Liquid ejection head and liquid ejection apparatus

Abstract

The invention provides a liquid ejecting head and a liquid ejecting apparatus, which can eliminate point offset and concentration unevenness caused by a driving type. According to one embodiment, a liquid ejection head includes a plurality of pressure chambers, an actuator, a plurality of individual electrodes, a nozzle plate, a plurality of switching elements, and a plurality of resistors. The actuator has a plurality of piezoelectric bodies that vary the volume of the pressure chamber in accordance with a drive signal. A plurality of individual electrodes are provided on the plurality of piezoelectric bodies, respectively. The nozzle plate is provided with a plurality of nozzles, and the plurality of nozzles are respectively communicated with the plurality of pressure chambers. The switching element selectively connects a driving signal of the piezoelectric body. A switching element is electrically connected to the plurality of individual electrodes. A resistor electrically connects the individual electrodes of the piezoelectric bodies adjacent to each other.

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid ejection head and a liquid ejection device. Background Art

[0002] In the past, there is a known push-mode piezoelectric inkjet head that ejects ink as liquid. The inkjet head has a plurality of nozzles, a plurality of pressure chambers, a vibration plate, and an actuator, and the actuator is formed by alternating a plurality of piezoelectric driving piezoelectric columns and a plurality of supporting piezoelectric columns electrically connected to a driving circuit. The actuator displaces the vibration plate by extending and contracting the driving piezoelectric columns, thereby making the volume of the pressure chamber variable and ejecting the ink from the nozzle.

[0003] However, if adjacent nozzles are driven simultaneously, the pillars are deformed by the reaction force of the actuator's driving force, resulting in a pressure drop compared to the case of driving a single nozzle, and the ink ejection speed and volume are reduced. If the ink ejection speed and volume are reduced, dot shift and concentration unevenness may occur depending on the driving type. Summary of the invention

[0004] Technical problem to be solved by the invention

[0005] An object of the present invention is to provide a liquid ejection head and a liquid ejection device capable of eliminating dot deviation and concentration unevenness caused by a driving type.

[0006] Solutions for solving technical problems

[0007] The liquid ejection head of the embodiment comprises a plurality of pressure chambers, an actuator, a plurality of individual electrodes, a nozzle plate, a plurality of switching elements, and a plurality of resistors. The actuator comprises a plurality of piezoelectric bodies, and the plurality of piezoelectric bodies make the volume of the pressure chamber variable according to a driving signal. The plurality of individual electrodes are respectively arranged on the plurality of piezoelectric bodies. The nozzle plate is formed with a plurality of nozzles, and the plurality of nozzles are respectively connected to the plurality of pressure chambers. The switching element selectively connects the driving signal of the piezoelectric body. The switching element is electrically connected to the plurality of individual electrodes. The resistor electrically connects the individual electrodes of the piezoelectric bodies adjacent to each other.

[0008] A liquid ejection device according to an embodiment includes the above-mentioned liquid ejection head. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a cross-sectional view showing the structure of the liquid ejection head according to the embodiment in a partially omitted manner.

[0010] Figure 2 It is a cross-sectional view showing the structure of the liquid ejection head according to the embodiment in a partially omitted manner.

[0011] Figure 3It is a cross-sectional view showing the structure of the liquid ejection head according to the embodiment in a partially omitted manner.

[0012] Figure 4 It is an explanatory diagram schematically showing the structure of a resistor of a liquid ejection head according to an embodiment.

[0013] Figure 5 This is an explanatory diagram showing a configuration of a driving circuit of a liquid ejecting head according to an embodiment in a partially omitted manner.

[0014] Figure 6 It is an explanatory diagram showing a configuration of a driving circuit in an example of driving a liquid ejecting head according to an embodiment.

[0015] Figure 7 This is an explanatory diagram showing an example of voltage in an example of driving the liquid ejection head according to the embodiment.

[0016] Figure 8 It is an explanatory diagram schematically showing the structure of the liquid ejecting device according to the embodiment.

[0017] Fig. 9 It is an explanatory diagram showing a configuration of a driving circuit in an example of driving a liquid ejecting head according to another embodiment.

[0018] Fig.10 This is an explanatory diagram showing an example of voltage in an example of driving a liquid ejection head according to another embodiment.

[0019] Description of Reference Numerals

[0020] 1: Liquid ejection head (inkjet head); 10: Base; 20: Actuator; 21: Driving piezoelectric column (piezoelectric body); 22: Support piezoelectric column (piezoelectric body); 23: Groove; 26: Connecting part; 30: Vibrating plate; 31: Pressure chamber; 32: Individual flow path; 33: Through hole; 40: Flow path component; 41: Peripheral wall; 43: Partition wall; 50: Nozzle plate; 51: Nozzle; 60: Frame; 61: Common chamber; 70: Driving circuit; 73: Printed wiring board; 731: Head control circuit; 81: Driving signal source; 82: Standby voltage source; 83: Switching element; 84: First resistor; 85: Second resistor; 851: Resistor; 852: Trimming part; 853: Slit ;100: liquid ejection device (inkjet recording device);111: housing;112: medium supply unit;113: image forming unit;114: medium discharge unit;115: conveying device;116: control unit;117: support unit;118: conveyor belt;119: support plate;120: belt roller;121: guide plate pair;122: conveying roller;130: head unit;132: ink tank;133: connecting flow path;134: supply pump;211: piezoelectric layer;212: virtual layer;221: first internal electrode;222: second internal electrode;223: first external electrode (individual electrode);224: second external electrode (common electrode);1161: control circuit. DETAILED DESCRIPTION

[0021] The following reference Figures 1 to 8 An inkjet head 1 as a liquid ejecting head and an inkjet recording apparatus 100 as a liquid ejecting device according to the embodiment will be described. Figures 1 to 3 It is a cross-sectional view schematically showing the structure of the inkjet head 1 . Figure 1 is a cross-sectional view showing the structure of the inkjet head 1 in a partially omitted manner, Figure 2 It is partially omitted. Figure 1 The cross-sectional views showing the structure of the inkjet head 1 from different directions are as follows: Figure 3 So with Figure 2 Various driving examples show cross-sectional views of the structure of the inkjet head 1 . Figure 4 It is an explanatory diagram schematically showing the structure of the inkjet head 1 , that is, the structure of the second resistor 85 . Figure 5 1 is an explanatory diagram showing the structure of the inkjet head driving circuit 70 in a partially omitted manner. Figure 6 It is an explanatory diagram showing the configuration of the driving circuit 70 in an example of driving the inkjet head 1 . Figure 7 This is an explanatory diagram showing an example of voltage in an example of driving the inkjet head 1 . Figure 8 The diagram schematically shows the structure of an inkjet recording apparatus 100 using the inkjet head 1. In each diagram, the structure is appropriately enlarged, reduced, or omitted for convenience of explanation.

