Liquid ejection device and article manufacturing method

Abstract

To provide an advantageous technique for restoring discharge performance while suppressing liquid consumption. [Solution] The liquid ejection device comprises an ejection head having a nozzle that ejects liquid, a piezoelectric element for ejecting liquid from the nozzle, and a detection circuit that detects the signal output from the piezoelectric element; a circulation path that circulates liquid through the ejection head; and a control unit that controls an agitation operation that drives the piezoelectric element to agitate liquid in the nozzle without ejecting liquid from the nozzle during a recovery operation from a stopped state in which the circulation of liquid in the circulation path has stopped, and the control unit determines the waveform of the drive signal given to the piezoelectric element during the agitation operation based on the residual vibration waveform detected by the detection circuit when the piezoelectric element is operated without ejecting liquid from the nozzle.

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection device and an article manufacturing method. [Background technology]

[0002] In recent years, a method of forming a pattern or film by disposing droplets on a substrate using a liquid ejection device has attracted attention. The method of forming a pattern using a liquid ejection device has advantages such as high material usage efficiency, easy miniaturization of the manufacturing device because it is a non-vacuum process, and the ability to process large-area substrates.

[0003] In a liquid ejection device, the circulation of liquid may be stopped when maintenance is performed. When the circulation of liquid is stopped, the liquid in the nozzles that are open to the outside air may dry out and the viscosity of the liquid may increase. Therefore, when returning from a state in which the circulation of liquid has been stopped, it is necessary to restore the ability to eject droplets from the nozzles.

[0004] Patent Document 1 describes detecting residual vibrations that occur within a pressure chamber after driving a pressure generating element provided for the pressure chamber, and determining whether ejection is necessary based on the residual vibrations. Patent Document 1 also describes setting a blank ejection waveform according to the increased viscosity detected based on the residual vibrations when it is determined that ejection is necessary. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6547422 Summary of the Invention [Problem to be solved by the invention]

[0006] When liquid is ejected from the nozzles during a recovery operation to restore the liquid ejection performance of the nozzles, droplets are consumed. Therefore, it is desirable to restore the ejection performance without ejecting liquid as much as possible.

[0007] An object of the present invention is to provide an advantageous technique for restoring ejection performance while suppressing liquid consumption. [Means for solving the problem]

[0008] One aspect of the present invention relates to a liquid ejection device comprising an ejection head having a nozzle for ejecting liquid, a piezoelectric element for ejecting liquid from the nozzle, and a detection circuit for detecting a signal output from the piezoelectric element, and a circulation path for circulating liquid through the ejection head, wherein the liquid ejection device comprises a control unit that controls an agitation operation to drive the piezoelectric element to agitate the liquid in the nozzle without ejecting liquid from the nozzle during a recovery operation from a stopped state in which the circulation of liquid in the circulation path has stopped, and the control unit determines the waveform of the drive signal given to the piezoelectric element during the agitation operation based on the residual vibration waveform detected by the detection circuit when the piezoelectric element is operated without ejecting liquid from the nozzle. [Effects of the Invention]

[0009] According to the present invention, an advantageous technique for restoring ejection performance while suppressing liquid consumption is provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram schematically illustrating a configuration of a liquid ejection apparatus according to an embodiment. [Figure 2] FIG. 1 is a diagram schematically illustrating the configuration of a liquid head according to an embodiment. [Figure 3] 4A and 4B are diagrams illustrating a drive waveform for detecting a residual vibration waveform (a drive waveform for detection) and an example of a residual vibration waveform. [Figure 4]5A and 5B are diagrams illustrating examples of waveforms of drive signals for ejecting droplets and waveforms of drive signals for detection. [Figure 5] 10A and 10B are diagrams illustrating examples of changes in the residual vibration waveform due to changes in the viscosity of the liquid in the nozzle. [Figure 6] 5A to 5C are diagrams illustrating the operation of the liquid ejection device according to the first embodiment. [Figure 7] 10A and 10B are diagrams for explaining a method for determining the waveform of a drive signal in a stirring operation based on the waveform of a residual vibration waveform. [Figure 8] 10A to 10C are diagrams illustrating the operation of a liquid ejection device according to a second embodiment. [Figure 9] 10A to 10C are diagrams illustrating the operation of a liquid ejection device according to a third embodiment. [Figure 10] 10A to 10C are diagrams illustrating the operation of a liquid ejection device according to a fourth embodiment. [Figure 11] 13A to 13C are diagrams illustrating the operation of a liquid ejection device according to a fifth embodiment. [Figure 12] 13A to 13C are diagrams illustrating the operation of the liquid ejection device according to the sixth embodiment. [Figure 13] FIG. 1 is a perspective view schematically illustrating a process of disposing droplets on a substrate. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0012] In this embodiment, the directions are described according to an XYZ coordinate system, in which the Z axis is vertically upward and the XY plane is a horizontal plane.

