Liquid discharge apparatus

Abstract

To provide a liquid discharge apparatus capable of suppressing occurrence of meniscus collapse and a failure to eliminate thickening of liquid in a nozzle.SOLUTION: A liquid discharge apparatus includes: a liquid discharge head including individual flow paths including pressure chambers and nozzles, a common supplying flow path, a common discharging flow path, and piezoelectric elements provided corresponding to the pressure chambers; and a drive control unit for performing discharge control and micro-vibration control, where the nozzles are configured by coupling a first nozzle portion and a second nozzle portion in a height direction, the second nozzle portion being provided closer to the individual flow paths than the first nozzle portion and having a larger diameter than the first nozzle portion, and where the nozzle satisfies B<20 [μm] and C+D>70 [μm] and the drive control unit is configured to perform the micro-vibration control so as to satisfy C / 3<M<C+D / 2 when A is a diameter of the first nozzle portion, B is a diameter of the second nozzle portion, C is a height of the first nozzle portion, D is a height of the second nozzle portion, and M is a maximum pull-in amount of meniscuses of liquid at the time of the micro-vibration control by the drive control unit.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a liquid ejection device.

Background Art

[0002] Liquid ejection devices that eject a liquid such as ink onto a medium such as printing paper have been conventionally proposed. For example, the liquid ejection device described in Patent Document 1 includes a pressure chamber filled with a liquid, a piezoelectric element that causes a pressure change in the liquid in the pressure generation chamber, and a nozzle that ejects the liquid in the pressure chamber in accordance with the pressure change.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the liquid at the nozzle opening is in contact with the atmosphere, evaporation of moisture occurs. Then, the liquid at the nozzle opening thickens because the solvent component decreases. As a result, there is a risk of nozzle clogging or poor ejection, which may adversely affect the ejection characteristics of the droplets. In order to solve this problem, an operation of ejecting a large amount of liquid, so-called flushing, may be performed before the recording operation on the medium by liquid ejection. However, flushing has a drawback of consuming the liquid.

[0005] In order to solve the above problems, it is known to perform a circulation operation and a fine vibration operation. The circulation operation is an operation of discharging liquid while supplying liquid to an individual flow path communicating with a nozzle. By this circulation operation, it is possible to supply new liquid into the individual flow path while discharging the liquid that can be thickened by evaporation at the nozzle opening from the individual flow path. Therefore, thickening of the liquid in the nozzle can be suppressed. The fine vibration operation is an operation of applying a fine vibration waveform to a piezoelectric element to cause meniscus vibration of the liquid at the nozzle opening to such an extent that the liquid is not discharged, and stirring the liquid in the nozzle. By this fine vibration operation, local thickening in the nozzle can be eliminated.

[0006] Normally, thickening of the ink can be sufficiently suppressed by performing either the circulation operation or the fine vibration operation. However, there are cases where both the circulation operation and the fine vibration operation must be performed simultaneously, such as in the liquid ejection device of Patent Document 1. If the nozzle has a straight pipe structure without a step, there is no particular problem in using the circulation operation and the fine vibration operation in combination. However, when using a so-called two-stage nozzle divided into an upper-stage nozzle and a lower-stage nozzle, it has been found that when the circulation operation and the fine vibration operation are used in combination, there are problems such as meniscus breakdown or poor elimination of thickening of the liquid in the nozzle.

[0007] As a result of the inventors' studies, it has been found that by setting the diameter of the upper-stage nozzle and the total length of the nozzle within a predetermined range and setting the fine vibration operation under predetermined conditions in the two-stage nozzle, meniscus breakdown and poor elimination of thickening of the liquid in the nozzle are less likely to occur.

Means for Solving the Problems

[0008] A liquid ejection device according to one aspect of the present disclosure includes an individual flow path including a pressure chamber and a nozzle, a common supply flow path communicating with the plurality of individual flow paths and supplying liquid to the plurality of individual flow paths, a common discharge flow path communicating with the plurality of individual flow paths and discharging liquid from the plurality of individual flow paths, and a liquid ejection head including a piezoelectric element provided corresponding to the pressure chamber, a discharge control for driving the piezoelectric element to eject liquid, and a drive control unit for performing a fine vibration control for driving the piezoelectric element to finely vibrate the liquid in the nozzle. The nozzle is configured by connecting a first nozzle portion and a second nozzle portion provided on the individual flow path side with respect to the first nozzle portion and having a diameter larger than that of the first nozzle portion in the height direction. Let the diameter of the first nozzle portion be A, the diameter of the second nozzle portion be B, the height of the first nozzle portion be C, the height of the second nozzle portion be D, and the maximum retraction amount of the liquid meniscus during the fine vibration control by the drive control unit be M. The nozzle satisfies B < 20 [μm] and C + D > 70 [μm], and the drive control unit performs the fine vibration control so as to satisfy C / 3 < M < C + D / 2.

Brief Description of Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments according to the present disclosure will be described with reference to the accompanying drawings. Note that the dimensions and scales of each part in the drawings are appropriately different from the actual ones, and there are also some parts schematically shown for easy understanding. In addition, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description.

[0011] The following description will be made using the X-axis, Y-axis, and Z-axis that intersect each other as appropriate. Also, hereinafter, one direction along the X-axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, the directions opposite to each other along the Y-axis are the Y1 direction and the Y2 direction. The directions opposite to each other along the Z-axis are the Z1 direction and the Z2 direction. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z-axis does not have to be a vertical axis. Also, the X-axis, Y-axis, and Z-axis typically intersect at right angles to each other, but are not limited thereto, and may intersect at an angle within a range of 80° or more and 100° or less, for example.

