Droplet observation method, droplet observation device, droplet observation program, and recording medium

Abstract

To stably generate a liquid filament while enabling observation of the filament.SOLUTION: An ink jet head 2 is used to discharge ink by means of an ink jet system. Thus, by using the ink jet system for ink ejection, droplet-shaped ink, namely a droplet L, can be discharged, and a filament Lf can be generated stably in the droplet L. Such a stable filament Lf generation is presumably due to the fact that the ink jet system can discharge the droplet L of a fixed amount of ink precisely, unlike the ink jet system that discharges ink from a syringe. By capturing the droplet L with the filament Lf by a camera 6, an image of the droplet L is obtained.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to a technique for observing a liquid, primarily for measuring the extensional viscosity of the liquid. [Background technology]

[0002] Patent Document 1 describes a method for measuring the extensional viscosity of a liquid. According to this method, a syringe and a small-diameter glass tube attached to the tip of the syringe are prepared. Then, the extensional viscosity is measured based on the results of measuring the extensional pressure applied to the liquid in the glass tube when the liquid in the syringe is pushed into the glass tube by a plunger and the velocity of the liquid flow. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-153334 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application have investigated methods different from those described above for measuring the extensional viscosity of primarily low-viscosity liquids and have found that the following method is effective. According to this method, a syringe for storing the liquid and a cylindrical nozzle attached to the tip of the syringe are prepared. Then, when the liquid is forced out of the syringe into the nozzle by a plunger, the liquid falls from the nozzle. At this time, due to the viscosity of the liquid in the extensional direction, a thread-like stretch of the liquid (referred to as a "filament" in this specification) is generated in the opposite direction to the direction of the liquid fall. The width of this filament depends on the extensional viscosity of the liquid. Therefore, information about the extensional viscosity of the liquid can be obtained by observing the filament of the liquid ejected from the nozzle. However, it was difficult to stably generate a filament when using the method of forcing the liquid out of the syringe into the nozzle by a plunger, causing the liquid to fall from the nozzle.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a technique that enables stable generation of liquid filaments while enabling observation of the filaments. [Means for solving the problem]

[0006] The droplet observation method according to the present invention includes a first step of ejecting droplets of liquid using an inkjet head that ejects liquid using an inkjet method, and a second step of capturing an image of the droplets by using an imaging unit to capture the droplets ejected by the inkjet head.

[0007] A droplet observation device according to the present invention includes an inkjet head that ejects liquid by an inkjet method, and an imaging unit that captures an image of the droplet by imaging the droplet of the liquid ejected by the inkjet head.

[0008] The droplet observation program of the present invention causes a computer to execute a first step of ejecting droplets of liquid using an inkjet head that ejects liquid using an inkjet method, and a second step of acquiring an image showing the droplets by capturing an image of the droplets ejected by the inkjet head using an imaging unit.

[0009] The recording medium of the present invention records the above-mentioned droplet observation program in a computer-readable manner.

[0010] In the present invention (droplet observation method, droplet observation device, droplet observation program, and recording medium) configured as described above, an inkjet head that ejects liquid by an inkjet method is used. By using the inkjet method to eject liquid in this way, it is possible to eject liquid in droplet form, i.e., droplets, and stably generate filaments in the droplets. An image of the droplet is obtained by capturing an image of the droplet from which the filament has been generated using an imaging unit. As a result, it is possible to stably generate a liquid filament and observe the filament.

[0011] The speed of the droplets ejected from the inkjet head may be 9 meters / second or more and 15 meters / second or less, which is advantageous for stably generating filaments.

[0012] The droplet observation method may be configured to further include a third step of optimizing, based on the image, the discharge conditions for discharging droplets from the inkjet head in the first step. In this configuration, droplets are discharged from the inkjet head under the discharge conditions optimized based on the droplet image, and filaments can be stably generated and observed.

[0013] Furthermore, the droplet observation method may be configured so that the first and second steps are repeatedly performed while changing the discharge conditions to obtain multiple images showing droplets discharged from the inkjet head under different discharge conditions, and in the third step, the discharge conditions are optimized based on the multiple images. With this configuration, optimal discharge conditions corresponding to images in which appropriate filament generation can be confirmed can be selected from the multiple images corresponding to different discharge conditions. Then, by discharging droplets from the inkjet head under the optimal discharge conditions, filaments can be stably generated and observed.