[0013] FIG. 1 schematically illustrates the configuration of a liquid ejection device 1 according to one embodiment. The liquid ejection device 1 can be configured to eject a liquid 4 in the form of droplets. The liquid 4 is sometimes called ink. The liquid 4 may be, for example, a liquid containing a solute and a solvent for forming an organic layer of an OLED (organic light emitting diode), but may also be another liquid, such as a liquid containing a conductive material or a resin. The liquid ejection device 1 can be configured to deposit droplets of the liquid 4 at multiple target positions (or target areas) on a substrate 2.

[0014] The liquid ejection device 1 may include a substrate stage 3 that holds a substrate 2. The liquid ejection device 1 may include a drive mechanism (not shown) that drives the substrate stage 3 along the X-axis, Y-axis, and Z-axis, and the substrate 2 may be driven by driving the substrate stage 3 with the drive mechanism. The drive mechanism may further include a mechanism that drives the substrate stage 3 in rotation about each of the X-axis, Y-axis, and Z-axis. The substrate 2 may be a glass substrate or a plastic substrate. The substrate 2 is typically a rectangular plate member, but is not limited to a particular shape as long as it can function as a substrate. For example, the substrate 2 may be a deformable sheet or may have a disk shape. The substrate 2 may have a pixel array area 201 on which the liquid 4 can be applied or placed.

[0015] The liquid ejection device 1 may include one or more ejection heads 5 that eject droplets of a liquid 4. FIG. 2 schematically illustrates the configuration of the ejection head 5. The ejection head 5 may include nozzles 19 that eject the liquid 4 and piezoelectric elements 502 that eject the liquid 4 from the nozzles 19 in droplet form. The liquid ejection device 1 may include a circulation path 13 that circulates the liquid 4 through the ejection head 5. Typically, the ejection head 5 may include multiple nozzles 19 and multiple piezoelectric elements 502 that respectively correspond to the multiple nozzles 19. The liquid ejection device 1 may further include a detection circuit DC. The detection circuit DC may be configured to detect signals output from each piezoelectric element 502. The liquid ejection device 1 may further include a tank 7 that stores the liquid 4, and a pump 12 that circulates the liquid 4 through the tank 7 and the circulation path 13. The liquid ejection device 1 may further include a recovery unit 8 that recovers the function of the ejection head 5 by cleaning the nozzles 19, etc., of the ejection head 5.

[0016] A placement error may occur when the substrate 2 is placed on the substrate stage 3 by a transport mechanism (not shown). Furthermore, shape distortion may occur in the X and Y directions as the substrate 2 undergoes various manufacturing processes. For this reason, the liquid ejection device 1 may be provided with an alignment scope 9 for measuring the position of the substrate 2 and the amount of distortion of the substrate 2. In order to measure the positions of multiple alignment marks on the substrate 2, the alignment scope 9 and the substrate stage 3 may be driven relatively along the XY plane. That is, at least one of the alignment scope 9 and the substrate stage 3 may be driven along the XY plane.

[0017] Each substrate 2 mounted on the substrate stage 3 has a thickness distribution, and multiple substrates 2 sequentially mounted on the substrate stage 3 may have thickness variations. Therefore, in a droplet placement process (coating process) in which droplets of liquid 4 are discharged from the discharge head 5 while the substrate stage 3 is scanned, variations in the positions at which the droplets land on the substrate 2 may occur due to the thickness distribution and thickness variations of the substrate 2. Therefore, the liquid discharge device 1 may be equipped with a height sensor 10 that measures the position (height) of the surface of the substrate 2 in the Z direction. To measure the height of the entire surface of the substrate 2, the height sensor 10 and the substrate stage 3 may be driven relatively along the XY plane. That is, at least one of the height sensor 10 and the substrate stage 3 may be driven along the XY plane.

[0018] The liquid ejection device 1 may further include a main control unit 11. The main control unit 11 controls the drive mechanism of the substrate stage 3, the ejection head 5, the pump 12, the alignment scope 9, the height sensor 10, etc. The main control unit 11 may be configured, for example, by a PLD (abbreviation for Programmable Logic Device) such as an FPGA (abbreviation for Field Programmable Gate Array), an ASIC (abbreviation for Application Specific Integrated Circuit), a general-purpose computer with an embedded program, or a combination of all or part of these.

[0019] As illustrated in FIG. 2 , the ejection head 5 may include multiple drive circuits 501 that drive multiple piezoelectric elements 502, respectively, and an ejection head control unit 507 that controls the multiple drive circuits 501. The ejection head control unit 507 issues drive commands to the drive circuits 501, and the drive circuits 501 may supply drive signals according to the drive commands to the corresponding piezoelectric elements 502 via signal lines 508. The drive commands may be, for example, a time-series data string or an analog signal that defines the waveform of the drive signal (drive waveform). The drive circuit 501 may be an amplifier, a DA converter, or the like. The ejection head control unit 507 may be configured using a PLD such as an FPGA, or an ASIC. Some or all of the functions of the ejection head control unit 507 may be incorporated into the main control unit 11. Hereinafter, the ejection head control unit 507 and the main control unit 11 constitute a control unit CNT. Hereinafter, matters described as functions of the control unit CNT are functions that can be provided by at least one of the ejection head control unit 507 and the main control unit 11.