[0022] like Figures 1 to 4 As shown, the inkjet head 1 includes a base 10, a pair of actuators 20 having a plurality of piezoelectric posts 21 and 22, a vibration plate 30, a flow path member 40, a nozzle plate 50 having a plurality of nozzles 51, a frame portion 60 as a structural portion, and a drive circuit 70. The inkjet head 1 forms a plurality of pressure chambers 31 by means of the vibration plate 30, the flow path member 40, and the nozzle plate 50, and the piezoelectric posts 21 of the actuator 20 vibrate the vibration plate 30, thereby ejecting ink as liquid in the pressure chambers 31 from the nozzles 51.

[0023] The inkjet head 1 includes one actuator 20 or two actuators 20. The two actuators 20 are arranged, for example, in a direction perpendicular to the arrangement direction of the plurality of piezoelectric columns 21 and 22 as piezoelectric bodies.

[0024] The base 10 is a supporting member that supports the actuator 20. The base 10 is formed in a block shape or a plate shape, for example.

[0025] The actuator 20 is fixed to the base 10. The actuator 20 has a plurality of piezoelectric columns 21 and 22 as piezoelectric materials (piezoelectric elements). The actuator 20 forms a piezoelectric column array by the plurality of piezoelectric columns 21 and 22. The actuator 20 has a plurality of driving piezoelectric columns (piezoelectric bodies) 21, a plurality of supporting piezoelectric columns (piezoelectric bodies) 22 alternately arranged along the column direction of the piezoelectric column array with the plurality of driving piezoelectric columns 21, and a connecting portion 26 connecting these plurality of piezoelectric columns 21 and 22 as a whole on the side of the base 10. The actuator 20 is formed by a stacked piezoelectric component. Here, the stacked piezoelectric component is formed by stacking a plurality of piezoelectric layers 211 and a plurality of internal electrodes 221 and 222. In addition, the actuator 20 has external electrodes 223 and 224 formed on the plurality of driving piezoelectric columns 21.

[0026] For example, the stacked piezoelectric component constituting the actuator 20 is formed by stacking and sintering a sheet-shaped piezoelectric material having an electrode layer formed thereon as the internal electrodes 221 and 222. In addition, with respect to the actuator 20, the stacked piezoelectric component previously bonded to the base 10 is cut from the end surface on the side opposite to the base 10 side to form a groove 23, thereby forming a plurality of piezoelectric columns 21 and 22 formed in a rectangular columnar shape at predetermined intervals. Then, external electrodes 223, 224, etc. are provided in the plurality of columnar piezoelectric materials (piezoelectric elements) formed. Through these processes, a plurality of driving piezoelectric columns 21 and a plurality of supporting piezoelectric columns 22 that are alternately arranged in the connecting portion 26 and have external electrodes 223 and 224 formed on the outer surface are formed.

[0027] A plurality of driving piezoelectric posts 21 and a plurality of supporting piezoelectric posts 22 are arranged at predetermined intervals along the long side direction of the actuator 20. The vibration direction of the driving piezoelectric posts 21 and the supporting piezoelectric posts 22 is the stacking direction of the plurality of piezoelectric layers 211. The driving piezoelectric posts 21 are driven by applying a voltage and are actuators that vibrate the vibration plate 30. The supporting piezoelectric posts 22 support the vibration plate 30 and are non-driving piezoelectric posts that limit the vibration of the vibration plate 30 by the flow path component 40 even if a voltage is applied.

[0028] As an example, a plurality of driving piezoelectric columns 21 and a plurality of supporting piezoelectric columns 22 are all formed into rectangular columns having the same outer shape. In addition to the connecting portion 26, the stacked piezoelectric component is divided into a plurality of grooves 23 of a predetermined depth formed in the actuator 20 (stacked piezoelectric component), thereby forming a plurality of driving piezoelectric columns 21 and a plurality of supporting piezoelectric columns 22. For example, the plurality of grooves 23 formed in the actuator 20 are formed to have the same width and the same interval. Thus, the plurality of driving piezoelectric columns 21 and the plurality of supporting piezoelectric columns 22 that are alternately arranged are arranged in one direction at the same interval. For example, the plurality of driving piezoelectric columns 21 and the plurality of supporting piezoelectric columns 22 are respectively formed into rectangular columns.

[0029] The plurality of driving piezoelectric posts 21 are arranged at positions facing the plurality of pressure chambers 31 formed by the vibration plate 30, the flow path member 40, and the nozzle plate 50, respectively, across the vibration plate 30 in the stacking direction of the plurality of piezoelectric layers 211. As an example, regarding the driving piezoelectric posts 21 and the pressure chambers 31, the center position of the driving piezoelectric posts 21 in the column direction of the piezoelectric post array and the center position of the pressure chambers 31 in the column direction of the piezoelectric post array are arranged in the stacking direction of the plurality of piezoelectric layers 211 across the vibration plate 30.

[0030] The plurality of supporting piezoelectric posts 22 are arranged at positions facing the plurality of partition wall portions 43 described later of the flow path member 40 respectively via the vibration plate 30 in the stacking direction of the plurality of piezoelectric layers 211. As an example, the center position of the supporting piezoelectric posts 22 in the column direction of the piezoelectric post array and the center position of the partition wall portion 43 in the same direction as the column direction of the piezoelectric post array are arranged along the stacking direction of the plurality of piezoelectric layers 211.

