Liquid discharging head and liquid discharging device

Abstract

To provide a liquid discharging head and a liquid discharging device capable of solving a dot deviation or density unevenness due to driving patterns.SOLUTION: A liquid discharging head is equipped with a plurality of pressure chambers, an actuator, a plurality of individual electrodes, a nozzle plate, a plurality of switching elements, and a plurality of electric resistances. The actuator has a plurality of piezoelectric elements that can change the capacity of the pressure chambers according to driving signals. The plurality of individual electrodes are respectively provided on the plurality of piezoelectric elements. The nozzle plate has a plurality of nozzles respectively communicating with the plurality of pressure chambers. The switching element selectively connects the driving signals of the piezoelectric elements. The switching element is electrically connected with the plurality of individual electrodes. The electric resistances electrically connect the individual electrodes of the piezoelectric element adjacent to each other.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] An embodiment of the present invention relates to a liquid ejection head and a liquid ejection apparatus. [Background technology]

[0002] Conventionally, there is known a push mode type piezoelectric inkjet head that ejects ink as a liquid. This inkjet head has a plurality of nozzles, a plurality of pressure chambers, a vibration plate, and an actuator in which a plurality of piezoelectric driving columns and a plurality of support columns are alternately formed and electrically connected to a drive circuit. The actuator expands and contracts the driving piezoelectric columns to displace the vibration plate, thereby varying the volume of the pressure chamber and ejecting ink from the nozzle.

[0003] However, when adjacent nozzles are driven simultaneously, the support pillars are deformed by the reaction force of the actuator driving force, which reduces the generated pressure compared to when a single nozzle is driven, and reduces the ink ejection speed and volume. When the ink ejection speed and volume are reduced, dot misalignment and density unevenness occur depending on the drive pattern. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-174404 A Summary of the Invention [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 apparatus that can eliminate dot misalignment and density unevenness caused by drive patterns. [Means for solving the problem]

[0006] The liquid ejection head of the embodiment 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 electrical resistors. The actuator has a plurality of piezoelectric bodies that vary the volume of the pressure chambers in response to a drive signal. The plurality of individual electrodes are provided on the plurality of piezoelectric bodies, respectively. The nozzle plate has a plurality of nozzles formed thereon that respectively communicate with the plurality of pressure chambers. The switching element selectively connects the drive signal of the piezoelectric body. The switching element is electrically connected to the plurality of individual electrodes. The electrical resistor electrically connects the individual electrodes of adjacent piezoelectric bodies. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a cross-sectional view showing the configuration of a liquid ejection head according to the embodiment, with some parts omitted. [Diagram 2] FIG. 2 is a cross-sectional view showing the configuration of a liquid ejection head according to the embodiment, with some parts omitted. [Diagram 3] FIG. 2 is a cross-sectional view showing the configuration of a liquid ejection head according to the embodiment, with some parts omitted. [Figure 4] FIG. 2 is an explanatory diagram illustrating a schematic configuration of an electrical resistor of the liquid ejection head according to the embodiment. [Diagram 5] FIG. 2 is an explanatory diagram showing, with some parts omitted, the configuration of a drive circuit of the liquid ejection head according to the embodiment. [Figure 6] FIG. 4 is an explanatory diagram showing the configuration of a drive circuit in an example of driving a liquid ejection head according to the embodiment. [Figure 7] FIG. 4 is an explanatory diagram showing an example of voltage in an example of driving the liquid ejection head according to the embodiment. [Figure 8] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a liquid ejection device according to an embodiment. [Figure 9] FIG. 10 is an explanatory diagram showing the configuration of a drive circuit in an example of driving a liquid ejection head according to another embodiment. [Figure 10] FIG. 11 is an explanatory diagram showing an example of voltage in an example of driving a liquid ejection head according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An inkjet head 1, which is a liquid ejection head according to an embodiment, and an inkjet recording device 100, which is a liquid ejection device, will be described below with reference to FIGS. 1 to 8. FIGS. 1 to 3 are cross-sectional views that show a schematic configuration of the inkjet head 1. FIG. 1 is a cross-sectional view showing the configuration of the inkjet head 1 with some parts omitted, FIG. 2 is a cross-sectional view showing the configuration of the inkjet head 1 with some parts omitted in a direction different from that of FIG. 1, and FIG. 3 is a cross-sectional view showing the configuration of the inkjet head 1 in an example of driving different from that of FIG. 2. FIG. 4 is an explanatory diagram showing a schematic configuration of the second electric resistor 85 of the inkjet head 1. FIG. 5 is an explanatory diagram showing a schematic configuration of the drive circuit 70 of the inkjet head with some parts omitted, and FIG. 6 is an explanatory diagram showing a configuration of the drive circuit 70 in an example of driving the inkjet head 1. FIG. 7 is an explanatory diagram showing an example of voltage in an example of driving the inkjet head 1. FIG. 8 is an explanatory diagram showing a schematic configuration of the inkjet recording device 100 in which the inkjet head 1 is used. In each drawing, the configuration is enlarged, reduced, or omitted as appropriate for the purpose of explanation.

[0009] 1 to 4, the inkjet head 1 includes a base 10, a pair of actuators 20 having a plurality of piezoelectric pillars 21, 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 the vibration plate 30, the flow path member 40, and the nozzle plate 50, and ejects ink as a liquid in the pressure chambers 31 from the nozzles 51 by vibrating the vibration plate 30 by the piezoelectric pillars 21 of the actuator 20.

[0010] The inkjet head 1 includes one or two actuators 20. The two actuators 20 are arranged, for example, side by side in a direction perpendicular to the direction in which a plurality of piezoelectric columns 21 and 22 serving as piezoelectric bodies are arranged.

