Liquid discharge device and method for discharging liquid

Abstract

To solve such a problem that, when a driving signal is not suitable, degradation of printing quality may be caused.SOLUTION: A liquid discharge device includes: an ink jet head which discharges a liquid on the basis of a driving signal; an observation part which observes the liquid discharged from the ink jet head; and a control unit which changes the driving signal according to the discharging state of the liquid which the observation part has observed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a liquid ejection apparatus and a liquid ejection method. [Background technology]

[0002] In recent years, liquid ejection heads such as inkjet heads are used to manufacture electronic devices and to decorate the housings of products. A liquid suitable for a particular application is used as the liquid to be ejected from the liquid ejection head. In addition, a drive signal for ejecting the liquid from the liquid ejection head is appropriately set depending on the type of liquid.

[0003] Conventionally, ink ejected from an inkjet head is photographed continuously over time, and a drive signal is output so as not to generate mist (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-133571 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the drive signal is not appropriate, the volume and velocity of the ejected liquid will be inappropriate, which can result in variations in the amount of liquid applied and its position on the print target, leading to poor print quality.

[0006] An object of the present disclosure is to provide a liquid ejection device and a liquid ejection method that make it possible to appropriately generate a drive signal for a liquid ejection head. [Means for solving the problem]

[0007] A liquid ejection device in one embodiment of the present disclosure includes an inkjet head that ejects liquid based on a drive signal, an observation unit that observes the liquid ejected from the inkjet head, and a control unit that changes the drive signal depending on the ejection state of the liquid observed by the observation unit.

[0008] A liquid ejection method in one embodiment of the present disclosure includes a step of observing liquid ejected from an inkjet head that ejects liquid based on a drive signal, and a step of changing the drive signal depending on the ejection state of the liquid. Effect of the Invention

[0009] According to an embodiment of the present disclosure, it is possible to appropriately generate a drive signal for a liquid ejection head. [Brief description of the drawings]

[0010] [Figure 1] Cross-sectional view showing the configuration of an inkjet head [Diagram 2] A diagram showing an inkjet head and a flight observation device. [Diagram 3] FIG. 1 is a diagram showing a plurality of images captured by an imaging unit; [Figure 4] FIG. 1 is a diagram showing an example of a voltage waveform signal S. [Diagram 5] FIG. 13 is a diagram showing an example of the relationship between the resonance period T1 and the ejection speed. [Figure 6] A diagram showing an example of the relationship between the vibration suppression timing T4 and the time when the seepage disappears [Figure 7] FIG. 1 is a diagram showing an example of a plurality of images captured by an imaging unit; [Figure 8] Schematic diagram of a cross section of a nozzle through which ink is ejected [Figure 9] FIG. 1 is a diagram showing the relationship between the ink ejection state and the control parameters. [Figure 10] A diagram showing the relationship between vibration suppression depth Vcal and number of mist particles [Figure 11] A diagram showing the relationship between the vibration control timing T4 and the number of mist droplets [Figure 12] Diagram showing ligament bending [Figure 13] A diagram showing the relationship between the midpoint potential Vmid and the variation in flight angle [Figure 14] A diagram showing the relationship between preliminary vibration depth V1 and the variation in flight angle [Figure 15] A diagram showing the relationship between the vibration damping timing T4 and the variation in flight angle [Figure 16] A diagram showing the relationship between preliminary vibration depth V1 and drop velocity [Figure 17] A diagram showing the relationship between the damping depth Vcal, the drop velocity, and the seepage time [Figure 18] A graph showing the relationship between the slew rate SR and the ink volume at a discharge speed of 4.8 m / s [Figure 19] A graph showing the relationship between the midpoint potential Vmid and the ink volume at a discharge speed of 5 m / s. [Figure 20] 1 is a flowchart showing a control process of a drive signal performed by a control unit. [Figure 21] 11 is another flowchart showing the drive signal control process performed by the control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are merely examples, and the present disclosure is not limited to the following embodiments.

[0012] However, in some cases, more detailed explanations than necessary may be omitted. For example, detailed explanations of already well-known matters or duplicate explanations of substantially the same configurations may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

[0013] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings, assuming that the liquid ejection device is an ink ejection device.

[0014] Fig. 1 is a cross-sectional view showing the configuration of an inkjet head 1. In the following, as shown by the arrows in Fig. 1, the height direction of the inkjet head 1 is referred to as the Z-axis direction, the width direction of the inkjet head 1 is referred to as the X-axis direction, and the depth direction of the inkjet head 1 is referred to as the Y-axis direction.

[0015] The inkjet head 1 ejects ink to print on an object. The ink is, for example, a printing ink. The ink may be other liquid materials, for example, a solder paste, a silver paste, a seal paste, a phosphor paste, or a cell suspension.

[0016] The inkjet head 1 is configured so that ink circulates between it and a liquid delivery device (not shown). That is, ink is supplied from the liquid delivery device to the inkjet head 1, and ink that is not ejected from the inkjet head 1 flows back to the liquid delivery device. Note that the inkjet head 1 may not be of a circulation type, but may be of a non-circulation type in which the ink supplied to the inkjet head 1 remains inside the inkjet head 1.

[0017] The inkjet head 1 includes a head body 10, a vibration plate 20, a pressure member 30, and a control device 40.

[0018] The head body 10 is formed, for example, in a rectangular parallelepiped shape. The head body 10 is composed of a first body portion 11, a second body portion 12, and a nozzle plate 13. As shown in Fig. 1, the head body 10 is formed by stacking the nozzle plate 13, the second body portion 12, and the first body portion 11 in this order.

[0019] The first body portion 11 is formed, for example, in a rectangular parallelepiped shape, and constitutes the upper portion of the head body 10. The first body portion 11 forms a common supply flow path 51 and a common discharge flow path 55, which will be described later. The first body portion 11 is formed, for example, by cutting an alloy steel such as stainless steel.