[0020] The ejection head 5 may include a detection circuit DC that detects signals output from each piezoelectric element 502 to a signal line 508. The detection circuit DC may include, for example, a multiplexer 504, an amplifier 505, and an AD converter (ADC) 506. It may select one piezoelectric element 502 from the plurality of piezoelectric elements 502 and provide the signal output from the selected piezoelectric element 502 to the amplifier 505. The amplifier 505 may amplify the signal provided from the multiplexer 504 and provide it to the ADC 506. The ADC 506 may convert the signal provided from the amplifier 505 to a digital signal and provide the converted signal to the control unit CNT. The ejection head 5 may include a switch 503 between the signal line 508 and the multiplexer 504. The switch 503 may be in an off state during a period when the drive circuit 501 outputs a drive signal to the signal line 508, and in an on state during a period when the detection circuit DC detects a signal output from the piezoelectric element 502 to the signal line 508.

[0021] Problems such as poor ejection or reduced ejection performance can occur while the liquid ejection device 1 is placing or applying droplets of the liquid 4 onto the substrate 2, or while the liquid ejection device 1 is on standby. Such problems can be caused by, for example, foreign matter adhering to the outlet of the nozzle 19, an increase in the viscosity of the liquid 4 inside the nozzle 19, sedimentation of components of the liquid 4, electrophoresis, etc. Furthermore, the timing at which such problems occur depends on various factors, such as the total ejection time, the shape of the circulation path 13, and the duration of non-ejection, and can differ for each nozzle 19.

[0022] When a malfunction such as poor ejection or a decrease in ejection performance occurs, the malfunctioning nozzles 19 can be restored to a normal state by ejecting droplets of liquid 4 from the multiple nozzles 19 of the ejection head 5 onto the preliminary ejection area 20. This type of ejection is called preliminary ejection. If the malfunction cannot be remedied by preliminary ejection, a recovery sequence can be performed using the recovery unit 8. However, a recovery sequence performed using the recovery unit 8 requires a long time and may produce a large amount of liquid 4. For this reason, a recovery sequence using the recovery unit 8 can be performed when the malfunction cannot be remedied by preliminary ejection or at the timing of regular maintenance. During normal operation, preliminary ejection, in which droplets of liquid 4 are ejected from the multiple nozzles 19 of the ejection head 5 onto the preliminary ejection area 20, can be used to recover from and prevent malfunctions.

[0023] During maintenance such as periodic maintenance of the liquid ejection device 1, the circulation of the liquid 4 in the circulation path 13 may be stopped. Below, a description will be given of a recovery operation from a stopped state in which the circulation of the liquid 4 in the circulation path 13 has been stopped for maintenance or the like. During the recovery operation, the control unit CNT can control an agitation operation that drives the piezoelectric element 502 to agitate the liquid 4 in the nozzle 19 without ejecting the liquid 4 from the nozzle 19. If the stopped state continues for a long time, the liquid 4 may dry out near the outlet of the nozzle 19 (that is, the solvent that makes up the liquid 4 may volatilize), and the viscosity of the liquid 4 may increase. This may cause the nozzle 19 to become clogged.

[0024] The ejection head control unit 507 can determine the waveform of the drive signal (drive waveform) given to the piezoelectric element 502 during the stirring operation based on the residual vibration waveform detected by the detection circuit DC when the piezoelectric element 502 is operated without ejecting the liquid 4 from the nozzle 19. By using a method of obtaining the residual vibration waveform by operating the piezoelectric element 502 without ejecting the liquid 4 from the nozzle 19, it is possible to reduce consumption of the liquid 4.

[0025] 3 shows an example of a drive waveform for detecting the residual vibration waveform (a drive waveform for detection) and the residual vibration waveform. sw The switch 503 is in the off state during the period before time t sw During a period after this, the switch 503 can be in an on state. The drive circuit 501 supplies the piezoelectric element 502 with a drive signal for detecting a residual vibration waveform. The waveform of this drive signal is shown in FIG. 3 as a drive waveform. The piezoelectric element 502 is driven by the drive signal to vibrate the liquid 4 without ejecting the liquid 4 from the nozzle 19. Even after the piezoelectric element 502 is driven by the detection drive signal, vibrations of the liquid 4 in the nozzle 19 remain. This is called residual vibration. This residual vibration is converted into an electrical signal by the piezoelectric element 502 and detected as a residual vibration waveform by the detection circuit DC. The residual vibration waveform has periodicity, and the period depends on the dry state of the liquid 4 in the nozzle 19 (or the viscosity of the liquid 4). In other words, in a stopped state in which the circulation of the liquid 4 in the circulation path 13 is stopped, the period of the residual vibration waveform can change in accordance with changes in the viscosity of the liquid 4 in the nozzle 19.

[0026] In Fig. 4, the waveform of the drive signal for ejecting droplets of liquid 4 from the nozzle 19 is illustrated by a dashed line as the "ejection drive signal," and the waveform of the detection drive signal is illustrated by a solid line as the "detection drive signal." As illustrated in Fig. 4, the amplitude of the ejection drive signal is greater than the amplitude of the detection drive signal.