[0012] A: Embodiment A1: Overall Configuration of Liquid Discharge Device FIG. 1 is a schematic diagram showing a configuration example of a liquid discharge device 100 according to an embodiment. The liquid discharge device 100 is an inkjet printing device that discharges a liquid such as ink as droplets onto a medium 90. The medium 90 is, for example, printing paper. Note that the medium 90 is not limited to printing paper, and may be a printing target of any material such as a resin film or a fabric, for example.

[0013] As shown in FIG. 1, the liquid discharge device 100 includes a liquid container 10, a drive control unit 20, a transport mechanism 30, a movement mechanism 40, a liquid discharge head 50, and a circulation mechanism 60.

[0014] The liquid container 10 stores ink. Specific examples of the liquid container 10 include a cartridge that is detachable from the liquid discharge device 100, a bag-shaped ink pack made of a flexible film, and an ink tank that can be refilled with ink. Note that the type of ink stored in the liquid container 10 is arbitrary.

[0015] The drive control unit 20 controls the operations of the respective elements of the liquid ejection device 100. The drive control unit 20 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory.

[0016] The transport mechanism 30 transports the medium 90 in the Y1 direction under the control of the drive control unit 20. The movement mechanism 40 reciprocates the liquid ejection head 50 along the X-axis under the control of the drive control unit 20. The movement mechanism 40 has a substantially box-shaped carriage 41 that houses the liquid ejection head 50, and an endless conveyor belt 42 to which the carriage 41 is fixed. Note that the number of liquid ejection heads 50 mounted on the carriage 41 is not limited to one, and a plurality may be used. In addition to the liquid ejection head 50, the aforementioned liquid container 10 may be mounted on the carriage 41.

[0017] The liquid ejection head 50 ejects ink supplied from the liquid container 10 from each of a plurality of nozzles onto the medium 90 under the control of the drive control unit 20 based on the print data Img. By performing this ejection in parallel with the transport of the medium 90 by the transport mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, an image corresponding to the print data Img with ink is formed on the surface of the medium 90.

[0018] The liquid container 10 is connected to the liquid ejection head 50 via a circulation mechanism 60. The circulation mechanism 60 is a mechanism that supplies ink to the liquid ejection head 50 and collects the ink discharged from the liquid ejection head 50 for re-supplying it to the liquid ejection head 50 under the control of the drive control unit 20. By the operation of the circulation mechanism 60, it is possible to suppress an increase in the viscosity of the ink and reduce the retention of air bubbles in the ink.

[0019] A2: Electrical Configuration of Liquid Ejection Device 100 FIG. 2 is a diagram showing the electrical configuration of the liquid ejection apparatus 100 according to the embodiment. As shown in FIG. 2, the liquid ejection head 50 includes a head chip 51 and a supply circuit 52. The head chip 51 has a plurality of piezoelectric elements 51e. As will be described later, for example, two piezoelectric elements 51e are provided for one nozzle. Note that one piezoelectric element 51e may be provided for one nozzle N.

[0020] The supply circuit 52 switches whether to supply the drive signal Com output from the drive control unit 20 as a supply signal Vin to each of the plurality of piezoelectric elements 51e under the control of the drive control unit 20.

[0021] As shown in FIG. 2, the drive control unit 20 includes a control circuit 21, a storage circuit 22, a power supply circuit 23, and a drive signal generation unit 24.

[0022] The control circuit 21 has a function of controlling the operations of the respective parts of the liquid ejection apparatus 100 and a function of processing various data. The control circuit 21 includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the control circuit 21 may include a programmable logic device such as an FPGA (field-programmable gate array) instead of or in addition to the CPU. Further, when the control circuit 21 is configured by a plurality of processors, the plurality of processors may be mounted on different substrates or the like. Note that the control circuit 21 may be regarded as the “drive control unit”.

[0023] The memory circuit 22 stores various programs executed by the control circuit 21 and various data such as print data Img processed by the control circuit 21. The memory circuit 22 includes, for example, one or both semiconductor memories of a volatile memory such as a RAM (Random Access Memory) and a non-volatile memory such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a PROM (Programmable ROM). The print data Img is supplied from an external device 200 such as a personal computer or a digital camera. Note that the memory circuit 22 may be configured as a part of the control circuit 21.

[0024] The power supply circuit 23 receives power supply from a commercial power supply (not shown) and generates various predetermined potentials. The generated various potentials are appropriately supplied to each part of the liquid ejection device 100. For example, the power supply circuit 23 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the liquid ejection head 50. Also, the power supply potential VHV is supplied to the drive signal generation unit 24.

[0025] The drive signal generation unit 24 is a circuit that repeatedly generates a drive signal Com for driving each piezoelectric element 51e. Specifically, the drive signal generation unit 24 includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation unit 24, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 21 from a digital signal to an analog signal. The drive signal Com is generated by the amplification circuit amplifying the analog signal using the power supply potential VHV from the power supply circuit 23. The signal of the waveform actually supplied to each piezoelectric element 51e among the waveforms included in the drive signal Com is the aforementioned supply signal Vin. The waveform designation signal dCom is a digital signal for defining the waveform of the drive signal Com.

[0026] The control circuit 21 controls the operations of each part of the liquid ejection device 100 by executing a program stored in the memory circuit 22. Here, the control circuit 21 generates a control signal Sk1, a control signal Sk2, a print data signal SI, a waveform designation signal dCom, a latch signal LAT, a change signal CNG, and a clock signal CLK as signals for controlling the operations of each part of the liquid ejection device 100 by executing the program.

