WO2024181187A1 - Tête de décharge de gouttelettes et procédé de commande d'entraînement - Google Patents

Tête de décharge de gouttelettes et procédé de commande d'entraînement Download PDF

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Publication number
WO2024181187A1
WO2024181187A1 PCT/JP2024/005644 JP2024005644W WO2024181187A1 WO 2024181187 A1 WO2024181187 A1 WO 2024181187A1 JP 2024005644 W JP2024005644 W JP 2024005644W WO 2024181187 A1 WO2024181187 A1 WO 2024181187A1
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ink
drive
liquid
refill
value
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PCT/JP2024/005644
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English (en)
Japanese (ja)
Inventor
大輝 石黒
宏之 森
太弥 宗仲
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コニカミノルタ株式会社
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Publication of WO2024181187A1 publication Critical patent/WO2024181187A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads

Definitions

  • This invention relates to a droplet ejection head and a drive control method.
  • microdroplets In droplet ejection heads, which eject droplets of ink or other liquid from nozzles and land them on a target recording medium to record an image, microdroplets called satellites may be generated in addition to the droplets being ejected.
  • the image referred to here includes coatings and flat structures. If these satellites adhere to the surroundings, such as the recording medium or the droplet ejection head, they may reduce the quality of the formed image or adversely affect the normal ejection of droplets by the droplet ejection head.
  • Patent Document 1 discloses a technology for suppressing satellites by optimizing the drive waveform in a multi-drop type inkjet recording device that combines multiple ejected droplets and causes them to reach the same target position (pixel).
  • droplets are ejected and landed at close range and without contact between the nozzle face and the recording medium, so the distance between the nozzle face and the recording medium must be precisely adjusted.
  • increasing this distance increases the effect that satellites have on image quality, which can lead to a deterioration in image quality.
  • the object of this invention is to provide a droplet ejection head and drive control method that can perform image recording operations more flexibly while suppressing degradation of image quality.
  • the present invention provides a liquid flow path having a pressure chamber for storing a liquid and applying a pressure fluctuation to the liquid; a nozzle communicating with the liquid flow path and configured to eject droplets of the liquid to which the pressure fluctuation is applied; Equipped with The droplet ejection head has a structure in which the refill Q value related to the vibration of the liquid surface in the nozzle is 1.17 or more when the liquid viscosity is 5.7 mPa ⁇ s, the liquid density is 1080 kg/m 3 , the sound speed in the liquid is 1521 m/s, and the surface tension is 42 mN/m.
  • the present invention has the advantage of being able to perform image recording operations more flexibly while minimizing degradation of image quality.
  • FIG. 2 is a diagram showing a cross section of an ink flow path of the inkjet head of the present embodiment.
  • FIG. 2 is a diagram showing an equivalent circuit of an ink flow path of an inkjet head.
  • 5A to 5C are diagrams illustrating a driving operation for ejecting ink.
  • FIG. 4 is a diagram showing an example of a driving waveform.
  • 11A and 11B are diagrams illustrating an example of a formation target image used for image quality determination.
  • 11A and 11B are diagrams illustrating an example of a formation target image used for image quality determination.
  • 1 is a table showing some of the standards related to image quality judgment.
  • 11 is a table showing an example of combinations of equivalent circuit values according to refill Q values.
  • FIG. 11 is a chart showing an example of the result of an image quality inspection.
  • 11 is a chart showing an example of the result of an image quality inspection.
  • FIG. 13 is a diagram showing the relationship between the refill Q value and the maximum droplet velocity when ink is ejected in a multi-drop system. 13 is a diagram showing the effect that reverberation vibration of a meniscus caused by a first ink ejection of two ink ejections has on the droplet velocity caused by a second ink ejection.
  • FIG. 13 is a diagram showing another example of a driving voltage waveform related to ink ejection.
  • FIG. FIG. 11 is a diagram illustrating another example of an ink flow path.
  • FIG. 11 is a diagram illustrating an equivalent circuit of another example of an ink flow path.
  • FIG. 11 is a diagram illustrating another example of an ink flow path.
  • FIG. 11 is a diagram illustrating an equivalent circuit of another example of an ink flow path.
  • FIG. 11 is a diagram illustrating another example of an ink flow path.
  • FIG. 11 is a diagram illustrating an equivalent circuit of another example of an ink flow path.
  • 1A and 1B are diagrams illustrating an ink flow path of an ink-jet head 1 according to the present embodiment.
  • 1A shows a cross-sectional view of an ink flow path.