[0020] The second main body portion 12 is formed, for example, in a rectangular parallelepiped shape, and constitutes the lower portion of the head main body 10. The second main body portion 12 forms supply flow paths 52, ink chambers 53, and discharge flow paths 54 corresponding to each nozzle 56 described below. The second main body portion 12 is formed, for example, by laminating stainless steel plates formed by etching or press processing.

[0021] The nozzle plate 13 is disposed on the bottom surface of the second main body portion 12. The nozzle plate 13 is formed, for example, by molding a stainless steel plate by etching or pressing.

[0022] The head main body 10 includes one common supply flow path 51, multiple supply flow paths 52, multiple ink chambers 53, multiple discharge flow paths 54, one common discharge flow path 55, and multiple nozzles 56. The multiple nozzles 56 are arranged along the Y axis shown in FIG. 1. Hereinafter, the positive direction of the Y axis will be referred to as the arrangement direction. Each set of a supply flow path 52, an ink chamber 53, and a discharge flow path 54 corresponds one-to-one to a nozzle 56. That is, in the head main body 10, there are the same number of sets of supply flow paths 52, ink chambers 53, and discharge flow paths 54 as there are nozzles 56.

[0023] The common supply flow path 51 is formed to extend along the arrangement direction in the first main body portion 11. Ink is supplied to the common supply flow path 51 from a liquid delivery device. The common supply flow path 51 is connected to a plurality of supply flow paths 52. The ink flowing through the common supply flow path 51 is branched to each of the plurality of supply flow paths 52.

[0024] The supply flow passage 52 is formed in the second main body portion 12. The ink supplied to the supply flow passage 52 is supplied to the ink chamber 53 via the first throttle flow passage 57.

[0025] The ink chamber 53 is formed in the second main body portion 12. The upper wall of the ink chamber 53 is formed by the vibration plate 20. Of the ink supplied to the ink chamber 53, the ink that is not ejected from the nozzle 56 is discharged to the discharge flow path 54 via the second throttle flow path 58.

[0026] The discharge flow path 54 is formed in the second main body portion 12. The ink discharged into the discharge flow path 54 is discharged into a common discharge flow path 55.

[0027] The common discharge flow path 55 is formed in the first main body portion 11 so as to extend along the arrangement direction, and is connected to the plurality of discharge flow paths 54. The ink discharged from the plurality of discharge flow paths 54 joins together in the common discharge flow path 55 and flows back to the liquid delivery device.

[0028] The nozzles 56 are holes formed in the nozzle plate 13, and eject the ink in the ink chamber 53 to the outside. Note that a liquid-repellent film having liquid-repellent properties that repel ink may be formed on the bottom surface of the nozzle plate 13.

[0029] The diaphragm 20 is located between the first main body portion 11 and the second main body portion 12, and is disposed so as to form the upper wall of the ink chamber 53. The diaphragm 20 is a thin elastic plate that deforms to become convex toward the inside and outside of the ink chamber 53. In other words, the diaphragm 20 deforms so as to increase or decrease the volume (capacity) of the ink chamber 53.

[0030] The pressure applying member 30 is attached to the plate surface of the vibration plate 20 opposite to the ink chambers 53. The inkjet head 1 includes a plurality of pressure applying members 30. The pressure applying members 30 correspond one-to-one to the ink chambers 53, and are arranged in the same number as the ink chambers 53. The pressure applying members 30 are, for example, piezoelectric elements.

[0031] When a drive signal (voltage waveform signal S) of the inkjet head 1 described later is applied to the pressure member 30, the pressure member 30 expands and contracts, thereby deforming the diaphragm 20. The diaphragm 20 deforms so as to reduce the volume of the ink chamber 53, and the ink in the ink chamber 53 is pressurized, causing the ink to be ejected from the nozzle 56.

[0032] The control device 40 controls the ejection of ink. Specifically, the control device 40 outputs a voltage waveform signal S, which will be described later, to the pressure member 30, thereby vibrating the diaphragm 20.

[0033] 2 is a diagram showing an ink discharge device including an inkjet head 1 and a flight observation device 2. The flight observation device 2 observes the ink discharged from the inkjet head 1 and the periphery of the nozzle 56 on the bottom surface of the nozzle plate 13. The flight observation device 2 includes a light source unit 2a, an imaging unit 2b, and a control unit 2c.

[0034] The light source unit 2a irradiates light onto the periphery of the nozzle 56 and onto the ink ejected from the nozzle 56. The light source unit 2a includes a light source (for example, a light emitting diode) and an optical system that adjusts the traveling direction of the light emitted by the light emitting diode.

[0035] The imaging unit 2b observes the ink ejected from the inkjet head 1. The imaging unit 2b is an imaging device that captures an image of the periphery of the nozzle 56 and the ink ejected from the nozzle 56, and generates an image of the captured image of the periphery of the nozzle 56 and the ink. The imaging unit 2b outputs the generated image to the control unit 2c.

[0036] The control unit 2c controls the light source unit 2a and the imaging unit 2b. Specifically, the control unit 2c controls the light source unit 2a to emit a strobe light that flashes at relatively short intervals. The control unit 2c also controls the strobe light emission of the light source unit 2a in synchronization with a drive signal to the inkjet head 1, and controls the imaging unit 2b to capture images of the ink ejected from the inkjet head 1 and the periphery of the nozzle 56 at multiple timings.

[0037] The control unit 2c calculates the ejection speed and volume of the ink ejected from the inkjet head 1 based on the multiple images output from the imaging unit 2b. Specifically, the control unit 2c calculates the ejection speed of the ink based on the position of the ink in the multiple images. The control unit 2c also calculates the volume of the ink based on the area of ​​the ink in the multiple images. The volume of the ink may be measured by other means.