[0027] Referring to FIG. 5, the change in the residual vibration waveform due to the change in the viscosity of the liquid 4 in the nozzle 19 will be exemplarily described. In FIG. 5, the vertical axis represents voltage and the horizontal axis represents time. In FIG. 5(a), the residual vibration waveform in the ideal state or the reference state where the liquid 4 in the nozzle 19 is not dried is exemplified. This can be used as the reference waveform. In the ideal state or the reference state, the residual vibration waveform has a period T0 and is a decaying waveform. In FIG. 5(a), the time indicating the first peak is t0 and the time indicating the second peak is t1.

[0028] When the viscosity of the liquid 4 in the nozzle 19 increases due to the drying of the liquid 4, as exemplified in FIG. 5(b), the period of the residual vibration waveform increases as T0→T1→T2→. Here, the dashed line 1 is the residual vibration waveform detected at the stage when the time a has elapsed after the circulation of the liquid 4 is stopped, and the dashed line 2 is the residual vibration waveform detected at the stage when the time b (a < b) has elapsed after the circulation of the liquid 4 is stopped. When the viscosity of the liquid 4 in the nozzle 19 increases due to the drying of the liquid 4, the time indicating the first peak is delayed as t0→t1→t2→, and the time indicating the second peak is also t 01 →t 11 →t 21 → and so on. When the viscosity of the liquid 4 in the nozzle 19 increases due to the drying of the liquid 4, the discharge rate of the liquid 4 from the nozzle 19 decreases.

[0029] When the circulation of the liquid 4 in the circulation path 13 is restarted, the viscosity of the liquid 4 in the nozzle 19 decreases, and as exemplified in FIG. 5(c), the period of the residual vibration waveform decreases as T4→T3→T0→. Here, the dashed line 3 is the residual vibration waveform detected at the stage when the time a has elapsed after the circulation of the liquid 4 is restarted, and the dashed line 4 is the residual vibration waveform detected at the stage when the time b (b < a) has elapsed after the circulation of the liquid 4 is stopped. When the viscosity of the liquid 4 in the nozzle 19 decreases, the time indicating the first peak becomes earlier as t4→t3→t0, and the time indicating the second peak is also t 41 →t 31 →t 01When the viscosity of the liquid 4 in the nozzle 19 decreases, the ejection speed of the liquid 4 from the nozzle 19 increases.

[0030] 6 shows the operation of the liquid ejection device 1 of the first embodiment. In step S601, the liquid ejection device 1 is in an operating state or a standby state. The operating state can include, for example, a state in which an operation of placing droplets of liquid 4 on the substrate 2 is being performed, a state in which measurement is being performed using the alignment scope 9, or a state in which measurement is being performed using the height sensor 10. The standby state can include a state in which the liquid ejection device 1 is waiting for the substrate 2 to be carried in.

[0031] In step S602, the control unit CNT stops the pump 12 based on an event that requires stopping the circulation of the liquid 4 in the circulation path 13 (for example, a command from a user, a command from a scheduler, etc.), thereby stopping the circulation of the liquid 4 in the circulation path 13. In step S603, maintenance of the liquid ejection device 1 is performed. This maintenance may be performed under the control of the control unit CNT, or may be performed by the user, or may be performed by another maintenance device.

[0032] In step S604, the control unit CNT starts the pump 12 based on an event (for example, a command from a user) that should start the circulation of the liquid 4 in the circulation path 13, thereby starting the circulation of the liquid 4 in the circulation path 13. Here, it may be understood that a return operation is started in step S604, and in the return operation, the control unit CNT operates the pump 12 so that the circulation of the liquid 4 in the circulation path 13 is started.

[0033] In step S605, the ejection head control unit 507 controls the drive circuit 501 to supply a detection drive signal to the piezoelectric element 502, and the piezoelectric element 502 vibrates the liquid 4 in the nozzle 19 in response to the drive signal. This generates residual vibrations that correspond to the state inside the nozzle 19. The residual vibrations converted into an electrical signal by the piezoelectric element 502 are then detected as a residual vibration waveform (residual vibration signal) by the detection circuit DC and can be provided to the control unit CNT. The detection drive signal is a drive signal for detecting the residual vibration waveform without ejecting liquid from the nozzle 19.

[0034] In step S606, the control unit CNT determines, based on the residual vibration waveform, the waveform of the drive signal to be provided to the drive circuit to agitate the liquid 4 in the nozzle 19 without ejecting the liquid from the nozzle 19 (drive waveform). For example, if the residual vibration waveform is the first residual vibration waveform, the ejection head control unit 507 can set the drive waveform to the first drive waveform, and if the residual vibration waveform is the second residual vibration waveform, the drive waveform to the second drive waveform. Note that the first residual vibration waveform and the second residual vibration waveform have different characteristics from each other, and the first drive waveform and the second drive waveform have different characteristics from each other.