[0014] Various specific ejection conditions are conceivable, for example, the ejection condition may be the speed of droplets ejected from the inkjet head.

[0015] The inkjet head may have a nozzle for ejecting the liquid, a liquid storage section connected to the nozzle via a flow path for storing the liquid, and a drive element for driving the liquid stored in the liquid storage section, and the droplet observation method may be configured so that the liquid stored in the liquid storage section is driven by the drive element to eject droplets from the nozzle using an inkjet method. By ejecting droplets from an inkjet head configured in this manner, it is possible to stably generate liquid filaments. [Effects of the Invention]

[0016] As described above, according to the present invention, it is possible to stably generate a liquid filament and observe the filament. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram schematically showing an example of a liquid observation device according to the present invention. [Figure 2] FIG. 2 is a partial cross-sectional view schematically illustrating an example of the internal configuration of an inkjet head. [Figure 3] FIG. 2 is a block diagram showing an example of an electrical configuration for controlling the liquid observation device of FIG. [Figure 4] 4 is a flowchart showing a first example of droplet observation performed using the liquid observation device of FIG. [Figure 5] FIG. 3 is a diagram schematically illustrating an example of a droplet image showing an ink droplet L ejected from a nozzle. [Figure 6] 10 is a flowchart showing a second example of droplet observation performed using the liquid observation device of FIG. [Figure 7A] 10A and 10B are diagrams showing droplet images obtained in an ink ejection experiment using simulated ink A. [Figure 7B] 10A and 10B are diagrams showing droplet images obtained in an ink ejection experiment using simulated ink A. [Figure 8A] 10A and 10B are diagrams showing droplet images obtained in an ink ejection experiment using simulant ink B. [Figure 8B] 10A and 10B are diagrams showing droplet images obtained in an ink ejection experiment using simulant ink B. [Figure 9] An example of the results obtained from droplet images acquired in an ink ejection experiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 1 is a diagram schematically showing an example of a liquid observation device according to the present invention. The liquid observation device 1 includes an inkjet head 2 that ejects ink by an inkjet method, and a waste liquid pan 3 that receives the ink ejected from the inkjet head 2. The inkjet head 2 is disposed parallel to the vertical direction Z and faces downward in the vertical direction Z. Therefore, the ink ejected from the inkjet head 2 flies (in other words, falls) along a flight path Pf that faces downward parallel to the vertical direction Z. The waste liquid pan 3 faces the inkjet head 2 from below, and the ink ejected from the inkjet head 2 lands in the waste liquid pan 3.

[0019] In this example, ink used for printing on paper, film, etc. is ejected from the inkjet head 2. However, the type of liquid observed using the liquid observation device 1 is not limited to ink, and the device may be configured to eject various liquids to be observed from the inkjet head 2.

[0020] Furthermore, the liquid observation device 1 is provided with a configuration for capturing an image of a predetermined imaging range Ri of the flight path Pf. This imaging range Ri is provided in a range from the bottom surface 211 of the inkjet head 2 to a predetermined position below the bottom surface 211. However, the setting mode of the imaging range Ri is not limited to this example and can be changed as appropriate.

[0021] That is, the liquid observation device 1 includes an illumination 4 that irradiates the imaging range Ri with light from the horizontal direction X, and a light diffusion plate 5 that is arranged between the illumination 4 and the imaging range Ri in the horizontal direction X. The illumination 4 has a plurality of LEDs (Light Emitting Diodes) that are arranged two-dimensionally, and each LED emits light in the horizontal direction X toward the imaging range Ri. The light diffusion plate 5 diffuses the light that passes through the light diffusion plate 5, and the light emitted from the illumination 4 is diffused as it passes through the light diffusion plate 5, and then irradiated onto the imaging range Ri. This makes it possible to irradiate the imaging range Ri with relatively uniform light.

[0022] Moreover, the liquid observation device 1 comprises a camera 6 that captures an image of the imaging range Ri from the horizontal direction X, and a microlens 7 that is arranged between the camera 6 and the imaging range Ri in the horizontal direction X. The camera 6 is a high-speed camera that has a solid-state imaging element 61 that detects light, and the microlens 7 forms an image of the light from the imaging range Ri on the solid-state imaging element 61.

[0023] The lighting 4 and the camera 6 are disposed on opposite sides of the imaging range Ri in the horizontal direction X, and the lighting 4 irradiates the camera 6 with light from behind the ink that is the imaging target. In other words, the camera 6 uses the solid-state imaging element 61 to capture a silhouette image of the ink flying in the imaging range Ri.