  • ink liquid flows from an ink tank through a common ink flow path or a manifold, etc., into an individual flow path F (liquid flow path) that communicates with an individual nozzle N.
  • the ink that has flowed in passes through the individual flow path F and is supplied to the nozzle N.
  • the individual flow path F includes a pressure chamber P.
  • the pressure chamber P is a portion that applies pressure fluctuations to the ink in the pressure chamber P by its deformation, and has a wider width compared to other portions of the individual flow path F, giving it an appropriate volume and temporarily storing ink.
  • the pressure chamber P is, for example, circular or rectangular with rounded corners in a plan view, but is not limited to these shapes.
  • a vibration plate and piezoelectric element are located along the upper surface of the pressure chamber P, which has such a shape in a plan view.
  • the pressure chamber P is deformed by applying a voltage to the piezoelectric element in a voltage pattern that corresponds to the pressure fluctuation pattern to be given to the ink, causing it to deform.
  • Nozzle N is not particularly limited, but may be a tapered shape (frustum shape) that narrows toward the ink ejection port (nozzle opening) at the tip.
  • the nozzle opening is a circle with a diameter D0 in a plan view (bottom view).
  • D(x) the nozzle diameter (diameter) at that point x is expressed as D(x).
  • D(x) is equal to or greater than D0, and is a linear function that varies depending on x. D0 is determined according to the resolution of the recorded image and the amount of ink droplets to be ejected.
  • the amount of ink ejected once per pixel that is, the amount of droplets ejected per dot
  • the amount of droplets referred to here is the total amount of droplets for one cycle of the multi-drop.
  • the individual flow paths F in the other parts are basically rectangular or cylindrical in shape and of uniform thickness.
  • the individual flow paths F extend within the stacked substrates, and the size, represented by the cross-sectional area, cross-sectional shape, and length, is generally fixed for each part of the substrate.
  • the nozzle N is located in the nozzle substrate 11.
  • the nozzle substrate 11 is made of, for example, metal or resin, but is not limited to this.
  • the pressure chamber P is located in the pressure chamber substrate 14.
  • the flow path substrate 12 and intermediate substrate 13 are, for example, glass (silicon dioxide) substrates and/or metal substrates such as SUS and 42 alloy.
  • a downstream individual flow path L that connects the nozzle N and the pressure chamber P extends through the flow path substrate 12 and intermediate substrate 13.
  • a spacer substrate 15 is located above the pressure chamber substrate 14.
  • the spacer substrate 15 has a hollow portion, which contains the pressure chamber P in a plan view.
  • a vibration plate 51 is located at the boundary between the spacer substrate 15 and the pressure chamber P.
  • a piezoelectric element 52 sandwiched between electrodes is located in the hollow portion on the upper surface side of the vibration plate 51. When a voltage is applied to the piezoelectric element 52 and it deforms, the vibration plate 51 deforms in response to this deformation, changing the volume of the pressure chamber P. This causes a pressure fluctuation to be applied to the pressure chamber P.
  • the vibration plate 51 may be a conductive metal member and may also serve as one of the electrodes that sandwich the piezoelectric element 52.
  • the piezoelectric element 52 is not particularly limited, but may be, for example, lead zirconate titanate (PZT).
  • the wiring board 16 is located above the spacer substrate 15.
  • the electrodes sandwiching the piezoelectric elements 52 are connected to the wiring of the wiring board 16 via bumps or the like.
  • the wiring board 16 is connected to a drive board on its upper surface, and a drive voltage signal related to the voltage applied to the piezoelectric elements 52 is input from the drive board.
  • the drive board is not particularly limited, and may be an FPC (Flexible Printed Circuits) or the like.
  • Upstream individual flow paths U that communicate with the pressure chambers P extend through the pressure chamber substrate 14, the spacer substrate 15, and the wiring board 16.
  • the upstream individual flow paths U are connected to a manifold or a common ink flow path that stores and delivers ink supplied to the multiple nozzles N on the upper surface of the wiring board 16.
  • the above substrates may be joined together by adhesive or the like.
  • the pressure fluctuations applied to the ink due to the deformation of the pressure chambers P are transmitted and reflected as vibrations.
  • the ink protrudes from the nozzles N, separates, and ink droplets are ejected.
  • the ink level position changes in response to the above pressure fluctuations, as well as the reduction in ink due to the separation of ink droplets and the supply of ink to compensate for this.
  • Surface tension applies a force in a direction that maintains the appropriate position and shape of this ink level position (meniscus).