[0035] Here, with reference to FIG. 7, an exemplary method for determining the waveform of a drive signal for a stirring operation based on the waveform of a residual vibration waveform will be described. As illustrated in FIG. 7(a), the residual vibration waveform has a specific period (in other words, frequency) that depends on the state of the liquid in the nozzle 19. The control unit CNT can determine a drive waveform having a period corresponding to the period of the residual vibration waveform. In FIG. 7(b), "stirring waveform" illustrates a drive waveform having a period corresponding to the period of the residual vibration waveform illustrated in FIG. 7(a). If the period of the residual vibration waveform is another period, a drive waveform having another period, such as "stirring waveform 2," can be determined.

[0036] Here, the period of the residual vibration waveform is a natural period that indicates the state of the nozzle 19 (particularly the viscosity of the liquid 4) when the residual vibration waveform was acquired, and is a period that is likely to cause resonance. Therefore, by applying a drive signal having a period identical to or similar to the period of the residual vibration waveform to the piezoelectric element 502 during the stirring operation, resonance can be caused within the nozzle 19, thereby promoting the stirring of the liquid 4 within the nozzle 19. Therefore, the ejection head control unit 507 can determine the period of the drive signal during the stirring operation within the range of 80% to 120% of the period of the residual vibration waveform. Furthermore, it is preferable to determine the period of the drive signal during the stirring operation within the range of 95% to 105% of the period of the residual vibration waveform, and more preferably within the range of 99% to 101% of the period of the residual vibration waveform.

[0037] In step S607, the ejection head control unit 507 causes the drive circuit 501 to generate a drive signal having the waveform determined in step S606 and supplies the drive signal to the piezoelectric element 502. As a result, the liquid 4 in the nozzle 19 is agitated by the drive signal having a waveform determined based on the residual vibration waveform, and the viscosity of the liquid 4 in the nozzle 19 can be reduced by the agitation effect.

[0038] In step S608, the control unit CNT executes an evaluation process to evaluate the state of the nozzle 19. In this evaluation process, for example, whether the nozzle 19 has a defect can be evaluated based on the viscosity of the liquid 4 in the nozzle 19 or the discharge speed of the liquid 4. In step S609, the control unit CNT can determine whether to end the processes of steps S605 to S609 based on the result of the evaluation process in step S608. Then, if the evaluation result indicates that the nozzle 19 has a defect, the control unit CNT executes the processes of steps S605 to S609 again. On the other hand, if the evaluation result indicates that the nozzle 19 does not have a defect, the control unit CNT can transition to a standby state in step S610.

[0039] According to the first embodiment, a drive signal waveform is determined so as to agitate the liquid 4 within the nozzle 19 without ejecting the liquid from the nozzle 19, and the agitation operation is performed in accordance with the drive signal waveform. The drive signal waveform is determined based on the residual vibration waveform (for example, the period of the residual vibration waveform). This makes it possible to effectively restore the liquid ejection performance from the nozzle 19 while suppressing the consumption of liquid due to the recovery process.

[0040] The operation of the liquid ejection device 1 of the second embodiment will be described below with reference to Fig. 8. Matters not mentioned in the second embodiment may follow those of the first embodiment. Fig. 8 shows the operation of the liquid ejection device 1 of the second embodiment.

[0041] In step S601, the liquid ejection device 1 is in an operating state or a standby state. In the second embodiment, step S601 includes step S620. In step S620, the control unit CNT controls the drive circuit 501 to supply a drive signal for detection to the piezoelectric element 502, and the piezoelectric element 502 vibrates the liquid 4 in the nozzle 19 in response to the drive signal. This generates residual vibrations according to the state inside the nozzle 19. The residual vibrations converted into an electrical signal by the piezoelectric element 502 can then be detected by the detection circuit DC as a residual vibration waveform (residual vibration signal) and provided to the control unit CNT. The control unit CNT acquires this residual vibration waveform as a reference waveform.

[0042] In the second embodiment, step S608 of the first embodiment is replaced with step S608'. Step S608' is performed after the stirring operation in step S607 in order to evaluate its effect. In step S608', the control unit CNT performs an evaluation process to evaluate the state of the nozzle 19. In this evaluation process, the control unit CNT acquires a residual vibration waveform by a method similar to step S605, and evaluates the discharge performance of the nozzle 19 by comparing the residual vibration waveform with the reference waveform acquired in step S620.

[0043] The operation of the liquid ejection device 1 of the third embodiment will be described below with reference to Figure 9. Matters not mentioned in the third embodiment may follow the first and second embodiments. Figure 9 shows the operation of the liquid ejection device 1 of the third embodiment. In the third embodiment, when the result of the evaluation process indicates that the nozzle 19 is defective, the control unit CNT increases the flow rate of the liquid 4 circulating through the circulation path 13 in the recovery operation above normal.

[0044] In the third embodiment, step S607 of the first or second embodiment is replaced with step S607'. The control unit CNT can control the pump 12 to increase the flow rate of the liquid 4 circulating through the circulation path 13, for example, each time step S607' is repeated. For example, when step S607' is executed for the second or subsequent times, the control unit CNT makes the flow rate of the liquid 4 circulating through the circulation path 13 in the return operation greater than the flow rate of the liquid circulating through the circulation path 13 in the ejection operation that ejects the liquid from the nozzle 19.

