Inkjet head module with hybrid type, inkjet printing apparatus and method for controlling the same

Abstract

In a hybrid inkjet head module, an inkjet printing device including the same, and a control method thereof, the inkjet head module comprises a nozzle unit, a piezoelectric module, and an electrode module. The nozzle unit comprises a chamber portion in which ink is stored, and a nozzle extending to the lower part of the chamber portion to discharge the ink to the outside. The piezoelectric module is located above the nozzle unit and provides pressure to the nozzle unit during a first period. The electrode module is located below the nozzle and induces an electric field in the nozzle during a second period included in the first period.

Description

Technology Field

[0001] The present invention relates to a hybrid inkjet head module, an inkjet printing device including the same, and a control method thereof. More specifically, it relates to a hybrid inkjet head module that improves or optimizes ink ejection speed and ink ejection amount by combining a piezoelectric method and an electro-hydro dynamic (EHD) method of droplet ejection to eject ink droplets, an inkjet printing device including the same, and a control method thereof. Background Technology

[0002] Conventional inkjet printing technology has been implemented through the principle in which ink is ejected from a nozzle by the generation of a strong pressure wave within an ink storage chamber generated by a piezoelectric driving device.

[0003] However, in the case of dispensing ink using the conventional piezoelectric driving method, there was a limitation in that it was only possible to dispense ink with a viscosity of 10 cp or less, which is about 10 times that of water, and it was difficult to dispense high-viscosity ink.

[0004] However, as the application range of inkjet printing technology has recently increased significantly, there is a demand for technology to eject higher viscosity ink, and thus, a technology has been developed to reduce the viscosity of the ink by simultaneously performing heating.

[0005] Furthermore, in addition to simple piezoelectric driving methods, technology for ejecting droplets using electrostatic force with electrostatic electrodes is being developed, as described in Korean Registered Patent No. 10-1366076, and such droplet ejection technology utilizing an electric field is also disclosed in Japanese Registered Patent No. 3776317.

[0006] However, even in the case of the technology that simply uses electric force to eject ink as described above, there are limitations in easily ejecting high-viscosity ink, and thus, further development of related technology is required. Prior art literature

[0007] Republic of Korea Registered Patent No. 10-1366076, Japan Registered Patent No. 3776317 The problem to be solved

[0008] Accordingly, the technical problem of the present invention is conceived from this point, and the objective of the present invention is to provide a hybrid inkjet head module that improves or optimizes the ink ejection speed and ink ejection amount by combining a piezoelectric method and an electro-hydro dynamic (EHD) method of droplet ejection to eject ink droplets.

[0009] In addition, another objective of the present invention is to provide an inkjet printing device comprising the inkjet head module.

[0010] In addition, another objective of the present invention is to provide a method for controlling the inkjet head module. means of solving the problem

[0011] An inkjet head module according to one embodiment for realizing the purpose of the present invention described above includes a nozzle unit, a piezoelectric module, and an electrode module. The nozzle unit includes a chamber portion in which ink is stored, and a nozzle extending from the lower part of the chamber portion to discharge the ink to the outside. The piezoelectric module is located above the nozzle unit and provides pressure to the nozzle unit during a first period. The electrode module is located below the nozzle and induces an electric field in the nozzle during a second period included in the first period.

[0012] In one embodiment, the first section may include a first increasing section (Tr1) in which the voltage applied to the piezoelectric module increases, a first maintaining section (Td1) in which the voltage applied to the piezoelectric module is maintained at a constant level, and a first decreasing section (Tf1) in which the voltage applied to the piezoelectric module decreases, and the second section may include a second increasing section (Tr2) in which the voltage applied to the electrode module increases, a second maintaining section (Td2) in which the voltage applied to the electrode module is maintained at a constant level, and a second decreasing section (Tf2) in which the voltage applied to the electrode module decreases.

[0013] In one embodiment, the second section may fall within the range of the first maintenance section (Td1).

[0014] In one embodiment, the second section may be shorter than the first maintenance section (Td1).

[0015] In one embodiment, the voltage of the second holding period (Td2) may be greater than the voltage of the first holding period (Td1).

[0016] In one embodiment, a control unit for controlling the operation of the piezoelectric module and the electrode module may be further included.

[0017] In one embodiment, the control unit can control the first increase section (Tr1) to increase the ink discharge speed and discharge amount while maintaining the second section constant.

[0018] In one embodiment, the control unit can control the ink discharge speed to decrease by increasing any one of the second increase section (Tr2), the second maintenance section (Td2), and the second decrease section (Tf2) while maintaining the first section at a constant level.

[0019] In one embodiment, the control unit can control the ink discharge amount by increasing either the second maintenance section (Td2) or the second reduction section (Tf2) by more than a preset value while maintaining the first section at a constant level.

[0020] In one embodiment, the control unit can control the voltage applied during the second section to increase the voltage amplitude while maintaining the first section constant, thereby increasing the ink discharge speed and decreasing the ink discharge amount.

[0021] In one embodiment, the electrode module may include an upper electrode located at the bottom of the nozzle, and a lower electrode located at the bottom of the upper electrode and spaced apart from the upper electrode by a predetermined distance.

[0022] In one embodiment, the electrode module further includes an electrode module substrate portion interposed between the upper electrode and the lower electrode, and the electrode module substrate portion may have a dielectric constant higher than that of air.

[0023] An inkjet printing device according to one embodiment for realizing another objective of the present invention described above is configured such that a plurality of inkjet head modules are arranged at a predetermined interval from one another, and the interval between the adjacent inkjet head modules can be pre-set so that interference caused by an electric field induced by the electrode module of the adjacent inkjet head module does not occur.

[0024] In a control method for an inkjet head module according to an embodiment for realizing another objective of the present invention described above, a required ink ejection speed and an ink ejection amount are input. Based on the ejection speed and the ejection amount, a piezoelectric module is driven during a first section. Based on the ejection speed and the ejection amount, an electrode module is driven during a second section included in the first section. In accordance with the driving of the piezoelectric module and the electrode module, the ink is ejected.