  • the vibration parameters are represented by a combination of electrical elements, namely, resistive elements, capacitive elements (capacitors), and inductive elements (coils).
  • the upstream individual flow path U, downstream individual flow path L, and nozzle N are connected in series on either side of the pressure chamber P.
  • the upstream individual flow path U and downstream individual flow path L may each be further divided and represented for each flow path within each substrate.
  • the vibration of the ink liquid surface (meniscus) in nozzle N is important for normal ink ejection, particularly for suppressing satellites.
  • pressure fluctuations remain for a certain period of time while attenuating according to the vibration characteristics. If the damped vibration remains at an appropriate magnitude after ink is ejected, the occurrence of satellites is suppressed. On the other hand, if the damped vibration remains for too long, the remaining vibration will be superimposed on the vibration related to the next cycle of ink ejection, which can have a negative effect on continuous ejection.
  • the vibration characteristics, such as the resonant frequency, associated with this liquid surface vibration are variables that depend on the structure of the individual flow paths F and the characteristics (such as viscosity) of the ink. As described above, the shape and position of the liquid surface (meniscus) are maintained by the surface tension of the ink. In other words, the surface tension affects the restoring force of the liquid surface after ink ejection. Therefore, it can be said that stable ink ejection is possible by using an inkjet head that has individual flow paths F with a structure that has appropriate vibration characteristics according to the characteristics of the ink to be ejected.
  • the Q value is known as a parameter related to vibration (and its damping).
  • the Q value is a dimensionless parameter that becomes smaller as the amount of energy lost in one cycle of vibration in the system increases. If the Q value is too small, the energy loss is large, and not only does the vibration converge quickly, but the pressure fluctuations actually related to the ejection of ink are suppressed. If the Q value is too large, the energy loss is small, and vibrations remain for a long time in response to one drive pulse.
  • the Q value related to the above-mentioned liquid surface vibration is referred to as the refill Q value.
  • the refill Q value Q for the individual flow path F is calculated as follows.
  • Q ⁇ ⁇ Ln / Rn ...
  • Ln is the composite inertance of the m inductors Lm included in the above equivalent circuit.
  • Rn is the combined resistance of k resistors Rk included in the equivalent circuit.
  • Cn is the compliance of the ink surface.
  • ⁇ is the surface tension of the ink, and is a value determined according to the ink.
  • R 4 ⁇ l/( ⁇ d 2 )... (Formula 9)
  • L 128 ⁇ l/( ⁇ d 4 ) ...
  • Formula 10 is the viscosity of the ink, ⁇ is the density of the ink, d is the radius of the cylinder, and l is the length of the cylinder.
  • the resistance value R and inertance L of that portion can be analytically determined as follows.
  • R 8 ⁇ (a+b) 2 ⁇ w/(a 3 ⁇ b 3 ) ...
  • L ⁇ w/(a ⁇ b)...
  • a and b are the lengths of two sides of the cross section of the passage of the rectangular prism, and w is the passage length of the rectangular prism.
  • the resistance value R and inertance L of that portion can be analytically determined as follows.
  • R 128 ⁇ /(3 ⁇ ) ⁇ (w/( ⁇ 2 ⁇ 1) ⁇ ( ⁇ 1 ⁇ 3 ⁇ 2 ⁇ 3 )) ...
  • L 4 ⁇ / ⁇ w/( ⁇ 2 ⁇ 1) ⁇ ( ⁇ 1 ⁇ 1 ⁇ 2 ⁇ 1 ) ...
  • ⁇ 1 and ⁇ 2 are the bottom and top diameters of the truncated cone, respectively.
  • the resistance value R and inertance L of a part with a complex shape such as the pressure chamber P can be obtained by using a numerical simulation.
  • the resistance values R and inertance L of each part arranged in series here are combined to obtain the combined resistance Rn and combined inertance Ln of the individual flow path F.
  • the refill Q value of the individual flow path F is obtained from the parameters (a, b, w, ⁇ 1, ⁇ 2, D0) related to the shape of the individual flow path F and the parameters ( ⁇ , ⁇ , ⁇ ) related to the ink characteristics.
  • flow path resistance may occur at bent portions of the ink flow path, but this is not taken into consideration here since it is smaller than the above in a typical individual flow path F.
  • the type of ink i.e., the characteristics, can be determined independently of the inkjet head.
  • the compatible inks used are generally determined. Therefore, it is sufficient to take into account the characteristics of the compatible ink.
  • the appropriate range of refill Q values can be identified by ejecting ink while changing the refill Q value of the inkjet head and examining the ejection characteristics.