[0045] In step S607′, the control unit CNT may control the plurality of piezoelectric elements 502 (the plurality of drive circuits 501) so that the stirring operation is performed for the defective nozzles 19 among the plurality of nozzles 19. At this time, the control unit CNT can control the plurality of piezoelectric elements 502 (the plurality of drive circuits 501) so that the stirring operation is not performed for the nozzles 19 that are not defective among the plurality of nozzles 19.

[0046] The operation of the liquid ejection device 1 of the fourth embodiment will be described below with reference to FIG. 10. Matters not mentioned in the fourth embodiment may follow at least one of the first to third embodiments. FIG. 10 shows the operation of the liquid ejection device 1 of the fourth embodiment. In the fourth embodiment, if the result of the evaluation process does not improve even after repeated recovery operations, the control unit CNT executes an enhanced recovery process in subsequent recovery operations.

[0047] In the fourth embodiment, for example, steps S620, S621, and S622 may be executed after step S609. In step S620, the control unit CNT returns to step S605 until the number of times the processes of steps S605 to S609 have been performed reaches a predetermined number, and then proceeds to step S621 once the number of times the processes of steps S605 to S609 have been performed reaches the predetermined number. Proceeding to step S621 means that the result of the evaluation process indicates that the nozzle 19 has a defect, or more specifically, that the result of the evaluation process does not improve even after repeated recovery operations. In such a case, the control unit CNT executes an enhanced recovery process in the recovery operation that is performed thereafter.

[0048] Specifically, in step S621, the control unit CNT executes an enhanced recovery process. Here, the control unit CNT may strengthen the content of the enhanced recovery process each time step S621 is repeated. Strengthening means strengthening the ability to stir the liquid 4 in the nozzle 19. The enhanced recovery process may be, for example, any of the following processes or a combination of two or more of the following processes.

[0049] A process of increasing or decreasing (for example, abruptly increasing or decreasing) the flow rate of the liquid 4 circulating through the circulation path 13 by controlling the pump 12; A process of switching the circulation direction of the liquid 4 circulating through the circulation path 13 by controlling the pump 12; The frequency of the drive signal is set to n times (n is a natural number greater than or equal to 2) the frequency corresponding to the period of the residual vibration waveform. A process of sweeping the drive signal in a frequency range including a frequency corresponding to the period of the residual vibration waveform; The operation of the liquid ejection device 1 of the fifth embodiment will be described below with reference to FIG. 11. The fifth embodiment is a modified example of the fourth embodiment, and matters not mentioned as the fifth embodiment may follow the fourth embodiment or at least one of the first to third embodiments that are incorporated in the fourth embodiment. FIG. 11 shows the operation of the liquid ejection device 1 of the fifth embodiment. In the fifth embodiment, step S630 is executed after step S608'. In step S608', the control unit CNT executes the enhanced recovery process of the fourth embodiment in accordance with the evaluation result in step S608'.

[0050] The operation of the liquid ejection device 1 of the sixth embodiment will be described below with reference to Fig. 12. Matters not mentioned in the sixth embodiment may follow those of the first to fifth embodiments. Fig. 12 shows the operation of the liquid ejection device 1 of the sixth embodiment. The operation shown in Fig. 12 can be controlled by the control unit CNT.

[0051] In step S1201, the control unit CNT acquires a reference waveform. In step S1202, the control unit CNT performs maintenance. Alternatively, in step S1202, a user performs maintenance work. In step S1203, the control unit CNT performs evaluation processing to evaluate the ejection performance of the plurality of nozzles 19. As described above, this evaluation processing may include acquiring a residual vibration waveform and comparing the residual vibration waveform with a reference waveform. In step S1204, the processing branches based on the result of the evaluation processing in step S1203. If the result of the evaluation processing indicates that the nozzle is defective, the recovery operation in the first to fifth embodiments (e.g., steps S604 to S609) is performed, and then the processing proceeds to step S1205. On the other hand, if the result of the evaluation processing in step S1204 does not indicate that the nozzle is defective, the processing proceeds to step S1205.

[0052] In step S1205, the substrate 2 is carried into the liquid ejection apparatus 1. In step S1206, the positions of a plurality of alignment marks on the substrate 2 can be measured using the alignment scope 9. In step S1207, the height distribution on the surface of the substrate 2 can be measured using the height sensor 10. Step S1207 may be performed before step S1206.

[0053] In step S1208, using the measurement results from steps S1206 and S1207, droplets of liquid 4 are placed or applied to a plurality of target positions on substrate 2. At this time, the timing of ejection of droplets from each nozzle 19 can be controlled based on the measurement results from steps S1206 and S1207 so that droplets are placed at each of the plurality of target positions on substrate 2.