[0038] FIG. 3 is a diagram showing a plurality of images captured by the imaging unit 2b. For example, the control unit 2c causes the light source unit 2a to emit a strobe light every 10 microseconds, and captures an image with the imaging unit 2b. FIG. 3 shows an image showing the ink ejection state from the ink ejection every 10 microseconds up to 90 microseconds. The ink ejection speed can be calculated from the positions of the two ink droplets at two different times. For example, the speed can be calculated with an accuracy of 0.2 m / s, the angle with an accuracy of 2.5 milliradians, and the volume with an accuracy of 0.1 picoliters.

[0039] Furthermore, when ink is ejected from the nozzle 56, a meniscus of the ink is exposed from the nozzle 56. This meniscus of the ink is drawn into the nozzle 56 due to a drop in the ink pressure in the ink chamber 53 after the ink is ejected. The control unit 2c calculates the time from when the ink is ejected until the meniscus of the ink exposed from the nozzle 56 is drawn into the nozzle 56, based on the multiple images output from the imaging unit 2b.

[0040] The control unit 2c controls the inkjet head 1 so as to eject ink from the nozzles 56. The control unit 2c generates a voltage waveform signal S and outputs it to a control device 40 of the inkjet head 1. The control unit 2c and the control device 40 may be integrated.

[0041] Next, a description will be given of the voltage waveform signal S output by the control device 40. Fig. 4 is a diagram showing an example of the voltage waveform signal S.

[0042] The voltage waveform signal S shown in FIG. 4 has a pulse waveform W1 (t10 to t15) and a second pulse waveform W2 (t1 to t4).

[0043] The pulse waveform W1 is a waveform that vibrates the diaphragm 20 so as to eject ink from the nozzle 56. The pulse waveform W1 vibrates the diaphragm 20 so as to increase the volume of the ink chamber 53 and then decrease the volume of the ink chamber 53. Specifically, the pulse waveform W1 is formed so that the potential value drops and then rises from the midpoint potential Vmid, which is the potential when the voltage waveform signal S is in a steady state.

[0044] More specifically, the pulse waveform W1 is formed so that the potential value starts to drop from the intermediate potential Vmid (time t10), reaches a first potential Va lower than the intermediate potential Vmid (time t11), and starts to rise after being held at the first potential Va (time t12). Furthermore, the pulse waveform W1 is formed so that the potential value reaches a second potential Vb higher than the intermediate potential Vmid (time t13), and is held at the second potential Vb.

[0045] Moreover, the pulse waveform W1 is formed so that the potential value rises and then falls. Specifically, the pulse waveform W1 is formed so that the potential value starts to fall (time t14) after being held at the second potential Vb, and then reaches the intermediate potential Vmid (time t15).

[0046] In the pulse waveform W1, the potential value drops from the midpoint potential Vmid to the first potential Va, which causes the diaphragm 20 to deform so as to increase the volume of the ink chamber 53. Then, the potential value rises to the second potential Vb, which causes the diaphragm 20 to deform so as to decrease the volume of the ink chamber 53, and the ink in the ink chamber 53 is pressurized and ejected from the nozzle 56.

[0047] The second pulse waveform W2 is a waveform for resonating the pressure wave generated in the ink chamber 53 by the vibration of the diaphragm 20.

[0048] The second pulse waveform W2 is located temporally before the pulse waveform W1. The second pulse waveform W2 vibrates the diaphragm 20 so that the volume of the ink chamber 53 changes. Specifically, the second pulse waveform W2 is formed so that the potential value drops and then rises. More specifically, the second pulse waveform W2 is formed so that the potential value starts to drop from the intermediate potential Vmid (time t1), the potential value reaches a third potential Vc between the intermediate potential Vmid and the first potential Va (time t2), the potential value starts to rise after being held at the third potential Vc (time t3), and returns from the third potential Vc to the intermediate potential Vmid (time t4).

[0049] In the second pulse waveform W2, the potential value drops from the intermediate potential Vmid to the third potential Vc, causing the vibration plate 20 to deform so that the volume of the ink chamber 53 increases, and then the potential value returns to the intermediate potential Vmid, causing the vibration plate 20 to return to its original shape.

[0050] Here, the time from the point in time t1 when the potential value starts to change from the intermediate potential Vmid to the third potential Vc to the point in time t3 when the potential value starts to change from the third potential Vc to the intermediate potential Vmid is defined as a first resonance period T1.

[0051] The time from the time (time t3) when the potential value starts to change from the third potential Vc to the intermediate potential Vmid to the time (time t10) when the potential value starts to change from the intermediate potential Vmid to the first potential Va is defined as a second resonance period T2.

[0052] The time from the time (time t10) when the potential value starts to change from the midpoint potential Vmid to the first potential Va to the time (time t12) when the potential value starts to change from the first potential Va to the second potential Vb is defined as a third resonance period T3.

[0053] The time from the time point (time t12) when the potential value starts to change from the first potential Va to the second potential Vb to the time point (time t14) when the potential value starts to change from the second potential Vb to the midpoint potential Vmid is defined as vibration suppression timing T4.

[0054] The potential difference between the midpoint potential Vmid and the third potential Vc is defined as the preliminary vibration depth V1.

[0055] The slope of the potential value from the time when the potential value starts to change from the first potential Va to the second potential Vb (time t12) to the time when the potential value changes from the first potential Va to the second potential Vb (time t13) is the slew rate SR1, and the slope of the propagation from the time when the potential value starts to change from the second potential Vb to the intermediate potential Vmid (time t14) to the time when the potential value reaches the intermediate potential Vmid (time t15) is the slew rate SR2. The slopes of other parts (for example, the slope of the potential value from time t1 to time t2) are also called slew rates SR, but this paper mainly deals with the slope of the potential value SR1 from time t12 to time t13.

[0056] The preliminary vibration is the time from the time t1 when the potential value starts to change from the midpoint potential Vmid to the third potential Vc to the time t4 when the potential value returns from the third potential Vc to the midpoint potential Vmid.

[0057] The main oscillation is the time from when the potential value starts to change from the midpoint potential Vmid to the first potential Va (time t10) to when it reaches the second potential Vb (time t13).

