B are arranged at or near both ends of the second common electrode  403 _B in the nozzle array direction DN, and are arranged in the nozzle array direction DN on the same straight line as the plurality of terminal sections  401   a  and the plurality of terminal sections  401   b  described above. In the example illustrated in  FIG.  7   , the above-described two terminal sections  403   a _A are arranged between the two terminal sections  403   a _B. 
     The piezoelectric elements  400 _A 1  to  400 _An are configured by the above individual electrodes  401 _A 1  to  401 _An, the piezoelectric bodies  402 _A 1  to  402 _An, and the first common electrode  403 _A. The piezoelectric elements  400 _A 1  to  400 _An are piezoelectric elements  400  corresponding to the pressure chambers Ca_ 1  to Ca_n. Similarly, the piezoelectric elements  400 _B 1  to  400 _Bn are configured by the individual electrodes  401 _B 1  to  401 _Bn, the piezoelectric bodies  402 _B 1  to  402 _Bn, and the second common electrode  403 _B. The piezoelectric elements  400 _B 1  to  400 _Bn are piezoelectric elements  400  corresponding to the pressure chambers Cb_ 1  to Cb_n. 
     Here, of the two nozzles N selected from the nozzles N_ 1  to N_n in any manner, one is the “first nozzle” and the other is the “second nozzle”. Of the pressure chambers Ca and Cb communicating with the first nozzle, one is a “first pressure chamber” and the other is a “second pressure chamber”. Of the pressure chambers Ca and Cb communicating with the second nozzle, one is a “third pressure chamber” and the other is a “fourth pressure chamber”. However, in the following, for convenience of explanation, the nozzle N_ 1  is referred to as a “first nozzle”, the nozzle N_ 2  is referred to as a “second nozzle”, the pressure chamber Ca_ 1  is referred to as a “first pressure chamber”, the pressure chamber Cb_ 1  is referred to as a “second pressure chamber”, the pressure chamber Ca_ 2  is referred to as a “third pressure chamber”, and the pressure chamber Cb_ 2  is referred to as a “fourth pressure chamber”. 
     1-6. Wiring Substrate 
       FIG.  8    is a schematic diagram for explaining the wiring substrate  430  according to the first embodiment. As illustrated in  FIG.  8   , the wiring substrate  430  includes a first common wiring  431 _A 1 , a second common wiring  431 _B 1 , a third common wiring  431 _A 2 , a fourth common wiring  431 _B 2 , two signal lines  432 _A, two signal lines  432 _B, wirings  433   a ,  433   b ,  433   c ,  434   a ,  434   b ,  434   c , and  434   d , and individual wirings  435 _ 1  to  435 _ n.    
     Here, the wiring substrate  430  has a first end E 1  and a second end E 2  facing in the direction opposite to the first end E 1 . The first end E 1  is an end coupled to the relay substrate  440 . The second end E 2  is an end coupled to the actuator substrate  420 . As illustrated in  FIG.  5   , the wiring substrate  430  of the present embodiment is bent such that the first end E 1  and the second end E 2  are respectively along a plane perpendicular to the direction along the Z axis. In the example illustrated in  FIG.  8   , the length of the first end E 1  is shorter than the length of the second end E 2 . Further, the driving circuit  410  is mounted on the wiring substrate  430  as described above. 
     The first common wiring  431 _A 1 , the second common wiring  431 _B 1 , the third common wiring  431 _A 2 , and the fourth common wiring  431 _B 2  are wirings for transmitting the offset potential VBS, respectively. The first common wiring  431 _A 1 , the second common wiring  431 _B 1 , the third common wiring  431 _A 2 , and the fourth common wiring  431 _B 2  are each provided from the first end E 1  to the second end E 2  without passing through the driving circuit  410 . 
     Here, when viewed in the thickness direction of the wiring substrate  430 , that is, in the direction along the W axis, the driving circuit  410  is arranged between the first common wiring  431 _A 1  and the second common wiring  431 _B 1  and the third common wiring  431 _A 2  and the fourth common wiring  431 _B 2 . In the example illustrated in  FIG.  8   , the first common wiring  431 _A 1  and the second common wiring  431 _B 1  are arranged on the left side part of the wiring substrate  430  in  FIG.  8   , and the third common wiring  431 _A 2  and the fourth common wiring  431 _B 2  are arranged on the right side part of the wiring substrate  430  in  FIG.  8   . Further, the first common wiring  431 _A 1  and the third common wiring  431 _A 2  are arranged between the second common wiring  431 _B 1  and the fourth common wiring  431 _B 2 . 
     Each of the first common wiring  431 _A 1  and the third common wiring  431 _A 2  is coupled to the two terminal sections  403   a _A of the actuator substrate  420  described above at the second end E 2 . Specifically, of the two terminal sections  403   a _A, the first common wiring  431 _A 1  is coupled to one of these, and the third common wiring  431 _A 2  is coupled to the other one of these. Therefore, the offset potential VBS, which is a constant potential, is supplied to the first common electrode  403 _A via the first common wiring  431 _A 1  and the third common wiring  431 _A 2 . As described above, each of the first common wiring  431 _A 1  and the third common wiring  431 _A 2  electrically couples the outside of the wiring substrate  430  and the first common electrode  403 _A without going through the driving circuit  410 . 