[0054] Fig. 13 shows a schematic diagram of a substrate 2. A surface 101 of the substrate 2 is a surface on which a plurality of functional elements 102 are formed. Arrows 103, 104, 105, and 106 indicate the scanning direction of the substrate 2. Fig. 13 shows 7 x 5 functional elements 102, but typically, more functional elements can be formed.

[0055] An article manufacturing method according to one embodiment will be described below. The article manufacturing method is suitable for manufacturing articles such as display panels (e.g., OLEDs), microdevices (e.g., semiconductor devices), or devices with microstructures. The article manufacturing method according to this embodiment may include a disposing step of disposing droplets on a substrate using the liquid ejection device described above, and a processing step of processing the substrate that has undergone the disposing step to obtain an article. The processing step may include a drying step of drying the droplets disposed on the substrate. The processing step may also include other well-known processes (e.g., baking, cooling, cleaning, oxidation, film formation, deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The article manufacturing method according to this embodiment is advantageous over conventional methods in at least one of article performance, quality, productivity, and production cost.

[0056] The present specification and drawings include the following disclosure. (Item 1) A liquid ejection device comprising: an ejection head having a nozzle for ejecting liquid, a piezoelectric element for ejecting liquid from the nozzle, and a detection circuit for detecting a signal output from the piezoelectric element; and a circulation path for circulating liquid through the ejection head, a control unit that controls an agitation operation of driving the piezoelectric element so as to agitate the liquid in the nozzle without ejecting the liquid from the nozzle during a recovery operation from a stopped state in which circulation of the liquid in the circulation path has been stopped, the control unit determines a waveform of a drive signal to be applied to the piezoelectric element during the stirring operation based on a residual vibration waveform detected by the detection circuit when the piezoelectric element is operated without ejecting liquid from the nozzle. A liquid ejection device characterized by: (Item 2) the residual vibration waveform has periodicity, the control unit determines a period of the drive signal based on a period of the residual vibration waveform. 2. The liquid ejection device according to item 1, (Item 3) the control unit determines the period of the drive signal within a range of 80% to 120% of the period of the residual vibration waveform. 2. The liquid ejection device according to item 1, (Item 4) the control unit determines the period of the drive signal within a range of 95% to 105% of the period of the residual vibration waveform. 2. The liquid ejection device according to item 1, (Item 5) the period of the residual vibration waveform changes in accordance with a change in viscosity of the liquid in the nozzle; 5. The liquid ejection device according to any one of items 1 to 4. (Item 6) the viscosity of the liquid in the nozzle changes in the stopped state, and the period of the residual vibration waveform changes in accordance with the change in viscosity; 5. The liquid ejection device according to any one of items 1 to 4. (Item 7) further comprising a pump for circulating liquid through the circulation path; 7. The liquid ejection device according to any one of items 1 to 6, characterized in that: (Item 8) the control unit operates the pump so as to circulate the liquid through the circulation path during the return operation. 8. The liquid ejection device according to item 7, (Item 9) the control unit makes the flow rate of the liquid circulating through the circulation path during the return operation greater than the flow rate of the liquid circulating through the circulation path during a discharge operation in which the liquid is discharged from the nozzle. The liquid ejection device according to item 7 or 8. (Item 10) the control unit executes an evaluation process for evaluating a state of the nozzle after the stirring operation. 10. The liquid ejection device according to any one of items 1 to 9, characterized in that: (Item 11) evaluating the ejection performance of the nozzle based on a comparison between the residual vibration waveform detected during the return operation and a reference waveform; Item 11. A liquid ejection device according to item 10. (Item 12) the control unit increases a flow rate of the liquid circulating through the circulation path in the recovery operation when a result of the evaluation process indicates that the nozzle has a malfunction. 12. The liquid ejection device according to item 10 or 11, (Item 13) The control unit executes an enhanced recovery process when the result of the evaluation process does not improve even after repeating the recovery operation. 12. The liquid ejection device according to item 10 or 11, (Item 14) when a result of the evaluation process indicates that the nozzle has a defect, the control unit increases or decreases a flow rate of the liquid circulating through the circulation path in the subsequent recovery operation. 12. The liquid ejection device according to item 10 or 11, (Item 15) when a result of the evaluation process indicates that the nozzle has a defect, the control unit switches a circulation direction of the liquid circulating through the circulation path in the subsequent recovery operation. 12. The liquid ejection device according to item 10 or 11, (Item 16) when the result of the evaluation process indicates that the nozzle is defective, the control unit sets the frequency of the drive signal in the subsequent recovery operation to n times (n is a natural number equal to or greater than 2) the frequency corresponding to the period of the residual vibration waveform. 12. The liquid ejection device according to item 10 or 11, (Item 17) when a result of the evaluation process indicates that the nozzle has a defect, the control unit sweeps the drive signal in a frequency range including a frequency corresponding to a period of the residual vibration waveform in the recovery operation. 12. The liquid ejection device according to item 10 or 11, (Item 18) the ejection head has a plurality of nozzles and a plurality of piezoelectric elements for ejecting liquid from each of the plurality of nozzles; the control unit evaluates the states of the plurality of nozzles in the evaluation process, the control unit controls the plurality of piezoelectric elements so that the stirring operation is performed for a nozzle having a defect among the plurality of nozzles, and so that the stirring operation is not performed for a nozzle having no defect among the plurality of nozzles. 18. The liquid ejection device according to any one of items 10 to 17. (Item 19) A disposing step of disposing droplets on a substrate using the liquid ejection device according to any one of items 1 to 18; a processing step of processing the substrate that has been subjected to the placement step to obtain an article; A method for manufacturing an article, comprising: (others) The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0057] 1: liquid ejection device, 2: substrate, 3: substrate stage, 4: liquid, 5: ejection head, 7: tank, 11: main control unit, 12: pump, 13: circulation path, 19: nozzle, 501: drive circuit, 502, piezoelectric element, DC: detection circuit, 507: ejection head control unit, control unit: CNT