[0011] The base 10 is a support member that supports the actuator 20. The base 10 is formed, for example, in the shape of a block or a plate.

[0012] The actuator 20 is fixed to the base 10. The actuator 20 has a plurality of piezoelectric pillars 21, 22 which are piezoelectric materials (piezoelectric elements). The actuator 20 has a piezoelectric pillar row formed by the plurality of piezoelectric pillars 21, 22. The actuator 20 includes a plurality of driving piezoelectric pillars (piezoelectric bodies) 21, a plurality of supporting piezoelectric pillars (piezoelectric bodies) 22 which are arranged alternately with the plurality of driving piezoelectric pillars 21 along the row direction of the piezoelectric pillar row, and a connecting portion 26 which integrally connects the plurality of piezoelectric pillars 21, 22 on the base 10 side. The actuator 20 is formed of a laminated piezoelectric member. Here, the laminated piezoelectric member is formed by laminating a plurality of piezoelectric layers 211 and a plurality of internal electrodes 221, 222. The actuator 20 also has external electrodes 223, 224 formed on the plurality of driving piezoelectric pillars 21.

[0013] For example, the laminated piezoelectric member constituting the actuator 20 is formed by stacking and sintering sheet-like piezoelectric materials on which electrode layers are formed as internal electrodes 221, 222. The actuator 20 is also formed by dicing the laminated piezoelectric member previously joined to the base 10 from the end face opposite the base 10 side to form grooves 23, thereby forming a plurality of rectangular pillar-shaped piezoelectric pillars 21, 22 at predetermined intervals. Then, external electrodes 223, 224, etc. are provided on the formed plurality of pillar-shaped piezoelectric materials (piezoelectric elements). Through these steps, a plurality of driving piezoelectric pillars 21 and a plurality of support piezoelectric pillars 22 are formed, which are alternately arranged in the connecting portion 26 and have external electrodes 223, 224 formed on their outer surfaces.

[0014] The multiple driving piezoelectric pillars 21 and the multiple supporting piezoelectric pillars 22 are aligned at predetermined intervals in the longitudinal direction of the actuator 20. The vibration direction of the driving piezoelectric pillars 21 and the supporting piezoelectric pillars 22 is the stacking direction of the multiple piezoelectric layers 211. The driving piezoelectric pillars 21 are actuators that are driven by application of a voltage and vibrate the vibration plate 30. The supporting piezoelectric pillars 22 are non-driving piezoelectric pillars that support the vibration plate 30 and are restricted from vibrating the vibration plate 30 by the flow path member 40 even when a voltage is applied.

[0015] As an example, the multiple driving piezoelectric columns 21 and the multiple supporting piezoelectric columns 22 are both formed in the shape of a rectangular parallelepiped column with the same external shape. The multiple grooves 23 of a predetermined depth formed in the actuator 20 (laminated piezoelectric member) divide the laminated piezoelectric member into multiple parts except for the connecting portion 26, thereby forming the multiple driving piezoelectric columns 21 and the multiple supporting piezoelectric columns 22. For example, the multiple grooves 23 formed in the actuator 20 are formed with the same width and the same intervals. As a result, the multiple driving piezoelectric columns 21 and the multiple supporting piezoelectric columns 22 arranged alternately are arranged in one direction with the same pitch. For example, the multiple driving piezoelectric columns 21 and the multiple supporting piezoelectric columns 22 are each formed in a rectangular column shape.

[0016] The multiple driving piezoelectric pillars 21 are arranged in positions facing the multiple pressure chambers 31 formed by the vibration plate 30, the flow path member 40, and the nozzle plate 50, respectively, via the vibration plate 30, in the stacking direction of the multiple piezoelectric layers 211. As an example, the driving piezoelectric pillars 21 and the pressure chambers 31 are arranged such that the center position in the row direction of the piezoelectric pillar row of the driving piezoelectric pillars 21 and the center position in the row direction of the piezoelectric pillar row of the pressure chambers 31 are aligned in the stacking direction of the multiple piezoelectric layers 211 via the vibration plate 30.

[0017] The multiple support piezoelectric columns 22 are arranged in positions facing the multiple partition wall sections 43 (described later) of the flow path member 40 via the vibration plate 30 in the stacking direction of the multiple piezoelectric layers 211. As an example, the center position in the row direction of the piezoelectric columns of the support piezoelectric columns 22 and the center position in the same direction as the row direction of the piezoelectric columns of the partition wall sections 43 are aligned in the stacking direction of the multiple piezoelectric layers 211.

[0018] The multiple driving piezoelectric pillars 21 and the multiple supporting piezoelectric pillars 22 include multiple piezoelectric layers 211 stacked in the Z direction, and internal electrodes 221, 222 formed on the main surface of each piezoelectric layer 211. As an example, the driving piezoelectric pillars 21 and the supporting piezoelectric pillars 22 have the same stacked structure. Each driving piezoelectric pillar 21 includes external electrodes 223, 224 as surface wiring formed on the surface.

[0019] The piezoelectric layer 211 is formed in a thin plate shape from a piezoelectric ceramic material such as PZT (lead zirconate titanate) or lead-free KNN (potassium sodium niobate). The thickness direction of the piezoelectric layer 211 is aligned with the lamination direction in which the multiple piezoelectric layers 211 are laminated. The multiple laminated piezoelectric layers 211 are bonded to each other. In this embodiment, the thickness direction and lamination direction of the piezoelectric layer 211 are aligned with the vibration direction of the piezoelectric pillar 21 when driven.