[0024] FIG. 2 is a partial cross-sectional view schematically illustrating an example of the internal configuration of an inkjet head. The inkjet head 2 has a housing 21 and a nozzle 22 that opens at a bottom surface 211 of the housing 21. Inside the housing 21, there are a cavity 23 connected to the nozzle 22 via a flow path, and a storage chamber 24 connected to the cavity 23 via a flow path. The storage chamber 24 has a larger volume than the cavity 23 and stores ink to be supplied to the cavity 23. The cavity 23 also stores ink supplied from the storage chamber 24. The inkjet head 2 also has a piezoelectric element 25 provided for the cavity 23. When a drive signal (voltage signal) is applied to the piezoelectric element 25, the piezoelectric element 25 deforms in response to the drive signal, thereby causing a pressure fluctuation in the ink in the cavity 23. This pressure fluctuation then forces a certain amount of ink in the cavity 23 out of the nozzle 22. In this way, a fixed amount (picoliter) of ink droplet L is ejected from the nozzle 22.

[0025] 3 is a block diagram showing an example of an electrical configuration for controlling the liquid observation device of FIG. 1. In order to control the above-mentioned lighting 4, camera 6, and piezoelectric element 25 provided in the liquid observation device 1, a control device 8 shown in FIG. 3 can be used. Specifically, the control device 8 is a personal computer, a tablet computer, or the like. The control device 8 includes a calculation unit 81 which is a processor such as a CPU (Central Processing Unit), a storage unit 82 which is an HDD (Hard Disk Drive) or SSD (Solid State), and a UI (User Interface) 83.

[0026] When the calculation unit 81 executes the droplet observation program 821 (stored in the storage unit 82), the calculation unit 81 develops various controls by the illumination control unit 811, the imaging control unit 812, the image receiving unit 813, and the discharge control unit 814. The illumination control unit 811 controls the brightness of the light emitted from the illumination unit 4 and the timing of emitting light from the illumination unit 4. The imaging control unit 812 controls the timing (frame rate, etc.) at which the camera 6 captures images, and the image receiving unit 813 receives the images captured by the camera 6. The discharge control unit 814 controls the drive signal applied to the piezoelectric element 25 in accordance with discharge conditions 822 (stored in the storage unit 82), such as the waveform of the drive signal to be applied to the piezoelectric element 25 and the timing at which the drive signal is applied to the piezoelectric element 25.

[0027] The storage unit 82 stores the droplet observation program 821 and the discharge conditions 822. Furthermore, the storage unit 82 stores a droplet image I showing the droplet L captured by the camera 6. The droplet observation program 821 is provided in a state recorded on a recording medium 84 that records the droplet observation program 821 so as to be readable by the control device 8, and is stored in the storage unit 82. The recording medium 84 is, for example, a USB (Universal Serial Bus) memory, a storage device mounted on an external computer, or the like.

[0028] The UI 83 has input devices such as a keyboard and a mouse that accept user operations, and output devices such as a display that displays images to the user. Note that the input and output devices of the UI 83 do not need to be configured separately, and may be configured as an integrated device, such as a touch panel display.

[0029] Fig. 4 is a flowchart showing a first example of droplet observation performed using the liquid observation device of Fig. 1. In step S101, the discharge control unit 814 applies a drive signal to the piezoelectric element 25 to discharge ink from the nozzle 22 of the inkjet head 2. As a result, a certain amount of ink droplet L flies downward from the nozzle 22 along a flight path Pf.

[0030] Furthermore, in synchronization with the application of the drive signal to the piezoelectric element 25 in step S101, the imaging control unit 812 causes the camera 6 to start imaging the imaging range Ri (step S102). As a result, the camera 6 captures an image of the droplet L at the time it is ejected from the nozzle 22 into the imaging range Ri, and acquires a droplet image I showing the droplet L. The droplet image I acquired by the camera 6 in step S102 is transmitted from the camera 6 to the image receiving unit 813, and the image receiving unit 813 stores the droplet image I received from the camera 6 in the storage unit 82.

[0031] In step S103, the imaging control unit 812 determines whether or not the acquisition of the planned predetermined number (plurality of images) of droplet images I has been completed. If the number of images taken is less than the predetermined number (if "NO" in step S103), the image receiving unit 813 confirms that the imaging period (seconds) has elapsed since the image of the droplet L was taken in the previous step S102, and then returns to step S102. This imaging period corresponds to the reciprocal of the frame rate (number of frames / second).