[0027] The control signal Sk1 is a signal for controlling the drive of the conveyance mechanism 30. The control signal Sk2 is a signal for controlling the drive of the moving mechanism 40. The print data signal SI is a digital signal for designating the operation state of each piezoelectric element 51e. The latch signal LAT and the change signal CNG are timing signals that are used in combination with the print data signal SI and define the ink ejection timing from each nozzle. These timing signals are generated based on, for example, the output of an encoder that detects the position of the carriage 41 described above.

[0028] A3: Flow path of the liquid ejection head 50 FIG. 3 is a schematic diagram for explaining the circulation flow path of the liquid ejection head 50. As shown in FIG. 3, the liquid ejection head 50 is provided with a plurality of individual flow paths IP, a common supply flow path R1, and a common discharge flow path R2. A circulation mechanism 60 is connected to the common supply flow path R1 and the common discharge flow path R2. The plurality of individual flow paths IP, the common supply flow path R1, and the common discharge flow path R2 constitute the circulation flow path.

[0029] Each individual flow path IP has a nozzle N, a pressure chamber C1a, a pressure chamber C1b, a communication flow path Nf, an individual supply flow path Ra1, and an individual discharge flow path Ra2.

[0030] The plurality of nozzles N are arranged along the Y axis. Each of the plurality of nozzles N ejects ink in the Z2 direction. The set of the plurality of nozzles N constitutes a nozzle row L0. Also, the plurality of nozzles N are arranged at equal intervals.

[0031] Each nozzle N communicates with an individual flow path IP. Each of the plurality of individual flow paths IP extends along the X-axis and communicates with different nozzles N. Further, the plurality of individual flow paths IP are arranged along the Y-axis. Each individual flow path IP supplies ink to the pressure chamber C1a and discharges ink from the pressure chamber C1b.

[0032] Each of the pressure chamber C1a and the pressure chamber C1b extends along the X-axis and is a space where the ink discharged from the nozzle N communicating with the individual flow path IP is stored. In the example shown in FIG. 3, the plurality of pressure chambers C1a are arranged along the Y-axis. Similarly, the plurality of pressure chambers C1b are arranged along the Y-axis. Note that, in each individual flow path IP, the positions of the pressure chamber C1a and the pressure chamber C1b in the direction along the Y-axis are the same as each other in the example shown in FIG. 3, but may be different from each other. Further, hereinafter, when the pressure chamber C1a and the pressure chamber C1b are not particularly distinguished, they are simply referred to as "pressure chamber C1".

[0033] A communication flow path Nf is arranged between the pressure chamber C1a and the pressure chamber C1b in each individual flow path IP. In each individual flow path IP, the communication flow path Nf is a flow path that communicates the pressure chamber C1a and the pressure chamber C1b. Further, the plurality of communication flow paths Nf are arranged along the Y-axis at intervals from each other. A nozzle N is provided in each communication flow path Nf. In each communication flow path Nf, ink is discharged from the nozzle N due to the pressure fluctuations in the pressure chamber C1a and the pressure chamber C1b described above.

[0034] An individual supply flow path Ra1 is provided between the pressure chamber C1a and the common supply flow path R1 in each individual flow path IP. The individual supply flow path Ra1 is a flow path that communicates the pressure chamber C1a and the common supply flow path R1. Similarly, an individual discharge flow path Ra2 is provided between the pressure chamber C1b and the common discharge flow path R2 in each individual flow path IP. The individual discharge flow path Ra2 is a flow path that communicates the pressure chamber C1b and the common discharge flow path R2.

[0035] Each of the plurality of individual flow paths IP communicates with a common supply flow path R1 and a common discharge flow path R2, respectively, which are common to them. Each of the common supply flow path R1 and the common discharge flow path R2 is a space extending along the Y-axis over the entire range where the plurality of nozzles N are distributed. When viewed in the direction along the Z-axis, a plurality of individual flow paths IP are located between the common supply flow path R1 and the common discharge flow path R2.

[0036] The common supply flow path R1 is connected to an end portion E1 in the X2 direction of each individual flow path IP. The common supply flow path R1 communicates with the plurality of individual flow paths IP and supplies ink to the plurality of individual flow paths IP. Also, ink for supplying each individual flow path IP is stored in the common supply flow path R1. On the other hand, the common discharge flow path R2 is connected to an end portion E2 in the X1 direction of each individual flow path IP. The common discharge flow path R2 communicates with the plurality of individual flow paths IP and discharges ink from the plurality of individual flow paths IP. Also, ink discharged from each individual flow path IP is stored in the common discharge flow path R2.

[0037] A circulation mechanism 60 is connected to the common supply flow path R1 and the common discharge flow path R2. The circulation mechanism 60 supplies ink to the common supply flow path R1 and collects the ink discharged from the common discharge flow path R2 for re-supplying it to the common supply flow path R1. The circulation mechanism 60 includes a first supply pump 61, a second supply pump 62, a storage container 63, a recovery flow path 64, and a supply flow path 65.

[0038] The first supply pump 61 is a pump that supplies the ink stored in the liquid container 10 to the storage container 63. The storage container 63 is a sub-tank that temporarily stores the ink supplied from the liquid container 10. The recovery channel 64 connects the common discharge channel R2 and the storage container 63, and is a channel for recovering the ink from the common discharge channel R2 to the storage container 63. In addition to the ink stored in the liquid container 10 being supplied to the storage container 63 from the first supply pump 61, the ink discharged from each individual channel IP to the common discharge channel R2 is also supplied to the storage container 63 via the recovery channel 64. The second supply pump 62 is a pump that sends out the ink stored in the storage container 63. The supply channel 65 connects the common supply channel R1 and the storage container 63, and is a channel for supplying the ink from the storage container 63 to the common supply channel R1.

