Ink supply device and inkjet printing system including the same

Abstract

To provide an ink supply device which may effectively circulate an ink for inkjet printing to stably maintain a state of the ink, and to provide an inkjet printing system including the ink supply device.SOLUTION: An ink supply device includes: an ink storage unit configured to store an ink at least temporarily; a first passage tube configured to supply the ink stored in the ink storage unit to an inkjet head unit; a second passage tube configured to collect the ink from the inkjet head unit; an ink circulation unit configured to move the ink flowing thereinto through the second passage tube along one direction; and a third passage tube configured to supply the ink flowing out from the ink circulation unit to the ink storage unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ink supplying device and an inkjet printing system including the same, and more particularly, to an ink supplying device capable of effectively circulating ink for inkjet printing and stably maintaining the state of the ink, and an inkjet printing system including the same. [Background technology]

[0002] 2. Description of the Related Art Inkjet printing, which involves spraying liquid ink in the form of droplets onto the surface of a print target, is used not only for printing documents and flyers, but also for solution processes in the semiconductor and display fields.

[0003] Small inkjet printers for creating documents have a design that stores ink in an inkjet head that ejects ink droplets, but large printers for creating documents and inkjet printers made for industrial use in the manufacture of electronic components and displays use large amounts of ink, so they have a structure in which the ink storage section and the inkjet head are separated.

[0004] In order for inkjet printing devices to be actually used in industry, they are required to be highly precise and to be able to form high-resolution patterns and print ultra-thin films by ejecting ink from multiple nozzle heads. To achieve such results, it is essential to maintain the condition of the ink. To maintain the condition of the ink, it is necessary to remove air bubbles and foreign matter that may be generated during the process of ink clumping, hardening, gelling, etc. By removing air bubbles or foreign matter from the ink passage and circulating the ink, a large amount of ink can be stably ejected without problems such as ink clogging and instability in the ink flow.

[0005] In order to remove air bubbles from the ink and foreign matter generated by ink clumping, etc., various attempts have been made, such as inserting a filter unit above the ink flow path and increasing the flow rate, etc. However, new problems have arisen, such as congestion caused by the filter unit and the inflow of new outside air due to the pressure change required to increase the flow rate, and therefore there is still a demand for an effective technology that can stably maintain the state of the ink without ink congestion or the inflow of outside air. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Republic of Korea Publication Patent No. 10-2008-0098266 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides an ink supplying device capable of removing air bubbles present in ink and circulating the ink to maintain the ink in a stable state, and an inkjet printing system equipped with the ink supplying device. [Means for solving the problem]

[0008] An ink supply device according to an embodiment of the present invention may include an ink storage section that stores ink at least temporarily, a first flow path pipe that supplies the ink stored in the ink storage section to an inkjet head section, a second flow path pipe that recovers ink from the inkjet head, an ink circulation section that moves the ink flowing in through the second flow path pipe in one direction, and a third flow path pipe that supplies the ink flowing out from the ink circulation section to the ink storage section.

[0009] The ink circulation unit may include a cylinder portion that provides a hollow internal space extending in the one direction, a screw portion that extends in the one direction and is inserted into the internal space and arranged to be freely rotatable, and a motor portion that selectively rotates the screw portion.

[0010] The internal space may be cylindrical and have a uniform inner diameter along the one direction, and the screw portion may have a uniform outer diameter along the one direction.

[0011] The outer diameter of the screw portion may be smaller than the inner diameter of the internal space and may be 80% or more of the inner diameter of the internal space.

[0012] The screw portion comprises a shaft portion extending in the one direction and a blade portion arranged to form a spiral shape along the outer wall of the shaft portion, and the outer diameter and pitch of the blade portion may be the same along the one direction.

[0013] A separation space may be provided between one end of the screw portion and one end inside the internal space, and the third flow passage pipe may be connected to the separation space.

[0014] The ink supply device may further include a flow meter unit that measures the flow rate of ink flowing inside the third flow path pipe, and a control unit that controls at least one of the rotational speed, rotational amount or rotational force of the motor unit in accordance with the flow rate of ink measured by the flow meter unit.

[0015] The ink supply device may further include a capacity detection unit that detects the volume of ink stored in the ink storage unit, and an ink refill unit that is connected to the ink storage unit and refills the missing ink if the volume of ink detected by the capacity detection unit does not meet a standard volume.

[0016] The ink supply device may further include a negative pressure setting unit connected to the ink reservoir unit and configured to set the pressure of the internal space of the ink reservoir unit to a pressure lower than atmospheric pressure.