  • 2A and 2B are diagrams for explaining a driving operation for ejecting ink.
  • 2A shows the flow of the drive signal.
  • the head drive unit 5 performs an operation of deforming the piezoelectric element 52 based on the control of the signal control unit 41 of the head drive control unit 4.
  • the signal control unit 41 has a processor such as a CPU (Central Processing Unit) and performs control operations related to the image recording operation.
  • the signal control unit 41 may be a general-purpose CPU of the inkjet recording device, or may be a separate dedicated CPU. In this case, the signal control unit 41 may be located together with the drive circuit 50 on the drive board.
  • the head drive unit 5 includes a drive circuit 50 on a drive board and a piezoelectric element 52.
  • the drive circuit 50 outputs a drive voltage signal with an appropriate waveform (drive waveform) to the piezoelectric element 52, which causes the piezoelectric element 52 to deform so as to generate pressure fluctuations in the ink to eject the ink.
  • the drive circuit 50 has a signal generation unit 53. Based on the control of the signal control unit 41, the signal generation unit 53 converts the digital waveform into an appropriate analog waveform, amplifies the power (voltage and current), and outputs it. The output drive voltage signal is selectively output to a piezoelectric element 52 corresponding to the nozzle N that ejects ink based on image data.
  • FIG. 2B is a diagram showing an example of a driving waveform.
  • the driving method of the piezoelectric element 52 for ink ejection in this embodiment there are a one-drop method and a multi-drop method for ejecting ink.
  • the one-drop method one droplet is ejected with one drive pulse.
  • the multi-drop method a drive waveform is used that combines multiple droplets ejected from each nozzle N by multiple drive pulses and causes them to land on the same pixel position.
  • the inkjet head 1 may be usable with either method, or may be specialized for use mainly in one of the methods.
  • the drive waveform of the multi-drop method will be described.
  • three drive pulses are output per pixel (dot) at intervals twice the AL (Acoustic Length).
  • AL is half the resonance period (acoustic resonance period) of the pressure vibrations occurring in the ink in the pressure chamber P.
  • the resonance period is determined according to the ink ejection frequency required for the inkjet head.
  • a specific resonance frequency is, for example, 10-250 ⁇ s, and in the currently common range, 70 ⁇ s or less.
  • the interval between the rising edges of the drive pulses i.e., the time between the start timing of the rising edges of adjacent drive pulses, may deviate slightly from 2 AL.
  • this interval is set to be approximately 1.8 AL or more and 2.3 AL or less.
  • the width of each drive pulse i.e., the time from when the voltage starts to rise to when the drive voltage ends, is 1.2 AL, which is slightly longer than AL. This prevents the vibration of the liquid surface caused by the preceding drive pulse from remaining too large.
  • the width of the drive pulse is in the range of 0.8 AL or more and 1.3 or less.
  • the drive pulses are, for example, rectangular waves, but may also be trapezoidal waves. In the case of trapezoidal waves, the ratio between the period of voltage change and the period of constant drive voltage may be determined appropriately.
  • the voltage amplitude V1 of the third pulse is greater than the voltage amplitude V2 of the first and second pulses. This ensures that the last ink droplet ejected catches up with the preceding ink droplet and merges into one.
  • the absolute values of the voltage amplitudes V1 and V2 are preferably large within a range that does not cause abnormalities in the ink ejection, i.e., it is preferable for the droplet speed to be high.
  • Such driving pulses suppress satellites and allow stable ejection of ink.
  • the extent to which the effect of satellites on image quality is suppressed ultimately depends on the structure of the inkjet head 1 and the characteristics of the ink.
  • the degree to which desirable ink ejection with minimal degradation in image quality is actually achieved can be determined by the image quality of the image formed by the ink ejection.
  • 3A to 3C are diagrams for explaining image quality determination.
  • 3A and 3B are examples of images to be formed that are used for image quality assessment.
  • FIG. 3A shows a one-dimensional barcode (Code 1)
  • FIG. 3B shows a two-dimensional code (Code 2). If these are not displayed accurately, problems may occur in reading them, and therefore evaluation standards have been established.
  • the quality evaluation standards for one-dimensional barcodes are stipulated in ISO 15416 (JIS X 0520).
  • the quality evaluation standards for two-dimensional codes are stipulated in ISO 15415 (JIS X 0521).
  • Figure 3C shows part of the contents of ISO15415.