[0039] A4: Specific structure of the head chip 51 FIG. 4 is a view corresponding to the cross-section taken along line A1-A1 in FIG. 3. In FIG. 4, a cross-section of the head chip 51 cut along a plane orthogonal to the Y-axis along the individual channel IP is shown. The head chip 51 includes a nozzle substrate 51a, a flow path substrate 51b, a pressure chamber substrate 51c, a diaphragm 51d, a plurality of piezoelectric elements 51e, a case 51f, a protective plate 51g, and a wiring substrate 51h.

[0040] The nozzle substrate 51a, the flow path substrate 51b, the pressure chamber substrate 51c, and the diaphragm 51d are laminated in this order in the Z1 direction. These members extend along the Y-axis and are manufactured, for example, by processing a single-crystal silicon substrate using semiconductor processing technology. Also, these members are joined to each other by an adhesive or the like. Note that other layers or substrates such as an adhesive layer may be appropriately interposed between two adjacent members among these members.

[0041] The nozzle substrate 51a is provided with a plurality of nozzles N. Each of the plurality of nozzles N extends along the Z-axis and penetrates the nozzle substrate 51a, and is a through-hole for allowing ink to pass through.

[0042] The flow path substrate 51b is provided with a liquid chamber R1a which is a part of the common supply flow path R1 and a liquid chamber R2a which is a part of the common discharge flow path R2, together with the portions of the plurality of individual flow paths IP described above excluding the pressure chambers C1a and C1b. That is, the flow path substrate 51b is provided with a communication flow path Nf, an individual supply flow path Ra1, an individual discharge flow path Ra2, a liquid chamber R1a, and a liquid chamber R2a.

[0043] Each of the liquid chamber R1a and the liquid chamber R2a is a space penetrating the flow path substrate 51b. An absorber 51i for closing the opening due to the space is installed on the surface of the flow path substrate 51b facing the Z2 direction.

[0044] The absorber 51i is a layered member made of an elastic material. The absorber 51i constitutes a part of the wall surfaces of the common supply flow path R1 and the common discharge flow path R2, and absorbs pressure fluctuations in the common supply flow path R1 and the common discharge flow path R2.

[0045] The communication flow path Nf has a first communication flow path Na1, a second communication flow path Na2, and a nozzle flow path Nfa. Each of the first communication flow path Na1 and the second communication flow path Na2 is a space penetrating the flow path substrate 51b. The first communication flow path Na1 and the second communication flow path Na2 communicate with each other via the nozzle flow path Nfa. The first communication flow path Na1 communicates the pressure chamber C1a and the nozzle flow path Nfa. The second communication flow path Na2 communicates the pressure chamber C1b and the nozzle flow path Nfa. The nozzle flow path Nfa is a space in a groove provided on the surface of the flow path substrate 51b facing the Z2 direction and extends along the X axis. The nozzle substrate 51a constitutes a part of the wall surface of the nozzle flow path Nfa.

[0046] Each of the individual supply channel Ra1 and the individual discharge channel Ra2 is a space penetrating the flow path substrate 51b. The individual supply channel Ra1 communicates the common supply channel R1 and the pressure chamber C1a, and supplies the ink from the common supply channel R1 to the pressure chamber C1a. One end of the individual supply channel Ra1 opens to the surface of the flow path substrate 51b facing the Z1 direction. On the other hand, the other end of the individual supply channel Ra1 is the upstream end of the individual channel IP, and opens to the wall surface of the common supply channel R1 in the flow path substrate 51b. In contrast, the individual discharge channel Ra2 communicates the common discharge channel R2 and the pressure chamber C1b, and discharges the ink from the pressure chamber C1b to the common discharge channel R2. One end of the individual discharge channel Ra2 opens to the surface of the flow path substrate 51b facing the Z1 direction. On the other hand, the other end of the individual discharge channel Ra2 is the downstream end of the individual channel IP, and opens to the wall surface of the common discharge channel R2 in the flow path substrate 51b.

[0047] The pressure chamber substrate 51c is provided with the pressure chambers C1a and C1b of a plurality of individual channels IP. Each of the pressure chambers C1a and C1b penetrates the pressure chamber substrate 51c, and is a gap between the flow path substrate 51b and the diaphragm 51d. The pressure chamber C1a communicates with the nozzle N via the first communication channel Na1 and the nozzle channel Nfa. The pressure chamber C1b communicates with the nozzle N via the second communication channel Na2 and the nozzle channel Nfa.

[0048] The diaphragm 51d is an elastically vibratable plate-like member. The diaphragm 51d is, for example, a laminate including a first layer made of silicon oxide (SiO 2 ) and a second layer made of zirconium oxide (ZrO 2 ). Another layer such as a metal oxide may be interposed between the first layer and the second layer. Note that part or all of the diaphragm 51d may be integrally formed of the same material as the pressure chamber substrate 51c. For example, the diaphragm 51d and the pressure chamber substrate 51c can be integrally formed by selectively removing a part in the thickness direction of a region corresponding to the pressure chamber C1 in a plate-like member having a predetermined thickness. Further, the diaphragm 51d may be composed of a single material layer.