[0058] The time from when the potential value starts to change from the second potential Vb to the intermediate potential Vmid (time t14) to when it reaches the intermediate potential Vmid (time t15) is the damped vibration.

[0059] The control device 40 controls the ejection of ink based on the ink droplet velocity, residual vibration (ink seepage time), the presence or absence of ink mist (Mist), the presence or absence of ink ligament bending (Angle), the presence or absence of ink satellites (Satellite), and the ejection volume of ink (Volume). If the ink seepage time is long, a lot of ink is ejected, and the ligament length becomes long.

[0060] The control device 40 controls the ejection of ink by controlling at least one of the parameters that define the voltage waveform signal S of the inkjet head, namely, the resonance period (T1, T2, T3), the vibration damping timing (T4), the vibration damping depth (Vcal), the intermediate potential (Vmid), the preliminary vibration depth (V1), and the slew rate (SR).

[0061] Next, the determination of the ink ejection state based on the imaging data will be described. The control unit 2c determines the ink ejection state based on the image captured by the imaging unit 2b. The ejection state refers to the presence or absence of mist, the presence or absence of ligament bending, the presence or absence of satellites, and the ejection volume. The control unit 2c may determine the ejection state by AI (Artificial Intelligence) based on the results of machine learning of the ink ejection state.

[0062] Here, the mist is a droplet or mist of ink ejected from the nozzles of an inkjet head, and the droplets are not reproducible in terms of the position where they are generated. In other words, the position where the mist is generated is uncontrollable. Furthermore, the timing at which the mist is generated is also uncontrollable. Since the mist adheres to a workpiece and causes the workpiece to become dirty, it is desirable to suppress the generation of the mist.

[0063] A ligament is a long, thin piece of ink that extends after the main droplet after the ink droplet is ejected. Bent ligaments are a state in which the ligaments are bent midway.

[0064] A satellite is a small droplet that separates from the main droplet of ejected ink.

[0065] The ejection volume is the volume of the ejected ink, and is calculated by the control unit 2c based on the area of ​​the ink in multiple images.

[0066] Next, a method of controlling the discharge will be described. First, the control unit 2c adjusts the basic waveform.

[0067] For example, the control unit 2c sets the vibration damping timing after setting the resonance periods T1, T2, and T3 to adjust the basic waveform.

[0068] FIG. 5 is a diagram showing an example of the relationship between T1 and the discharge speed. As shown in FIG. 5, the discharge speed, which is the speed of droplets discharged from the nozzle, changes by changing the resonance period T1. Although not shown in the figure, the discharge speed also changes by changing the resonance periods T2 and T3. In setting the resonance periods T1, T2, and T3, the control unit 2c sets T1 and T3 to the same value, and then sets T2. The control unit 2c may set T1, T2, and T3 to the same value, for example, and set T1, T2, and T3 to values ​​that provide the fastest discharge speed.

[0069] 6 is a diagram showing an example of the relationship between T4 and the time it takes for the seepage of ink to disappear. The time it takes for the meniscus of the ink exposed from the nozzle 56 to be drawn back into the nozzle 56.

[0070] As shown in Fig. 6, the time it takes for the seepage to disappear is changed by controlling the vibration suppression timing T4. The control unit 2c sets the vibration suppression timing T4 to a value that minimizes the time it takes for the seepage to disappear.

[0071] The basic waveform adjusted as described above has, for example, a midpoint potential Vmid of 0.5, a preliminary vibration depth V1 of 0.2, a slew rate SR of 30 V / microsecond, and a vibration damping depth Vcal of 0.5, when the amplitude of the entire waveform is 1.

[0072] Fig. 7 is a diagram showing an example of a plurality of images captured by the imaging unit 2b. Fig. 7 shows six images captured in synchronization with strobe light emission, in order from the left. Reference numeral 610 indicates the bleeding of the meniscus.

[0073] 8 is a schematic diagram of a cross section of a nozzle 56 from which ink is ejected. The tip of the nozzle 56 from which ink is ejected is a straight portion that is a cylindrical space, and it is necessary for the meniscus to be contained within the straight portion of the nozzle 56.

[0074] After adjusting the basic waveform, the control unit 2c determines the ejection state based on a plurality of images of the ink captured by the imaging unit 2b, and changes the basic waveform.

[0075] Here, the ejection state refers to the presence or absence of ink mist, the presence or absence of ink ligament bending, the presence or absence of ink satellites, and the ejection volume of ink.

[0076] 9 is a diagram showing the relationship between the ink ejection state and the parameters to be controlled. A circle indicates a parameter that is strongly related to the ink ejection state, and a double circle indicates a parameter that is most strongly related to the ink ejection state.

[0077] As shown in FIG. 9, the ejection speed is most strongly related to the resonance periods T1, T2, and T3, and is also strongly related to the midpoint potential Vmid.

[0078] The residual vibration is most strongly related to the vibration suppression timing T4, and is also strongly related to the vibration suppression depth Vcal.

[0079] The mist is most strongly related to the vibration suppression depth Vcal, and is also strongly related to the vibration suppression timing T4, the midpoint potential Vmid, and the pre-vibration depth Vcal.

[0080] The ligament bending is most strongly related to the midpoint potential Vmid, and is also strongly related to the vibration damping timing T4 and the pre-vibration depth Vcal.

[0081] The satellites are most strongly related to the pre-vibration depth V1 and are strongly related to the damping depth Vcal.

[0082] The volume is most strongly related to the slew rate SR, and is strongly related to the resonance periods T1, T2, T3, the damping depth Vcal, the midpoint potential Vmid, and the pre-vibration depth V1.

[0083] The control unit 2c may determine the ejection state using AI such as machine learning. For example, the control unit 2c may acquire multiple images from the imaging unit 2b and perform image analysis on the images to identify the ejection state. The multiple images show the behavior of ink ejected by multiple different drive signals. The drive signal includes a waveform formed by at least four parameters (vibration control depth Vcal, midpoint potential Vmid, preliminary vibration depth V1, and slew rate SR).