  • the inspection contents include the contrast between white and black cells, bias, finder pattern, quiet zone, alignment pattern, timing pattern, etc., the percentage of errors within the range where the positions of white and black cells are fixed, reading abnormalities, the amount of distortion of the 2D code itself, the variation in the size of each cell (relative uniformity), and the utilization rate of error correction codes (data recovery codes) used when reading stains and missing parts.
  • Each item is evaluated using a numerical value of 0.0 to 4.0 (2016 revised version) or a five-level alphabetical scale of A-D and F (2000 version). The overall evaluation is determined by the lowest evaluation level among the evaluations of each item.
  • FIG. 4 is a diagram showing the composite inertance Ln, composite resistance Rn, and compliance Cn of the equivalent circuit corresponding to each refill Q value tested according to the test standards of Code 1 and Code 2 above.
  • the refill Q value can be calculated based on the above (Equation 8) or the like.
  • the shape of the individual flow path F can be changed so as to decrease the composite resistance Rn or increase the composite inertance Ln as described above.
  • Fig. 5A is a chart showing the results of an inspection according to the inspection standard of Code 1.
  • Fig. 5B is a chart showing the results of an inspection according to the inspection standard of Code 2.
  • These inspection results were obtained by varying the distance from the ink ejection surface to the ink landing surface (image recording surface) for each inkjet head with different structural parameters related to the refill Q value. This distance, i.e., the head/media gap, will be referred to as the gap below.
  • an overall rating of C or higher is considered to be OK. Even if the overall rating is D or lower, it cannot be said that the image quality is necessarily NG, but in order to obtain images (image quality) of consistent and appropriate quality, it is preferable for the overall rating to be C or higher.
  • the ink used to record the image in this test has a viscosity of 5.7 mPa ⁇ s, a density (liquid density) of 1080 kg/m 3 , a sound velocity in the ink of 1521 m/s, and a surface tension of 42 mN/m.
  • the recorded Code 1 and Code 2 were read by a Keyence (registered trademark) code reader "SR-1000". The code reader outputs the above overall evaluation.
  • the refill Q value when the refill Q value was 2.44, appropriate quality was not obtained at a gap of 15 mm.
  • the refill Q value was 2.32 or less, images of appropriate quality were obtained even with a gap of 15 mm.
  • the refill Q value it is preferable that the refill Q value be 1.17 or more, and it is even more preferable that the refill Q value be 1.85 or more.
  • the refill Q value it is even more preferable that the refill Q value be 2.32 or less.
  • Figure 6 shows the relationship between the refill Q value and the maximum droplet speed that can be stably ejected using the multi-drop method.
  • the maximum droplet velocity that can be stably ejected shown here is the velocity at a position 0.5 mm from the ink ejection surface. It can be seen that the maximum droplet velocity has a positive correlation with the refill Q value. When the refill Q value is 1.31 or more, the maximum droplet velocity is 5 m/s or more, whereas when the refill Q value is less than 1.31, the maximum droplet velocity is 5 m/s or less, which is insufficient for practical use. In other words, if the refill Q value is low in the multi-drop method, it is thought that the supply of ink to the nozzle N cannot keep up with the high-speed ejection in which the interval between drive pulses is short and the AL is small. As a result, ejection may become unstable.
  • the refill Q value is 1.31 or more.
  • the refill Q value is 1.31 or more.
  • the inkjet head 1 it is more preferable for the inkjet head 1 to have the above refill Q value that allows an appropriate droplet speed to be obtained regardless of the ink ejection method.
  • Fig. 7 shows the effect of reverberation vibration of the meniscus caused by the first of two ink ejections on the droplet velocity of the second ink ejection.
  • the difference in the ink droplet velocity of the second ink ejection relative to the ink droplet velocity of the first ink ejection is shown for the drive cycles for the two ink ejections.
  • Each line corresponds to six different refill Q values.
  • the drive cycle is shown based on the AL.
  • the refill Q value is 2.12 or less, the difference will be kept to about 1 m/s or less.
  • the droplet speed is set to about 5 m/s or more, so a difference of 1 m/s will be 20% or less of the droplet speed.
  • FIG. 8 is a diagram showing another example of the driving voltage waveform related to ink ejection. Regardless of the structure of the inkjet head 1, it is preferable to use a driving voltage waveform that is less likely to produce satellites and can stably and continuously eject ink in the multi-drop method.
  • a pulse waveform with a voltage amplitude V3 larger than the voltage amplitude V1 of the last pulse waveform is added after the last pulse waveform shown in FIG. 2B at an interval of 4.0 AL, which is twice the normal interval.