     On the other hand, each of the second common wiring  431 _B 1  and the fourth common wiring  431 _B 2  is coupled to the two terminal sections  403   a _B of the above-described actuator substrate  420  at the second end E 2 . Specifically, of the two terminal sections  403   a _B, the second common wiring  431 _B 1  is coupled to one of these, and the fourth common wiring  431 _B 2  is coupled to the other one of these. Therefore, the offset potential VBS having the same constant potential as the potential of the first common wiring  431 _A 1  is supplied to the second common electrode  403 _B via the second common wiring  431 _B 1  and the fourth common wiring  431 _B 2 . As described above, the second common wiring  431 _B 1  and the fourth common wiring  431 _B 2  are independent of the first common wiring  431 _A 1  and the third common wiring  431 _A 2 , respectively, and electrically couples the outside of the wiring substrate  430  to the second common electrode  403 _B without passing through the driving circuit  410 . 
     Each of the two signal lines  432 _A is a wiring for transmitting the driving signal COM_A. On the other hand, each of the two signal lines  432 _B is a wiring for transmitting the driving signal COM_B. Each of the signal lines  432 _A and  432 _B extends from the first end E 1  toward the driving circuit  410  and is coupled to the driving circuit  410 . Further, each of the signal lines  432 _A and  432 _B is coupled to the individual wirings  435 _ 1  to  435 _ n  via the driving circuit  410 . As a result, each of the signal lines  432 _A and  432 _B electrically couples the outside of the wiring substrate  430  and the individual wirings  435 _ 1  to  435 _ n  via the driving circuit  410 . 
     Here, the two signal lines  432 _B and the two signal lines  432 _A are arranged between the first common wiring  431 _A 1  and the third common wiring  431 _A 2 . In the example illustrated in  FIG.  8   , the two signal lines  432 _B are arranged between the two signal lines  432 _A. Further, one of the two signal lines  432 _A and one of the two signal lines  432 _B are respectively arranged on the left side part of the wiring substrate  430  in  FIG.  8   , and the other one of the two signal lines  432 _A and the other one of the two signal lines  432 _B are respectively arranged in the right side part of the wiring substrate  430  in  FIG.  8   . 
     The wiring  433   a  is a wiring for transmitting the power supply potential VDD. The wiring  433   b  is a wiring for transmitting the power supply potential VHV. The wiring  433   c  is a wiring for transmitting the ground potential GND. The wiring  434   a  is a wiring for transmitting the clock signal SCK. The wiring  434   b  is a wiring for transmitting the print data signal SI. The wiring  434   c  is a wiring for transmitting the latch signal LAT. The wiring  434   d  is a wiring for transmitting the change signal CH. Each of these wirings extends from the first end E 1  toward the driving circuit  410  and is coupled to the driving circuit  410 . 
     In the example illustrated in  FIG.  8   , the wiring  433   a , the wiring  433   b , the wiring  433   c , the wiring  434   a , the wiring  434   b , the wiring  434   c , and the wiring  434   d  are arranged in this order. Further, the order of arrangement of these wirings is not limited to the example illustrated in  FIG.  8   , and is any order. 
     The individual wirings  435 _ 1  to  435 _ n  are wirings for transmitting the driving signal VOUT. Each of the individual wirings  435 _ 1  to  435 _ n  extends from the second end E 2  toward the driving circuit  410  and is coupled to the driving circuit  410 . 
     Here, the individual wirings  435 _ 1  to  435 _ n  correspond to the above-described nozzles N_ 1  to N_n, respectively, and are arranged in the order of the individual wirings  435 _ 1  to  435 _ n . As described above, the individual wirings  435 _ 1  to  435 _ n  correspond to the individual electrodes  401 _A 1  to  401 _An, respectively. Further, the individual wirings  435 _ 1  to  435 _ n  correspond to the individual electrodes  401 _B 1  to  401 _Bn, respectively. Then, each of the individual wirings  435 _ 1  to  435 _ n  is coupled to the corresponding individual electrode  401  of the actuator substrate  420  described above at the second end E 2 . 
     In the present embodiment, each of the individual wirings  435 _ 1  to  435 _ n  branches in the middle and extends toward the second end E 2 . Therefore, each of the individual wirings  435 _ 1  to  435 _ n  has two parts provided at the second end E 2  by branching. Then, the two parts are coupled to the corresponding terminal sections  401   a  and  401   b . For example, the individual wiring  435 _ 1  is electrically coupled to each of the individual electrodes  401 _A 1  and the individual electrodes  401 _B 1  by branching on the wiring substrate  430 . As a result, a common driving signal VOUT is supplied to the two individual electrodes  401  corresponding to the common nozzle N. 
     Here, the switching element  410   sw  of the driving circuit  410  will be described with reference to  FIG.  9   .  FIG.  9    is a schematic diagram for explaining an operation of the driving circuit  410 . The plurality of switching elements  410   sw  include switching elements  410   swa _ 1  to  410   swa _n and switching elements  410   swb _ 1  to  410   swb _n. The switching elements  410   swa _ 1  to  410   swa _n are switching elements  410   sw  corresponding to each of the individual electrodes  401 _A 1  to  401 _An and each of the individual electrodes  401 _B 1  to  401 _Bn. The switching elements  410   swa _ 1  to  410   swa _n select whether to supply the driving signal COM_A to each piezoelectric element. The switching elements  410   swb _ 1  to  410   swb _n are switching elements  410   sw  corresponding to each of the individual electrodes  401 _A 1  to  401 _An and each of the individual electrodes  401 _B 1  to  401 _Bn. The switching elements  410   swb _ 1  to  410   swb _n select whether to supply the driving signal COM_B to each piezoelectric element  400 . 