[0084] Alternatively, the user may determine the ejection state from the image of ink captured by the imaging unit 2b, input the ejection state from an input unit (not shown), and the control unit 2c may determine the ejection state based on the input information (ejection state information). The control unit 2c adjusts (changes) the basic waveform according to the ejection state. The control unit 2c may adjust the basic waveform based on the results of a test print performed in advance, or may adjust the basic waveform based on actual printing. The adjustment is performed quasi-statically or dynamically. The control unit 2c changes the parameters little by little to adjust the ejection state to the best state.

[0085] 9, the control unit 2c first adjusts the parameter most strongly related to the discharge state, and then adjusts the parameter most strongly related to the discharge state. If it is determined that multiple events, such as mist and ligament bending, have occurred, the control unit 2c adjusts the parameters in descending order of the number of related parameters.

[0086] Next, the adjustment of parameters when mist occurs will be described. When the control unit 2c determines that mist has occurred in the ink, it first changes the vibration suppression depth Vcal. FIG. 10 is a diagram showing the relationship between the vibration suppression depth Vcal and the number of mist particles. As shown in FIG. 10, the number of mist particles changes by changing the vibration suppression depth Vcal. Therefore, the control unit 2c sets the vibration suppression depth Vcal so that the number of mist particles is minimized.

[0087] For example, the control unit 2c acquires a plurality of images showing the behavior of ink ejected by a plurality of drive signals having a plurality of different vibration damping depths Vcal. The control unit 2c performs image analysis on the plurality of images and measures the number of mist particles in each image. The control unit 2c identifies the vibration damping depth Vcal corresponding to the image with the smallest number of mist particles.

[0088] Changing the vibration damping depth Vcal may lengthen the time it takes for the seepage of ink to disappear (the meniscus retraction time), so the control unit 2c may change the vibration damping timing T4, which is related to the time it takes for the seepage of ink to disappear.

[0089] In this case, the control unit 2c changes the vibration control timing T4 after changing the vibration control depth Vcal. Fig. 11 is a diagram showing the relationship between the vibration control timing T4 and the number of mist. As shown in Fig. 11, the number of mist changes by changing the vibration control timing T4. Therefore, the control unit 2c sets the vibration control timing T4 to a value that minimizes the number of mist.

[0090] For example, the control unit 2c acquires a plurality of images showing the behavior of ink ejected by a plurality of drive signals having a plurality of different vibration damping timings T4. In the plurality of drive signals, the vibration damping depth Vcal is a common vibration damping depth Vcal that has already been determined. The control unit 2c performs image analysis on the plurality of images and measures the number of mist particles in each image. The control unit 2c identifies the vibration damping timing T4 corresponding to the image with the smallest number of mist particles.

[0091] Furthermore, the control unit 2c may change the intermediate potential Vmid and the preliminary vibration depth V1 to values ​​that minimize the number of mist particles.

[0092] As shown in Fig. 9, the mist is most strongly related to the vibration suppression depth Vcal, and is also strongly related to the vibration suppression timing T4, the intermediate potential Vmid, and the preliminary vibration depth V1. The control unit 2c first determines the vibration suppression depth Vcal, and then determines the vibration suppression timing T4, the intermediate potential Vmid, and the preliminary vibration depth V1. This determination order can minimize the number of mist.

[0093] Next, adjustment of parameters when ligament bending occurs will be described. Fig. 12 is a diagram showing a state in which ligament bending occurs. It can be seen that ligament bending occurs in a region 1110 in the image captured by the imaging unit 2b.

[0094] When the control unit 2c determines that the ink has ligament bending, it first changes the midpoint potential Vmid. The ink flight direction deviates from the vertical downward direction due to the ligament bending. In other words, when the ligament bending occurs, the flight angle deviates from the vertical downward direction.

[0095] Fig. 13 is a diagram showing the relationship between the intermediate potential Vmid and the variation (three times the variance) of the flight angle (millaradian). As shown in Fig. 13, the flight angle of the ink changes by changing the intermediate potential Vmid. The control unit 2c sets the intermediate potential Vmid so that the variation (variance) of the flight angle of the ink is minimized.

[0096] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected by a plurality of drive signals having a plurality of different intermediate potentials Vmid. The control unit 2c performs image analysis on the plurality of images to measure the variation in the ink flight angle in each image. The control unit 2c identifies the intermediate potential Vmid corresponding to the image with the smallest variation in the ink flight angle.

[0097] Changing the intermediate potential Vmid may cause mist to be generated or the single drop speed to slow down. The single drop speed is the fastest speed at which ink becomes a single drop at a position a predetermined distance (e.g., 0.4 mm) from the nozzle. Therefore, the control unit 2c may further change the vibration control preliminary vibration depth V1 related to the single drop speed and the vibration control depth Vcal related to the generation of mist.

[0098] In this case, the control unit 2c changes the preliminary vibration depth V1 and the vibration damping timing T4 after changing the intermediate potential Vmid. FIG. 14 is a diagram showing the relationship between the preliminary vibration depth V1 and the variation (three times the variance) of the flight angle (milliradian). FIG. 15 is a diagram showing the relationship between the vibration damping timing T4 and the variation (three times the variance) of the flight angle (milliradian). The flight angle changes by changing the preliminary vibration depth V1 and the vibration damping timing T4. The control unit 2c sets the preliminary vibration depth V1 and the vibration damping timing T4 to values ​​that minimize the variation (variance) of the ink flight angle.

[0099] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected by a plurality of drive signals having a plurality of different preliminary vibration depths V1 and vibration damping timings T4. In the plurality of drive signals, the midpoint potential Vmid is a common midpoint potential Vmid that has already been determined. The control unit 2c performs image analysis on the plurality of images to measure the variation in the ink flight angle in each image. The control unit 2c identifies the preliminary vibration depth V1 and vibration damping timing T4 that correspond to the image with the smallest variation in the ink flight angle.