[0025] In one embodiment, in the step of driving the electrode module, the second section may fall within the range of the first maintenance section (Td1) in which the voltage is maintained constant among the first sections. Effects of the invention

[0026] According to embodiments of the present invention, by providing pressure to a nozzle unit through a piezoelectric module and inducing an electric field in the nozzle through an electrode module within the operating range of the piezoelectric module, the discharge speed of the formed droplet can be improved through the force of the electrostatic field, thereby inducing more effective discharge. Through this, in particular, high-viscosity ink can be discharged more easily and quickly, allowing for inkjet printing using various high-viscosity inks.

[0027] In this case, the electrode module induces droplet discharge by inducing an electrostatic field using the so-called EHD (electro-hydro dynamic) method. Since it induces instantaneous operation during a relatively short range of a certain range within the operating period of the piezoelectric module, it is possible to induce instantaneous discharge of high-viscosity ink, and problems such as uneven droplet discharge caused by the long-term induction of the electrostatic field can be minimized.

[0028] In particular, in inducing such droplet discharge, the electrode module is controlled to operate only within the range where the voltage is maintained constant during the operation period of the piezoelectric module, thereby enabling faster and greater discharge of droplets.

[0029] In addition, regarding the voltage applied to the piezoelectric module, by controlling the voltage increase interval differently, it is possible to control the ink ejection speed and ejection amount, thereby enabling optimal ink ejection control.

[0030] In addition, regarding the voltage applied to the electrode module, the ink ejection speed can be controlled by selectively controlling the voltage increase section, the maintenance section, and the decrease section, and the ink ejection amount can be controlled by selectively controlling the voltage maintenance section and the decrease section, and the ink ejection speed and amount can be controlled by controlling the amplitude of the applied voltage, thereby enabling the implementation of the necessary optimal ink ejection control through various ejection controls.

[0031] In particular, by interposing an electrode module substrate portion containing a material having a dielectric constant higher than that of air, such as aluminum oxide, between the upper electrode and the lower electrode included in the electrode module, the generation of electrostatic force can be enhanced, thereby further improving the ink ejection speed.

[0032] Furthermore, in an inkjet printing device configured with a plurality of the above-mentioned inkjet head modules arranged, by setting the spacing between adjacent inkjet head modules by considering a spacing distance at which interference caused by the electric field induced by the electrode module in adjacent inkjet head modules is minimized, independent operation of the inkjet head modules and inkjet printing with higher precision can be achieved. Brief explanation of the drawing

[0033] FIG. 1 is a schematic diagram illustrating an inkjet head module according to one embodiment of the present invention. FIG. 2a is a schematic diagram illustrating an inkjet printing device in which a plurality of inkjet head modules of FIG. 1 are arranged, and FIG. 2b is an image illustrating an ink ejection state through the inkjet head module of FIG. 2a. Figure 3 is a graph showing the operating state of the piezoelectric module and electrode module of Figure 1. FIGS. 4a to 4f are graphs illustrating the ink ejection state according to the variable driving state of the piezoelectric module in the inkjet head module of FIG. 1. FIGS. 5a to 5j are graphs and images illustrating the ink ejection state according to the variable driving time of the electrode module in the inkjet head module of FIG. 1. FIGS. 6a and 6b are graphs illustrating the ink ejection state according to the time change of the voltage waveform during the operation of the electrode module in the inkjet head module of FIG. 1. FIGS. 7a and 7b are graphs illustrating the ink ejection state according to the change in amplitude during the operation of the electrode module in the inkjet head module of FIG. 1. FIG. 8 is a flowchart illustrating a control method for the inkjet head module of FIG. 1. FIG. 9 is a schematic diagram illustrating an inkjet head module according to another embodiment of the present invention. FIGS. 10a to 10c are graphs and images illustrating the ink ejection state in the inkjet head module of FIGS. 1 and FIG. 9. Specific details for implementing the invention

[0034] The present invention is susceptible to various modifications and may take various forms, and embodiments are to be described in detail in the text. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each figure. Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms.

[0035] The above terms are used solely for the purpose of distinguishing one component from another. The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0036] In this application, terms such as "comprising" or "consisting of" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0037] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0038] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings.

[0039] FIG. 1 is a schematic diagram illustrating an inkjet head module according to one embodiment of the present invention.

[0040] Referring to FIG. 1, the inkjet head module (10) according to the present embodiment includes a nozzle unit (100), a cover frame (200), a piezoelectric module (300), an electrode module (400), a control unit (500), and an input unit (600).

[0041] The above inkjet head module (10) is provided in an inkjet printing device (not shown) that performs a predetermined printing by dropping ink (150) as a droplet, and corresponds to a module that induces the dropping (discharge) of the ink (150).

[0042] Accordingly, only the minimum configuration required for the discharge of the ink (150) is shown as an inkjet head module (10) in FIG. 1, and the essential configuration for other operations of the inkjet head module (10) may be identical to or within the obvious range of the conventional configuration of an inkjet head module disclosed in the prior art.

[0043] Furthermore, this is also the same in the inkjet printing device described below, and the structure in which the inkjet head module (10) is mounted in the inkjet printing device may also be the same as or within the obvious range of the conventional configuration in the inkjet printing device disclosed through the prior art.

[0044] Specifically, the inkjet head module (10) according to the present embodiment is described as follows.

[0045] First, the nozzle unit (100) forms the central body portion of the inkjet head module (10) and includes a chamber portion (110), a vibrating plate (120), an upper nozzle (130), and a lower nozzle (140).

[0046] The above chamber part (110) is a chamber structure that forms a predetermined space. Although the above chamber part (110) is shown as having a rectangular cross-section in the cross-section through FIG. 1, it can have a three-dimensional shape such as a cuboid shape or a cylinder shape overall.