[0031] The plurality of driving piezoelectric posts 21 and the plurality of supporting piezoelectric posts 22 include a plurality of piezoelectric layers 211 stacked in the Z direction, and internal electrodes 221 and 222 formed on the main surface of each piezoelectric layer 211. It should be noted that, as an example, the driving piezoelectric posts 21 and the supporting piezoelectric posts 22 have the same stacked structure. Furthermore, the driving piezoelectric posts 21 each include external electrodes 223 and 224 formed on the surface as surface wiring.

[0032] The piezoelectric layer 211 is formed into a thin plate by, for example, a piezoelectric ceramic material such as PZT (lead zirconate titanate) or lead-free KNN (sodium potassium niobate). The thickness direction of the piezoelectric layer 211 is along the stacking direction of the stacked piezoelectric layers 211. The stacked piezoelectric layers 211 are bonded to each other. In the present embodiment, the thickness direction and stacking direction of the piezoelectric layer 211 are along the vibration direction of the piezoelectric column 21 when it is driven.

[0033] It should be noted that the stacked piezoelectric component forming the driving piezoelectric column 21 and the supporting piezoelectric column 22 may also have a dummy layer 212 at one or both of the ends on the base 10 side and the nozzle plate 50 side. The dummy layer 212 is made of the same material as the piezoelectric layer 211, and has an electrode only on one side. Since no electric field is applied, it does not deform. For example, the dummy layer 212 does not function as a piezoelectric body, but becomes a base for fixing the actuator 20 to the base 10, or becomes a grinding allowance for grinding for accuracy during or after assembly.

[0034] The internal electrodes 221 and 222 are conductive films formed of a sinterable conductive material such as silver or palladium in a predetermined shape. The internal electrodes 221 and 222 are formed in a predetermined region of the main surface of each piezoelectric layer 211. The internal electrodes 221 and 222 have different polarities.

[0035] For example, in the width direction orthogonal to both the row direction and the vibration direction of the arrangement direction of the plurality of driving piezoelectric columns 21 and the plurality of supporting piezoelectric columns 22, an internal electrode 221 is formed in a region that reaches one end of the piezoelectric layer 211 but does not reach the other end of the piezoelectric layer 211. Hereinafter, the internal electrode 221 is sometimes described as a first internal electrode 221.

[0036] In the width direction orthogonal to both the column direction and the vibration direction, another internal electrode 222 is formed in a region that does not reach one end of the piezoelectric layer 211 but reaches the other end of the piezoelectric layer 211. Hereinafter, the internal electrode 222 may also be described as a second internal electrode 222.

[0037] The external electrodes 223 and 224 are respectively formed on the surfaces of the plurality of driving piezoelectric columns 21, and are configured in a manner that concentrates the ends of the internal electrodes 221 and 222. For example, the external electrode 223 is formed on an end face of the piezoelectric layer 211 in the width direction. Hereinafter, the external electrode 223 is sometimes described as the first external electrode 223. The external electrode 224 is formed on the other end face of the piezoelectric layer 211 in the width direction. In addition, the external electrode 224 may also extend to the end face of the piezoelectric layer 211 on the base 10 side. Hereinafter, the external electrode 224 is sometimes described as the second external electrode 224.

[0038] The external electrodes 223 and 224 are formed of Ni, Cr, Au, etc. by known methods such as electroplating and sputtering. The external electrodes 223 and 224 are different in polarity. The first external electrode 223 and the second external electrode 224 are formed on different sides of the plurality of driving piezoelectric columns 21, respectively.

[0039] In this embodiment, as an example, the first external electrode 223 is a separate electrode, and the second external electrode 224 is a common electrode. Figure 4 As shown, the first external electrodes 223 are respectively formed on the plurality of driving piezoelectric columns 21. One second external electrode 224 is provided and connects all of the plurality of driving piezoelectric columns 21. The plurality of first external electrodes 223 and the single second external electrode 224 are configured independently of each other.

[0040] The first external electrode 223 is connected to the plurality of first internal electrodes 221 formed on one driving piezoelectric column 21. For example, the single second external electrode 224 is a ground electrode. The single second external electrode 224 is connected to the plurality of second internal electrodes 222 formed on the plurality of driving piezoelectric columns 21 provided.

[0041] The plurality of first external electrodes 223 and the single second external electrode 224 are connected to an FPC 71 as a flexible substrate described later of the drive circuit 70. For example, the single second external electrode 224 is provided on the outer surfaces of the pair of actuators 20 facing each other.

[0042] For example, each of the external electrodes 223 and 224 is connected to the control unit 116 as a driving unit via the driving circuit 70 , and a signal capable of driving and controlling each of the piezoelectric columns 21 is inputted under the control of the control circuit 1161 .

[0043] When a driving signal is input to the internal electrodes 221 and 222 via the external electrodes 223 and 224 and an electric field is applied, each piezoelectric column 21 is displaced in the direction d33 . The vibration direction of each piezoelectric column 21 is along the stacking direction of the piezoelectric layer 211 .

[0044] To explain a specific example, the piezoelectric column 21 is driven to apply a voltage to the internal electrodes 221 and 222 via the external electrodes 223 and 224, thereby vibrating longitudinally along the stacking direction of the piezoelectric layer 211. The longitudinal vibration referred to here is, for example, "vibration in the thickness direction defined by the piezoelectric constant d33". The piezoelectric column 21 is driven to vibrate longitudinally, so that the vibration plate 30 is displaced in the stacking direction of the piezoelectric layer 211, and the pressure chamber 31 is deformed.

[0045] As an example, each piezoelectric column 21 has three or more and fifty or less piezoelectric layers 211 , the thickness of each piezoelectric layer 211 is set to be 10 μm or more and 40 μm or less, and the product of the thickness and the total number of stacked layers is set to be less than 1000 μm.

[0046] The vibration plate 30 is fixed to the ends of the plurality of driving piezoelectric posts 21 and the plurality of supporting piezoelectric posts 22 of the pair of actuators 20 on the side opposite to the connecting portion 26 in the Z direction. In other words, the vibration plate 30 is bonded to the surfaces of the plurality of piezoelectric posts 21 and 22 on the side opposite to the base 10 in the vibration direction of the plurality of piezoelectric posts 21, that is, the surfaces of the plurality of piezoelectric posts 21 and 22 on the nozzle plate 50 side.