[0049] On the surface of the diaphragm 51d facing the Z1 direction, a plurality of piezoelectric elements 51e provided corresponding to different pressure chambers C1 are installed. The plurality of piezoelectric elements 51e are provided one-to-one with respect to the plurality of pressure chambers C1. The piezoelectric element 51e gives a pressure fluctuation to the ink in the pressure chamber C1 according to the drive signal Com. Each piezoelectric element 51e is composed of, for example, a laminate of a first electrode and a second electrode facing each other and a piezoelectric layer disposed between both electrodes. Each piezoelectric element 51e discharges the ink in the pressure chamber C1 from the nozzle N by varying the pressure of the ink in the pressure chamber C1. When the drive signal Com is supplied, the piezoelectric element 51e vibrates the diaphragm 51d as it deforms. Along with this vibration, the pressure chamber C1 expands and contracts, so that the pressure of the ink in the pressure chamber C1 fluctuates.

[0050] The case 51f is a case for storing ink. The case 51f is provided with a liquid chamber R1b which is a part other than the liquid chamber R1a of the common supply channel R1, a liquid chamber R2b which is a part other than the liquid chamber R2a of the common discharge channel R2, an inlet R01, and an outlet R02. Each of the liquid chamber R1b and the liquid chamber R2b is a recess provided on the surface of the case 51f facing the Z2 direction. The inlet R01 is a through hole formed by an inner peripheral surface extending between the surface of the case 51f facing the Z1 direction and the wall surface of the liquid chamber R1b. The supply channel 65 of the aforementioned circulation mechanism 60 is connected to the inlet R01. The outlet R02 is a through hole formed by an inner peripheral surface extending between the surface of the case 51f facing the Z1 direction and the wall surface of the liquid chamber R2b. The recovery channel 64 of the aforementioned circulation mechanism 60 is connected to the outlet R02.

[0051] The protective plate 51g is a plate-like member installed on the surface of the diaphragm 51d facing the Z1 direction, protecting the plurality of piezoelectric elements 51e and reinforcing the mechanical strength of the diaphragm 51d. A space for accommodating the plurality of piezoelectric elements 51e is formed between the protective plate 51g and the diaphragm 51d.

[0052] The wiring board 51h is mounted on the surface of the diaphragm 51d facing the Z1 direction, and is a mounting component for electrically connecting the drive control unit 20 and the head chip 51. For example, a flexible wiring board 51h such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably used. The supply circuit 52 described above is mounted on the wiring board 51h.

[0053] In the head chip 51 having the above configuration, due to the operation of the circulation mechanism 60 described above, the ink flows through the common supply channel R1, the individual supply channel Ra1, the pressure chamber C1a, the communication channel Nf, the pressure chamber C1b, the individual discharge channel Ra2, and the common discharge channel R2 in this order. Further, by driving the piezoelectric elements 51e corresponding to both the pressure chamber C1a and the pressure chamber C1b simultaneously by the supply signal Vin from the supply circuit 52, the pressures in the pressure chamber C1a and the pressure chamber C1b are varied, and the ink is discharged from the nozzle N along with the pressure variation.

[0054] A5: Nozzle N FIG. 5 is an enlarged cross-sectional view of the nozzle N. In FIG. 5, a view of a part of the nozzle channel Nfa of the individual channel IP and the nozzle N in a cross-section orthogonal to the Y axis is shown. As shown in FIG. 5, the nozzle N branches from the nozzle channel Nfa of the individual channel IP and extends in a direction different from that of the nozzle channel Nfa. Specifically, while the nozzle channel Nfa extends in the direction along the X axis, the nozzle N extends in the direction along the Z axis.

[0055] The nozzle N is a through hole formed in the nozzle substrate 51a, and includes a discharge-side opening end N1 and a connection portion N2. The discharge-side opening end N1 is the opening end on the surface of the nozzle N facing the Z2 direction of the nozzle substrate 51a. The connection portion N2 is the boundary portion of the nozzle N with the nozzle channel Nfa. The length along the Z axis from the discharge-side opening end N1 to the connection portion N2 is the total length E of the nozzle N.

[0056] The nozzle N has a first nozzle portion NP1 and a second nozzle portion NP2. The nozzle N is a so-called two-stage nozzle. The first nozzle portion NP1 and the second nozzle portion NP2 are arranged in the Z1 direction in this order and are connected in the direction along the Z axis which is the height direction. Each of the first nozzle portion NP1 and the second nozzle portion NP2 extends along the Z axis. The second nozzle portion NP2 is provided on the nozzle flow path Nfa side of the individual flow path IP rather than the first nozzle portion NP1. The nozzle flow path Nfa and the first nozzle portion NP1 communicate with each other via the second nozzle portion NP2. Further, the first nozzle portion NP1 includes a discharge-side opening end N1. The second nozzle portion NP2 includes a connection portion N2.

[0057] The cross-sectional areas of the first nozzle portion NP1 and the second nozzle portion NP2 are circular. The central axis along the Z axis of the first nozzle portion NP1 and the central axis along the Z axis of the second nozzle portion NP2 coincide. Therefore, the first nozzle portion NP1 and the second nozzle portion NP2 are provided coaxially. The central axis of the first nozzle portion NP1 refers to an axis passing through the center of the first nozzle portion NP1 and extending along the Z axis direction. The central axis of the second nozzle portion NP2 refers to an axis passing through the center of the second nozzle portion NP2 and extending along the Z axis direction. The center mentioned here refers to, for example, a point where the position in the X-axis direction bisects the maximum width in the X-axis direction of each portion equally, and the position in the Y-axis direction bisects the maximum width in the Y-axis direction of each portion equally.