  • the width (pulse length) of the last added pulse waveform is 1.0 AL.
  • the pulse length of the pulse waveform with the voltage amplitude V1 that is no longer the last pulse waveform is 1.3 AL, which is the same as the pulse length of the previous pulse waveform.
  • 9A, 9B, 10A, 10B, 11A and 11B are diagrams for explaining other examples of ink flow paths.
  • 9A the specific structure of the ink flow path may be other than that shown in the above embodiment.
  • the individual flow paths Fa are each formed in a common ink flow path Sc located in a flow path substrate 12a between a nozzle substrate 11a and a pressure chamber substrate 14a.
  • FIG. 9B is a diagram showing an equivalent circuit of this ink flow path.
  • Corresponding resistance values R and inertance L are applied to each structural part of the upstream individual flow path U, pressure chamber P, downstream individual flow path L, and nozzle N. Even if the structures are different, by combining these, the refill Q value can be found in the same manner as above.
  • the inkjet head 1b may have a structure in which a pressure change is applied by a piezoelectric element 52 that deforms in shear mode.
  • Ink that flows into the individual flow path Fb is supplied to the nozzle N through the upstream individual flow path U, the pressure chamber P of the pressure chamber substrate 14b, and the downstream individual flow path L of the intermediate substrate 13b.
  • the piezoelectric element is located on the side of the pressure chamber P.
  • a pressure change is applied to the ink in the individual flow path Fb in the pressure chamber substrate 14b by deformation in shear mode, which is deformation of the piezoelectric element in a direction along the individual supply flow path S. In this way, even if the inkjet head 1a has a different deformation mode of the piezoelectric element 52, the refill Q value can be found according to the parameters of each structural part shown in FIG. 10B.
  • FIG. 11A shows the ink flow path of another example of an inkjet head 1c.
  • the ink that flows from the common ink flow path Sc into the upstream individual flow path U passes through the pressure chamber P of the pressure chamber substrate 14c and the downstream individual flow path L of the intermediate substrate 13c, and is ejected from the nozzle N of the nozzle substrate 11c.
  • the ink may be separated into individual discharge flow paths E1, E2 in the flow path substrate 12c and the intermediate substrate 13c.
  • the ink that passes through the common discharge flow paths Ec1, Ec2 may be returned to the ink tank.
  • the inkjet head 1c having such a circulation flow path, the components of the ink can be separated due to stagnation in the individual supply flow paths S including the upstream individual flow path U, the pressure chamber P, and the downstream individual flow path L, and mixed air bubbles and dust can be quickly discharged. Therefore, the inkjet head 1c can perform a more stable image recording operation.
  • the individual supply flow paths S and individual discharge flow paths E1, E2 included in the individual flow paths Fc of ink corresponding to each nozzle N, and the above-mentioned equivalent circuit corresponding to the nozzle N can be taken into consideration.
  • the individual discharge flow paths E1, E2 are located in parallel to the individual supply flow path S in the individual flow path Fc.
  • the refill Q value can be found using the parameters of the resistive elements, capacitors, and inductive elements of this circuit configuration as well as the characteristics of the ink.
  • the individual discharge channels E1, E2 and the common discharge channels Ec1, Ec2 are not limited to being applied to the individual channels Fc that deform in a shear mode to impart pressure fluctuations to ink, but may be applied to the individual channels F, Fa that impart pressure fluctuations to ink by the above-mentioned flexure mode deformation.
  • the inkjet head 1 of this embodiment includes an individual flow path F having a pressure chamber P that allows a liquid (ink) to pass and stores the ink to impart pressure fluctuation, and a nozzle N that communicates with the individual flow path F and ejects droplets of the ink to which the pressure fluctuation has been imparted.
  • the inkjet head 1 has a structure in which the refill Q value associated with the vibration of the liquid surface in the nozzle N is 1.17 or more when the liquid viscosity is 5.7 mPa ⁇ s, the liquid density is 1080 kg/m 3 , the sound speed in the liquid is 1521 m/s, and the surface tension is 42 mN/m.
  • the inkjet head 1 having such a structure, ink can be ejected while reducing the effect of satellites on image quality even when the distance between the nozzle opening and the recording medium is increased to about 5 mm, which is wider than the conventional distance of about 1 mm. This allows the inkjet head 1 to suppress deterioration in image quality of the recorded image. Therefore, the inkjet head 1 can be used more flexibly for various image recording operations than before.
  • the structure of the inkjet head 1 is determined based on the characteristics of the reference liquid. Therefore, if the characteristics of the liquid differ, the actual refill Q value also changes.