     Specifically, the switching element  410   swa _ 1  selects whether to supply the driving signal COM_A to the individual electrodes  401 _A 1  and the individual electrode  401 _B 1 , and the switching element  410   swa _ 2  selects whether to supply the driving signal COM_A to the individual electrodes  401 _A 2  and the individual electrodes  401 _B 2 , the switching element  410   swb _ 1  selects whether to supply the driving signal COM_B to the individual electrodes  401 _A 1  and the individual electrode  401 _B 1 , and the switching element  410   swb _ 2  selects whether to supply the driving signal COM_B to the individual electrodes  401 _A 2  and the individual electrodes  401 _B 2 . 
     That is, the plurality of switching elements  410   sw  are provided corresponding to each of the plurality of nozzles N. In other words, whether or not the driving signal COM_A or the driving signal COM_B is supplied to the two individual electrodes  401  by the common switching element  410   sw  is selected for the two individual electrodes  401  corresponding to the same nozzle N. With this configuration, the number of switching elements  410   sw  can be reduced as compared with the case where separate switching elements  410   sw  are provided corresponding to each of the two individual electrodes  401 , and it is possible to reduce the size of the driving circuit  410  and suppress the heat generation. 
     Here, the driving signal COM_A or the driving signal COM_B is an example of the “driving signal”. 
     Further, among the plurality of switching elements  410   sw , any of the switching element  410   swa _ 1  for selecting whether to supply the driving signal COM_A and the switching element  410   swb _ 1  for selecting whether to supply the driving signal COM_B to the individual electrode  401 _A 1  which is an example of the “first individual electrode” and the individual electrode  401 _B 1  which is an example of the “second individual electrode” corresponding to the nozzle N_ 1  which is an example of the “first nozzle”, is an example of a “first switching element”. 
     Further, among the plurality of switching elements  410   sw , any of the switching element  410   swa _ 2  for selecting whether to supply the driving signal COM_A and the switching element  410   swb _ 2  for selecting whether to supply the driving signal COM_B to the individual electrode  401 _A 2  which is an example of the “third individual electrode” and the individual electrode  401 _B 2  which is an example of the “fourth individual electrode” corresponding to the nozzle N_ 2  which is an example of the “second nozzle”, is an example of a “second switching element”. 
     1-7. Relay Substrate 
       FIG.  10    is a schematic diagram for explaining the relay substrate  440  according to the first embodiment. As illustrated in  FIG.  10   , the relay substrate  440  includes second relay wirings  441 _ 1  and  441 _ 2 , two first relay wirings  442 _A, two first relay wirings  442 _B, and wirings  443   a ,  443   b ,  443   c ,  444   a ,  444   b ,  444   c , and  444   d . In  FIG.  10   , the connector  445 , any one opening portion  447  among the plurality of opening portions  447 , the first end E 1  of the wiring substrate  430  inserted into the opening portion  447 , and the second relay wirings  441 _ 1  and  441 _ 2 , the two first relay wirings  442 _A, the two first relay wirings  442 _B, and the wirings  443   a ,  443   b ,  443   c ,  444   a ,  444   b ,  444   c , and  444   d  corresponding to the wiring substrate  430  are illustrated. In addition, in  FIG.  10   , for the sake of simplification of the drawing, the relative positional relationship of the connector  445  or the opening portion  447 , a coupling section  446 , the second relay wirings  441 _ 1  and  441 _ 2 , the two first relay wirings  442 _A, the two first relay wirings  442 _B, and the wirings  443   a ,  443   b ,  443   c ,  444   a ,  444   b ,  444   c , and  444   d  is different from the actual one. 
     Here, the relay substrate  440  has the connector  445 . The connector  445  is a component for coupling to the wiring member  43  described above. The relay substrate  440  has the above-described restoration circuit  41   b , but is not illustrated in  FIG.  10   . In addition, the restoration circuit  41   b  may be arranged outside the connector  445 . Although not illustrated, the connector  445  of the present embodiment is coupled to the second relay wirings  441 _ 1  and  441 _ 2 , the two first relay wirings  442 _A, the two first relay wirings  442 _B, and the wirings  443   a ,  443   b ,  443   c ,  444   a ,  444   b ,  444   c , and  444   d , corresponding to each of the head chips  41   a _ 1  to  41   a _ 6 . 
     The relay substrate  440  has the coupling section  446  which is a part coupled to a surface of the first end E 1  of the wiring substrate  430  facing the Z2 direction. 
     Each of the second relay wirings  441 _ 1  and  441 _ 2  is a wiring for transmitting the offset potential VBS. Each of the second relay wirings  441 _ 1  and  441 _ 2  is provided from the connector  445  to the coupling section  446 . 
     Here, the second relay wiring  441 _ 1  is coupled to both the first common wiring  431 _A 1  and the second common wiring  431 _B 1  of the wiring substrate  430  described above by the coupling section  446 . On the other hand, the second relay wiring  441 _ 2  is coupled to both the third common wiring  431 _A 2  and the fourth common wiring  431 _B 2  of the wiring substrate  430  described above by the coupling section  446 . 
     Each of the two first relay wirings  442 _A is a signal line for transmitting the driving signal COM_A. On the other hand, each of the two first relay wirings  442 _B is a signal line for transmitting the driving signal COM_B. Each of the first relay wirings  442 _A and  442 _B is provided from the connector  445  to the coupling section  446 . 
     Here, the two first relay wirings  442 _A are coupled to the two signal lines  432 _A of the wiring substrate  430  described above by the coupling section  446 . On the other hand, the two first relay wirings  442 _B are coupled to the two signal lines  432 _B of the wiring substrate  430  described above by the coupling section  446 . 