[0047] Additionally, the internal space formed by the chamber section (110) can be designed in various ways, and ink (150) is stored inside the chamber section (110). At this time, the ink (150) can be supplied into the interior of the chamber section (110) through a separate ink supply line (not shown).

[0048] The above vibration plate (120) is formed on the upper surface of the chamber portion (110). If the chamber portion (110) has a cuboid shape, the vibration plate (120) may have a square plate shape, and if the chamber portion (110) has a cylinder shape, the vibration plate (120) may have a circular plate shape.

[0049] Additionally, the vibration plate (120) may be formed to cover the entire upper surface of the chamber portion (110) as shown in FIG. 1, but is not limited thereto and may be formed only on a part of the upper surface of the chamber portion (100).

[0050] The above-mentioned vibration plate (120) is a structure whose shape is varied by the piezoelectric module (300) described later. In its initial state, it has a horizontally extended plate shape, but when the piezoelectric module (300) is operated, it can be deformed into a structure that bends and extends toward the chamber (110) where the ink (150) is stored, as shown by the dotted line.

[0051] That is, the vibration plate (120) comprises a flexible material that can bend downward according to the operation of the piezoelectric module (300), and at this time, the degree of bending of the vibration plate (120) can be varied by selecting various materials.

[0052] Additionally, as the vibration plate (120) bends downward according to the operation of the piezoelectric module (300), the ink (150) stored in the chamber (110) is subjected to pressure and, accordingly, is pushed downward, thereby inducing discharge.

[0053] Furthermore, in the case of the above-mentioned vibration plate (120), as illustrated, the central part may be bent by a larger amount than the side part, and thus the ink (150) is pressed downward with a higher pressure in the central part.

[0054] The upper nozzle (130) and lower nozzle (140) are extended to the lower part of the chamber (110). In the present embodiment, upper and lower nozzles (130, 140) having different diameters are shown connected in succession, but a nozzle having a single diameter may be extended as one.

[0055] That is, the upper nozzle (130) has a first diameter and extends in one direction from the center of the chamber portion (110), thereby forming an upper space (131) having the first diameter. Additionally, the lower nozzle (140) has a second diameter smaller than the first diameter and extends in one direction from the center of the upper nozzle (130), thereby forming a lower space (141) having the second diameter.

[0056] Thus, when the vibration plate (120) is pressed and bent downwards and pressure is applied to the ink (150) stored in the chamber (110), the ink (150) is pushed downwards while sequentially passing through the upper space (131) and the lower space (141), and finally, the ink (150) is discharged through the lower surface of the lower nozzle (140).

[0057] Meanwhile, as in the present embodiment, as the upper and lower nozzles (130, 140) are formed with sequentially decreasing diameters, the ink (150) pressurized from the top can be discharged more easily in the downward direction. That is, the ink (150) can be easily discharged in the downward direction with relatively low pressure.

[0058] The cover frame (200) is a frame structure that covers the exterior of the upper nozzle (130) and the lower nozzle (140), and is positioned at the bottom of the chamber (110) while having the same overall size as the chamber (110) of the nozzle unit (100). At this time, the shape of the cover frame (200) can be varied in various ways, and it is sufficient if it is a structure that covers the sides of the upper nozzle (130) and the lower nozzle (140) and extends to the same position as the lower surface of the lower nozzle (140).

[0059] The above piezoelectric module (300) is located above the nozzle unit (100) and is a module that pressurizes the nozzle unit (100).

[0060] That is, the piezoelectric module (300) is mounted on the upper surface of the vibration plate (120), and as the piezoelectric module (300) is driven, it presses the vibration plate (120) downward and thereby increases the pressure on the ink (150) stored inside the chamber (110), thereby inducing the ink (150) to be discharged through the upper and lower nozzles (130, 140).

[0061] Specifically, the piezoelectric module (300) includes a piezoelectric element (310), first and second electrodes (320, 330), and a first power supply unit (340). At this time, the first and second electrodes (320, 330) are mounted on the upper and lower surfaces, respectively, of the piezoelectric element (310), and the second electrode (330) may be provided on the vibration plate (120).

[0062] The first power supply unit (340) supplies power to or stops supplying power to the first and second electrodes (320, 330) under the control of the control unit (500), thereby operating or stopping the operation of the piezoelectric element (310).

[0063] That is, as the first power supply unit (340) provides power to the first and second electrodes (320, 330), the piezoelectric element (310) is driven, and when the supplied power is interrupted, the driving of the piezoelectric element (310) is interrupted.

[0064] At this time, the piezoelectric element (310) is a device that vibrates or changes its shape according to the supply of power. In the case of this embodiment, the vibration plate (120) may also be induced to vibrate according to the vibration of the piezoelectric element (310), or the shape of the vibration plate (120) may be induced to change so that the piezoelectric element (310) bends downward.

[0065] The electrode module (400) is provided at the bottom of the nozzle unit (100) and induces an electric field by receiving power. The electrode module (400) induces an electrostatic field by the supplied power, and induces the ink located at the lower nozzle (140) to be discharged in a downward direction by the electrostatic force thus induced. This method of inducing ink discharge by inducing an electrostatic field of the electrode module (400) is called the so-called EHD (electro-hydro dynamic) method.

[0066] The electrode module (400) includes an upper electrode (410), a lower electrode (420), a second power supply unit (430), and a space unit (450). As illustrated, the upper electrode (410) is located at the bottom of the lower nozzle (140), and is provided on the lower surface of the lower nozzle (140), that is, on the lower surface of the cover frame (200) while keeping the nozzle open.

[0067] At this time, if the lower nozzle (140) has a cylinder shape or a nozzle shape with a circular cross-section, the upper electrode (410) has an electrode structure in the shape of a circular ring with an open center.

[0068] The lower electrode (420) is spaced apart from the upper electrode (410) by a predetermined distance and is located below the upper electrode (410). At this time, the spacing between the upper electrode (410) and the lower electrode (420) can be varied and selected considering the degree of electrostatic field induction required.