[0047] The vibration plate 30 is formed in a flat plate shape. The vibration plate 30 is, for example, a metal plate. The vibration plate 30 is formed so as to be deformable by deforming the driving piezoelectric column 21. The vibration plate 30 forms a pressure chamber 31 together with the flow path component 40 and the nozzle plate 50. The vibration plate 30 is extended along the arrangement direction (column direction) of the plurality of piezoelectric columns 21 and 22. That is, the vibration plate 30 is extended along a plane orthogonal to the vibration direction of the piezoelectric column 21. One main surface of the vibration plate 30 is bonded to the driving piezoelectric column 21 and the supporting piezoelectric column 22 of the actuator 20 and the frame portion 60. The other main surface of the vibration plate 30 is bonded to the flow path component 40.

[0048] As an example, the vibration plate 30 is made of nickel or SUS plate, and the thickness dimension along the vibration direction is about 5 μm to 15 μm. It should be noted that the vibration plate 30 may also form wrinkles or steps at a portion adjacent to a vibration portion vibrated by the driving of the piezoelectric column 21 or between adjacent vibration portions, so that it is easy to be displaced by the driving of the piezoelectric column 21.

[0049] The vibration plate 30 has a through hole 33 formed in the region joined to the frame portion 60, which communicates with a common chamber 61 formed in the frame portion 60 described later. For example, a filter having many pores through which liquid can pass may be provided in the through hole 33. In addition, the through hole 33 may be single or multiple.

[0050] The flow path member 40 is provided between the vibration plate 30 and the nozzle plate 50. The flow path member 40 includes a peripheral wall portion 41 and a plurality of partition wall portions 43. In addition, when two actuators 20 are provided, a partition wall portion for partitioning the pressure chamber 31 driven by each actuator 20 is provided. The peripheral wall portion 41 and the partition wall portion 43 are provided between the vibration plate 30 and the nozzle plate 50, so that they form a predetermined ink flow path together with the vibration plate 30 and the nozzle plate 50, and the predetermined ink flow path includes a plurality of pressure chambers 31 separated from each other, and a plurality of individual flow paths 32 separated from each other and connecting the pressure chambers 31 and the common chamber 61.

[0051] The peripheral wall portion 41 surrounds the area between the vibration plate 30 and the nozzle plate 50 where a plurality of pressure chambers 31 and a plurality of separate flow paths 32 are formed. A plurality of partition wall portions 43 divide the area within the peripheral wall portion 41 into a plurality of pressure chambers 31 and a plurality of separate flow paths 32. That is, the two side walls in the arrangement direction of the plurality of pressure chambers 31 (a plurality of separate flow paths 32) are formed by the partition wall portions 43. In addition, the plurality of partition wall portions 43 are provided at positions opposite to the support piezoelectric column 22 across the vibration plate 30 in the Z direction. Thus, the partition wall portions 43 restrict the displacement of the support piezoelectric column 22 and the support piezoelectric column 22 at the portion of the vibration plate 30 where the support piezoelectric column 22 is fixed.

[0052] The plurality of pressure chambers 31 are spaces formed on one side of the vibration region of the vibration plate 30, and are connected to the common chamber 61 through the individual flow paths 32 and the through holes 33. The plurality of pressure chambers 31 are connected to the nozzles 51 formed on the nozzle plate 50. In addition, the side of the pressure chambers 31 opposite to the nozzle plate 50 is blocked by the vibration plate 30.

[0053] The nozzle plate 50 has a plurality of nozzles 51 formed at positions facing the plurality of pressure chambers 31. The nozzle plate 50 is formed in a square plate shape with a thickness of about 10 μm to 100 μm, made of a metal such as SUS or Ni or a resin material such as polyimide. The nozzle plate 50 is bonded to the surface of the peripheral wall portion 41 and the partition wall portion 43 on the side opposite to the vibration plate 30 so as to cover the opening on one side of the pressure chamber 31.

[0054] The plurality of nozzles 51 are arranged in the same direction as the arrangement direction of the plurality of pressure chambers 31 to form a nozzle row. For example, in a configuration in which one actuator 20 is provided, one row of nozzles 51 is provided, and in a configuration in which a pair of actuators are provided, two rows of nozzles 51 are provided.

[0055] The frame portion 60 is a structure joined to the vibration plate 30 together with the piezoelectric columns 21 and 22. A pair of frame portions 60 are provided on the main surface of the piezoelectric columns 21 and 22 on the side of the vibration plate 30 opposite to the peripheral wall portion 41. For example, the pair of frame portions 60 are arranged adjacent to the actuator 20. The frame portion 60 constitutes the outline of the inkjet head 1. In addition, in the frame portion 60, for example, a common chamber 61 that serves as a flow path for liquid is formed inside. The common chamber 61 is formed on the inner side of the frame portion 60. The common chamber 61 is connected to the through hole 33 formed in the vibration plate 30, and is connected to the pressure chamber 31 through the separate flow path 32. For example, a pair of frame portions 60 that form the common chamber 61 are provided, a pair of separate flow paths 32 are provided, and the pair of separate flow paths 32 are respectively connected to the pair of common chambers 61. For example, one common chamber 61 and one separate flow path 32 are used to supply ink to the pressure chamber 31, and another common chamber 61 and another separate flow path 32 are used to discharge ink from the pressure chamber 31. It should be noted that the pair of common chambers 61 and the pair of individual flow paths 32 may be structures for supplying ink, or may be structures for both supplying and discharging ink.

[0056] The driving circuit 70 includes an FPC 71 (Flexible printed circuits) having one end connected to the external electrodes 223 and 224 , a driving IC 72 mounted on the FPC 71 , and a printed wiring board 73 attached to the other end of the FPC 71 .

[0057] The driving circuit 70 applies a driving voltage to the external electrodes 223 and 224 via the driving IC 72 , thereby driving the piezoelectric column 21 to increase or decrease the volume of the pressure chamber 31 , thereby ejecting a droplet from the nozzle 51 .