     The wiring  443   a  is a wiring for transmitting the power supply potential VDD. The wiring  443   b  is a wiring for transmitting the power supply potential VHV. The wiring  443   c  is a wiring for transmitting the ground potential GND. The wiring  444   a  is a wiring for transmitting the clock signal SCK. The wiring  444   b  is a wiring for transmitting the print data signal SI. The wiring  444   c  is a wiring for transmitting the latch signal LAT. The wiring  444   d  is a wiring for transmitting the change signal CH. Each of these wirings is provided from the connector  445  to the coupling section  446 . 
     In the example illustrated in  FIG.  10   , the wiring  443   a , the wiring  443   b , the wiring  443   c , the wiring  444   a , the wiring  444   b , the wiring  444   c , and the wiring  444   d  are arranged in this order. Further, the order of arrangement of these wirings is not limited to the example illustrated in  FIG.  10   , and is any order. 
     1-8. Head Chip Inspection 
       FIG.  11    is a diagram for explaining a performance inspection of the head chip  41   a . The performance inspection of the head chip  41   a  is performed using a measuring instrument  200  and switches  300 _A and  300 _B in a state where the relay substrate  440  is not coupled to the head chip  41   a.    
     The measuring instrument  200  has a positive terminal and a negative terminal, and is an impedance analyzer that measures the impedance therebetween. The inspection signal is, for example, a Sin wave signal. The measuring instrument  200  is not limited to the impedance analyzer, and may be, for example, a current measuring instrument or a capacitance measuring instrument. 
     The positive terminal of the measuring instrument  200  is electrically coupled to the input side of the driving circuit  410 , specifically, at least one of the signal line  432 _A and the signal line  432 _B. On the other hand, the negative terminal of the measuring instrument  200  is electrically coupled to the first common electrode  403 _A by being coupled to the first common wiring  431 _A 1  and the third common wiring  431 _A 2  via the switch  300 _A. Further, the negative terminal of the measuring instrument  200  is electrically coupled to the second common electrode  403 _B by being coupled to the second common wiring  431 _B 1  and the fourth common wiring  431 _B 2  via the switch  300 _B. The measuring instrument  200  outputs an inspection signal as the driving signal COM from the positive terminal. Further, when the performance inspection of the head chip  41   a  is performed, the drive of the driving circuit  410  is controlled by the control device by coupling the wiring  433   a ,  433   b ,  433   c ,  434   a ,  434   b ,  434   c , and  434   d  to the control device (not illustrated). 
     The switch  300 _A switches between a state where the first common electrode  403 _A is electrically coupled to the negative terminal of the measuring instrument  200  and a state where the first common electrode  403 _A is electrically coupled to a constant potential VMB. The switch  300 _B switches between a state where the second common electrode  403 _B is electrically coupled to the negative terminal of the measuring instrument  200  and a state where the second common electrode  403 _B is electrically coupled to the constant potential VMB. The constant potential VMB is not particularly limited, but is, for example, a constant potential within the range of 0 V or more and 35 V or less. 
     The inspection of the piezoelectric elements  400 _A 1  to  400 _An is performed in a state where the switch  300 _A electrically couples the first common electrode  403 _A to the negative terminal of the measuring instrument  200 , and the switch  300 _B electrically couples the second common electrode  403 _B to the constant potential VMB. Here, when inspecting one desired piezoelectric element  400  among the piezoelectric elements  400 _A 1  to  400 _An, the measuring instrument  200  controls the drive of the driving circuit  410  such that the driving signal VOUT which is an inspection signal is input only into the desired one piezoelectric element  400 . Specifically, for example, when inspecting the piezoelectric element  400 _A 1 , the driving circuit  410  supplies the driving signal VOUT only to the individual wiring  435 _ 1  coupled to the piezoelectric element  400 _A 1 . At this time, since the second common electrode  403 _B is electrically coupled to the constant potential VMB by the switch  300 _B, the piezoelectric element  400 _A 1  is arranged between the positive terminal and the negative terminal of the measuring instrument  200  instead of the piezoelectric element  400 _B 1 . Therefore, even when the individual wiring  435 _ 1  is a wiring common to the piezoelectric element  400 _A 1  and the piezoelectric element  400 _B 1 , the impedance of only the piezoelectric element  400 _A 1  can be measured. 
     This is because the first common electrode  403 _A coupled to the piezoelectric elements  400 _A 1  to  400 _An and the second common electrode  403 _B coupled to the piezoelectric elements  400 _B 1  to  400 _Bn are independent and the first common wiring  431 _A 1  and the third common wiring  431 _A 2  coupled to the first common electrode  403 _A and the second common wiring  431 _B 1  and the fourth common wiring  431 _B 2  coupled to the second common electrode  403 _B are independent, and thus the switch  300 _A coupled to the first common electrode  403 _A and the switch  300 _B coupled to the second common electrode  403 _B can be provided separately. 