[0032] In this way, steps S102 to S104 are repeated to repeatedly capture images of the droplets L at the imaging cycle until a predetermined number of droplet images I have been acquired. As a result, a plurality of droplet images I showing the change over time of the droplets L after being ejected from the nozzles 22 are acquired and stored in the storage unit 82.

[0033] Fig. 5 is a diagram schematically showing an example of a droplet image showing an ink droplet L ejected from a nozzle. As shown in Fig. 5, the droplet L flying downward in the vertical direction Z has a main droplet Lm located at the tip (in other words, the bottom end) in the flight direction, and a filament Lf stretched like a thread upward from the main droplet Lm (in other words, on the opposite side to the flight direction). The width Wf of this filament Lf depends on the elongational viscosity of the ink, so when observing the droplet L with the liquid observation device 1, the width Wf of the filament Lf of the droplet L is mainly of interest.

[0034] In the first example of liquid observation described above, an inkjet head 2 that ejects ink by an inkjet method is used. In this way, by using the inkjet method to eject ink, droplet-shaped ink, i.e., droplets L, can be ejected and filaments Lf can be stably generated from the droplets L. It is presumed that such stable generation of filaments Lf is due to the fact that ink ejection by the inkjet method, unlike ink ejection from a syringe, can accurately eject a constant amount of ink droplets L. Furthermore, an image of the droplets L is obtained by capturing an image of the droplets L from which the filaments Lf have been generated using a camera 6. As a result, it is possible to stably generate ink filaments Lf and observe the filaments Lf.

[0035] The inkjet head 2 also has a nozzle 22 that ejects ink, a cavity 23 (liquid storage section) that is connected to the nozzle 22 by a flow path and stores the ink, and a piezoelectric element 25 (drive element) that drives the ink stored in the cavity 23. The ink stored in the cavity 23 is driven by the piezoelectric element 25, thereby ejecting ink droplets L from the nozzle 22 by the inkjet method. By ejecting the droplets L from the inkjet head 2 configured in this manner, ink filaments Lf can be generated stably.

[0036] Fig. 6 is a flowchart showing a second example of droplet observation performed using the liquid observation device of Fig. 1. Here, parts that are different from the first example of Fig. 4 will be explained, and parts that are common to the first example will be given the same reference numerals and explanations will be omitted. In this second example, steps S101 to S104 are repeated while changing the ejection conditions 822 for the inkjet head 2 to eject ink droplets L.

[0037] In this example, a parameter correlated with the ejection speed (meters / second) of the droplets L, specifically the amplitude (voltage value) of the drive signal applied to the piezoelectric element 25, is changed as the ejection condition 822. Specifically, a plurality of different candidate amplitudes (voltage values) are prepared as candidates for the amplitude of the drive signal. Note that the higher the voltage value of the amplitude of the drive signal, the faster the ejection speed of the droplets L from the inkjet head 2.

[0038] When ejecting droplet L for the first time in step S101, a drive signal having the smallest candidate amplitude among a plurality of candidate amplitudes is applied to piezoelectric element 25. Then, a droplet image I showing droplet L ejected by the drive signal having that candidate amplitude is acquired by camera 6 and stored in storage unit 82 (steps S102 to S104).

[0039] When the first round of steps S101 to S104 is completed, the ejection control unit 814 determines whether step S101, in which ink is driven and ejected using a drive signal of a candidate amplitude, has been completed for all of the multiple candidate amplitudes. If step S101 has not been completed (if "NO" in step S105), the ejection control unit 814 changes the candidate amplitude to increase the amplitude of the drive signal by one step (step S106). Steps S101 to S104 are then executed using the drive signal having the changed candidate amplitude. Note that the manner in which the candidate amplitude of the drive signal is changed is not limited to a manner in which the candidate amplitude is increased in steps, and may be, for example, a manner in which the candidate amplitude is decreased in steps.