[0058] The FPC 71 is connected to one side surface of the stacked piezoelectric component and is connected to the plurality of external electrodes 223 and 224. A COF (Chip on Film) is used as the FPC 71, and a driver IC 72 is mounted on the COF as an electronic component.

[0059] The driving IC 72 is connected to the external electrodes 223 and 224 via the FPC 71. The driving IC 72 is an electronic component for ejection control.

[0060] The driver IC 72 generates a control signal and a drive signal for causing each driving piezoelectric column 21 to operate. The driver IC 72 generates a control signal for selecting the timing of ink ejection and the control of the driving piezoelectric column 21 for ejecting ink, etc., based on the image signal input from the control unit 116 of the inkjet recording device 100 equipped with the inkjet head 1. In addition, the driver IC 72 generates a voltage, i.e., a drive signal, applied to the driving piezoelectric column 21 based on the control signal from the control unit 116. If the driver IC 72 applies a drive signal to the driving piezoelectric column 21, the driving piezoelectric column 21 will be driven to displace the vibration plate 30, thereby changing the volume of the pressure chamber 31. As a result, the ink filled in the pressure chamber 31 generates pressure vibrations. Through the pressure vibrations, the ink is ejected from the nozzle 51 connected to the pressure chamber 31. It should be noted that it can also be set that the inkjet head 1 can achieve grayscale expression by changing the amount of ink droplets landing on one pixel. In addition, it can also be set that the inkjet head 1 can change the amount of ink droplets landing on one pixel by changing the number of times the ink is ejected. In this way, the driving IC 72 is an example of an application unit that applies a driving signal to the piezoelectric column 21 .

[0061] For example, the driver IC 72 includes a data buffer, a decoder, and a driver. The data buffer stores the print data for each driving piezoelectric column 21 in a time series. For each driving piezoelectric column 21, the decoder controls the driver based on the print data stored in the data buffer. The driver outputs a drive signal for causing each driving piezoelectric column 21 to operate based on the control of the decoder. The drive signal is, for example, a voltage applied to each driving piezoelectric column 21.

[0062] The printed wiring board 73 is a PWA (Printing Wiring Assembly) on which various electronic components and connectors are mounted, and includes a head control circuit 731. The printed wiring board 73 is connected to the control unit 116 of the inkjet recording apparatus 100.

[0063] The driving circuit 70 selects a driving signal or a standby voltage and supplies it to a plurality of driving piezoelectric columns 21 according to the command and print data from the control unit 116 of the inkjet recording device 100. In addition, the driving circuit 70 drives the driving piezoelectric columns 21 by single nozzle driving and multi-nozzle simultaneous driving as driving types. Single nozzle driving is a driving type in which adjacent driving piezoelectric columns 21 are not driven and a driving signal is applied to the first external electrode 223 of one channel to drive one driving piezoelectric column 21. Multi-nozzle simultaneous driving is a driving type in which a driving signal is applied to the first external electrodes 223 of multiple channels to simultaneously drive all of the driving piezoelectric columns 21 among the multiple driving piezoelectric columns 21 or some of the driving piezoelectric columns 21 among the adjacent driving piezoelectric columns 21.

[0064] like Figure 5As shown, the driving circuit 70 includes a driving signal source 81 that outputs a driving signal applied to a first external electrode 223 serving as an individual electrode, a standby voltage source 82 that outputs a standby voltage applied to a second external electrode 224 serving as a common electrode, a switching element 83 that selectively connects each driving piezoelectric column 21 to one of the driving signal source 81 and the standby voltage source 82, a plurality of first resistors 84 that serve as internal impedances of the switching elements 83 between the driving piezoelectric column 21 and the driving signal source 81 or the standby voltage source 82, and a single or multiple second resistors 85 that connect multiple and adjacent driving piezoelectric columns 21 of at least some of the multiple driving piezoelectric columns 21.

[0065] The switch element 83 is switched based on the print data. The switch element 83 connects the driving piezoelectric column 21 driven to eject ink to the driving signal source 81, and connects the non-driven driving piezoelectric column 21 that does not eject ink to the standby voltage source 82. For example, a plurality of switch elements 83 are built into the driver IC 72.

[0066] The first resistor 84 is the internal impedance of the switch element 83. Here, the impedance value of the first resistor 84 is set to RA. It should be noted that the first resistor 84 can also be connected in series with the switch element 83 outside the switch element 83 to add impedance. In this case, the impedance value RA of the first resistor 84 becomes the total value of the internal impedance of the switch element and the impedance added to the outside of the switch element 83.

[0067] The second resistor 85 electrically connects the individual electrodes of the adjacent plurality of driving piezoelectric columns 21, i.e., the first external electrodes 223, between the driving piezoelectric column 21 and the switching element 83 at a predetermined impedance value. That is, the second resistor 85 includes a plurality of resistors 851 disposed between the first external electrodes 223 of the adjacent driving piezoelectric columns 21. Here, when the number of the connected first external electrodes 223 is set to n, the number of the resistors 851 is n-1. Here, the impedance value of the resistor 851 is set to RB. Since the smaller the impedance value RB of the resistor 851, the smaller the ejection speed and ejection volume during single nozzle driving, the impedance value RB of the resistor 851 is set to match the ejection speed and ejection volume during simultaneous multi-nozzle driving. Here, the reduction rate D of the voltage amplitude during single nozzle driving relative to simultaneous multi-nozzle driving is D=2 / (3+RB / RA).

[0068] The second resistor 85 is formed, for example, in the actuator 20 and is formed by a thin film formed across the first external electrodes 223 of the plurality of driving piezoelectric posts 21 driven simultaneously by the plurality of nozzles. As a specific example, the second resistor 85 electrically connects the first external electrodes 223 of all the driving piezoelectric posts 21. It should be noted that the following structure may also be adopted: a plurality of second resistors 85 are provided, and each second resistor 85 is connected to the first external electrodes 223 of a plurality of driving piezoelectric posts 21 driven simultaneously by the plurality of nozzles.