     On the other hand, the inspection of the piezoelectric elements  400 _B 1  to  400 _Bn is performed in a state where the switch  300 _A electrically couples the first common electrode  403 _A to the constant potential VMB, and the switch  300 _B electrically couples the second common electrode  403 _B to the negative terminal of the measuring instrument  200 . Here, when inspecting one desired piezoelectric element  400  among the piezoelectric elements  400 _B 1  to  400 _Bn, the measuring instrument  200  controls the drive of the driving circuit  410  such that the driving signal VOUT which is an inspection signal is input only into the desired one piezoelectric element  400 . Specifically, for example, when inspecting the piezoelectric element  400 _B 1 , the driving circuit  410  supplies the driving signal VOUT only to the individual wiring  435 _ 1  coupled to the piezoelectric element  400 _B 1 . At this time, since the first common electrode  403 _A is electrically coupled to the constant potential VMB by the switch  300 _A, the piezoelectric element  400 _B 1  is arranged between the positive terminal and the negative terminal of the measuring instrument  200  instead of the piezoelectric element  400 _A 1 . Therefore, even when the individual wiring  435 _ 1  is a wiring common to the piezoelectric element  400 _A 1  and the piezoelectric element  400 _B 1 , the impedance of only the piezoelectric element  400 _B 1  can be measured. 
     As described above, the head chip  41   a  includes the nozzle N_ 1  which is an example of a “first nozzle”, the nozzle N_ 2  which is an example of a “second nozzle”, the pressure chamber Ca_ 1  which is an example of a “first pressure chamber”, the pressure chamber Cb_ 1  which is an example of a “second pressure chamber”, the pressure chamber Ca_ 2  which is an example of a “third pressure chamber”, the pressure chamber Cb_ 2  which is an example of a “fourth pressure chamber”, the piezoelectric body  402 _A 1  which is an example of a “first piezoelectric body”, the piezoelectric body  402 _B 1  which is an example of a “second piezoelectric body”, the piezoelectric body  402 _A 2  which is an example of a “third piezoelectric body”, the piezoelectric body  402 _B 2  which is an example of a “fourth piezoelectric body”, the individual electrode  401 _A 1  which is an example of a “first individual electrode”, the individual electrode  401 _B 1  which is an example of a “second individual electrode”, the individual electrode  401 _A 2  which is an example of a “third individual electrode”, the individual electrode  401 _B 2  which is an example of a “fourth individual electrode”, the first common electrode  403 _A, and the second common electrode  403 _B. 
     Each of the nozzle N_ 1  and the nozzle N_ 2  ejects ink, which is an example of a “liquid”. Each of the pressure chamber Ca_ 1  and the pressure chamber Cb_ 1  communicates with the nozzle N_ 1 . Each of the pressure chamber Ca_ 2  and the pressure chamber Cb_ 2  communicates with the nozzle N_ 2 . The piezoelectric body  402 _A 1  generates pressure in the pressure chamber Ca_ 1 . The piezoelectric body  402 _B 1  generates pressure in the pressure chamber Cb_ 1 . The piezoelectric body  402 _A 2  generates pressure in the pressure chamber Ca_ 2 . The piezoelectric body  402 _B 2  generates pressure in the pressure chamber Cb_ 2 . The individual electrode  401 _A 1  is coupled to the piezoelectric body  402 _A 1 . The individual electrode  401 _B 1  is coupled to the piezoelectric body  402 _B 1 . The individual electrode  401 _A 2  is coupled to the piezoelectric body  402 _A 2 . The individual electrode  401 _B 2  is coupled to the piezoelectric body  402 _B 2 . The first common electrode  403 _A is commonly coupled to the piezoelectric body  402 _A 1  and the piezoelectric body  402 _A 2 . The second common electrode  403 _B is independent of the first common electrode  403 _A and is commonly coupled to the piezoelectric body  402 _B 1  and the piezoelectric body  402 _B 2 . 
     In the above head chip  41   a , since the first common electrode  403 _A and the second common electrode  403 _B are independent of each other, even when a configuration is adopted in which the common driving signal VOUT is supplied to the individual electrodes  401  corresponding to the common nozzle N, the individual electrode  401 _A 1  or the individual electrode  401 _A 2  and the first common electrode  403 _A, and the individual electrode  401 _B 1  or the individual electrode  401 _B 2  and the second common electrode  403 _B can be individually supplied with signals. Therefore, the size of the head chip  41   a  can be reduced, and the performance of the piezoelectric element  400  can be individually inspected for each pressure chamber C. 
     Further, as described above, the head chip  41   a  includes a first common liquid chamber R 1  communicating with the pressure chamber Ca_ 1  and the pressure chamber Ca_ 2 , and a second common liquid chamber R 2  communicating with the pressure chamber Cb_ 1  and the pressure chamber Cb_ 2 . Therefore, ink is supplied to each pressure chamber Ca from the first common liquid chamber R 1  or the second common liquid chamber R 2 , and ink is collected from each pressure chamber Cb to the first common liquid chamber R 1  or the second common liquid chamber R 2 . 
     Here, as described above, the first common liquid chamber R 1  is a flow path for supplying ink to the pressure chamber Ca_ 1  and the pressure chamber Ca_ 2 . The second common liquid chamber R 2  is a flow path for collecting ink from the pressure chamber Cb_ 1  and the pressure chamber Cb_ 2 . Therefore, it is possible to realize an ink circulation configuration in which ink is supplied from the first common liquid chamber R 1  to each pressure chamber Ca and the ink from each pressure chamber Cb is collected to the second common liquid chamber R 2 . 