[0020] The laminated piezoelectric member forming the drive piezoelectric pillar 21 and the support piezoelectric pillar 22 may further include a dummy layer 212 on either or both of the ends on the base 10 side and the nozzle plate 50 side. The dummy layer 212 is made of, for example, the same material as the piezoelectric layer 211, has an electrode on only one side, and is not deformed because no electric field is applied. For example, the dummy layer 212 does not function as a piezoelectric body, but serves as a base for fixing the actuator 20 to the base 10, or serves as a polishing allowance for polishing to achieve precision during and after assembly.

[0021] The internal electrodes 221, 222 are conductive films formed into a predetermined shape from a sinterable conductive material such as silver-palladium. The internal electrodes 221, 222 are formed in predetermined regions on the main surface of each piezoelectric layer 211. The internal electrodes 221, 222 have mutually different polarities.

[0022] For example, one 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 in the width direction perpendicular to both the row direction in which the multiple driving piezoelectric columns 21 and the multiple support piezoelectric columns 22 are arranged and the vibration direction. Hereinafter, the internal electrode 221 may also be referred to as a first internal electrode 221.

[0023] The other internal electrode 222 is formed in a region that does not reach one end of the piezoelectric layer 211 in the width direction perpendicular to both the column direction and the vibration direction, but reaches the other end of the piezoelectric layer 211. Hereinafter, the internal electrode 222 may also be referred to as the second internal electrode 222.

[0024] The external electrodes 223, 224 are formed on the surfaces of the multiple driving piezoelectric columns 21, respectively, and are configured by collecting the ends of the internal electrodes 221, 222. For example, the external electrode 223 is formed on one end face in the width direction of the piezoelectric layer 211. Hereinafter, the external electrode 223 may be referred to as the first external electrode 223. The external electrode 224 is formed on the other end face in the width direction of the piezoelectric layer 211. 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 may be referred to as the second external electrode 224.

[0025] The external electrodes 223 and 224 are formed by a known method such as plating or sputtering using Ni, Cr, Au, etc. The external electrodes 223 and 224 have different polarities. The first external electrode 223 and the second external electrode 224 are formed on different side surfaces of the multiple driving piezoelectric pillars 21, respectively.

[0026] In this embodiment, as an example, the first external electrode 223 is an individual electrode, and the second external electrode 224 is a common electrode. As shown in Fig. 4, the first external electrode 223 is formed on each of the multiple driving piezoelectric pillars 21. One second external electrode 224 is provided and connects all of the multiple driving piezoelectric pillars 21. The multiple first external electrodes 223 and the single second external electrode 224 are arranged independently of each other.

[0027] The first external electrode 223 is connected to the multiple first internal electrodes 221 formed on one driving piezoelectric pillar 21. For example, the single second external electrode 224 is a ground electrode. The single second external electrode 224 is connected to the multiple second internal electrodes 222 formed on the multiple driving piezoelectric pillars 21 provided.

[0028] The multiple first external electrodes 223 and the single second external electrode 224 are connected to an FPC 71, which serves as a flexible substrate described below, of the drive circuit 70. For example, the single second external electrode 224 is provided on outer surfaces of the pair of actuators 20 that face each other.

[0029] For example, each of the external electrodes 223, 224 is connected to the control unit 116 as a drive unit via a drive circuit 70, and a signal capable of driving and controlling each of the piezoelectric pillars 21 under the control of a control circuit 1161 is input.

[0030] When a drive 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 pillar 21 is displaced in the direction d33, and the vibration direction of each piezoelectric pillar 21 is aligned with the lamination direction of the piezoelectric layers 211.

[0031] To explain a specific example, the driving piezoelectric pillar 21 vibrates longitudinally along the stacking direction of the piezoelectric layer 211 when a voltage is applied to the internal electrodes 221, 222 via the external electrodes 223, 224. The longitudinal vibration here means, for example, "vibration in the thickness direction defined by the piezoelectric constant d33." The longitudinal vibration of the driving piezoelectric pillar 21 displaces the vibration plate 30 in the stacking direction of the piezoelectric layer 211, thereby deforming the pressure chamber 31.

[0032] As an example, each piezoelectric pillar 21 has 3 to 50 piezoelectric layers 211, each of which has a thickness of 10 to 40 μm, with the product of the thickness and the total number of layers being less than 1000 μm.

[0033] The vibration plate 30 is fixed to the ends of the driving piezoelectric pillars 21 and the support piezoelectric pillars 22 of the pair of actuators 20 on the opposite side in the Z direction from the connecting portion 26. In other words, the vibration plate 30 is joined to the surfaces of the piezoelectric pillars 21, 22 on the opposite side from the base 10 in the vibration direction of the piezoelectric pillars 21, i.e., the surfaces of the piezoelectric pillars 21, 22 on the nozzle plate 50 side.

[0034] 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 to be deformable by the deformation of the driving piezoelectric pillar 21. The vibration plate 30 forms a pressure chamber 31 together with the flow path member 40 and the nozzle plate 50. The vibration plate 30 extends in the arrangement direction (column direction) of the multiple piezoelectric pillars 21, 22. In other words, the vibration plate 30 extends along a plane perpendicular to the vibration direction of the piezoelectric pillars 21. One main surface of the vibration plate 30 is bonded to the driving piezoelectric pillars 21 and support piezoelectric pillars 22 of the actuator 20 and to the frame portion 60. The other main surface of the vibration plate 30 is bonded to the flow path member 40.