[0058] In the illustrated example, the height C of the first nozzle portion NP1 is smaller than the height D of the second nozzle portion NP2. However, the height C may be equal to the height D or may be larger than the height D. The height C is the length along the Z axis from the discharge-side opening end N1 to the boundary portion between the first nozzle portion NP1 and the second nozzle portion NP2. The height D is the length along the Z axis from the boundary portion between the first nozzle portion NP1 and the second nozzle portion NP2 to the connection portion N2.

[0059] The diameter B of the second nozzle portion NP2 is larger than the diameter A of the first nozzle portion NP1. Therefore, the nozzle N has a shape in which the width gradually increases in the Z1 direction. Also, since the diameter A is smaller than the diameter B, it is possible to eject fine ink droplets and improve the landing accuracy of the ink droplets as compared with the case where the diameter of the nozzle N is constant. Further, it is preferable that the diameter B is smaller than the width of the nozzle flow path Nfa, that is, the length along the Z axis. By the diameter B being smaller than the width of the nozzle flow path Nfa, it is possible to reduce crosstalk between two adjacent second nozzle portions NP2 in the direction along the Y axis.

[0060] At the discharge-side opening end N1 of the nozzle N described above, the ink is in contact with the outside air. For this reason, the viscosity of the ink increases due to the evaporation of the solvent component contained in the ink at the discharge-side opening end N1. As a result, there is a risk of nozzle clogging or poor discharge. To suppress this, so-called flushing in which a large amount of ink is discharged is known. However, this flushing has the drawback of consuming a large amount of ink.

[0061] Therefore, in order to suppress nozzle clogging and poor discharge without wasting a large amount of ink, the liquid ejection device 100 performs a circulation operation and a fine vibration operation.

[0062] The liquid ejection device 100 has a circulation mechanism 60. By providing the circulation mechanism 60, it is possible to perform a circulation operation of supplying and discharging ink to the individual flow path IP having the nozzle N. For this reason, even if the viscosity of the ink increases due to the evaporation of the ink at the discharge-side opening end N1 of the nozzle N, the ink is discharged to the common discharge flow path R2 through the individual flow path IP, and fresh ink is supplied from the common supply flow path R1. Therefore, it is possible to suppress the increase in the viscosity of the ink at the discharge-side opening end N1.

[0063] Further, the aforementioned drive control unit 20 performs ejection control for driving the piezoelectric element 51e to eject ink and fine vibration control for driving the piezoelectric element 51e to finely vibrate the ink in the nozzle N. The fine vibration control is performed during a non-ejection period when ink is not ejected from the nozzle N. By the fine vibration control, the meniscus MN can be finely vibrated to such an extent that ink is not ejected from the nozzle N. When the fine vibration control is performed, the ink in the nozzle N is agitated during the non-ejection period. Therefore, it is possible to suppress the increase in the viscosity of the ink near the ejection-side opening end N1.

[0064] In a nozzle with a normal constant width, the increase in the viscosity of the ink can be suppressed by performing at least one of the aforementioned circulation operation and fine vibration operation. On the other hand, in the case of a so-called two-stage nozzle, it may be necessary to use both the circulation operation and the fine vibration operation in combination.

[0065] For example, the total length E of the nozzle N, which is a two-stage nozzle, tends to be longer than the total length of a nozzle N with a normal constant width in order to ensure a certain length in the Z-axis direction of each of the first nozzle portion NP1 and the second nozzle portion NP2. Therefore, in a two-stage nozzle, it is difficult for the circulating flow of the ink in the individual flow path IP to reach the first nozzle portion NP1. For this reason, in a two-stage nozzle, it is preferable to use both the circulation operation and the fine vibration operation in combination.

[0066] By using the circulation operation and the fine vibration operation in combination, in addition to the generation of an ink flow in the nozzle N by the fine vibration operation, the action of the circulating flow of the ink by the circulation mechanism 60 is combined, and the replacement of the ink between the nozzle N and the nozzle flow path Nfa can be smoothly performed. Therefore, it is possible to suppress the thickening of the ink in the nozzle N while avoiding the waste of ink due to flushing.

[0067] However, in the two-stage nozzle, when the circulation operation and the micro-vibration operation are used in combination, problems that are unlikely to occur in a normal nozzle with a constant width occur. Specifically, in the two-stage nozzle, when the circulation operation and the micro-vibration operation are used in combination, problems such as meniscus breakdown or poor thickening resolution of the ink in the nozzle N may occur. Meniscus breakdown means that the meniscus MN during micro-vibration collides with the circulation flow of the nozzle flow path Nfa into which the nozzle N has flowed, causing interface breakdown. Due to this meniscus breakdown, the bubbles that may exist in the nozzle N are refined, resulting in deterioration of the ink ejection characteristics.

[0068] The inventors have intensively studied to solve such problems in the two-stage nozzle. As a result, it has been found that by setting the diameter A of the first nozzle portion NP1 and the total length E of the nozzle N within a predetermined range and performing micro-vibration control under predetermined conditions, meniscus breakdown and poor thickening resolution of the ink in the nozzle N are less likely to occur.

[0069] Specifically, the nozzle N satisfies Equation [1], and the drive control unit 20 performs micro-vibration control so as to satisfy Equation [2]. B < 20 [μm], and C + D > 70 [μm] … [1] C / 3 < M < C + D / 2 … [2] In Equation [1], B is the diameter of the second nozzle portion NP2. C is the height of the first nozzle portion NP1. D is the height of the second nozzle portion NP2. In Equation [2], M is the maximum drawing amount of the ink meniscus MN during micro-vibration control by the drive control unit 20. The maximum drawing amount M is the state in which the meniscus MN is located most in the Z1 direction in the nozzle N. Note that the diameters A, B and the heights C, D in each part refer to the maximum diameter or height among a plurality of diameters or heights in each part such as an elliptical shape.