[0069] Additionally, the lower electrode (420) may also have the same shape as the upper electrode (410) and may have a circular ring-shaped electrode structure with an open center. Thus, the upper electrode (410) and the lower electrode (420) are positioned on the side, forming a space as a predetermined discharge portion (401) on the lower side of the lower nozzle (140).

[0070] Accordingly, the ink (150) discharged through the lower nozzle (140) falls downward without interfering with the upper electrode (410) as well as the lower electrode (420).

[0071] The second power supply unit (430) supplies power to or stops supplying power to the upper and lower electrodes (410, 420) under the control of the control unit (500), thereby inducing or eliminating an electrostatic field by the electrode module (400).

[0072] That is, as the second power supply unit (430) provides power to the upper and lower electrodes (410, 420), the electrostatic field is induced on the lower nozzle (140) side, and when the supplied power is interrupted, the induced electrostatic field is eliminated.

[0073] In the present embodiment, the space (450) is formed between the upper electrode (410) and the lower electrode (420), but the space (450) is not filled with a separate material. That is, air is located in the space (450), and it is not a structure in which a separate material or structure is filled, and accordingly, a predetermined electrostatic field is induced in the space (450) by the upper electrode (410) and the lower electrode (420).

[0074] As previously described, the control unit (500) controls the operation of the first power supply unit (340) to control the driving of the piezoelectric element (310), and controls the operation of the second power supply unit (430) to control the induction of the electrostatic field.

[0075] Thus, through the operation of the piezoelectric module (300) and the electrode module (400), the ink (150) is effectively discharged to the outside of the lower nozzle (140), that is, to the discharge part (401).

[0076] Meanwhile, the operation control of the piezoelectric module (300) and the electrode module (400) in the above-mentioned control unit (500) will be explained in detail with reference to the drawings described later.

[0077] The input unit (600) provides information for the control unit (500) to operate the piezoelectric module (300) and the electrode module (400), and the provided information may be, for example, the speed of the ejected ink and the amount of the ejected ink.

[0078] That is, when information regarding the speed and amount of ink to be ejected through inkjet printing is input through the input unit (600), the control unit (500) controls the operation of the piezoelectric module (300) and the electrode module (400) based on the input information. That is, it controls the operation of the first power supply unit (340) of the piezoelectric module (300) and the operation of the second power supply unit (430) of the electrode module (400).

[0079] Although it will be explained in detail with reference to the drawings described below, in the case of the inkjet head module (10) in this embodiment, even if it includes the same hardware configuration, the speed and amount of ink discharged through the discharge unit (401) can be varied by controlling the operation of the piezoelectric module (300) and the electrode module (400) in various ways.

[0080] Accordingly, the input unit (600) provides information regarding the discharge speed and discharge amount of the ink required to the control unit (500), and based on this, the control unit (500) controls the individual operation of the first and second power supply units (340, 430).

[0081] FIG. 2a is a schematic diagram illustrating an inkjet printing device in which a plurality of inkjet head modules of FIG. 1 are arranged, and FIG. 2b is an image illustrating an ink ejection state through the inkjet head module of FIG. 2a.

[0082] Referring to FIG. 2a, the inkjet printing device (1) includes a plurality of inkjet head modules (10, 11). At this time, the configuration of each of the inkjet head modules (10, 11) has the same structure as the inkjet head module described with reference to FIG. 1, except that for convenience of explanation, only the nozzle unit (100) and the electrode module (400) are schematically illustrated.

[0083] As shown in the illustration, the inkjet head modules (10, 11) can be spaced apart from each other by a predetermined spacing (d). Additionally, although the illustration shows an example in which two inkjet head modules are arranged, the number of inkjet head modules arranged is not limited and can be three or more.

[0084] As described above, the inkjet printing device (1) includes a plurality of inkjet head modules to perform inkjet printing on a substrate (30), and at this time, the operation of each of the plurality of inkjet head modules can be controlled individually.

[0085] Furthermore, in the case of the inkjet printing device (1), as in the inkjet head module described above, the essential configuration for the operation of the inkjet printing device (1) may be identical to or within an obvious range of the conventional configuration for an inkjet printing device disclosed through the prior art.

[0086] Meanwhile, in the inkjet printing device (1), the inkjet head modules (10, 11) adjacent to each other (referred to as the first and second inkjet head modules for convenience) each have their electrode modules (400) driven, so that a separate electrostatic field is induced in each.

[0087] However, referring to FIG. 2b, in the case of a droplet (16) discharged through the second inkjet head module (11), the droplet may be discharged while bending toward the first inkjet head module (10) due to the electrostatic field induced in the first inkjet head module (10).

[0088] That is, in the case of first and second inkjet head modules (10, 11) adjacent to each other, the direction of the discharged droplet can be bent toward the adjacent inkjet head module by the electrostatic field induced in the adjacent inkjet head module.

[0089] Meanwhile, experimental results showed that when the inkjet head modules (10, 11) have a pitch (distance) of approximately 150 μm, it was confirmed that the droplet bends toward the adjacent inkjet head module as shown in FIG. 2b. Additionally, when the inkjet head modules (10, 11) have a pitch (distance) of approximately 300 μm, it was confirmed that the problem of the droplet bending toward the adjacent inkjet head module as shown in FIG. 2b did not occur.

[0090] However, this is merely an exemplary experimental result, and the separation distance needs to be controlled in various ways depending on the strength of the electrostatic force induced in each of the adjacent inkjet head modules.

[0091] Accordingly, when the inkjet printing device (1) is configured to include a plurality of inkjet head modules arranged adjacent to each other, the spacing between adjacent inkjet head modules should be designed by taking into account the strength (maximum value) of the electrostatic force induced in each inkjet head module.

[0092] Thus, electrostatic field interference caused by electrostatic force induced by adjacent inkjet head modules does not occur, and droplets discharged through the inkjet head module can fall in a downward direction without bending.