[0035] As an example, the vibration plate 30 is made of a nickel or SUS plate, and the thickness dimension along the vibration direction is set to about 5 μm to 15 μm. Note that the vibration plate 30 may have folds or steps formed in a portion adjacent to a vibration part vibrating when driven by the driving piezoelectric pillar 21 or between adjacent vibration parts, so that the vibration plate 30 can be easily displaced when driven by the driving piezoelectric pillar 21.

[0036] The vibration plate 30 has a through hole 33 formed in a region joined to the frame portion 60, the through hole 33 communicating with a common chamber 61 (described later) formed in the frame portion 60. For example, the through hole 33 may be provided with a filter having a large number of pores through which liquid can pass. The through hole 33 may be singular or plural.

[0037] 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. When two actuators 20 are provided, the flow path member 40 includes partition wall portions that separate the pressure chambers 31 driven by each actuator 20. The peripheral wall portion 41 and the partition wall portion 43 are provided between the vibration plate 30 and the nozzle plate 50, thereby forming a predetermined ink flow path including the plurality of pressure chambers 31 separated from each other and the plurality of individual flow paths 32 separated from each other and communicating the pressure chambers 31 with a common chamber 61 together with the vibration plate 30 and the nozzle plate 50.

[0038] The peripheral wall portion 41 surrounds an area between the vibration plate 30 and the nozzle plate 50 that forms the multiple pressure chambers 31 and the multiple individual flow paths 32. The multiple partition wall portions 43 divide the area inside the peripheral wall portion 41 into the multiple pressure chambers 31 and the multiple individual flow paths 32. That is, both side walls in the parallel direction of the multiple pressure chambers 31 (multiple individual flow paths 32) are formed by the partition wall portions 43. The multiple partition wall portions 43 are also provided at positions facing the piezoelectric support columns 22 across the vibration plate 30 in the Z direction. As a result, the partition wall portions 43 regulate the displacement of the piezoelectric support columns 22 and the piezoelectric support columns 22 at the portions of the vibration plate 30 where the piezoelectric support columns 22 are fixed.

[0039] The multiple pressure chambers 31 are spaces formed on one side of the vibration region of the vibration plate 30, and communicate with a common chamber 61 via individual flow paths 32 and through holes 33. The multiple pressure chambers 31 communicate with nozzles 51 formed in the nozzle plate 50. Moreover, the pressure chambers 31 are closed on the side opposite to the nozzle plate 50 by the vibration plate 30.

[0040] The nozzle plate 50 has a plurality of nozzles 51 formed in positions facing the plurality of pressure chambers 31. The nozzle plate 50 is configured as a rectangular plate 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 surfaces of the peripheral wall portion 41 and the partition wall portion 43 on the opposite side to the vibration plate 30 so as to cover the openings on one side of the pressure chambers 31.

[0041] A plurality of nozzles 51 are arranged in the same direction as the parallel direction of the plurality of pressure chambers 31 to form a nozzle row. For example, the nozzles 51 are provided in one row in a configuration in which one actuator 20 is provided, and in a configuration in which a pair of actuators are provided, the nozzles 51 are provided in two rows.

[0042] The frame portion 60 is a structure that is joined to the vibration plate 30 together with the piezoelectric pillars 21 and 22. A pair of frame portions 60 are provided on the main surface of the vibration plate 30 opposite to the peripheral wall portion 41 of the piezoelectric pillars 21 and 22. For example, a pair of frame portions 60 are arranged adjacent to the actuator 20. The frame portion 60 constitutes the outer shell of the inkjet head 1. In addition, for example, a common chamber 61 that serves as a liquid flow path is formed inside the frame portion 60. The common chamber 61 is formed inside the frame portion 60. The common chamber 61 communicates with the through hole 33 formed in the vibration plate 30, and communicates with the pressure chamber 31 through the individual flow path 32. For example, a pair of frame portions 60 in which the common chamber 61 is formed are provided, a pair of individual flow paths 32 are provided, and the pair of individual flow paths 32 are connected to the pair of common chambers 61, respectively. For example, one common chamber 61 and one individual flow path 32 are used to supply ink to the pressure chamber 31, and the other common chamber 61 and the other individual flow path 32 are used to discharge ink from the pressure chamber 31. Note that the pair of common chambers 61 and the pair of individual flow paths 32 may be configured to be used for supplying ink, or may be configured to be shared for supplying and discharging ink.

[0043] The drive circuit 70 includes an FPC 71 (Flexible Printed Circuit) having one end connected to the external electrodes 223, 224, a drive IC 72 mounted on the FPC 71, and a printed wiring board 73 mounted on the other end of the FPC 71.

[0044] The drive circuit 70 applies a drive voltage to the external electrodes 223 and 224 via the drive IC 72 to drive the drive piezoelectric pillar 21 , thereby increasing or decreasing the volume of the pressure chamber 31 and causing droplets to be ejected from the nozzle 51 .

[0045] The FPC 71 is connected to one side of the laminated piezoelectric member, and is connected to a plurality of external electrodes 223, 224. As the FPC 71, a COF (Chip on Film) on which a driving IC 72 is mounted as an electronic component is used.

[0046] The driving IC 72 is connected to external electrodes 223 and 224 via the FPC 71. The driving IC 72 is an electronic component used for ejection control.