[0017] The ink supply device may further include a buffer section that is connected to the first flow path pipe, is disposed between the ink reservoir section and the inkjet head section, and provides a buffer space having a cross-sectional area larger than that of the first flow path pipe.

[0018] The first flow path pipe may be provided in a plurality of pipes, and the inner diameter of the third flow path pipe may be greater than the inner diameter of the first flow path pipe.

[0019] The ink may contain solids.

[0020] An inkjet printing system according to another embodiment of the present invention may include an inkjet head unit having a plurality of nozzle units that eject ink onto a substrate, and an ink supply device according to an embodiment of the present invention that supplies ink to the inkjet head unit.

[0021] The inkjet head unit may be provided in a plurality of units.

[0022] The first flow path pipe, the second flow path pipe, and the like may be arranged in a plurality of pipes corresponding to the plurality of inkjet head units, and each of the first flow path pipes may be connected to one side of the corresponding inkjet head unit, and each of the second flow path pipes may be connected to the other side of the corresponding inkjet head unit. Effect of the Invention

[0023] The ink supply device of the present invention and the inkjet printing system equipped with the same can remove air bubbles present in the ink or on the ink flow path, making it possible to stably supply ink to the inkjet head without interrupting the ink flow.

[0024] In order to provide various functions to the applied coating layer, in the case of inks that contain various solids mixed in or that clump together, harden, or gel when the flow is interrupted or stagnated, the ink can be uniformly agitated by continuously circulating between the inkjet head and the ink reservoir, and the ink state can be maintained. Furthermore, the precipitation of solids contained in the ink, the phenomenon of ink clumping, and localized hardening or gelling of the ink can be suppressed, and damage to the inkjet head due to clogging of the nozzle caused by these factors can be prevented.

[0025] Furthermore, air bubbles can be removed from the ink and the ink flow path, and sudden pressure changes or pulsation phenomena in the ink reservoir and ink flow path can be suppressed, allowing for the formation and maintenance of an accurate meniscus, thereby effectively improving the stability of ink ejection and the accuracy of the ink landing position. [Brief description of the drawings]

[0026] [Figure 1] 1 is a configuration diagram showing an ink supply device and an inkjet printing system according to the present invention; [Diagram 2] FIG. 2 is a diagram showing an ink circulation section of the ink supply device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, the embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms. These embodiments are provided merely to complete the disclosure of the present invention and to fully inform those skilled in the art of the scope of the invention. In describing the present invention, the same reference numerals are used for the same components, and the drawings may be partially exaggerated in size to accurately describe the embodiments of the present invention, and the same numerals in the drawings indicate the same components.

[0028] FIG. 1 is a configuration diagram showing an ink supply device and an inkjet printing system according to the present invention, and FIG. 2 is a diagram showing an ink circulation section of the ink supply device according to the present invention.

[0029] 1 and 2, an ink supplying device 100 according to an embodiment of the present invention may include an ink storage section 110 for at least temporarily storing ink, a first flow path pipe 120 for supplying the ink stored in the ink storage section 110 to an inkjet head section 200, a second flow path pipe 130 for recovering ink from the inkjet head 200, an ink circulation section 140 for moving the ink flowing in through the second flow path pipe 130 in one direction, and a third flow path pipe 150 for supplying the ink flowing out from the ink circulation section 140 to the ink storage section 110.

[0030] The ink reservoir 110 may have an internal space for at least temporarily storing ink, and may be connected to a plurality of flow pipes for ink to flow into and out of the internal space. A partition may be disposed in the internal space so that the ink can naturally mix as it flows in and out. In general, the internal space may not be completely filled with ink, and a portion of the internal space may remain open.

[0031] The first flow path pipe 120 may be connected to the ink reservoir 110 to provide a flow path for supplying the ink stored in the ink reservoir 110 to the inkjet head unit 200 .

[0032] The second flow path pipe 130 may provide a flow path for recovering at least a portion of the ink supplied to the inkjet head 200. When the inkjet head 200 ejects ink for a printing operation, the second flow path pipe 130 may recover the remaining ink from the inkjet head 200, or may recover all of the ink supplied to the inkjet head 200 while the inkjet head 200 is waiting without performing a printing operation.

[0033] The ink circulating unit 140 may have one side connected to the second flow passage pipe 130 and may function to move the ink flowing in through the second flow passage pipe 130 in one direction. By moving the ink flowing in through the second flow passage pipe 130 in one direction, a space into which the ink remaining in the inkjet head 200 can flow is formed, allowing the ink to continue to flow in one direction.

[0034] The third flow path pipe 150 may be connected to the other side of the ink circulation unit 140 to provide a flow path for supplying ink that is moved in one direction by the ink circulation unit 140 and flows out of the ink circulation unit 140 to the ink reservoir unit 110.