[0093] Hereinafter, various states for controlling the operation of the piezoelectric module (300) and the electrode module (400) through the control unit (500) will be described. In particular, as previously explained, the operation of the piezoelectric module (300) and the electrode module (400) is controlled through the control unit (500) by considering the required ink discharge amount and discharge speed. Therefore, the description will focus on the factors that can be controlled through the control unit (500) and the variable states of the ink discharge speed and discharge amount accordingly.

[0094] Figure 3 is a graph showing the operating state of the piezoelectric module and electrode module of Figure 1.

[0095] First, referring to FIG. 3, in the inkjet head module (10) according to the present embodiment, the piezoelectric module (300) is controlled to operate during a first interval (T1), and the electrode module (400) is controlled to operate during a second interval (T2).

[0096] At this time, the second section (T2) is included in the first section (T1) and is shorter than the first section (T). That is, the operating section of the electrode module (400) is shorter than the operating section of the piezoelectric module (300), and the section in which the electrode module (400) operates is always included in the section in which the piezoelectric module (300) operates.

[0097] Ultimately, when the electrode module (400) is in operation, the piezoelectric module (300) is always in operation, but the piezoelectric module (300) can be operated even when the electrode module (400) is not in operation.

[0098] More specifically, the first section (T1), that is, the section in which the piezoelectric module (300) is operated, includes a first increasing section (Tr1) in which the voltage applied to the piezoelectric module (300) increases, a first maintaining section (Td1) in which the voltage applied to the piezoelectric module (300) is maintained at a constant level, and a first decreasing section (Tf1) in which the voltage applied to the piezoelectric module (300) decreases.

[0099] This is a control characteristic according to the control of power application of the first power supply unit (340), and in order to increase the voltage to the voltage required for the operation of the piezoelectric module (300), maintain the voltage, and lower the voltage to stop the operation, the first increase section (Tr1), the first maintenance section (Td1), and the first decrease section (Tf1) are indispensably required.

[0100] Likewise, the second section (T2), that is, the section in which the electrode module (400) is operated, includes a second increasing section (Tr2) in which the voltage applied to the electrode module (400) increases, a second maintaining section (Td2) in which the voltage applied to the electrode module (400) is maintained at a constant level, and a second decreasing section (Tf2) in which the voltage applied to the electrode module (400) decreases.

[0101] In addition, these control characteristics are also indispensable due to the power application of the second power supply unit (430), and the intervals can be distinguished as above when performing the application and interruption of voltage.

[0102] Furthermore, as shown in FIG. 3, the magnitude of the voltage maintained during the second maintenance period (Td2) is greater than the magnitude of the voltage maintained during the first maintenance period (Td1). That is, the voltage applied to the electrode module (400) is supplied at a greater magnitude than the voltage applied to the piezoelectric module (300) and is supplied for a short period.

[0103] Thus, at the moment when the ink (150) is jetted by the piezoelectric module (300) through the lower nozzle (140), a large voltage is supplied to the electrode module (400) to induce a large electrostatic force, thereby causing the ink (150) to be jetted at a high speed instantaneously.

[0104] Accordingly, even for inks of relatively high viscosity, easy ejection can be induced through the instantaneous induction of a large electrostatic force.

[0105] FIGS. 4a to 4f are graphs illustrating the ink ejection state according to the variable driving state of the piezoelectric module in the inkjet head module of FIG. 1.

[0106] In FIGS. 4a to 4f, the results showing the change in speed and discharge amount of the discharged ink are illustrated by varying the driving conditions of the piezoelectric module (300) while maintaining the driving conditions of the electrode module (400) at the same level (i.e., maintaining the second section at a constant level).

[0107] In particular, referring to FIG. 4a, it can be seen that if the first increase section (Tr1) is controlled to decrease, the amount of ink ejected (Vd) increases, and similarly, referring to FIG. 4d, it can be seen that if the first increase section (Tr1) is controlled to decrease, the ejection speed (vj) of the ink also increases.

[0108] In contrast, referring to FIGS. 4b and FIGS. 4c, the first maintenance section (Td1) or the first reduction section (Tf1) is not a factor that affects the change in the ink discharge amount, and simply the ink discharge amount is maximum in a specific maintenance section or a specific reduction section.

[0109] Likewise, referring to FIGS. 4e and FIGS. 4f, the first maintenance section (Td1) or the first reduction section (Tf1) is not a factor that affects the change in the ink ejection speed, and simply the ink ejection speed shows a maximum in a specific maintenance section or a specific reduction section.

[0110] As described above, when the operating conditions of the electrode module (400) are maintained identically, the discharge speed and discharge amount of the ink can be controlled by controlling the first increase section (Tr1). Accordingly, the control unit (500) can perform control for the same inkjet head module (10) to match the discharge speed and discharge amount input through the input unit (600) by controlling the first increase section (Tr1).

[0111] FIGS. 5a to 5j are graphs and images illustrating the ink ejection state according to the variable driving time of the electrode module in the inkjet head module of FIG. 1.

[0112] In FIGS. 5a to 5j, the results showing the change in speed and discharge amount of the discharged ink are illustrated by varying the driving conditions of the electrode module (400) while maintaining the driving conditions of the piezoelectric module (300) at the same level (i.e., maintaining the first section at a constant level).

[0113] The second section (T2) in FIGS. 5a to 5j is entirely included in the first section (T1), and the interval of the second section (T2) is shorter than the interval of the first section (T1).

[0114] Additionally, FIG. 5a shows the case where the starting section of the second increment section (Tr2) is set to be the same as the starting section of the first increment section (Tr1), FIG. 5c shows the case where the starting section of the second increment section (Tr2) is set to be the same as the starting section of the first maintenance section (Td1), and FIG. 5e shows the case where the starting section of the second increment section (Tr2) is set after the starting section of the first maintenance section (Td1).