[0047] The driving IC 72 generates a control signal and a driving signal for operating each driving piezoelectric pillar 21. The driving IC 72 generates a control signal for controlling the timing of ink ejection and the selection of the driving piezoelectric pillar 21 for ejecting ink according to an image signal input from the control unit 116 of the inkjet recording device 100 on which the inkjet head 1 is mounted. The driving IC 72 also generates a voltage to be applied to the driving piezoelectric pillar 21, i.e., a driving signal, according to a control signal from the control unit 116. When the driving IC 72 applies a driving signal to the driving piezoelectric pillar 21, the driving piezoelectric pillar 21 is driven to displace the vibration plate 30 to change the volume of the pressure chamber 31. This causes the ink filled in the pressure chamber 31 to generate pressure vibration. The pressure vibration causes ink to be ejected from the nozzle 51 communicating with the pressure chamber 31. The inkjet head 1 may be configured to realize gradation expression by changing the amount of ink droplets that land on one pixel. The inkjet head 1 may also be configured to change the amount of ink droplets that land on one pixel by changing the number of times ink is ejected. In this manner, the driving IC 72 is an example of an application unit that applies a driving signal to the driving piezoelectric pillar 21 .

[0048] For example, the driving IC 72 includes a data buffer, a decoder, and a driver. The data buffer stores print data for each driving piezoelectric pillar 21 in chronological order. The decoder controls the driver for each driving piezoelectric pillar 21 based on the print data stored in the data buffer. The driver outputs a drive signal that operates each driving piezoelectric pillar 21 based on the control of the decoder. The drive signal is, for example, a voltage applied to each driving piezoelectric pillar 21.

[0049] The printed wiring board 73 is a PWA (Printing Wiring Assembly) on which various electronic components and connectors are mounted, and has a head control circuit 731. The printed wiring board 73 is connected to the control unit 116 of the inkjet recording apparatus 100.

[0050] The driving circuit 70 selects and supplies a driving signal or a standby voltage to the multiple driving piezoelectric pillars 21 based on a command from the control unit 116 of the inkjet recording device 100 and print data. The driving circuit 70 also drives the driving piezoelectric pillars 21 by single-nozzle driving and multiple-nozzle simultaneous driving as driving patterns. The single-nozzle driving is a driving pattern in which adjacent driving piezoelectric pillars 21 are not driven, and a driving signal is applied to the first external electrode 223 of one channel to drive one driving piezoelectric pillar 21. The multiple-nozzle simultaneous driving is a driving pattern in which a driving signal is applied to the first external electrodes 223 of multiple channels to drive all of the multiple driving piezoelectric pillars 21 or some of the adjacent driving piezoelectric pillars 21 at the same time.

[0051] As shown in FIG. 5, the drive circuit 70 includes a drive signal source 81 that outputs a drive signal to be applied to the first external electrode 223, which is an individual electrode; a standby voltage source 82 that outputs a standby voltage to be applied to the second external electrode 224, which is a common electrode; a switching element 83 that selectively connects each drive piezoelectric pillar 21 to one of the drive signal source 81 and the standby voltage source 82; a plurality of first electrical resistors 84 that are internal resistances of the switching element 83 between the drive piezoelectric pillar 21 and the drive signal source 81 or the standby voltage source 82; and one or more second electrical resistors 85 that connect adjacent drive piezoelectric pillars 21 to at least some of the multiple drive piezoelectric pillars 21.

[0052] The switching elements 83 are switched based on print data. The switching elements 83 connect the driving piezoelectric pillars 21 that are driven to eject ink to the driving signal source 81, and connect the non-driven driving piezoelectric pillars 21 that do not eject ink to the standby voltage source 82. The multiple switching elements 83 are included in the driving IC 72, for example.

[0053] The first electrical resistor 84 is an internal resistance of the switching element 83. Here, the resistance value of the first electrical resistor 84 is taken as RA. Note that the first electrical resistor 84 may be a resistor added externally to the switching element 83 in series with the switching element 83. In this case, the resistance value RA of the first electrical resistor 84 is the total value of the internal resistance of the switching element and the resistance added externally to the switching element 83.

[0054] The second electric resistor 85 electrically connects the first external electrodes 223, which are individual electrodes of some adjacent driving piezoelectric columns 21, between the driving piezoelectric column 21 and the switching element 83 with a predetermined resistance value. That is, the second electric resistor 85 includes a plurality of electric resistors 851 provided between the first external electrodes 223 of the adjacent driving piezoelectric columns 21. Here, the number of electric resistors 851 is n-1 when the number of first external electrodes 223 to be connected is n. Here, the resistance value of the electric resistor 851 is RB. The smaller the resistance value RB of the electric resistor 851, the smaller the ejection speed and ejection volume during single nozzle driving, so the resistance value RB of the electric resistor 851 is set to match the ejection speed and ejection volume during simultaneous multiple nozzle driving. Here, the reduction rate D of the voltage amplitude with respect to simultaneous multiple nozzle driving during single nozzle driving is D=2 / (3+RB / RA).

[0055] The second electric resistor 85 is formed, for example, on the actuator 20, and is formed by a thin film formed across the first external electrodes 223 of the multiple driving piezoelectric pillars 21 that are simultaneously driven in the multiple nozzle configuration. As a specific example, the second electric resistor 85 electrically connects the first external electrodes 223 of all the driving piezoelectric pillars 21. Note that a configuration may be adopted in which a plurality of second electric resistors 85 are provided, and each second electric resistor 85 connects the first external electrodes 223 of some of the driving piezoelectric pillars 21 that are simultaneously driven in the multiple nozzle configuration.

[0056] The second electric resistor 85 is formed of, for example, a metal with high resistivity, such as a nickel-chromium alloy or titanium, or a carbon coating. The thickness of the second electric resistor 85 is several nanometers to several micrometers, and is formed by deposition using a method such as vacuum deposition or sputtering, or by printing using a printing method such as screen printing.