[0040] In this way, multiple droplet images I showing droplets L ejected by drive signals with different candidate amplitudes are stored in the storage unit 82. Therefore, the user can display these droplet images I on the display of the UI 83 by operating the UI 83. Furthermore, the user can visually inspect the filaments Lf of the droplets L shown in these droplet images I, select one droplet image I showing the best filament Lf, and set the candidate amplitude when the droplet L shown in the selected droplet image I is ejected from the inkjet head 2 as the amplitude of the drive signal to be used in step S101, which will be executed subsequently. For example, the user can set the amplitude of the drive signal by executing an operation to store the selected amplitude in the storage unit 82 as the ejection condition 822 using the UI 83. In this way, the amplitude of the drive signal (ejection condition 822) can be optimized (step S107).

[0041] It is also possible to configure the calculation unit 81 to automatically execute step S107 instead of the user. In this example, a neural network that has been machine-learned to determine the quality of the filament Lf is configured in the calculation unit 81, one droplet image I is selected by the neural network, and a candidate amplitude when the droplet L shown in the selected droplet image I is ejected from the inkjet head 2 is stored in the storage unit 82 as an ejection condition 822.

[0042] The second example of liquid observation described above includes step S107, in which the ejection conditions 822 (amplitude of the drive signal) for ejecting droplets L from the inkjet head 2 in step S101 are optimized based on the droplet image I. In this configuration, droplets L are ejected from the inkjet head 2 under the ejection conditions 822 optimized based on the droplet image I, and the filaments Lf can be stably generated and observed.

[0043] Furthermore, by repeatedly ejecting droplets L (step S101) and capturing images of droplets L (steps S102 to S104) while changing the amplitude of the drive signal (ejection condition 822) (steps S105 to S106), multiple droplet images I showing droplets L ejected from the inkjet head 2 using drive signals with mutually different amplitudes are acquired. Then, in step S107, the amplitude of the drive signal is optimized based on the multiple droplet images I. With this configuration, it is possible to select a drive signal with an optimal amplitude corresponding to a droplet image I in which the generation of an appropriate filament Lf can be confirmed from the multiple droplet images I corresponding to the amplitudes of the drive signals. Then, by ejecting droplets L from the inkjet head 2 using a drive signal with the optimal amplitude, the filament Lf can be stably generated and observed.

[0044] As described above, the amplitude (voltage value) of the drive signal correlates with the speed of the droplets L ejected from the inkjet head 2. Therefore, in the above example, the ejection speed of the droplets L from the inkjet head 2 is essentially optimized as the ejection condition 822. In other words, it is possible to eject the droplets L from the inkjet head 2 at the ejection speed (ejection condition 822) that is optimal for generating the filaments Lf.

[0045] Next, we will explain a specific example of an experiment to optimize the ejection speed of droplets L. Figures 7A and 7B show droplet images acquired in an ink ejection experiment using simulated ink A, Figures 8A and 8B show droplet images acquired in an ink ejection experiment using simulated ink B, and Figure 9 shows an example of the results obtained from the droplet images acquired in the ink ejection experiment.

[0046] The experimental conditions are as follows: Nozzle 22 diameter: 40 (μm) Candidate amplitudes: 15, 20, 25, 30, 35, 40 (V) Frequency: 100(Hz) Discharge direction: Vertical downward Number of shots: 10 Here, the frequency is the frequency at which droplets L are repeatedly ejected from the nozzle 22, and the number of times that images are taken is the number of times that operations corresponding to steps S101 to S106 in Fig. 6 were performed. That is, in this experiment, steps S101 to S106, which eject droplets L and capture images while changing the amplitude of the drive signal, were performed 10 times.

[0047] The equipment used in this experiment is as follows: Camera 6: High-speed camera FASTCAM-Mini WX100 Micro Lens 7: Microscope Lens Z16 APO Wave Builder: PIJD-1SET Pulse injector: PIJ-40ASET Here, the wave builder is a device that generates a drive signal.

[0048] The imaging conditions in this experiment were as follows. Magnification: 2.5x Number of pixels: 32 x 512 (pixels) Imaging range Ri: 128 × 2048 (μm 2 ) Frame rate: 72000 (fps) Shutter speed: 1 / 300000(s) Resolution: 4.0(μm / pixel)

[0049] The physical properties of the simulated ink A are as follows: Surface tension: 21.48 (mN / m) Shear viscosity: 4.74 (mPas) Temperature: 25±1(℃)

[0050] The physical properties of the simulated ink B are as follows: Surface tension: 35.25 (mN / m) Shear viscosity: 4.76 (mPas) Temperature: 25±1(℃)

[0051] 7A, 7B, 8A, and 8B, 14 droplet images I are arranged along the time axis (horizontal axis) at time intervals of 13.9 μs, and are obtained by applying a drive signal having an amplitude of the voltage value shown in the column to the piezoelectric element 25, and capturing an image of the droplet L 14 times while ejecting the droplet L from the nozzle 22. The speed shown below the time axis in each column indicates the speed at which the droplet L is ejected from the nozzle 22 (the speed of the main droplet Lm). As described above, steps S101 to S106 are performed 10 times, so that 10 sets of droplet images I shown in FIGS. 7A and 7B are obtained for the simulant ink A, and 10 sets of droplet images I shown in FIGS. 8A and 8B are obtained for the simulant ink B.