[0115] Additionally, FIG. 5g is a case where the starting section of the second increasing section (Tr2) is set after the starting section of the first maintaining section (Td1) and at the same time the ending section of the second decreasing section (Tf2) is set to be the same as the starting section of the first decreasing section (Tf1), and FIG. 5i is a case where the starting section of the second increasing section (Tr2) is set after the starting section of the first maintaining section (Td1) and at the same time the ending section of the second decreasing section (Tf2) is set to be the same as the ending section of the first decreasing section (Tf1).

[0116] In this way, when each section of the second section (T2) is set in various ways, the ink discharge speed (Vel) and discharge amount (Vol) in each case are illustrated in images in FIG. 5b, FIG. 5d, FIG. 5f, FIG. 5h, and FIG. 5j.

[0117] Accordingly, looking at FIGS. 5a to 5j, it can be seen that in the case of the sections set in FIGS. 5c and 5e, the ink discharge speed (Vel) and discharge amount (Vol) are controlled to be relatively high. That is, as in FIG. 5c, the starting section of the second increase section (Tr2) is set to be the same as the starting section of the first maintenance section (Td1), and accordingly, the second section (T2) is set so that the end section of the second decrease section (Tf2) is also included within the first maintenance section (Td1); or as in FIG. 5e, the starting section of the second increase section (Tr2) is set after the starting section of the first maintenance section (Td1), and accordingly, the second section (T2) is set so that the end section of the second decrease section (Tf2) is also included within the first maintenance section (Td1), and accordingly, the ink discharge speed (Vel) and discharge amount (Vol) can be controlled to be high.

[0118] Ultimately, as confirmed by the above, the control unit (500) can control the operation of the electrode module (400) such that the second section (T2) is included in the first maintenance section (Td1) of the first section (T1) in order to relatively increase the ink discharge speed and discharge amount.

[0119] As described above, when the driving conditions of the piezoelectric module (300) are maintained identically, the discharge speed and discharge amount of the ink can be controlled by controlling the second section (T2). Accordingly, the control unit (500) can perform control for the same inkjet head module (10) to match the discharge speed and discharge amount input through the input unit (600) by controlling the second section (T2).

[0120] FIGS. 6a and 6b are graphs illustrating the ink ejection state according to the time change of the voltage waveform during the operation of the electrode module in the inkjet head module of FIG. 1.

[0121] In FIGS. 6a and 6b, the results showing the change in speed and discharge amount of the discharged ink are illustrated by varying the driving conditions of the electrode module (400) while maintaining the driving conditions of the piezoelectric module (300) at the same level (i.e., maintaining the first section at a constant level).

[0122] That is, referring to FIG. 6a, it can be seen that when the first section (T1) is maintained at a constant level, the speed of the discharged ink decreases even when any one of the second increase section (Tr2), the second maintenance section (Td2), and the second decrease section (Tf2) is increased during the second section (T2).

[0123] In particular, among the second section (T2), it can be confirmed that the degree of reduction of the ink speed increases in the order of the second increase section (Tr2), the second maintenance section (Td2), and the second decrease section (Tf2). That is, when the second decrease section (Tf2) is varied, the ink ejection speed can be controlled to be reduced most sensitively.

[0124] Meanwhile, referring to FIG. 6b, when the first section (T1) is maintained at a constant level, if either the second maintenance section (Td2) or the second reduction section (Tf2) within the second section (T2) is increased by more than a preset value (4μs in FIG. 6b), it can be seen that the amount of ink ejected increases.

[0125] However, even if the above second increase section (Tr2) is varied, it does not show any significant change in the amount of ink discharged.

[0126] In particular, when the second maintenance period (Td2) is changed beyond the preset value, the amount of ink ejected can be controlled to increase most sensitively.

[0127] At this time, the above-mentioned preset value (4μs in FIG. 6b) is pre-set considering the structure or characteristics of the inkjet head module (10), and with information regarding the above-mentioned preset value provided, the ink discharge amount or discharge speed can be controlled by controlling the second maintenance section (Td2) and the second reduction section (Tf2) among the second section (T2).

[0128] As described above, when the driving conditions of the piezoelectric module (300) are maintained identically, the discharge speed and discharge amount of the ink can be controlled by controlling a portion of the second section (T2). Accordingly, the control unit (500) can perform control for the same inkjet head module (10) to match the discharge speed and discharge amount input through the input unit (600) by controlling a portion of the second section (T2).

[0129] FIGS. 7a and 7b are graphs illustrating the ink ejection state according to the change in amplitude during the operation of the electrode module in the inkjet head module of FIG. 1.

[0130] In FIGS. 7a and 7b, the results showing the change in speed and discharge amount of the discharged ink are illustrated by varying the driving conditions of the electrode module (400) while maintaining the driving conditions of the piezoelectric module (300) at the same level (i.e., maintaining the first section at a constant level).

[0131] That is, referring to FIG. 7a, it can be seen that when the amplitude of the voltage applied during the second section (T2) is increased while the first section (T1) is maintained constant, the discharge speed of the discharged ink increases.

[0132] In contrast, referring to FIG. 7b, it can be seen that when the amplitude of the voltage applied during the second section (T2) is increased while the first section (T1) is maintained constant, the amount of ink discharged is reduced.

[0133] Ultimately, by increasing the amplitude of the voltage applied to the electrode module (400) during the second interval (T2), the discharge speed of the discharged ink can be increased and the discharge amount can be reduced.

[0134] Accordingly, the control unit (500) can perform control for the same inkjet head module (10) by controlling the amplitude of the voltage in the second section (T2) to match the discharge speed and discharge amount input through the input unit (600).

[0135] FIG. 8 is a flowchart illustrating a control method for the inkjet head module of FIG. 1.

[0136] Referring to FIG. 8, in the control method of the inkjet head module (10) of FIG. 1, first, information regarding the ink ejection speed and ink ejection amount required to perform inkjet printing is input to the control unit (500) through the input unit (600) (step S10).