[0057] As a specific example, the second electric resistor 85 is formed of a thin film extending in the arrangement direction of the first external electrodes 223 and having a uniform width in a direction (width direction) perpendicular to the longitudinal direction and thickness direction. The multiple electric resistors 851 formed in the second electric resistor 85 are formed by trimming portions 852 formed by multiple slits 853 formed by laser processing or the like between the multiple first external electrodes 223. In other words, the second electric resistor 85 is partially narrowed in width and elongated in length by the multiple slits 853 formed between adjacent connected first external electrodes 223, thereby forming the multiple electric resistors 851.

[0058] The resistance value RB of the electric resistor 851 can be set by adjusting the shape of the trimming portion 852, specifically, the number, length, and width of the slits 853. In the example of FIG. 4, the trimming portion 852 is formed by forming three rectangular slits 853 arranged in the longitudinal direction of the second electric resistor 85, shifted in the width direction perpendicular to the longitudinal direction and thickness direction of the second electric resistor 85, and alternately arranged. The number, width, length, and shape of the slits 853 are appropriately set in accordance with the resistance value RB of the electric resistor 851. For this reason, the slits 853 do not have to be rectangular, but may be long in the width direction of the second electric resistor 85 and have curved ends, a semicircular shape, a polygonal shape other than a rectangle, or the like.

[0059] In this embodiment, the second electric resistor 85 is an integrated thin film on the actuator 20 so as to connect the first external electrodes 223, and a plurality of trimming portions 852 are provided to form a plurality of electric resistors 851. However, the second electric resistor 85 is not limited to this configuration, and may be configured such that the electric resistor 851 is provided between the first external electrode 223 that performs the multi-nozzle simultaneous drive and the switching element 83, and between the adjacent first external electrodes 223. For example, the second electric resistor 85 may be configured to be provided on the FPC 71 or the driving IC 72. The second electric resistor 85 may be formed of a semiconductor such as a transistor. However, it is preferable that the resistance value RB of the electric resistor 851 of the second electric resistor 85 can be adjusted by trimming or the like.

[0060] According to the inkjet head 1 configured in this manner, when the switching element 83 is switched and a voltage is applied to the driving piezoelectric pillar 21 by the driving signal, the driving piezoelectric pillar 21 expands. The expanded driving piezoelectric pillar 21 deforms the vibration plate 30, and the volume of the pressure chamber 31 decreases. That is, the vibration plate 30 pressurizes the ink in the pressure chamber 31, and ink droplets are ejected from the nozzle 51. When a certain driving piezoelectric pillar 21 expands, the supporting piezoelectric pillar 22 also expands due to a mechanical reaction force.

[0061] Generally, in the case of single-nozzle drive, the driving piezoelectric pillar 21 adjacent to the driven driving piezoelectric pillar 21 is not driven, so the extension of the support piezoelectric pillar 22 is small, as shown in Fig. 2. Generally, in the case of multiple-nozzle simultaneous drive, the adjacent driving piezoelectric pillars 21 are driven simultaneously, as shown in Fig. 3, so the extension of the support piezoelectric pillars 22 between the driven driving piezoelectric pillars 21 becomes large.

[0062] For this reason, in a conventional inkjet head not having the second electric resistor 85, the amount of deformation of the diaphragm 30 relative to the amount of deformation of the driving piezoelectric pillar 21 is smaller in the multiple nozzle simultaneous drive than in the single nozzle drive. And because the amount of deformation of the diaphragm 30 in the multiple nozzle simultaneous drive is smaller than in the single nozzle drive, in the conventional technology, the pressure generated in the pressure chamber 31 is smaller in the multiple nozzle simultaneous drive than in the single nozzle drive. This causes variations in the speed and volume of the ink droplets ejected depending on the print pattern, deteriorating the print quality, which is the problem of so-called crosstalk.

[0063] In contrast, the inkjet head 1 according to the embodiment, as shown in Figures 4 to 6, electrically connects adjacent first external electrodes 223 that perform multi-nozzle simultaneous drive by a second electric resistor 85, and has an electric resistor 851 between the first external electrodes 223. As a result, in the case of single-nozzle drive, part of the current of the drive signal applied to the first external electrode 223 provided on the drive piezoelectric pillar 21 to be driven flows to the first external electrode 223 of the adjacent drive piezoelectric pillar 21 via the electric resistor 851. Therefore, the voltage amplitude that drives the drive piezoelectric pillar 21 to be driven decreases. In the case of multi-nozzle simultaneous drive, the voltages of the multiple first external electrodes 223 that are driven simultaneously are the same, so no current flows through the electric resistor 851 and the voltage amplitude does not decrease.

[0064] In this way, the pressure generated in the pressure chamber 31 when a single nozzle is driven is reduced by the second electrical resistor 85, so that the pressure generated in the pressure chamber 31 when a single nozzle is driven and when multiple nozzles are simultaneously driven can be made the same or approximated. Therefore, the inkjet head 1 can eliminate dot misalignment and density unevenness due to the drive pattern.