     Further, as described above, the head chip  41   a  includes the pressure chamber substrate  412  having the pressure chamber Ca_ 1 , the pressure chamber Cb_ 1 , the pressure chamber Ca_ 2 , and the pressure chamber Cb_ 2 , and the vibrating plate  415  laminated on the pressure chamber substrate  412 . Then, the piezoelectric body  402 _A 1  is located between the individual electrode  401 _A 1  and the first common electrode  403 _A. The piezoelectric body  402 _B 1  is located between the individual electrode  401 _B 1  and the second common electrode  403 _B. The piezoelectric body  402 _A 2  is located between the individual electrode  401 _A 2  and the first common electrode  403 _A. The piezoelectric body  402 _B 2  is located between the individual electrode  401 _B 2  and the second common electrode  403 _B. With such an arrangement of electrodes, the performance inspection of the head chip  41   a  can be performed for each pressure chamber C. 
     Furthermore, as described above, the head chip  41   a  includes the nozzle array LN composed of the plurality of nozzles N arranged in the nozzle array direction DN. In addition, the nozzle N_ 1  and the nozzle N_ 2  are arranged in the nozzle array direction DN, and form a part of the nozzle array LN. Therefore, the nozzle N_ 1  is arranged between the pressure chamber Ca_ 1  and the pressure chamber Cb_ 1  and the nozzle N_ 2  is arranged between the pressure chamber Ca_ 2  and the pressure chamber Cb_ 2  when viewed in the ejection direction of ink from the nozzle N_ 1  or the nozzle N_ 2 . 
     Further, as described above, the pressure chamber Ca_ 1  and the pressure chamber Cb_ 1  are arranged in the direction intersecting the nozzle array direction DN. The pressure chamber Ca_ 2  and the pressure chamber Cb_ 2  are arranged in the direction intersecting the nozzle array direction DN. The pressure chamber Ca_ 1  and the pressure chamber Ca_ 2  are arranged in the nozzle array direction DN. The pressure chamber Cb_ 1  and the pressure chamber Cb_ 2  are aligned in the nozzle array direction DN. Then, the nozzle N_ 1  is arranged between the pressure chamber Ca_ 1  and the pressure chamber Cb_ 1  when viewed in the ejection direction of ink from the nozzle N_ 1  or the nozzle N_ 2 . The nozzle N_ 2  is arranged between the pressure chamber Ca_ 2  and the pressure chamber Cb_ 2  when viewed in the ejection direction of ink from the nozzle N_ 1  or the nozzle N_ 2 . Therefore, it is possible to individually apply a voltage between the individual electrode  401 _A 1  or the individual electrode  401 _A 2  and the first common electrode  403 _A, and between the individual electrode  401 _B 1  or the individual electrode  401 _B 2  and the second common electrode  403 _B. 
     Furthermore, as described above, the head chip  41   a  includes the wiring substrate  430  that mounts the driving circuit  410  that drives the piezoelectric body  402 _A 1 , the piezoelectric body  402 _B 1 , the piezoelectric body  402 _A 2 , and the piezoelectric body  402 _B 2 . In addition, the wiring substrate  430  includes the individual wiring  435 _ 1  which is an example of a “first individual wiring”, the individual wiring  435 _ 2  which is an example of a “second individual wiring”, the signal lines  432 _A and  432 _B, the first common wiring  431 _A 1 , and the second common wiring  431 _B 1 . The signal lines  432 _A and  432 _B electrically couple the outside of the wiring substrate  430  to the individual wiring  435 _ 1  and the individual wiring  435 _ 2  via the driving circuit  410 . The individual wiring  435 _ 1  electrically couples the driving circuit  410  to the individual electrodes  401 _A 1  and the individual electrodes  401 _B 1 . Therefore, a common driving signal can be supplied to the individual electrode  401 _A 1  and the individual electrode  401 _B 1  by using the individual wiring  435 _ 1 . The individual wiring  435 _ 2  electrically couples the driving circuit  410  to the individual electrodes  401 _A 2  and the individual electrodes  401 _B 2 . Therefore, a common driving signal can be supplied to the individual electrodes  401 _A 2  and the individual electrodes  401 _B 2  by using the individual wiring  435 _ 2 . 
     The first common wiring  431 _A 1  electrically couples the outside of the wiring substrate  430  and the first common electrode  403 _A without going through the driving circuit  410 . The second common wiring  431 _B 1  is independent of the first common wiring  431 _A 1  and electrically couples the outside of the wiring substrate  430  and the second common electrode  403 _B without going through the driving circuit  410 . Therefore, a constant potential can be supplied from the outside of the wiring substrate  430  to the first common electrode  403 _A by using the first common wiring  431 _A 1 , and a constant potential can be supplied to the second common wiring  403 _B from the outside of the wiring substrate  430  by using the second common electrode  431 _B 1 . 
     Further, as described above, the head chip  41   a  includes the actuator substrate  420 . The actuator substrate  420  has the pressure chamber Ca_ 1 , the pressure chamber Cb_ 1 , the pressure chamber Ca_ 2 , and the pressure chamber Cb_ 2 , and the individual electrode  401 _A 1 , the individual electrode  401 _B 1 , the individual electrode  401 _A 2 , and the individual electrode  401 _B 2  are mounted thereon. The individual wiring  435 _ 1  is electrically coupled to each of the individual electrodes  401 _A 1  and the individual electrodes  401 _B 1  by branching on the wiring substrate  430 . The individual wiring  435 _ 2  is electrically coupled to each of the individual electrodes  401 _A 2  and the individual electrodes  401 _B 2  by branching on the wiring substrate  430 . Therefore, it is possible to realize the wiring substrate  430  that can be used for the actuator substrate  420  having a configuration in which individual electrodes are independent for each pressure chamber C. Unlike the wiring substrate  430 , such an actuator substrate  420  is independent without branching individual wiring, and when each of the individual wirings is coupled to the wiring substrate having a configuration corresponding to each of the individual electrodes, it is possible to realize a head chip that separately drives the two piezoelectric elements  400  corresponding to the same nozzle N. 