[0137] As previously explained, even for the inkjet head module (10) having the same configuration, the ink discharge speed and the amount of ink discharged can be varied and controlled according to the specific method of controlling the piezoelectric module (300) and the electrode module (400) in the control unit (500).

[0138] Accordingly, the input unit (600) provides information regarding the discharge speed and discharge amount of the ink required in advance to the control unit (500), and the control unit (500) controls the operation of the piezoelectric module (300) and the electrode module (400) based on the corresponding ink discharge speed and discharge amount.

[0139] That is, when information is provided from the input unit (600) as described above, the control unit (500) drives the piezoelectric module (300) during the first period (step S20). At this time, the first time (T1) for driving the piezoelectric module (300) is described in detail as previously explained, so a redundant description is omitted.

[0140] In addition, the control unit (500) drives the electrode module (400) during the second section (T2) included in the first section (T1) (step S30). At this time, the second time (T2) for driving the electrode module (400) is also as described in detail above, so a redundant description is omitted.

[0141] In particular, the second section (T2) is included in the first section (T1), and the second section (T2) begins after the first section (T1) begins, but the specific overlap between the first section (T1) and the second section (T2) is ultimately determined based on the information input from the input unit (600).

[0142] That is, since it is not necessary to control the discharge speed and discharge amount of the ink to always be the fastest and most abundant, the control unit (500) determines the detailed sections of the first and second sections (T1, T2) in consideration of the required discharge speed and discharge amount to control the discharge of the ink.

[0143] At this time, the method for determining the detailed sections of the first and second sections (T1, T2) can be implemented based on the control method of the control unit (500) described with reference to FIGS. 3 to 7b.

[0144] Thus, by determining the detailed sections of the first and second sections (T1, T2) as described above and driving the piezoelectric module (300) and the electrode module (400), the ink (150) is finally discharged through the discharge unit (401) (step S40).

[0145] Furthermore, although not illustrated, in a state where multiple inkjet head modules (10, 11) are arranged as in FIG. 2a, each inkjet head module is independently controlled to eject ink, and it is sufficient to control the ink ejection of each inkjet head module by considering the pattern to be printed overall.

[0146] FIG. 9 is a schematic diagram illustrating an inkjet head module according to another embodiment of the present invention.

[0147] The inkjet head module (20) according to the present embodiment is substantially the same as the inkjet head module (10) described with reference to FIG. 1, except that an electrode module substrate part (460) is provided in place of the space part (450). Therefore, the same reference numbers are used for identical components and redundant descriptions are omitted.

[0148] Referring to FIG. 9, in the inkjet head module (20) according to the present embodiment, the electrode module (400) includes an electrode module substrate portion (460).

[0149] That is, in the inkjet head module (10) of the preceding Fig. 1, the space portion (405) is interposed between the upper electrode (410) and the lower electrode (420), and the space portion (405) is not composed of a separate material or structure but is made of air.

[0150] However, in the case of the present embodiment, the electrode module substrate portion (460) is filled in place of the space portion (405). That is, the electrode module substrate portion (460) is a structure interposed between the upper electrode (410) and the lower electrode (420), and includes an adjacent portion (461) and a spaced portion (462).

[0151] The above-mentioned separation portion (462) is a structure interposed between the upper electrode (410) and the lower electrode (420), and the above-mentioned adjacent portion (461) is a structure extending to the side of the separation portion (462). At this time, the separation portion (462) and the above-mentioned adjacent portion (461) are integrally formed from the same material.

[0152] That is, the space between the upper electrode (410) and the lower electrode (420), as well as the lower space of the cover frame (200), is filled through the electrode module substrate portion (460).

[0153] The electrode module substrate (460) may include a material with a dielectric constant higher than that of air, for example, aluminum oxide (Al2O3). In addition, when the electrode module substrate (460) includes a material with a dielectric constant higher than that of air, such as aluminum oxide, the ink ejection speed is improved compared to the case where air is interposed, and this is explained below.

[0154] FIGS. 10a to 10c are graphs and images illustrating the ink ejection state in the inkjet head module of FIGS. 1 and FIG. 9.

[0155] FIG. 10a is a graph illustrating the ink ejection speed when only the piezoelectric module (300) is driven to eject ink, when both the piezoelectric module (300) and the electrode module (400) are driven to eject ink but the space portion (450) is filled with air as in FIG. 1, and when both the piezoelectric module (300) and the electrode module (400) are driven to eject ink but the electrode module substrate portion (460) containing aluminum oxide is filled as in FIG. 9.

[0156] In particular, FIG. 10b illustrates the ink discharge state when the space portion (450) is filled with air, and FIG. 10c illustrates the ink discharge state when the electrode module substrate portion (460) containing aluminum oxide is filled.

[0157] That is, referring to FIGS. 10a to 10c, it is confirmed that when the electrode module (400) is operated together with the piezoelectric module (300), the ink ejection speed increases, and in particular, it can be confirmed that the ink ejection speed when filled with aluminum oxide is improved compared to the ink ejection speed when filled with air.

[0158] This is interpreted as being due to the high dielectric constant of the aluminum oxide, in particular, when an electric field is induced by the electrode module (400). Ultimately, while air may be filled between the upper electrode (410) and the lower electrode (420), if it is filled with a material having a dielectric constant higher than that of air, a higher ink ejection speed can be achieved.

[0159] According to the embodiments of the present invention as described above, by providing pressure to the nozzle unit through the piezoelectric module and inducing an electric field in the nozzle through the electrode module within the operating range of the piezoelectric module, the discharge speed of the formed droplet can be improved through the force of the electrostatic field, thereby inducing more effective discharge. Through this, in particular, high-viscosity ink can be discharged more easily and quickly, allowing for inkjet printing using various high-viscosity inks.

[0160] In this case, the electrode module induces droplet discharge by inducing an electrostatic field using the so-called EHD (electro-hydro dynamic) method. Since it induces instantaneous operation during a relatively short range of a certain range within the operating period of the piezoelectric module, it is possible to induce instantaneous discharge of high-viscosity ink, and problems such as uneven droplet discharge caused by the long-term induction of the electrostatic field can be minimized.