Claims

1. A liquid ejection device comprising: an ejection head having a nozzle for ejecting liquid, a piezoelectric element for ejecting liquid from the nozzle, and a detection circuit for detecting a signal output from the piezoelectric element; and a circulation path for circulating liquid through the ejection head, a control unit that controls an agitation operation of driving the piezoelectric element so as to agitate the liquid in the nozzle without ejecting the liquid from the nozzle during a recovery operation from a stopped state in which circulation of the liquid in the circulation path has been stopped, the control unit determines a waveform of a drive signal to be applied to the piezoelectric element during the stirring operation based on a residual vibration waveform detected by the detection circuit when the piezoelectric element is operated without ejecting liquid from the nozzle. A liquid ejection device characterized by:

2. the residual vibration waveform has periodicity, the control unit determines a period of the drive signal based on a period of the residual vibration waveform. The liquid ejection device according to claim 1 .

3. the control unit determines the period of the drive signal within a range of 80% to 120% of the period of the residual vibration waveform. The liquid ejection device according to claim 1 .

4. the control unit determines the period of the drive signal within a range of 95% to 105% of the period of the residual vibration waveform. The liquid ejection device according to claim 1 .

5. the period of the residual vibration waveform changes in accordance with a change in viscosity of the liquid in the nozzle; The liquid ejection device according to claim 1 .

6. the viscosity of the liquid in the nozzle changes in the stopped state, and the period of the residual vibration waveform changes in accordance with the change in viscosity; The liquid ejection device according to claim 1 .

7. further comprising a pump for circulating liquid through the circulation path; The liquid ejection device according to claim 1 .

8. the control unit operates the pump so as to circulate the liquid through the circulation path during the return operation.

8. The liquid ejection device according to claim 7.

9. the control unit makes the flow rate of the liquid circulating through the circulation path during the return operation greater than the flow rate of the liquid circulating through the circulation path during a discharge operation in which the liquid is discharged from the nozzle. The liquid ejection device according to claim 7 .

10. the control unit executes an evaluation process for evaluating a state of the nozzle after the stirring operation. The liquid ejection device according to claim 1 .

11. evaluating the ejection performance of the nozzle based on a comparison between the residual vibration waveform detected during the return operation and a reference waveform; The liquid ejection device according to claim 10 .

12. the control unit increases a flow rate of the liquid circulating through the circulation path in the recovery operation when a result of the evaluation process indicates that the nozzle has a malfunction. The liquid ejection device according to claim 10 .

13. The control unit executes an enhanced recovery process when the result of the evaluation process does not improve even after repeating the recovery operation. The liquid ejection device according to claim 10 .

14. when a result of the evaluation process indicates that the nozzle has a defect, the control unit increases or decreases a flow rate of the liquid circulating through the circulation path in the subsequent recovery operation. The liquid ejection device according to claim 10 .

15. when a result of the evaluation process indicates that the nozzle has a defect, the control unit switches a circulation direction of the liquid circulating through the circulation path in the subsequent recovery operation. The liquid ejection device according to claim 10 .

16. when the result of the evaluation process indicates that the nozzle is defective, the control unit sets the frequency of the drive signal in the subsequent recovery operation to n times (n is a natural number of 2 or more) the frequency corresponding to the period of the residual vibration waveform. The liquid ejection device according to claim 10 .

17. when a result of the evaluation process indicates that the nozzle has a defect, the control unit sweeps the drive signal in a frequency range including a frequency corresponding to a period of the residual vibration waveform in the recovery operation. The liquid ejection device according to claim 10 .

18. the ejection head has a plurality of nozzles and a plurality of piezoelectric elements for ejecting liquid from each of the plurality of nozzles; the control unit evaluates the states of the plurality of nozzles in the evaluation process, the control unit controls the plurality of piezoelectric elements so that the stirring operation is performed for a nozzle having a defect among the plurality of nozzles, and so that the stirring operation is not performed for a nozzle having no defect among the plurality of nozzles. The liquid ejection device according to claim 10 .

19. a disposing step of disposing droplets on a substrate using the liquid ejection device according to any one of claims 1 to 18; a processing step of processing the substrate that has been subjected to the placement step to obtain an article; A method for manufacturing an article, comprising:

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