[0100] 9, the ligament bending is most strongly related to the mid-potential Vmid, and is also strongly related to the vibration damping timing T4 and the preliminary vibration depth V1. The control unit 2c first determines the mid-potential Vmid, and then determines the vibration damping timing T4 and the preliminary vibration depth V1. This determination order can minimize the variation in the ink flight angle.

[0101] Next, adjustment of parameters when satellites occur will be described. When the control unit 2c determines that satellites have occurred in the ink, it first changes the preliminary vibration depth V1. FIG. 16 is a diagram showing the relationship between the preliminary vibration depth V1 and the single drop speed. When the single drop speed becomes the fastest, satellites are suppressed. Furthermore, the single drop speed changes by changing the preliminary vibration depth V1. Therefore, the control unit 2c sets the preliminary vibration depth V1 so that the single drop speed by the nozzle becomes the fastest.

[0102] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected by a plurality of drive signals having a plurality of different preliminary vibration depths V1. The control unit 2c performs image analysis on the plurality of images to measure the single drop forming speed in each image. The control unit 2c identifies the preliminary vibration depth V1 corresponding to the image with the fastest single drop forming speed.

[0103] Furthermore, when the preliminary vibration depth V1 is changed, there is a possibility that mist may be generated or ligament bending may occur. Therefore, the control unit 2c may further change the vibration control depth Vcal related to the generation of mist.

[0104] In this case, the control unit 2c changes the vibration suppression depth Vcal after changing the preliminary vibration depth V1. Fig. 17 is a diagram showing the relationship between the vibration suppression depth Vcal and the single drop speed and seeping-out time. As shown in Fig. 17, the single drop speed changes by changing the vibration suppression depth Vcal. The control unit 2c sets the vibration suppression depth Vcal to a value at which the single drop speed by the nozzle is the fastest.

[0105] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected by a plurality of drive signals having a plurality of different vibration suppression depths Vcal. In the plurality of drive signals, the preliminary vibration depth V1 is a common preliminary vibration depth V1 that has already been determined. The control unit 2c performs image analysis on the plurality of images and measures the single drop speed in each image. The control unit 2c identifies the vibration suppression depth Vcal corresponding to the image with the fastest single drop speed.

[0106] As shown in Fig. 9, satellites are most strongly related to the preliminary vibration depth V1 and are strongly related to the vibration suppression depth Vcal. The control unit 2c first determines the preliminary vibration depth V1, and then determines the vibration suppression depth Vcal. This determination order can maximize the single drop speed, thereby suppressing satellites.

[0107] Next, adjustment of the ink volume will be described. When changing the ink volume, the control unit 2c first changes the through rate SR. FIG. 18 is a diagram showing the relationship between the through rate SR and the ink volume when the ejection speed is 4.8 m / s. As shown in FIG. 18, the ink volume changes when the through rate SR is changed. The relationship when the ejection speed is 5 m / s is similar. Also, when the amplitude (damping depth and intermediate potential) changes when the through rate SR is changed, the ink ejection speed also changes. Therefore, the control unit 2c sets the through rate SR so that the volume of the ink when flying from the nozzle at, for example, 5 m / s becomes the volume to be set without changing the ejection speed.

[0108] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected by a plurality of drive signals having a plurality of different slew rates SR. The control unit 2c performs image analysis on the plurality of images to measure the volume of ink in each image. The control unit 2c identifies the slew rate SR corresponding to the image that is closest to the volume to be set.

[0109] Note that if the slew rate SR is changed, there is a possibility that the resonance period T1 may be shifted. Also, if the slew rate SR is small, there is a tendency that the resonance period T1 must be made small. Therefore, the control unit 2c may further change the resonance period T1.

[0110] After changing the slew rate SR and the resonance period T1, the control unit 2c may change the resonance periods T2, T3, the vibration suppression timing T4, the vibration suppression depth Vcal, the intermediate potential Vmid, and the preliminary vibration depth V1.

[0111] Moreover, the control unit 2c may change the intermediate potential Vmid instead of the slew rate SR or together with the slew rate SR. FIG. 19 is a diagram showing the relationship between the intermediate potential Vmid and the volume of the ink when the ejection speed is 5 m / s. By changing the intermediate potential Vmid, the ink volume and the ejection speed change. For example, the control unit 2c sets the intermediate potential Vmid so that the volume of the ink when flying from the nozzle at 5 m / s becomes the volume to be set. However, if the intermediate potential Vmid is changed, the flying angle may deteriorate and ligament bending may occur. Therefore, the control unit 2c may further change the vibration damping timing T4 and the vibration damping depth Vcal, which are related to the occurrence of ligament bending.

[0112] Next, adjustment of parameters when multiple ejection states exist among the ejection states of ink mist, ligament bending, satellites, and ejection volume error will be described. When it is determined that multiple ejection states exist, the control unit 2c may adjust parameters for one of the ejection states, or may adjust parameters to improve the ejection state determined to have the greatest effect on print quality. Alternatively, the control unit 2c may control parameters to improve each ejection state in sequence.

[0113] In this case, the control unit 2c may adjust the parameters in the order of the discharge state having the largest number of parameters to be adjusted. According to FIG. 9, the number of parameters to be adjusted for the mist is 4, the number of parameters to be adjusted for the ligament bending is 3, the number of parameters to be adjusted for the satellite is 2, and the number of parameters to be adjusted for the discharge volume is 5. Therefore, the control unit 2c adjusts the parameters in the order of the parameters for the discharge volume, the parameters for the mist, the parameters for the ligament bending, and the parameters for the satellite. Note that the order of adjusting the parameters is not limited to this, and other orders may be used.

[0114] Next, the control of the drive signal performed by the control unit 2c will be described with reference to a flowchart of FIG 20, which shows the control process of the drive signal performed by the control unit 2c.

[0115] First, the control unit 2c sets the resonance periods T1 and T3 (step S2001), and then sets the resonance period T2 (step S2002). In this disclosure, T1 and T3 are set to the same value, but they may be set to different values. The resonance periods T1, T2, and T3 are set to values ​​that maximize the ejection speed.