[0161] In particular, in inducing such droplet discharge, the electrode module is controlled to operate only within the range where the voltage is maintained constant during the operation period of the piezoelectric module, thereby enabling faster and greater discharge of droplets.

[0162] In addition, regarding the voltage applied to the piezoelectric module, by controlling the voltage increase interval differently, it is possible to control the ink ejection speed and ejection amount, thereby enabling optimal ink ejection control.

[0163] In addition, regarding the voltage applied to the electrode module, the ink ejection speed can be controlled by selectively controlling the voltage increase section, the maintenance section, and the decrease section, and the ink ejection amount can be controlled by selectively controlling the voltage maintenance section and the decrease section, and the ink ejection speed and amount can be controlled by controlling the amplitude of the applied voltage, thereby enabling the implementation of the necessary optimal ink ejection control through various ejection controls.

[0164] In particular, by interposing an electrode module substrate portion containing a material having a dielectric constant higher than that of air, such as aluminum oxide, between the upper electrode and the lower electrode included in the electrode module, the generation of electrostatic force can be enhanced, thereby further improving the ink ejection speed.

[0165] Furthermore, in an inkjet printing device configured with a plurality of the above-mentioned inkjet head modules arranged, by setting the spacing between adjacent inkjet head modules by considering a spacing distance at which interference caused by the electric field induced by the electrode module in adjacent inkjet head modules is minimized, independent operation of the inkjet head modules and inkjet printing with higher precision can be achieved.

[0166] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims. Explanation of the symbols

[0167] 1: Inkjet printing device 10, 20: Inkjet head module 100: Nozzle unit 110: Chamber section 120 : Vibration plate 130 : Upper nozzle 140 : Bottom nozzle 150 : Ink 200 : Cover frame 300 : Piezoelectric module 310 : Piezoelectric element 400 : Electrode module 410 : Upper electrode 420 : Lower electrode 450 : Space section 460 : Electrode module substrate section 500 : Control unit 600 : Input unit

Claims

Claim 1 A nozzle unit comprising a chamber portion for storing ink, and a nozzle extending to the lower part of the chamber portion for discharging the ink to the outside; a piezoelectric module located above the nozzle unit and providing pressure to the nozzle unit during a first section; An inkjet head module comprising an electrode module located at the lower part of the nozzle and inducing an electric field in the nozzle during a second section included in the first section, wherein the first section includes a first maintenance section (Td1) in which the voltage applied to the piezoelectric module is maintained constant, and the second section includes a second increasing section (Tr2) in which the voltage applied to the electrode module is increased, a second maintenance section (Td2) in which the voltage applied to the electrode module is maintained constant, and a second decreasing section (Tf2) in which the voltage applied to the electrode module is decreased, wherein the second section starts from the first maintenance section (Td1), the entire second section forms a section shorter than the first maintenance section (Td1), and the voltage of the second maintenance section (Td2) is maintained to be greater than the voltage of the first maintenance section (Td1). Claim 2 An inkjet head module according to claim 1, wherein the first section further comprises a first increasing section (Tr1) in which the voltage applied to the piezoelectric module increases, and a first decreasing section (Tf1) in which the voltage applied to the piezoelectric module decreases. Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 An inkjet head module characterized by further including a control unit that controls the driving of the piezoelectric module and the electrode module in paragraph 2. Claim 7 In claim 6, the inkjet head module is characterized in that the control unit controls the first increase section (Tr1) to increase the ink discharge speed and discharge amount while maintaining the second section at a constant level. Claim 8 In claim 6, the control unit controls the ink ejection speed to decrease by increasing any one of the second increase section (Tr2), the second maintenance section (Td2), and the second decrease section (Tf2) while maintaining the first section at a constant level. Claim 9 In claim 6, the inkjet head module is characterized in that the control unit controls the ink discharge amount by increasing either the second maintenance section (Td2) or the second reduction section (Tf2) by more than a preset value while maintaining the first section at a constant level. Claim 10 In claim 6, the inkjet head module is characterized in that the control unit controls the voltage applied during the second section to increase the voltage amplitude while maintaining the first section constant, thereby increasing the ink ejection speed and decreasing the ink ejection amount. Claim 11 An inkjet head module according to claim 1, wherein the electrode module comprises: an upper electrode located at the lower part of the nozzle; and a lower electrode located at the lower part of the upper electrode and spaced apart from the upper electrode by a predetermined distance. Claim 12 In claim 11, the electrode module further comprises an electrode module substrate portion interposed between the upper electrode and the lower electrode, and the electrode module substrate portion is characterized by having a dielectric constant higher than that of air. Claim 13 An inkjet printing device according to claim 1, wherein a plurality of inkjet head modules are arranged at a predetermined interval from one another, characterized in that the interval between adjacent inkjet head modules is pre-set so as not to cause interference caused by an electric field induced by an electrode module of an adjacent inkjet head module. Claim 14 A step of inputting the required ink ejection speed and ink ejection amount; a step of driving a piezoelectric module during a first section based on the ejection speed and the ejection amount; a step of driving an electrode module during a second section included in the first section based on the ejection speed and the ejection amount; A method for controlling an inkjet head module, comprising the step of discharging ink according to the operation of the piezoelectric module and the electrode module, wherein the first section includes a first maintenance section (Td1) in which the voltage applied to the piezoelectric module is maintained at a constant level, and the second section includes a second increase section (Tr2) in which the voltage applied to the electrode module is increased, a second maintenance section (Td2) in which the voltage applied to the electrode module is maintained at a constant level, and a second decrease section (Tf2) in which the voltage applied to the electrode module is decreased, wherein the second section starts from the first maintenance section (Td1), the entire second section forms a section shorter than the first maintenance section (Td1), and the voltage of the second maintenance section (Td2) is maintained to be greater than the voltage of the first maintenance section (Td1).

Images