[0069] The second resistor 85 is formed of a metal with high resistivity such as nickel-chromium alloy or titanium or a carbon coating (carbon). The second resistor 85 has a thickness of several nanometers to several micrometers and is formed by vacuum deposition, sputtering, or printing such as screen printing.

[0070] As a specific example, the second resistor 85 is formed of a thin film that is extended along the arrangement direction of the first external electrodes 223 and has a uniform width in a direction (width direction) perpendicular to the long side direction and the thickness direction. In addition, the plurality of resistors 851 formed in the second resistor 85 are formed, for example, by a trimming portion 852 formed by a plurality of slits 853 formed between the plurality of first external electrodes 223 by laser processing or the like. In other words, the second resistor 85 is locally narrowed in width and lengthened in length by the plurality of slits 853 formed between the connected and adjacent first external electrodes 223, thereby forming a plurality of resistors 851.

[0071] It should be noted that the impedance value RB of the resistor 851 can be set by adjusting the shape of the trimming portion 852, and as a specific example, by adjusting the number, length, and width of the slits 853. Figure 4 In the example of FIG. 1 , the trimming portion 852 is arranged along the long side direction of the second resistor 85 and is formed by three rectangular slits 853 that are staggered and alternately formed in the width direction orthogonal to the long side direction and the thickness direction of the second resistor 85. The number, width, length, and shape of the slits 853 are appropriately set according to the impedance value RB of the resistor 851. Therefore, the slits 853 may not be rectangular, but may be a shape that is long in the width direction of the second resistor 85 and has a curved end, a semicircular shape, a polygonal shape other than a rectangle, or the like.

[0072] It should be noted that, in the present embodiment, the second resistor 85 is provided as an integral thin film on the actuator 20 in a manner of connecting a plurality of first external electrodes 223, and a plurality of trimming portions 852 are provided to form a plurality of resistors 851. However, the second resistor 85 is not limited to this configuration, and for example, a structure in which the resistors 851 are provided between the first external electrode 223 for simultaneously driving multiple nozzles and the switch element 83 and between a plurality of adjacent first external electrodes 223 may be sufficient. For example, the second resistor 85 may be provided in the FPC 71 or in the driving IC 72. In addition, the second resistor 85 may also be formed of a semiconductor such as a transistor. However, it is desirable that the second resistor 85 can adjust the impedance value RB of the resistor 851 by trimming or the like.

[0073] According to the inkjet head 1 constructed in this way, if the switch element 83 is switched and a voltage is applied to the driving piezoelectric column 21 by a driving signal, the driving piezoelectric column 21 is extended. The extended driving piezoelectric column 21 deforms the vibration plate 30, and the volume of the pressure chamber 31 is reduced. That is, the vibration plate 30 pressurizes the ink in the pressure chamber 31, and ink droplets are ejected from the nozzle 51. It should be noted that if a certain driving piezoelectric column 21 is extended, the supporting piezoelectric column 22 is also extended due to the mechanical reaction force.

[0074] Generally, in the case of single nozzle drive, such as Figure 2 As shown in FIG. 1 , since the driving piezoelectric column 21 adjacent to the driving piezoelectric column 21 is not driven, the extension of the supporting piezoelectric column 22 is small. Figure 3 As shown, since the adjacent driving piezoelectric columns 21 are driven simultaneously, the extension of the supporting piezoelectric columns 22 between the driven driving piezoelectric columns 21 becomes larger.

[0075] Therefore, in the inkjet head of the prior art that does not have the second resistor 85, the deformation amount of the vibration plate 30 relative to the deformation amount of the driving piezoelectric column 21 becomes smaller in the case of multi-nozzle simultaneous driving than in the case of single-nozzle driving. In addition, since the deformation amount of the vibration plate 30 in the case of multi-nozzle simultaneous driving is smaller than that in the case of single-nozzle driving, the pressure generated in the pressure chamber 31 in the case of multi-nozzle simultaneous driving becomes smaller in the prior art than in the case of single-nozzle driving. Therefore, there is a problem of deviation in the speed and volume of ink droplets ejected depending on the printing type, and the printing quality is deteriorated, which is the so-called crosstalk problem.

[0076] In contrast, Figures 4 to 6As shown, the inkjet head 1 involved in the embodiment electrically connects the adjacent first external electrodes 223 for simultaneous multi-nozzle driving through the second resistor 85, and has a resistor 851 between the first external electrodes 223. Therefore, in the case of single nozzle driving, a part of the current of the driving signal applied to the first external electrode 223 provided on the driving piezoelectric column 21 for driving flows to the first external electrode 223 of the adjacent driving piezoelectric column 21 via the resistor 851. Therefore, the voltage amplitude for driving the driving piezoelectric column 21 for driving is reduced. In the case of simultaneous multi-nozzle driving, since the voltages of the plurality of first external electrodes 223 for simultaneous driving are the same, the current does not flow to the resistor 851, and the voltage amplitude does not decrease.

[0077] In this way, since the pressure generated in the pressure chamber 31 is reduced when a single nozzle is driven by the second resistor 85, the pressure generated in the pressure chamber 31 can be made the same or similar in the single nozzle driving and the multi-nozzle simultaneous driving. Therefore, the inkjet head 1 can eliminate dot deviation and density unevenness caused by the driving type.

[0078] For example, in Figure 6 In the example of FIG. 1 , a single nozzle drive and a multi-nozzle simultaneous drive are shown in six channels ChA to ChF. Figure 6 In FIG. 1 , the driving piezoelectric posts 21 of the channels ChA to ChF are represented as CA to CF, respectively, and the first resistors 84 provided between the driving piezoelectric posts CA to CF and the switch element 83 in the channels ChA to ChF are respectively represented as 841 to 846. In addition, the resistance 851 of the second resistor 85 provided between the first external electrodes 223 of the driving piezoelectric posts CA to CF is respectively represented as 8511 to 8515. For example, in Figure 6 In the example, the driving piezoelectric column CB of the channel ChB is driven by a single nozzle, and the driving piezoelectric columns CD to CF of the channels ChD to ChF are driven by multiple nozzles simultaneously. As a result, ink is not ejected from the nozzles 51 of the channels ChA and ChC, and ink is ejected from the nozzles 51 of ChB and ChD to ChF. Figure 7 Shown in the Figure 6 1 is a simulation example of the voltage applied to the driving piezoelectric columns CA to CF (first external electrode 223) in the example shown. Here, the voltage values ​​applied to the driving piezoelectric columns CA to CF are represented by VA to VF. Figure 7 In FIG. 1 , the vertical axis shows voltage and the horizontal axis shows time.