[0052] Figure 9 shows the results of visually counting the number of droplet images I from the set of droplet images I acquired in this way that allow measurement of the filament Lf. Basically, the larger the amplitude of the drive signal, i.e., the faster the ejection speed of the droplet L, the more the filament Lf stretches, which is advantageous for measuring the width Wf of the filament Lf. However, if the ejection speed of the droplet L is too fast, the entire droplet L will not fit within the imaging range Ri, which is disadvantageous for measuring the width Wf. Due to this trade-off relationship, the optimal range of the amplitude of the drive signal, in other words, the optimal range of the ejection speed of the droplet L, is limited.

[0053] In this experiment, the optimum range for the amplitude of the drive signal was 20 to 30 (V), i.e., the optimum range for the ejection speed of the droplets L was 9 to 15 (meters / second). Therefore, when ejecting the droplets L in the subsequent step S101, it is advisable to set the speed of the droplets L ejected from the inkjet head 2 to a speed of 9 (meters / second) or more and 15 (meters / second) or less. A speed set in this manner is advantageous for stably generating the filament Lf.

[0054] In the embodiment described above, the liquid observation device 1 corresponds to an example of the “droplet observation device” of the present invention, the inkjet head 2 corresponds to an example of the “inkjet head” of the present invention, the nozzle 22 corresponds to an example of the “nozzle” of the present invention, the cavity 23 corresponds to an example of the “liquid storage section” of the present invention, the piezoelectric element 25 corresponds to an example of the “drive element” of the present invention, the camera 6 corresponds to an example of the “imaging section” of the present invention, the droplet observation program 821 corresponds to an example of the “droplet observation program” of the present invention, the discharge condition 822 corresponds to an example of the “discharge condition” of the present invention, the recording medium 84 corresponds to an example of the “recording medium” of the present invention, the droplet L corresponds to an example of the “droplet” of the present invention, step S101 corresponds to an example of the “first step” of the present invention, steps S102 to S104 correspond to an example of the “second step” of the present invention, and step S107 corresponds to an example of the “third step” of the present invention.

[0055] The present invention is not limited to the above-described embodiment, and various modifications other than those described above are possible without departing from the spirit of the present invention. For example, the specific configuration of the inkjet head 2 can be modified as appropriate. Therefore, the inkjet head 2 is not limited to having a single nozzle 22 as described above, but may have a plurality of nozzles 22. In this case, it is preferable that the droplets L are ejected from one of the plurality of nozzles 22.

[0056] Furthermore, the direction in which the droplets L are ejected from the nozzles 22 of the inkjet head 2 does not need to be parallel to the vertical direction Z, and may be inclined relative to the vertical direction Z.

[0057] Furthermore, the driving element provided to drive the ink in the cavity 23 is not limited to the above-described piezoelectric element 25, but may be a heating resistor. When a heating resistor is used, a driving signal (current signal) is applied to the heating resistor arranged in the cavity 23, causing the heating resistor to heat the ink in the cavity 23 and locally boil the ink. This forces the ink out of the cavity 23 and causes it to be ejected from the nozzle 22.

[0058] Furthermore, the specific content of the ejection conditions 822 when ejecting droplets L from the inkjet head 2 is not limited to the amplitude of the drive signal, in other words, the ejection speed of the droplets L, but may also be, for example, the amount (picoliters) of the droplets L. In this case, it is sufficient to optimize the amount of the droplets L in FIG. 6.

[0059] Also, various modifications may be made to the camera 6. For example, the arrangement of the camera 6 may be changed, and specifically, the orientation of the camera 6 may be tilted with respect to the horizontal direction X. Furthermore, the number of cameras 6 is not limited to one, and two cameras 6 may be provided that capture the imaging range Ri from different directions.