     Furthermore, as described above, the first common wiring  431 _A 1  supplies a constant potential to the first common electrode  403 _A. The second common wiring  431 _B 1  supplies a constant potential having the same potential as the first common wiring  431 _A 1  to the second common electrode  403 _B. Therefore, each piezoelectric body  402  can be driven in the same manner as when the first common electrode  403 _A and the second common electrode  403 _B are shared. 
     Further, as described above, the driving signal COM_A and the driving signal COM_B for driving the piezoelectric body  402 _A 1 , the piezoelectric body  402 _B 1 , the piezoelectric body  402 _A 2 , and the piezoelectric body  402 _B 2  are supplied to the signal line  432 _A and the signal line  432 _B, respectively. The driving circuit  410  has the plurality of switching elements  410   sw  for selecting whether to supply the driving signal COM_A to the individual electrodes  401 _A 1  and the individual electrodes  401 _B 1 , and the plurality of switching elements  410   sw  for selecting whether to supply the driving signal COM_A to the individual electrodes  401 _A 2  and the individual electrodes  401 _B 2 . Further, the driving circuit  410  has the plurality of switching elements  410   sw  for selecting whether to supply the driving signal COM_B to the individual electrodes  401 _A 1  and the individual electrodes  401 _B 1 , and the plurality of switching elements  410   sw  for selecting whether to supply the driving signal COM_B to the individual electrodes  401 _A 2  and the individual electrodes  401 _B 2 . Therefore, the number of switching elements  410   sw  can be reduced as compared with the configuration in which separate switching elements  410   sw  are provided for the plurality of individual electrodes  401  corresponding to the same nozzle N. As a result, the size of the driving circuit  410  can be reduced. 
     Furthermore, as described above, the wiring substrate  430  has the third common wiring  431 _A 2  and the fourth common wiring  431 _B 2 . The third common wiring  431 _A 2  is independent of the first common wiring  431 _A 1  and the second common wiring  431 _B 1  and electrically couples the outside of the wiring substrate  430  to the first common electrode  403 _A without going through the driving circuit  410 . The fourth common wiring  431 _B 2  is independent of the first common wiring  431 _A 1 , the second common wiring  431 _B 1 , and the third common wiring  431 _A 2 , and electrically couples the outside of the wiring substrate  430  and the second common electrode  403 _B without going through the driving circuit  410 . Then, the driving circuit  410  is arranged between the first common wiring  431 _A 1  and the second common wiring  431 _B 1  and the third common wiring  431 _A 2  and the fourth common wiring  431 _B 2  in the thickness direction of the wiring substrate  430 . Therefore, a constant potential for the common electrode  403  can be supplied to the vicinity of both ends of the actuator substrate  420  in the longitudinal direction. As a result, it is possible to reduce the potential drop of the common electrode  403  due to the different positions in the nozzle array direction DN. 
     Further, as described above, the liquid ejecting head  41  has at least one head chip  41   a  and the relay substrate  440 . The relay substrate  440  has the first relay wirings  442 _A and  442 _B that are electrically coupled in common to the signal lines  432 _A and  432 _B, and the second relay wiring  441 _ 1  electrically coupled to the first common wiring  431 _A 1  and the second common wiring  431 _B 1 . Therefore, since the first common wiring  431 _A 1  and the second common wiring  431 _B 1  are shared by the second relay wiring  441 _ 1 , it is possible to simplify the wiring routing. Further, the thickness of the second relay wiring  441 _ 1  can be increased, and as a result, it is possible to prevent a decrease in the potential for the first common wiring  431 _A 1  and the second common wiring  431 _B 1 . 
     In the present embodiment, as described above, the wiring substrates  430  of each of the plurality of head chips  41   a  are coupled to the relay substrate  440 . When one liquid ejecting head  41  includes the plurality of head chips  41   a  as described above, when the performance inspection cannot be performed for each head chip  41   a , the yield at the time of manufacturing the liquid ejecting head  41  is poor. Therefore, in this case, it is particularly useful to be able to inspect the performance of each head chip  41   a  in order to improve the yield. 
     2. Second Embodiment 
     Hereinafter, a second embodiment of the present disclosure will be described. Hereinafter, the differences from the first embodiment will be mainly described. 
       FIG.  12    is a schematic plan view for explaining the piezoelectric element  400  in the second embodiment. In the present embodiment, the individual electrodes  401 _A 1  to  401 _An and the individual electrodes  401 _B 1  to  401 _Bn are electrically coupled to each other on the actuator substrate  420  for each nozzle N. Here, the individual electrodes  401 _A 1  to  401 _An and the individual electrodes  401 _B 1  to  401 _Bn have a terminal section  401   c  for coupling to the wiring substrate  430  for each nozzle N. The terminal sections  401   c  are arranged in the nozzle array direction DN. In the example illustrated in  FIG.  12   , each of the nozzles N_ 1  to N_n overlaps the corresponding terminal section  401   c  in plan view. 
       FIG.  13    is a schematic diagram for explaining the wiring substrate  430  according to the second embodiment. In the present embodiment, each of the individual wirings  435 _ 1  to  435 _ n  extends toward the second end E 2  without branching. Then, each of the individual wirings  435 _ 1  to  435 _ n  is coupled to the corresponding terminal section  401   c . As a result, a common driving signal VOUT is supplied to the two individual electrodes  401  corresponding to the common nozzle N. 