  • the refill Q value is 1.38 or more. Increasing the refill Q value to this level allows for more appropriate high-speed flying over a gap of about 5 mm. Therefore, the inkjet head 1 can flexibly eject ink over a wider gap with even greater stability.
  • the refill Q value is 1.85 or more.
  • the distance between the nozzle opening and the recording medium can be increased to approximately 15 mm. Therefore, with this inkjet head 1, image recording can be performed stably without trouble, even on three-dimensional recording media with unevenness, while minimizing deterioration in image quality.
  • the inkjet head 1 has a structure that provides a refill Q value of 2.32 or less under the same configuration and ink conditions as above. This enables stable image recording over a wide gap while minimizing degradation of image quality, regardless of whether the method is multi-drop or one-drop. Therefore, this inkjet head 1 is capable of flexibly recording images on a wide range of recording media.
  • the refill Q value is 2.12 or less.
  • the refill Q value is 2.12 or less.
  • the width of the multiple drive pulses is AL 0.8 or more and 1.3 or less, and the interval between the rising edges of the drive pulses is AL 1.8 or more and 2.3 or less.
  • this drive control method By ejecting ink from the inkjet head 1 of this embodiment using such a drive control method, stable ink ejection with less effect of satellites can be performed more reliably than before, even if the gap is widened. As a result, this drive control method allows images to be recorded more flexibly while suppressing deterioration of image quality.
  • the last drive pulse of the multiple drive pulses may rise at an interval of AL 4.0 or more from the rising edge of the drive pulse immediately before the last drive pulse.
  • the influence of each drive pulse is superimposed on the subsequent drive pulse, making it easier for satellites to occur between the ejected droplets.
  • a larger interval than usual is provided between the last two drive pulses, thereby preventing satellites from remaining in the end. Therefore, most of the ejected ink can be coalesced and landed on the recording medium.
  • the drive waveform may be determined so that the droplet speed at a position 0.5 mm from the opening end of the nozzle N is 7 m/s or more.
  • the ink flight time becomes long, especially when the gap is wide.
  • the influence of external air currents and the like during flight is likely to become greater. Therefore, by achieving a droplet speed of about 7 m/s or more, the ejected ink can be more stably landed at the appropriate position, and a recorded image of suitable quality can be obtained.
  • the drive waveform may be determined so that the amount of droplets ejected per dot is 10 pL or more. If the droplet amount is small, it is likely to be significantly decelerated due to air resistance, especially while flying across a wide gap. By determining the drive waveform so that the droplet amount is 10 pL or more, the degree of deceleration can be suppressed even when subjected to air resistance, etc. As a result, in this drive control method, even when ink is landed on a recording medium across a wide gap using the inkjet head 1 of this embodiment, degradation of image quality is suppressed.
  • the present invention is not limited to the above-described embodiment, and various modifications are possible.
  • factors that cause degradation of image quality when the gap is widened include, in addition to the occurrence of satellites, droplet size, droplet speed, etc. Therefore, the lower limit and/or upper limit of the refill Q value may be determined in consideration of the conditions that take precedence, such as the gap, droplet size, and whether or not the multi-drop method is used, required for the recorded image and recording medium.
  • drive waveforms in the multi-drop method shown above are examples. Drive signals of other drive waveforms may be generated and output. Furthermore, in the above embodiment, an example in which trapezoidal drive pulses are combined is described, but this is not limited to this. Square wave pulses may also be used. Furthermore, in the above, only drive pulses that change from the reference voltage to the + side are shown, but this is not limited to this. Drive pulses that change only to the - side may also be used, or drive pulses that change to both the + and + sides may be combined.
  • the nozzle N does not have to have a tapered shape. It may be a short cylindrical shape, for example. Other shapes of the ink flow path may also be determined as appropriate.
  • the combined resistance and inertance of each part may be found analytically or by numerical simulation according to the shape. Furthermore, the found combined resistance and inertance do not have to depend only on the shape of the ink flow path. In other words, if a filter or the like is located, this may also be taken into consideration when calculating the combined resistance and inertance.
  • any inkjet head 1 may be used in which ink is ejected from a nozzle N by applying pressure fluctuations to the ink in the ink flow path.
  • the drive signal may be generated based on a different standard than that described above.
  • the specific configuration of the signal control unit 41 and the signal generation unit 53 is arbitrary, as long as an appropriate drive signal is generated and an output destination is selected according to image data.