[0070] By satisfying the above requirements, it has been found that it is possible to eliminate the breakdown of the meniscus MN and the occurrence of poor thickening resolution of the ink in the nozzle N. The two-stage nozzle has a more complex configuration than a normal nozzle with a constant width. In a configuration where only a two-stage nozzle is simply provided, it is difficult to solve problems specific to the two-stage nozzle that are unlikely to occur in a normal nozzle with a constant width. The above requirements are based on the actual experimental results of micro-vibration control in the two-stage nozzle.

[0071] FIG. 6 shows the evaluation results when the diameter B of the second nozzle portion NP2 is changed. Specifically, FIG. 6 shows the diameter B of the second nozzle portion NP2 and the result of evaluating the difficulty of ink flowing from the nozzle flow path Nfa into the nozzle N. In FIG. 6, "〇" indicates that it is difficult for ink to flow into the nozzle N and the amount of ink flowing into the nozzle N is appropriate. "△" indicates that there is no problem with the ink flowing into the nozzle N. "×" indicates that there is a problem with the ink flowing into the nozzle N. Note that "△" is inferior to "〇" but superior to "×".

[0072] In Examples 1, 2, 3, and 4, the amount of ink flowing into the nozzle N did not become excessive, and the amount of ink flowing into the nozzle N was appropriate. In Example 5, although the amount of ink flowing into the nozzle N was larger than that in Examples 1 to 4, there was no problem. In these Examples 1 to 5, it was difficult for the ink in the nozzle flow path Nfa to enter the second nozzle portion NP2 of the nozzle N, and thus it was difficult to form a flow that would break the meniscus MN in the nozzle N. On the other hand, in Comparative Examples 1, 2, and 3, the amount of ink flowing into the nozzle N became excessive, and meniscus breakdown occurred.

[0073] Note that from the viewpoint of the ease of manufacturing the nozzle N, it is preferable that the diameter B satisfies the relationship 1 [μm] ≦ B.

[0074] FIG. 7 shows the evaluation results when the total length of the nozzle N is changed. The total length E of the nozzle N is the sum of the height C of the first nozzle portion LP1 and the height D of the second nozzle portion NP2. Specifically, FIG. 7 shows the result of evaluating whether the total length E of the nozzle N and the meniscus MN reach a position where the meniscus MN reaches the circulating flow in the nozzle flow path Nfa in the nozzle N. In FIG. 7, that the circulating flow does not reach the meniscus MN is indicated by "〇". When the circulating flow does not reach the meniscus MN but the meniscus MN may be affected by the circulating flow, it is indicated by "△". That the circulating flow reaches the meniscus MN is indicated by "×". Note that "△" is inferior to "〇" but superior to "×".

[0075] In Examples 6, 7, 8, and 9, the meniscus MN did not reach the circulating flow, and thus, meniscus breakdown did not occur. In Example 10, although the meniscus MN did not reach the circulating flow and thus meniscus breakdown did not occur, the meniscus MN was slightly affected by the circulating flow. By increasing the total length E of the nozzle N as in these examples, it became difficult for the ink in the nozzle flow path Nfa to reach the meniscus MN located near the discharge-side opening end N1 of the nozzle N. For this reason, meniscus breakdown did not occur, and thus, the discharge characteristics were good. On the other hand, in Comparative Examples 4, 5, 6, 7, and 8, the meniscus MN reached the circulating flow. For this reason, in Comparative Examples 4 to 8, meniscus breakdown occurred, and thus, the discharge characteristics were not good.

[0076] As can be seen from FIGS. 6 and 7, by satisfying the above formula [1], meniscus breakdown can be prevented. On the other hand, when at least one of B < 20 and C + D > 70 in the formula [1] is not satisfied, it is difficult to prevent meniscus breakdown.

[0077] In a liquid ejection device 100 including a nozzle N satisfying formula [1], a drive control unit 20 performs fine vibration control so as to satisfy formula [2]. This formula [2] is based on experimental results. By causing the piezoelectric element 51e to perform fine vibration control so that the drive control unit 20 satisfies formula [2], in addition to suppressing meniscus breakdown, it is possible to prevent poor resolution of ink thickening.

[0078] Even for a nozzle N that satisfies formula [1], if fine vibration control is not performed so as to satisfy formula [2], it is difficult to prevent poor resolution of ink thickening. For example, when the drive control unit 20 performs fine vibration control so that the maximum retraction amount M is equal to or less than the lower limit value of formula [2], the fine vibration operation is insufficient, and poor resolution of ink thickening occurs. Further, when the drive control unit 20 performs fine vibration control so that the maximum retraction amount M is equal to or greater than the upper limit value of formula [2], since the maximum retraction amount M is too large, meniscus breakdown occurs.

[0079] Also, the diameter A of the first nozzle portion NP1 is not particularly limited. However, the nozzle N preferably satisfies A ≤ 15. The fact that the diameter A is 15 μm or less enables minute ink droplets to be ejected onto the medium 90. That is, the liquid ejection device 100 can form a large number of minute dot patterns on the medium 90. Conventionally, when the opening end of a two-stage nozzle is minute, it has been very difficult to prevent the occurrence of poor resolution of ink thickening and meniscus breakdown. According to the liquid ejection device 100 that satisfies the above [1] and [2], even if the diameter A of the nozzle N corresponding to the diameter of the opening end of the two-stage nozzle is minute, it is possible to suitably eliminate the occurrence of poor resolution of ink thickening and meniscus breakdown.