[0116] Next, the control unit 2c sets the vibration damping timing T4 (step S2003). The vibration damping timing T4 is set to a value that minimizes the time it takes for the ink seeping out of the nozzles to disappear (meniscus retraction time). The process of step S2003 ends the adjustment of the basic waveform.

[0117] After that, the control unit 2c judges whether or not there is mist (step S2004). When the control unit 2c judges that there is mist (step S2004, Yes), it sets the vibration control depth Vcal to a value that minimizes the number of mist (step S2005).

[0118] Incidentally, following the setting of the vibration control depth Vcal, the control unit 2c may set the vibration control timing T4 to a value that minimizes the number of mist droplets.

[0119] When the control unit 2c determines that there is no mist (No at step S2004), it determines whether or not there is a bent ligament (step S2006).

[0120] When the control unit 2c determines that there is ligament bending (Yes at step S2006), it sets the midpoint potential Vmid to a value that minimizes the variation (dispersion) in the ink flight angle (step S2007).

[0121] Incidentally, following the setting of the intermediate potential Vmid, the control unit 2c may set the preliminary vibration depth V1 and the vibration damping timing T4 to values ​​that minimize the variation in the ink flight angle.

[0122] When the control unit 2c determines that there is no ligament bending (No at step S2006), it determines whether or not a satellite has occurred (step S2008).

[0123] When it is determined that satellites have been generated (Yes at step S2008), the control unit 2c sets the preliminary vibration depth V1 to a value that maximizes the speed at which droplets are formed into a single droplet (step S2009).

[0124] Incidentally, following the setting of the midpoint potential Vmid, the control unit 2c may set the damping depth Vcal to a value that maximizes the speed at which the droplet is formed into a single droplet.

[0125] When it is determined that no satellites have occurred (No at step S2008), the control unit 2c determines whether or not to adjust the volume of ink (step S2010).

[0126] When adjusting the volume (Yes at step S2010), the control unit 2c sets the slew rate SR to a value that provides a desired volume for the ink when flying at 5 m / s (step S2011).

[0127] The control unit 2c may set the intermediate potential Vmid following the setting of the slew rate SR. In this case, the control unit 2c sets the intermediate potential Vmid to a value that provides a desired volume for the ink when flying at 5 m / s.

[0128] The control unit 2c terminates the control process of this drive signal after setting the vibration control depth Vcal in step S2005, after setting the intermediate potential Vmid in step S2007, after setting the preliminary vibration depth V1 in step S2009, after setting the slew rate SR in step S2011, or if no volume adjustment is performed (step S2019, No).

[0129] Fig. 21 is another flowchart showing the control process of the drive signal performed by the control unit 2c. Fig. 21 shows the control process of the drive signal when the control unit 2c determines that there are multiple ejection states among the ejection states of ink mist, ligament bending, satellite, and ejection volume error, and changes the parameters in the order of the ejection state with the largest number of parameters to be adjusted.

[0130] Steps S2101 to S2103 shown in FIG. 21 are the same as steps S2001 to S2003 shown in FIG.

[0131] After the process of step S2103, the control unit 2c judges whether or not to adjust the volume of the ink (step S2104). If the volume is to be adjusted (step S2104, Yes), the control unit 2c sets the slew rate SR to a value that makes the volume of the ink when flying at 5 m / s a desired volume (step S2105).

[0132] When the volume adjustment is not performed (step S2104, No), or when the process of step S2105 is completed, the control unit 2c judges whether or not there is mist (step S2106). Then, when the control unit 2c judges that there is mist (step S2106, Yes), it sets the vibration control depth Vcal to a value that minimizes the number of mist (step S2107).

[0133] When the control unit 2c determines that there is no mist (step S2106, No) or when the process of step S2107 ends, it determines whether or not there is ligament bending (step S2108). When the control unit 2c determines that there is ligament bending (step S2108, Yes), it sets the midpoint potential Vmid to a value that minimizes the variation (dispersion) of the ink flight angle (step S2109).

[0134] When the control unit 2c determines that there is no ligament bending (step S2108, No) or when step S2109 ends, it determines whether or not satellites have occurred (step S2110). When the control unit 2c determines that satellites have occurred (step S2110, Yes), it sets the preliminary vibration depth V1 to a value that maximizes the single droplet forming speed (step S2111).

[0135] When the control unit 2c determines that no satellites have occurred (step S2110, No), or when step S2111 ends, the control unit 2c ends this drive signal control process.

[0136] In the present disclosure, the liquid ejected from the inkjet head is ink, but the liquid may be a liquid other than ink.

[0137] Although the embodiments have been described above with reference to the drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or altered examples within the scope of the claims. It is understood that such modified or altered examples also belong to the technical scope of the present disclosure. In addition, the components in the embodiments may be arbitrarily combined within the scope of the present disclosure.

[0138] (1) A liquid ejection device in one embodiment of the present disclosure includes an inkjet head that ejects liquid based on a drive signal, an observation unit that observes the liquid ejected from the inkjet head, and a control unit that changes the drive signal in response to the ejection state of the liquid observed by the observation unit.

[0139] (2) In a liquid ejection device according to an embodiment of the present disclosure, in the liquid ejection device of (1), the control unit determines the type of parameter of the drive signal in accordance with the ejection state.

[0140] (3) In one embodiment of the liquid ejection device disclosed herein, in the liquid ejection device of (2), the drive signal is a signal having a preliminary vibration section, a main vibration section, and a vibration damping section, and when the control section determines that there is mist in the liquid, it controls the vibration damping depth of the vibration damping section.

[0141] (4) In one embodiment of the liquid ejection device disclosed herein, in the liquid ejection device of (3), the control unit controls at least one of the vibration damping timing of the vibration damping vibration unit, the intermediate potential of the drive signal, and the pre-vibration depth of the pre-vibration unit after controlling the vibration damping depth.