[0079] like Figure 7As shown, the voltage amplitude of the voltage value VB of the driving piezoelectric column CB for single nozzle driving is smaller than the voltage amplitude of the voltage values ​​VD to VF of the driving piezoelectric columns CD to CF for multi-nozzle simultaneous driving. Therefore, the crosstalk phenomenon that the pressure generated in the pressure chamber 31 is smaller when the multi-nozzle simultaneous driving is smaller than that when the single nozzle is driven is corrected, and the pressure generated in the pressure chamber 31 becomes approximately the same value in the single nozzle driving and the multi-nozzle simultaneous driving, and the crosstalk problem that the speed and volume of the ink droplets ejected according to the printing type are deviated and the printing quality is deteriorated is eliminated. In addition, the voltage values ​​VA and VC of the non-driven driving piezoelectric columns CA and CC adjacent to the driving piezoelectric column CB for single nozzle driving become standby voltages. The voltage values ​​VA and VC have a slight voltage amplitude, and although a small pressure is generated in the pressure chamber 31, since the pressure is not generated to the extent that the ink is ejected, the defect of ink ejecting from the non-driven nozzle will not occur.

[0080] The following reference Figure 8 An example of an inkjet recording apparatus 100 including the inkjet head 1 will be described. The inkjet recording apparatus 100 includes a housing 111 , a medium supply unit 112 , an image forming unit 113 , a medium discharge unit 114 , a transport device 115 , and a control unit 116 .

[0081] The inkjet recording device 100 is a liquid ejecting device that ejects liquid such as ink while transporting, for example, paper P as an ejection object, i.e., a printing medium, along a predetermined transport path R from a medium supply unit 112 through an image forming unit 113 to a medium discharge unit 114, thereby performing image formation processing on the paper P.

[0082] The housing 111 forms the outline of the inkjet recording apparatus 100. The housing 111 is provided with a discharge port at a predetermined position thereof for discharging the paper P to the outside.

[0083] The medium supply unit 112 includes a plurality of paper feed cassettes, and is configured to hold a plurality of paper P of various sizes in a stacked manner.

[0084] The medium discharge unit 114 includes a paper discharge tray configured to hold the paper P discharged from the discharge port.

[0085] The image forming section 113 includes a support section 117 that supports the paper P, and a plurality of head units 130 that are disposed above the support section 117 to face each other.

[0086] The support portion 117 includes a conveyor belt 118 provided in an endless shape in a predetermined region for image formation, a support plate 119 supporting the conveyor belt 118 from the rear side, and a plurality of belt rollers 120 provided on the rear side of the conveyor belt 118 .

[0087] When forming an image, the support portion 117 supports the paper P on the holding surface that is the upper surface of the conveying belt 118 , and conveys the conveying belt 118 by the rotation of the belt roller 120 at a predetermined timing, thereby conveying the paper P to the downstream side.

[0088] The head unit 130 includes a plurality of (eg, four color) inkjet heads 1 , ink tanks 132 as liquid tanks respectively mounted on the inkjet heads 1 , connection channels 133 connecting the inkjet heads 1 and the ink tanks 132 , and a supply pump 134 .

[0089] In this embodiment, for example, the inkjet heads 1 for four colors, cyan, magenta, yellow, and black, and the ink tanks 132 for storing the inks of the four colors are provided. The ink tanks 132 are connected to the inkjet heads 1 via the connection channels 133 .

[0090] In addition, a negative pressure control device such as a pump (not shown) is connected to the ink tank 132. In addition, the negative pressure in the ink tank 132 is controlled by the negative pressure control device in accordance with the head value of the inkjet head 1 and the ink tank 132, thereby forming a meniscus of a predetermined shape of the ink supplied to each nozzle 51 of the inkjet head 1.

[0091] The supply pump 134 is a liquid delivery pump composed of, for example, a piezoelectric pump. The supply pump 134 is provided in the supply flow path. The supply pump 134 is connected to the drive circuit 1161 of the control unit 116 via wiring and is configured to be controllable by the control unit 116. The supply pump 134 supplies liquid to the inkjet head 1.

[0092] The transport device 115 transports the paper P along a transport path R from the medium supply unit 112 to the medium discharge unit 114 via the image forming unit 113 . The transport device 115 includes a plurality of guide plate pairs 121 disposed along the transport path R and a plurality of transport rollers 122 .

[0093] Each of the plurality of guide plate pairs 121 includes a pair of plate members that are disposed opposite to each other with the paper P being transported interposed therebetween, and guides the paper P along the transport path R.

[0094] The conveying roller 122 is driven to rotate under the control of the control unit 116 , thereby conveying the paper P to the downstream side along the conveying path R. It should be noted that on the conveying path R, sensors for detecting the conveying status of the paper are arranged at various locations.

[0095] The control unit 116 includes a control circuit 1161 such as a CPU (Central Processing Unit) as a controller, a ROM (Read Only Memory) for storing various programs, a RAM (Random Access Memory) for temporarily storing various variable data, image data, etc., and an interface unit for inputting and outputting data from and to the outside.

[0096] In the inkjet recording device 100 configured as above, for example, if a print instruction given by the user by operating the operation input unit is detected in the interface, the control unit 116 drives the conveying device 115 to convey the paper P, and outputs a print signal to the head unit 130 at a predetermined timing, thereby driving the inkjet head 1. As a discharge operation, the inkjet head 1 sends a drive signal to the driver IC 72 based on an image signal corresponding to the image data, applies a drive voltage to the internal electrodes 221 and 222, and selectively drives the driving piezoelectric column 21 of the discharge object to vibrate longitudinally in the stacking direction, for example, to change the volume of the pressure chamber 31, thereby discharging ink from the nozzle 51 and forming an image on the paper P held on the conveyor belt 118. In addition, as a liquid discharge operation, the control unit 116 drives the supply pump 134 to supply ink from the ink tank 132 to the common chamber 61 of the inkjet head 1.