  • the specific configurations, contents and procedures of the processing operations, etc. shown in the above embodiments can be modified as appropriate without departing from the spirit of the present invention.
  • the scope of the present invention includes the scope of the invention described in the claims and its equivalents.
  • This invention can be used in droplet ejection heads and drive control methods.

Landscapes

  • Particle Formation And Scattering Control In Inkjet Printers (AREA)

Abstract

Est fournie une tête de décharge de gouttelettes et un procédé de commande d'entraînement grâce auxquels des opérations d'impression d'image peuvent être mises en oeuvre de manière plus flexible tout en supprimant des réductions de qualité d'image. Une tête à jet d'encre (1), qui est une tête de décharge de gouttelettes, comprend : un canal d'écoulement individuel (F) à travers lequel passe l'encre et qui comporte une chambre de pression (P) qui stocke l'encre et applique des fluctuations de pression ; et une buse (N) qui communique avec le canal d'écoulement individuel (F) et décharge des gouttelettes d'un liquide auquel les fluctuations de pression ont été appliquées. La tête à jet d'encre (1) présente une structure configurée de sorte que la valeur Q de recharge liée à la vibration de la surface liquide au niveau de la buse (N) est de 1,17 ou plus dans un cas dans lequel la viscosité du liquide est de 5,7 mPa·s, la densité de liquide est de 1080 kg/m3, la vitesse du son dans le liquide est de 1521 m/s, et la tension de surface est de 42 mN/m.
PCT/JP2024/005644 2023-02-27 2024-02-19 Tête de décharge de gouttelettes et procédé de commande d'entraînement WO2024181187A1 (fr)

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Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11123822A (ja) * 1997-10-23 1999-05-11 Seiko Epson Corp インクジェット式記録ヘッド
JP2002001956A (ja) * 2001-06-26 2002-01-08 Ricoh Co Ltd インクジェットヘッド
WO2006049982A2 (fr) * 2004-11-01 2006-05-11 Basf Corporation Encres d'imprimante jet d'encre activees par radiofrequence et appareil pour l'impression par jet d'encre
JP2006256151A (ja) * 2005-03-17 2006-09-28 Fuji Xerox Co Ltd 画像形成装置及び液体吐出状態判定方法
JP2009090649A (ja) * 2007-09-18 2009-04-30 Konica Minolta Holdings Inc 液滴吐出装置及び液滴吐出方法
JP2011194675A (ja) * 2010-03-18 2011-10-06 Ricoh Co Ltd 液滴吐出方法、液滴吐出装置及びインクジェット記録装置
WO2015033993A1 (fr) * 2013-09-06 2015-03-12 コニカミノルタ株式会社 Tête à jet d'encre et dispositif d'impression à jet d'encre
JP2022052804A (ja) * 2020-09-24 2022-04-05 コニカミノルタ株式会社 インクジェットヘッドの駆動設定方法及び駆動方法
JP2022533099A (ja) * 2019-05-21 2022-07-21 ザール テクノロジー リミテッド 高粘度流体に最適化された圧電液滴堆積装置、ならびにその方法および制御システム

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11123822A (ja) * 1997-10-23 1999-05-11 Seiko Epson Corp インクジェット式記録ヘッド
JP2002001956A (ja) * 2001-06-26 2002-01-08 Ricoh Co Ltd インクジェットヘッド
WO2006049982A2 (fr) * 2004-11-01 2006-05-11 Basf Corporation Encres d'imprimante jet d'encre activees par radiofrequence et appareil pour l'impression par jet d'encre
JP2006256151A (ja) * 2005-03-17 2006-09-28 Fuji Xerox Co Ltd 画像形成装置及び液体吐出状態判定方法
JP2009090649A (ja) * 2007-09-18 2009-04-30 Konica Minolta Holdings Inc 液滴吐出装置及び液滴吐出方法
JP2011194675A (ja) * 2010-03-18 2011-10-06 Ricoh Co Ltd 液滴吐出方法、液滴吐出装置及びインクジェット記録装置
WO2015033993A1 (fr) * 2013-09-06 2015-03-12 コニカミノルタ株式会社 Tête à jet d'encre et dispositif d'impression à jet d'encre
JP2022533099A (ja) * 2019-05-21 2022-07-21 ザール テクノロジー リミテッド 高粘度流体に最適化された圧電液滴堆積装置、ならびにその方法および制御システム
JP2022052804A (ja) * 2020-09-24 2022-04-05 コニカミノルタ株式会社 インクジェットヘッドの駆動設定方法及び駆動方法

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