[0080] Also, the drive control unit 20 preferably performs fine vibration control so as to satisfy C / 2 < M < C. That is, the drive control unit 20 causes the piezoelectric element 51e to perform fine vibration control so that the maximum retraction amount M fits within the first nozzle portion NP1. By the drive control unit 20 performing fine vibration control so as to satisfy the above relationship, it is possible to more reliably prevent meniscus breakdown compared to the case where the above relationship is not satisfied.

[0081] On the other hand, the drive control unit 20 may perform fine vibration control so as to satisfy C < M < C + D / 2. That is, the drive control unit 20 may cause the piezoelectric element 51e to perform fine vibration control so that the maximum pull-in amount M is within the second nozzle portion NP2. By performing fine vibration control such that the drive control unit 20 satisfies the above relationship, ink thickening can be particularly effectively suppressed as compared with the case where the above relationship is not satisfied.

[0082] Further, the drive control unit 20 performs fine vibration control in a state where ink is supplied from the common supply channel R1 to the individual channels IP and discharged from the individual channels IP to the common discharge channel R2. That is, the drive control unit 20 is performing a circulation operation and a fine vibration operation simultaneously. In the liquid ejection device 100 in which both the circulation operation and the fine vibration operation are performed simultaneously, by satisfying the above formulas [1] and [2], in the two-stage nozzle, meniscus breakdown and poor resolution of ink thickening in the nozzle N can be effectively suppressed.

[0083] 2. Modification Each of the forms exemplified above can be variously modified. Specific modification modes applicable to each of the above forms are exemplified below. Two or more modes arbitrarily selected from the following examples can be appropriately combined within a range where they do not conflict with each other.

[0084] The liquid ejection device 100 of the above-described embodiment had a configuration in which the ink in the individual channels IP circulated by including the circulation mechanism 60. However, for example, the ink in the individual channels IP may be circulated by driving two piezoelectric elements 51e provided for one nozzle N. In this case, the circulation mechanism 60 may be omitted.

[0085] In the above-described embodiment, two piezoelectric elements 51e were provided for one nozzle N. However, the liquid ejection device 100 may have a configuration in which only one piezoelectric element 51e is provided for one nozzle N.

[0086] In the foregoing embodiment, the liquid ejection device 100 was of the serial type that reciprocates the carriage 41, but it may be of the line type in which a plurality of nozzles N are distributed over the entire width of the medium 90.

[0087] The liquid ejection device 100 illustrated in the foregoing embodiment may be adopted not only for devices dedicated to printing but also for various devices such as facsimile machines and copiers, and the applications of the present disclosure are not particularly limited. However, the applications of the liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a coloring material is used as a manufacturing device for forming a color filter of a display device such as a liquid crystal display panel. Also, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wirings and electrodes of a wiring board. Further, a liquid ejection device that ejects a solution of an organic substance related to a living body is used, for example, as a manufacturing device for manufacturing a biochip.

[0088] Although the present invention has been described based on preferred embodiments, the present invention is not limited to the foregoing embodiments. Also, the configuration of each part of the present invention can be replaced with any configuration that exhibits the same functions as those of the foregoing embodiments, and any configuration can be added.

Description of Reference Numerals

[0089] 20... drive control unit, 50... liquid ejection head, 51... head chip, 60... circulation mechanism, 100... liquid ejection device, A... diameter, B... diameter, C... height, D... height, L... total length, C1... pressure chamber, IP... individual flow path, M... maximum suction amount, MN... meniscus, N... nozzle, N1... discharge side opening end, N2... connection part, NP1... first nozzle part, NP2... second nozzle part, Nf... communication flow path, Nfa... nozzle flow path, R1... common supply flow path, R2... common discharge flow path.

Claims

1. An individual flow path including a pressure chamber and a nozzle, A common supply flow path communicating with the plurality of individual flow paths and supplying liquid to the plurality of individual flow paths, A common discharge flow path communicating with the plurality of individual flow paths and discharging liquid from the plurality of individual flow paths, And a liquid discharge head provided corresponding to the pressure chamber, A liquid discharge device having a discharge control for driving the piezoelectric element to discharge liquid and a drive control unit for performing a fine vibration control for driving the piezoelectric element to finely vibrate the liquid in the nozzle, The nozzle is configured by connecting a first nozzle portion and a second nozzle portion provided on the individual flow path side with respect to the first nozzle portion and having a diameter larger than that of the first nozzle portion in the height direction, Let A be the diameter of the first nozzle portion, Let B be the diameter of the second nozzle portion, Let C be the height of the first nozzle portion, Let D be the height of the second nozzle portion, When the maximum drawing amount of the liquid meniscus during the fine vibration control by the drive control unit is M, The nozzle satisfies B < 20 [μm] and C + D > 70 [μm], The drive control unit performs the fine vibration control so as to satisfy C / 3 < M < C + D / 2. A liquid discharge device characterized by this.

2. The liquid discharge device according to claim 1, wherein the nozzle satisfies A ≤ 15 [μm].

3. The liquid discharge device according to claim 1 or 2, wherein the drive control unit performs the fine vibration control so as to satisfy C / 2 < M < C.

4. The liquid discharge device according to claim 1 or 2, wherein the drive control unit performs the fine vibration control so as to satisfy C < M < C + D / 2.

5. The liquid discharge device according to claim 1, wherein the drive control unit performs the fine vibration control in a state where liquid is supplied from the common supply flow path to the individual flow path and discharged from the individual flow path to the common discharge flow path.

6. The liquid discharge device according to claim 1, wherein the nozzle is configured such that the central axis of the first nozzle portion coincides with the central axis of the second nozzle portion.

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