[0065] For example, in the example of FIG. 6, an example of performing single nozzle driving and multiple nozzle simultaneous driving in six channels ChA to ChF is shown. In FIG. 6, the driving piezoelectric pillars 21 of the channels ChA to ChF are respectively indicated as CA to CF, and the first electric resistors 84 provided between the driving piezoelectric pillars CA to CF and the switching elements 83 in the channels ChA to ChF are respectively indicated as 841 to 846. Also, the electric resistances 851 of the second electric resistors 85 provided between the first external electrodes 223 of the driving piezoelectric pillars CA to CF are respectively indicated as 8511 to 8515. For example, in the example of FIG. 6, the driving piezoelectric pillar CB of the channel ChB is driven as a single nozzle, and the driving piezoelectric pillars CD to CF of the channels ChD to ChF are driven as multiple nozzle simultaneous driving. 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. An example of a simulation of the voltages applied to the driving piezoelectric pillars CA to CF (first external electrodes 223) in the example shown in Fig. 6 is shown in Fig. 7. Here, the voltage values ​​applied to the driving piezoelectric pillars CA to CF, respectively, are denoted as VA to VF. In Fig. 7, the vertical axis represents voltage and the horizontal axis represents time.

[0066] As shown in FIG. 7, the voltage amplitude of the voltage value VB of the driving piezoelectric pillar CB for driving a single nozzle is smaller than the voltage amplitude of the voltage values ​​VD to VF of the driving piezoelectric pillars CD to CF for simultaneously driving multiple nozzles. Therefore, the phenomenon of crosstalk, in which the pressure generated in the pressure chamber 31 is smaller in the simultaneous driving of multiple nozzles than in the single nozzle driving, is corrected, and the pressure generated in the pressure chamber 31 becomes approximately the same value in the single nozzle driving and the simultaneous driving of multiple nozzles, and the problem of crosstalk, in which the speed and volume of the ink droplets ejected depending on the printing pattern vary and the printing quality deteriorates, is eliminated. In addition, the voltage values ​​VA and VC of the non-driven driving piezoelectric pillars CA and CC adjacent to the driving piezoelectric pillar CB for driving a single nozzle, become standby voltages. The voltage values ​​VA and VC have a slight voltage amplitude, and a small pressure is generated in the pressure chamber 31, but the pressure is not high enough to eject ink, so that the problem of ink being ejected from the non-driven nozzle does not occur.

[0067] An example of an inkjet recording apparatus 100 including an inkjet head 1 will be described below with reference to Fig. 9. 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 conveying device 115, and a control unit 116.

[0068] The inkjet recording device 100 is a liquid ejection device that performs an image formation process on paper P by ejecting liquid such as ink while transporting the paper P as a printing medium, which is the ejection target, along a predetermined transport path R from a medium supply section 112 through an image forming section 113 to a medium ejection section 114.

[0069] The housing 111 constitutes the outer shell of the inkjet recording apparatus 100. The housing 111 is provided at a predetermined location with an outlet for discharging the paper P to the outside.

[0070] The medium supply unit 112 includes a plurality of paper feed cassettes, and is configured to be able to hold a plurality of sheets of paper P of various sizes in a stack.

[0071] The medium discharge unit 114 includes a paper discharge tray configured to be able to hold the paper P discharged from the discharge opening.

[0072] 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 so as to face the support section 117.

[0073] The support section 117 includes a conveyor belt 118 provided in a loop shape in a predetermined area where image formation is performed, a support plate 119 supporting the conveyor belt 118 from the back side, and a plurality of belt rollers 120 provided on the back side of the conveyor belt 118.

[0074] During image formation, the support section 117 supports the paper P on a holding surface, which is the upper surface of the conveyor belt 118, and conveys the paper P downstream by feeding the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120.

[0075] The head unit 130 includes multiple (e.g., four-color) inkjet heads 1, ink tanks 132 as liquid tanks mounted on each inkjet head 1, a connection flow path 133 connecting the inkjet heads 1 and the ink tanks 132, and a supply pump 134.

[0076] In this embodiment, for example, inkjet heads 1 of four colors, cyan, magenta, yellow, and black, and ink tanks 132 each containing an ink of each color are provided. The ink tanks 132 are connected to the inkjet heads 1 by connection flow paths 133.

[0077] In addition, a negative pressure control device such as a pump (not shown) is connected to the ink tank 132. Then, by controlling the negative pressure inside the ink tank 132 by the negative pressure control device according to the water head value between the inkjet head 1 and the ink tank 132, the ink supplied to each nozzle 51 of the inkjet head 1 is caused to form a meniscus of a predetermined shape.

[0078] The supply pump 134 is a liquid delivery pump constituted by, for example, a piezoelectric pump. The supply pump 134 is provided in a supply flow path. The supply pump 134 is connected to a control circuit 1161 of the control unit 116 by wiring and is configured to be controllable by the control unit 116. The supply pump 134 supplies liquid to the inkjet head 1.

[0079] The conveying device 115 conveys the paper P along a conveying path R that runs from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114. The conveying device 115 includes a plurality of guide plate pairs 121 and a plurality of conveying rollers 122 that are arranged along the conveying path R.

[0080] Each of the guide plate pairs 121 includes a pair of plate members disposed opposite each other with the paper P being transported therebetween, and guides the paper P along the transport path R.

[0081] The conveying rollers 122 are driven to rotate under the control of the control unit 116, thereby sending the paper P downstream along the conveying path R. Sensors for detecting the conveying status of the paper are disposed at various points along the conveying path R.

[0082] The control unit 116 includes a control circuit 1161 such as a CPU (Central Processing Unit) which serves as a controller, a ROM (Read Only Memory) which stores various programs, a RAM (Random Access Memory) which temporarily stores various variable data, image data, and the like, and an interface unit which inputs data from the outside and outputs data to the outside.