[0142] (5) In one embodiment of the liquid ejection device disclosed herein, in the liquid ejection device of (2), the drive signal is a signal having a preliminary vibration section, a main vibration section, and a damping vibration section, and when the control section determines that there is ligament bending in the liquid, it controls the intermediate potential of the drive signal.

[0143] (6) In one embodiment of the liquid ejection device of the present disclosure, in the liquid ejection device of (5), the control unit controls at least one of the vibration damping timing of the vibration damping section and the preparatory vibration depth of the preparatory vibration section after controlling the intermediate potential.

[0144] (7) In one embodiment of the liquid ejection device disclosed herein, in the liquid ejection device of (2), the drive signal is a signal having a pre-vibration section, a main vibration section, and a damping vibration section, and when the control section determines that there is a satellite in the liquid, it controls the pre-vibration depth of the pre-vibration section.

[0145] (8) In one embodiment of the liquid ejection device according to the present disclosure, in the liquid ejection device of (7), the control unit controls the vibration damping depth of the vibration damping vibration unit after controlling the preliminary vibration depth.

[0146] (9) A liquid ejection device in one embodiment of the present disclosure is the liquid ejection device of (2), wherein the drive signal is a signal having a preliminary vibration section, a main vibration section, and a damping vibration section, and the control section controls the slew rate of the main vibration section in accordance with the ejection volume of the liquid.

[0147] (10) In one embodiment of the liquid ejection device disclosed herein, in the liquid ejection device of (9), the control unit controls at least one of the resonance periods of the preliminary vibration section and the main vibration section, the vibration damping depth of the vibration damping section, the intermediate potential of the drive signal, and the preliminary vibration depth of the preliminary vibration section, after controlling the through rate.

[0148] (11) In one embodiment of the liquid ejection device of the present disclosure, in the liquid ejection device of (2), when a plurality of ejection states of the liquid are observed, including mist of the liquid, ligament bending of the liquid, satellites of the liquid, and an error in the ejection volume of the liquid, the control unit sequentially changes parameters that define the drive signal for each of the ejection states.

[0149] (12) In one embodiment of the liquid ejection device of the present disclosure, in the liquid ejection device of (11), when the liquid mist, the liquid ligament bend, and the liquid satellite are observed, the control unit changes the parameters that define the drive signal in the order of the liquid mist, the liquid ligament bend, and the liquid satellite.

[0150] (13) A liquid ejection method according to one embodiment of the present disclosure includes the steps of observing liquid ejected from an inkjet head that ejects liquid based on a drive signal, and changing the drive signal in accordance with an ejection state of the liquid. [Explanation of symbols]

[0151] 1: Inkjet head 2: Flight observation device 2a: Light source section 2b: Imaging unit 2c: Control section 10: Head body 11: First main body part 12: Second main body part 13: Nozzle plate 20: Vibration plate 30: Pressure member 40: Control device 51: Common supply channel 52: Supply channel 53: Ink chamber 54: Exhaust flow path 55: Common exhaust flow path 56: Nozzle 57: First throttle channel 58: Second throttle channel

Claims

1. an inkjet head that ejects liquid based on a drive signal; an observation unit for observing the liquid ejected from the inkjet head; a control unit that changes the drive signal in response to a discharge state of the liquid observed by the observation unit; A liquid ejection device comprising:

2. the control unit determines the type of the parameter of the drive signal in response to the ejection state. The liquid ejection device according to claim 1 .

3. The drive signal is a signal having a preliminary vibration section, a main vibration section, and a damping vibration section, When the control unit determines that the liquid contains mist, the control unit controls the vibration damping depth of the vibration damping unit. The liquid ejection device according to claim 2 .

4. The control unit controls at least one of a vibration damping timing of the vibration damping unit, an intermediate potential of the drive signal, and a preliminary vibration depth of the preliminary vibration unit after controlling the vibration damping depth. The liquid ejection device according to claim 3 .

5. The drive signal is a signal having a preliminary vibration section, a main vibration section, and a damping vibration section, When the control unit determines that the liquid has a ligament bend, the control unit controls the intermediate potential of the drive signal. The liquid ejection device according to claim 2 .

6. The control unit controls at least one of a vibration damping timing of the vibration damping unit and a preliminary vibration depth of the preliminary vibration unit after controlling the intermediate potential. The liquid ejection device according to claim 5 .

7. The drive signal is a signal having a preliminary vibration section, a main vibration section, and a damping vibration section, When the control unit determines that the liquid has a satellite, the control unit controls a preliminary vibration depth of the preliminary vibration unit. The liquid ejection device according to claim 2 .

8. The control unit controls the vibration damping depth of the vibration damping vibration unit after controlling the preliminary vibration depth. The liquid ejection device according to claim 7.

9. The drive signal is a signal having a preliminary vibration section, a main vibration section, and a damping vibration section, the control unit controls a slew rate of the main vibration unit in accordance with the ejection volume of the liquid. The liquid ejection device according to claim 2 .

10. After controlling the slew rate, the control unit controls at least one of the resonance periods of the preliminary vibration unit and the main vibration unit, the vibration damping depth of the vibration damping unit, the intermediate potential of the drive signal, and the preliminary vibration depth of the preliminary vibration unit. The liquid ejection device according to claim 9.

11. when a plurality of ejection states are observed as the ejection state of the liquid, including a mist of the liquid, a ligament bend of the liquid, a satellite of the liquid, and an error in the ejection volume of the liquid, the control unit sequentially changes a parameter that defines the drive signal for each ejection state. The liquid ejection device according to claim 2 .

12. When the mist of the liquid, the ligament bend of the liquid, and the satellite of the liquid are observed, the control unit changes a parameter that defines the drive signal in the order of the mist of the liquid, the ligament bend of the liquid, and the satellite of the liquid. The liquid ejection device according to claim 11.

13. Observing liquid ejected from an inkjet head that ejects liquid based on a drive signal; changing the drive signal in accordance with a discharge state of the liquid; A liquid ejection method comprising:

Images