[0060] Furthermore, various modifications may be made to the illumination 4. For example, the arrangement of the illumination 4 may be changed, and specifically, the orientation of the illumination 4 may be tilted with respect to the horizontal direction X. Furthermore, the specific configuration that can be used as the light source of the illumination 4 is not limited to the LED described above, and other light emitters may be used. Furthermore, the light diffusion plate 5 is not essential, and light may be irradiated onto the imaging range Ri without passing through the light diffusion plate 5.

[0061] Furthermore, the droplet image I obtained by capturing an image of the droplet L is not limited to a silhouette image. In short, regardless of the type of droplet image I, it is sufficient to obtain a droplet image I in which the filament Lf generated in the droplet L can be confirmed.

[0062] The position where the imaging range Ri is set may also be changed as appropriate. For example, in the above example, the imaging range Ri extends downward from the bottom surface 211 of the inkjet head 2. However, the imaging range Ri may also be spaced apart from the bottom surface 211 of the inkjet head 2.

[0063] Furthermore, in the above example, a filament Lf formed when a droplet L of printing ink is ejected from the inkjet head 2 is observed. The reason for selecting ink as the object of observation in this way is the inventor's knowledge that the extensional viscosity of ink can be an important factor in determining the conditions for accurately ejecting an appropriate amount of ink onto a printing medium such as paper or film with an inkjet printer. However, as mentioned above, the object of observation using the liquid observation device 1 may be a liquid other than ink.

[0064] The above embodiment can also be suitably applied to cases where the filament Lf of the droplet L is observed in order to obtain information other than information about the extensional viscosity of the liquid. [Industrial Applicability]

[0065] The present invention can be suitably applied to a technique for observing filaments that are generated when a liquid is ejected. [Explanation of symbols]

[0066] 1...Liquid observation device 2...Inkjet head 22...Nozzle 23...Cavity (liquid storage area) 25...Piezoelectric element (drive element) 6...Camera (imaging unit) 821...Droplet Observation Program 822…Discharge conditions 84...Recording media L…Droplet

Claims

1. a first step of ejecting droplets of the liquid using an inkjet head that ejects the liquid by an inkjet method; a second step of capturing an image of the droplets ejected by the inkjet head using an imaging unit to obtain an image of the droplets; a third step of optimizing the velocity of the droplets to be ejected from the inkjet head in the first step based on the image; Equipped with by repeatedly executing the first step and the second step while changing the speed, acquiring a plurality of images showing the droplets ejected from the inkjet head at mutually different speeds; In the third step, the speed is optimized based on the plurality of images so that the width of a filament generated by the ejection of the droplets can be measured.

2. 2. The droplet observation method according to claim 1, wherein the velocity is 9 (meters / second) or more and 15 (meters / second) or less.

3. 3. The droplet observation method according to claim 1, wherein the inkjet head has a nozzle that ejects the liquid, a liquid storage portion connected to a flow path of the nozzle and storing the liquid, and a drive element that drives the liquid stored in the liquid storage portion, and the liquid stored in the liquid storage portion is driven by the drive element to eject the droplets from the nozzle by an inkjet method.

4. an inkjet head that ejects liquid by an inkjet method; an imaging unit that captures an image of the droplet of the liquid ejected by the inkjet head, thereby acquiring an image of the droplet; a control device that optimizes the velocity of the droplets for ejecting the droplets from the inkjet head based on the image; Equipped with The control device repeatedly ejects the droplets from the inkjet head and acquires the images by the imaging unit while changing the speed, thereby acquiring multiple images showing the droplets ejected from the inkjet head at different speeds, and optimizes the speed based on the multiple images so that the width of the filament generated by the ejection of the droplets can be measured.

5. a first step of ejecting droplets of the liquid using an inkjet head that ejects the liquid by an inkjet method; a second step of capturing an image of the droplets ejected by the inkjet head using an imaging unit to obtain an image of the droplets; a third step of optimizing the velocity of the droplets to be ejected from the inkjet head in the first step based on the image; The computer executes the following. by repeatedly executing the first step and the second step while changing the speed, acquiring a plurality of images showing the droplets ejected from the inkjet head at mutually different speeds; In the third step, the droplet observation program causes the computer to optimize the speed based on the plurality of images so that the width of a filament generated by the ejection of the droplet can be measured.

6. A recording medium on which the droplet observation program according to claim 5 is recorded so as to be readable by a computer.

Images