[0035] As the ink circulates continuously along the circulation flow path that runs from the ink reservoir 110 through the first flow path 120, the inkjet head unit 200, the second flow path 130, the ink circulation unit 140, and the third flow path 150 back to the ink reservoir 110, the ink flows continuously, improving the ink's dispersibility and allowing the ink to maintain uniformity. As the ink circulates continuously along the circulation flow path, not only the ink but also the air present in the circulation flow path moves with the circulation of the ink, and can be discharged into the empty space inside the ink reservoir 110.

[0036] The ink supply device 100 may further include a negative pressure setting unit 173 that is connected to the ink reservoir 110 and sets the pressure of the internal space of the ink reservoir 110 to a pressure lower than atmospheric pressure. The negative pressure setting unit 173 includes an exhaust means for exhausting the internal space of the ink reservoir 110 in order to adjust the pressure of the internal space, and the ink or air present in the circulation flow path also moves as the ink circulates and is discharged into an empty space inside the ink reservoir 110, and then can be exhausted to the outside by the exhaust means of the negative pressure setting unit 173.

[0037] In order to eject a fixed amount of ink from the inkjet head 200 to a fixed position and form an accurate dot, it is necessary to apply a negative pressure to the internal space of the ink reservoir 110 so that the ink can maintain a meniscus state, which is a curved state where the ink is recessed inward due to capillary action, at the entrance of the nozzle part of the inkjet head 200. The negative pressure setting part 173 may adjust the pressure in the internal space of the ink reservoir 110 to a pressure lower than atmospheric pressure. If the negative pressure setting part 173 sets the internal space of the ink reservoir 110 to a negative pressure, the entire flow path through which the ink flows maintains an airtight state, except when the first flow path pipe 120, the inkjet head part 200, the second flow path pipe 130, the ink circulation part 140, and the third flow path pipe 150 connected to the ink reservoir 110 are filled with ink or the ink moves, so that the ink can maintain a meniscus state at the entrance of the nozzle part.

[0038] If the ink itself or solids present inside the ink partially aggregate and block the ink flow path, or if air is present in the ink flow path, the negative pressure cannot be transmitted to the internal space of the ink reservoir 110 set by the negative pressure setting unit 173 to the entrance of the nozzle, and as a result, there is a risk that the meniscus state cannot be maintained. However, according to the present invention, the ink continues to circulate by moving through the circulation path without any additional equipment, thereby maintaining a homogeneous ink state, effectively suppressing partial aggregation, and enabling the air to be discharged to the outside, thereby effectively maintaining and controlling the meniscus state at the entrance of the nozzle according to the negative pressure set by the negative pressure setting unit 173.

[0039] In order to circulate the ink along the circulation path, a driving force that allows the ink to move must be applied. In order to move the liquid ink, a wide variety of pumps can be used that apply pressure (applying positive pressure from the rear or negative pressure from the front) to the ink in the direction in which the ink moves. For example, a pump with an impeller may be used, or a pump module may be configured using multiple piezoelectric pumps. Such a normal circulation pump generates a pressure difference in the ink circulation path to move the ink, but the negative pressure set in the internal space of the ink reservoir 110 cannot be uniformly transmitted to the ink at the entrance of the nozzle due to changes in pressure generated in the ink circulation path, and as a result, there is a risk that the meniscus state cannot be maintained at the entrance of the nozzle. In addition, in the circulation pump, a pulsation phenomenon occurs in which the pressure periodically fluctuates during the operation of the pump, and such a pulsation phenomenon may make it even more difficult to control the meniscus state at the entrance of the nozzle. In other words, if a normal circulation pump is disposed in the ink circulation path including the inkjet head unit 200, it may become difficult to accurately maintain and control the meniscus at the entrance of the nozzle portion of the inkjet head unit.

[0040] To solve this problem, the ink may be circulated only between the ink reservoir and the inkjet head by blocking the nozzle of the inkjet head or by bypassing the nozzle of the inkjet head. However, this requires the installation of an additional shutoff valve or bypass flow path, which complicates the equipment configuration and may cause ink to stagnate in the nozzle of the inkjet head, which is the section where the ink is directly ejected, during actual inkjet printing.

[0041] The ink circulation unit 140 may include a cylinder portion 141 that provides a hollow internal space extending in the one direction, a screw portion 142 that extends in the one direction and is inserted into the internal space and arranged to be freely rotatable, and a motor portion 143 that selectively rotates the screw portion 142.