     Also in the above second embodiment, the size of the head chip  41   a  can be reduced and each pressure chamber C can be individually inspected. In the present embodiment, as described above, the individual electrodes  401 _A 1  and the individual electrodes  401 _B 1  are electrically coupled to each other by the actuator substrate  420 . Therefore, the number of terminals of the wiring substrate  430  can be reduced. 
     Further, as described above, one end of the individual wiring  435 _ 1  is a terminal common to the individual electrode  401 _A 1  and the individual electrode  401 _B 1 , and one end of the individual wiring  435 _ 2  is a terminal common to the individual electrode  401 _A 2  and the individual electrode  401 _B 2 . Therefore, the number of terminals of the wiring substrate  430  can be reduced. 
     3. Third Embodiment 
     Hereinafter, a third embodiment of the present disclosure will be described. Hereinafter, the differences from the first embodiment will be mainly described. 
       FIG.  14    is a schematic plan view for explaining the piezoelectric element  400  in the third embodiment. The present embodiment is the same as the above-described second embodiment except that four pressure chambers C communicate with one nozzle N. Therefore, the number of the piezoelectric elements  400  corresponding to the pressure chamber Ca and the number of the piezoelectric elements  400  corresponding to the pressure chamber Cb are n, respectively, whereas the number of the nozzles N constituting the nozzle array LN is n/2. 
     In the present embodiment, ink is discharged from the nozzle N by simultaneously driving the piezoelectric elements  400  corresponding to the four pressure chambers C communicating with the common nozzle N. 
     Here, of the two nozzles N selected from the nozzles N_ 1  to N_n/2 in any manner, one is the “first nozzle” and the other one is the “second nozzle”. Of the two pressure chambers Ca and the two pressure chambers Cb communicating with the first nozzle, any one of the pressure chambers Ca is an example of a “first pressure chamber”, and any one of the pressure chambers Cb is an example of a “second pressure chamber”. Of the two pressure chambers Ca and the two pressure chambers Cb communicating with the second nozzle, any one of the pressure chambers Ca is an example of a “third pressure chamber”, and any one of the pressure chambers Cb is an example of a “fourth pressure chamber”. Further, the individual electrode  401  corresponding to the “first pressure chamber” is the “first individual electrode”, the individual electrode  401  corresponding to the “second pressure chamber” is the “second individual electrode”, the individual electrode  401  corresponding to the “third pressure chamber” is the “third individual electrode”, and the individual electrode  401  corresponding to the “fourth pressure chamber” is the “fourth individual electrode”. 
     Also in the above third embodiment, the size of the head chip  41   a  can be reduced or heat generation can be suppressed, and each pressure chamber C can be individually inspected. 
     4-1. Modification Example 1 
     In each of the above-described aspects, a configuration using two types of driving signals COM_A and COM_B is exemplified, but the configuration is not limited thereto, and the number of types of driving signals input into the driving circuit  410  may be one or three or more. Further, the number of pulses included in the driving signal COM may be one or three or more. 
     4-2. Modification Example 2 
     In each of the above-described aspects, a configuration in which the plurality of head chips  41   a  are mounted on the liquid ejecting head  41  is exemplified, but the configuration is not limited thereto, and the number of the plurality of head chips  41   a _mounted on the liquid ejecting head  41  may be any number and may be one. 
     4-3. Modification Example 3 
     In each of the above-described aspects, a configuration in which two or four pressure chambers C correspond to one nozzle N is exemplified, but the configuration is not limited to the configuration, and the number of pressure chambers C corresponding to one nozzle N may be, for example, 6 or 8 or more. 
     4. Modification Example 
     Each of the aspects in the above-described examples can be modified in various manners. Specific modifications which may be applied to each of the above-described aspects will be described below. The aspects selected in any manner from the following examples can be appropriately combined with each other within a range of not being inconsistent with each other. 
     4-4. Modification Example 4 
     In each of the above-described aspects, a configuration in which the ink used for the liquid ejecting head is circulated by a circulation mechanism is exemplified, but the configuration is not limited to this configuration, and a configuration without such a circulation mechanism may be used. 
     4-5. Modification Example 5 
     In each of the above-described aspects, the line type liquid ejecting apparatus  100  in which the plurality of nozzles N are distributed over the entire width of the medium M is exemplified, but the present disclosure is also applied to a serial type liquid ejecting apparatus in which a transport body equipped with the liquid ejecting head  41  is reciprocated in the width direction of the medium M. 
     4-6. Modification Example 6 
     The liquid ejecting apparatus  100  exemplified in each of the above-described aspects may be adopted in various devices such as a facsimile machine and a copier, in addition to a device dedicated to printing, and the application of the present disclosure is not particularly limited. However, the application of the liquid ejecting apparatus is not limited to printing. For example, a liquid ejecting apparatus that ejects a solution of a coloring material is used as a manufacturing device for forming a color filter of a display device such as a liquid crystal display panel. Further, the liquid ejecting apparatus that emits a solution of a conductive material is used as a manufacturing device for forming wiring or electrodes on the wiring substrate. Further, a liquid ejecting apparatus that emits a solution of an organic substance related to a living body is used, for example, as a manufacturing device for manufacturing a biochip. 
     4-7. Modification Example 7 
     In each of the above aspects, the drive module  42  constitutes the head unit  40  together with the liquid ejecting head  41 , but the present disclosure is not limited to this configuration. For example, the drive module  42  may be a part of the control unit  20 .