[0097] In summary, the inkjet head 1 and the inkjet recording apparatus 100 according to the described embodiment can eliminate dot shift and density unevenness caused by the driving type by providing the resistors 851 between the plurality of first external electrodes 223 that apply voltages individually to the plurality of driving piezoelectric posts 21 .

[0098] It should be noted that the embodiment is not limited to the above example. For example, in the above example, the drive circuit 70 switches the switch element 83 and applies the standby voltage to the supporting piezoelectric column 22 that does not eject ink, but the present invention is not limited to this. For example, the switch element 83 may be configured to disconnect the driving signal source 81 from the supporting piezoelectric column 22 that does not eject ink. Fig.10 Shown in the application Fig. 9 1 is a simulation example of the voltage driving the piezoelectric columns CA to CF (first external electrodes 223) in the example shown. Fig.10 As shown in the figure, it can be seen that even if the inkjet head 1 is set to a structure in which the first external electrode 223 in the non-ejecting channel is opened, the voltage amplitude during single nozzle driving will decrease, and the deterioration of printing quality due to crosstalk can be prevented. However, since the driving piezoelectric column 21 that does not eject ink is also charged and discharged, there is a possibility that energy consumption increases, the meniscus changes in the non-ejecting nozzle 51, and there is a possibility of causing obstacles when there is an ink ejection operation later.

[0099] In addition, in the structure in which the first external electrode 223 is opened when not ejecting, there is a possibility that a difference in voltage occurs between the driving piezoelectric column 21 (first external electrode 223) located at the end of the plurality of driving piezoelectric columns 21 (first external electrode 223) electrically connected via the second resistor 85 and the adjacent driving piezoelectric column 21, that is, a so-called edge occurs. Therefore, in order to suppress the generation of an edge within the printing range, the driving piezoelectric column 21 located at the end of the plurality of driving piezoelectric columns 21 connected to the second resistor 85 may be set as a dummy that is not driven, or the corresponding nozzle 51 is not provided, and the same voltage as the second driving piezoelectric column 21 from the end is applied.

[0100] In addition, in the above example, the second resistor 85 is formed of a thin film that is extended along the arrangement direction of the first external electrode 223 and has a uniform width in the direction (width direction) perpendicular to the long side direction and the thickness direction, but the invention is not limited thereto. For example, in order to increase the impedance difference between the region connected to the first external electrode 223 and the trimmed portion 852 constituting the resistor 851, the second resistor 85 may also partially change its width. For example, the second resistor 85 may also be a structure in which the width of the region connected to the first external electrode 223 in the direction perpendicular to the long side direction and the thickness direction is larger than the width of the region constituting the resistor 851.

[0101] In addition, in the above example, the example in which the liquid ejection device 100 ejects ink as liquid from the liquid ejection head 1 is described, but the liquid is not limited to ink. That is, the liquid ejection head 1 and the liquid ejection device 100 can also be used for example in a 3D printer, industrial manufacturing machinery, and medical use, and can eject various liquids.

[0102] According to at least one embodiment described above, by providing resistors between a plurality of individual electrodes for individually applying voltages to a plurality of driving piezoelectric columns, a liquid ejection head and a liquid ejection device capable of eliminating dot shift and concentration unevenness caused by a driving type can be provided.

[0103] Several embodiments of the present invention have been described, but these embodiments are only presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and can be omitted, replaced, and changed in various ways without departing from the scope of the subject matter of the invention. These embodiments and their variations are included in the scope and subject matter of the invention, and are included in the invention described in the claims and their equivalents.

Claims

1. A liquid ejection head, characterized in that: have: Multiple pressure chambers; An actuator having a plurality of piezoelectric bodies, wherein the plurality of piezoelectric bodies make the volume of the pressure chamber variable according to a driving signal; A plurality of separate electrodes are respectively disposed on the plurality of piezoelectric bodies; A nozzle plate, formed with a plurality of nozzles, wherein the plurality of nozzles are respectively connected to the plurality of pressure chambers; A plurality of switch elements selectively connected to the driving signal of the piezoelectric body and electrically connected to the plurality of the individual electrodes; as well as A plurality of resistors electrically connect the individual electrodes of the piezoelectric bodies adjacent to each other.

2. The liquid ejection head according to claim 1, wherein: The liquid ejection head includes a resistor, the resistor being electrically connected to at least any one of the plurality of individual electrodes. The plurality of resistors are formed by slits provided between the individual electrodes of the resistor body.

3. The liquid ejection head according to claim 2, wherein: The resistor electrically connects all of the plurality of individual electrodes.

4. The liquid ejection head according to claim 1, wherein: The switch element selectively connects a drive signal for ejecting liquid and a standby voltage for not ejecting the liquid.

5. The liquid ejection head according to claim 2 or 3, characterized in that: The switch element disconnects the piezoelectric body that does not eject ink from a drive signal for ejecting liquid.

6. The liquid ejection head according to claim 5, wherein: The piezoelectric bodies located at the end portions among the plurality of piezoelectric bodies connected to the resistor are set as dummy bodies that are not driven.

7. The liquid ejection head according to claim 5, wherein: A corresponding nozzle is not provided to the piezoelectric body located at the end among the plurality of piezoelectric bodies connected to the resistor, and the same voltage as that of the second piezoelectric body from the end is applied.

8. The liquid ejection head according to claim 2 or 3, characterized in that: The resistor is formed of a thin film extending along the arrangement direction of the individual electrodes and having a uniform width in a width direction that is a direction orthogonal to the arrangement direction and vibration direction of the plurality of piezoelectric bodies.

9. The liquid ejection head according to claim 5, wherein: The resistor is formed of a thin film extending along the arrangement direction of the individual electrodes and having a uniform width in a width direction that is a direction orthogonal to the arrangement direction and vibration direction of the plurality of piezoelectric bodies.

10. A liquid ejection device, characterized in that: have: The liquid ejection head according to any one of claims 1 to 9.

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