[0083] In the inkjet recording device 100 configured as above, when the control unit 116 detects a print instruction by a user operating the operation input unit, for example, in an interface, the control unit 116 drives the transport device 115 to transport the paper P and outputs a print signal to the head unit 130 at a predetermined timing, thereby driving the inkjet head 1. As a discharge operation, the inkjet head 1 sends a drive signal to the drive IC 72 by an image signal corresponding to image data, applies a drive voltage to the internal electrodes 221 and 222, and selectively drives the drive piezoelectric pillars 21 to be discharged, for example, to vibrate vertically in the stacking direction, and changes the volume of the pressure chamber 31 to discharge ink from the nozzles 51, thereby forming an image on the paper P held on the conveyor belt 118. 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.

[0084] The inkjet head 1 and inkjet recording device 100 according to the embodiment described above can eliminate dot misalignment and density unevenness due to the drive pattern by providing electrical resistance 851 between each of the multiple first external electrodes 223 that apply voltages individually to the multiple driving piezoelectric pillars 21.

[0085] The embodiment is not limited to the above-mentioned example. For example, in the above-mentioned example, the driving circuit 70 switches the switching element 83 to apply a standby voltage to the support piezoelectric pillars 22 that do not eject ink, but the present invention is not limited to this example. For example, the switching element 83 may be configured to disconnect the support piezoelectric pillars 22 that do not eject ink from the driving signal source 81. For example, FIG. 10 shows an example of a simulation of the voltage applied to the driving piezoelectric pillars CA to CF (first external electrodes 223) in the example shown in FIG. 9. As shown in FIG. 10, even if the inkjet head 1 is configured to open the first external electrodes 223 in the non-ejecting channels, it is found that the voltage amplitude during single nozzle driving is reduced, and deterioration of print quality due to crosstalk can be prevented. However, since charging and discharging are also performed on the driving piezoelectric pillars 21 that do not eject ink, there is a risk that energy consumption will increase and that meniscus fluctuations will occur in the non-ejecting nozzles 51, causing problems when there is an ink ejection operation thereafter.

[0086] Furthermore, in a configuration in which the first external electrode 223 is open when not ejecting, there is a risk of a so-called edge occurring, in which a voltage difference occurs between the driving piezoelectric pillar 21 (first external electrode 223) located at the end and the adjacent driving piezoelectric pillar 21 among the multiple driving piezoelectric pillars 21 (first external electrode 223) electrically connected by the second electrical resistor 85. Therefore, in order to suppress the occurrence of edges in the printing range, the driving piezoelectric pillar 21 located at the end among the multiple driving piezoelectric pillars 21 connected to the second electrical resistor 85 may be made a dummy that is not driven, or a configuration may be used in which the corresponding nozzle 51 is not provided and the same voltage is applied to the second driving piezoelectric pillar 21 from the end.

[0087] In the above example, the second electric resistor 85 is formed of a thin film extending in the arrangement direction of the first external electrodes 223 and having a uniform width in the direction perpendicular to the longitudinal direction and the thickness direction (width direction), but the present invention is not limited to this. For example, the second electric resistor 85 may have a partially changed width in order to increase the resistance difference between the region connected to the first external electrode 223 and the trimmed portion 852 constituting the electric resistor 851. For example, the second electric resistor 85 may have a configuration in which the width of the region connected to the first external electrode 223 in the direction perpendicular to the longitudinal direction and the thickness direction is larger than the width of the region forming the electric resistor 851.

[0088] In the above example, the liquid ejection device 100 ejects ink as the liquid from the liquid ejection head 1, but the liquid is not limited to ink. That is, the liquid ejection head 1 and the liquid ejection device 100 can be used in, for example, 3D printers, industrial manufacturing machines, and medical applications, and can eject various liquids.

[0089] According to at least one of the embodiments described above, by providing electrical resistance between each of a number of individual electrodes that apply voltages individually to a number of driving piezoelectric columns, it is possible to provide a liquid ejection head and a liquid ejection device that can eliminate dot misalignment and density unevenness caused by the drive pattern.

[0090] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0091] 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 portion, 30...vibration plate, 31...pressure chamber, 32...individual flow path, 33...through hole, 40...flow path member, 41...peripheral wall portion, 43...partition wall portion, 50...nozzle plate, 51...nozzle, 60...frame portion, 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 electric resistor, 85...second electric resistor, 851...electrical resistance, 852...trimming portion, 853... Slit, 100...liquid ejection device (inkjet recording device), 111...housing, 112...medium supply section, 113...image forming section, 114...medium discharge section, 115...conveying device, 116...control section, 117...support section, 118...conveying belt, 119...support plate, 120...belt roller, 121...pair of guide plates, 122...conveying roller, 130...head unit, 132...ink tank, 133...connecting flow path, 134...supply pump, 211...piezoelectric layer, 212...dummy layer, 221...first internal electrode, 222...second internal electrode, 223...first external electrode (individual electrode), 224...second external electrode (common electrode), 1161...control circuit.

Claims

1. A plurality of pressure chambers; an actuator having a plurality of piezoelectric bodies that varies the volume of the pressure chamber in response to a drive signal; A plurality of individual electrodes provided on the plurality of piezoelectric bodies, respectively; a nozzle plate in which a plurality of nozzles are formed, each of which communicates with the plurality of pressure chambers; a plurality of switching elements electrically connected to the plurality of individual electrodes for selectively connecting a drive signal for the piezoelectric body; a plurality of electrical resistors electrically connecting the individual electrodes of the piezoelectric bodies adjacent to each other; A liquid ejection head comprising:

2. an electric resistor electrically connecting at least one of the plurality of individual electrodes; The liquid ejection head according to claim 1 , wherein the plurality of electrical resistors are formed by slits provided between the individual electrodes of the electrical resistor element.

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

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

5. A liquid ejection apparatus comprising the liquid ejection head according to claim 1 .

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