[0042] In the present invention, the ink circulation unit 140 is fitted into the ink flow path through which ink is supplied, expelled, and recovered during inkjet printing operations, so that the ink circulated by the ink circulation unit 140 can circulate including the nozzle portion of the inkjet head unit 200 without blocking or bypassing the nozzle portion of the inkjet head unit 200.

[0043] The cylinder portion 141 may provide a hollow internal space extending in one direction, and provide a space in which the ink can flow in one direction between the second flow path pipe 130 and the third flow path pipe 150. While the ink circulates, the internal space of the cylinder portion 141 may be in a state where it is completely filled with the ink.

[0044] The screw portion 142 may have a shape extending in one direction and be rotatably disposed in an internal space extending in one direction. The motor portion 143 may selectively rotate the screw portion 142 by applying a rotational force to the screw portion 142.

[0045] When the screw portion 142, which has a shape extending in one direction, is fitted into the hollow internal space of the cylinder portion 141 that provides the ink flow space and is continuously rotated, the ink flowing into the internal space of the cylinder portion 141 can move along the blade portion formed in a spiral shape along the screw axis of the screw portion 142. In other words, unlike a normal circulation pump, there is no need to generate a sudden change in pressure (differential pressure) in the flow path, and the ink can be stably and continuously moved at a consistent volumetric flow rate by the screw portion 142 rotating at a constant speed. In addition, since the ink is pushed by the screw portion 142 rotating constantly and in one direction and moves naturally, the pulsation phenomenon that is common to normal circulation pumps can also be completely eliminated or significantly suppressed.

[0046] Therefore, according to the present invention, by effectively suppressing sudden pressure changes and pulsation phenomena, a weak negative pressure can be applied to the ink reservoir 110, thereby accurately maintaining and controlling the meniscus state of the ink in the nozzle portion of the inkjet head unit 200, thereby enabling stable ink ejection and inkjet printing.

[0047] In order to accurately control the meniscus state of the ink using a weak negative pressure applied to the ink reservoir 110, the ink flowing through the ink circulation unit 140 must be able to move naturally as the screw unit 142 rotates, without experiencing a sudden change in pressure or a pulsation phenomenon (periodic change in pressure). For this reason, the internal space of the cylinder unit 141 may be cylindrical with a uniform inner diameter along the one direction, and the screw unit 142 may have a uniform outer diameter along the one direction.

[0048] In the present invention, the fact that the sizes of components are the same does not only mean that they are completely the same physically, but also means that they are the same including processing tolerances.

[0049] If the inner diameter of the internal space of the cylinder portion 141 and the outer diameter of the screw portion 142 are the same along one direction, which is the direction in which the ink moves, the moving ink will move naturally, being constantly pushed only by the blade portion of the rotating screw portion 142, without experiencing any pressure changes along that direction.

[0050] The screw portion 142 comprises a shaft portion 142a extending in the one direction, and a blade portion 142b arranged so as to form a spiral shape along the outer wall of the shaft portion 142a, and the outer diameter and pitch of the blade portion 142b may be the same along the one direction.

[0051] One end of the shaft portion 142a may be connected to the motor portion 143 that provides a rotational force, and may rotate by receiving the transmission of the rotational force. The blade portion 142b may be arranged to have a spiral shape along the outer wall of the rotating shaft portion 142a, but the shaft portion 142a and the blade portion 142b may be formed integrally, or may be manufactured separately and combined. In this case, the outer diameter and pitch of the blade portion 142b may be the same along the one direction. The outer diameter of the blade portion 142b may be the height from the outer wall of the shaft portion 142a, and the pitch may be the interval when the blade portion 142b is positioned at each of the same positions. Since the driving force required for the ink to move along one direction is the pushing force by the rotating blade portion 142b, in order for the ink to move uniformly along one direction, the outer diameter and pitch of the blade portion 142b must be the same along the one direction. In particular, as described below, in an inkjet printing system having a plurality of inkjet head units 200, ink flows into the ink circulation unit 140 through a plurality of second flow passage pipes 130 connected to the plurality of inkjet head units 200, respectively, and in order for the ink flowing through different paths to move naturally without experiencing a large change in pressure, a constant driving force must be transmitted to the ink regardless of the path through which it flows in. In other words, even if a plurality of second flow passage pipes 130 are connected to the internal space of the cylinder unit 141 at constant intervals along one direction, the ink flowing through each second flow passage pipe 130 is pushed along one direction by a constant force by the blade units 142b having the same outer diameter and pitch along that direction, and therefore can move uniformly.

[0052] The outer diameter D1 of the screw portion 142 may be smaller than the inner diameter D2 of the internal space of the cylinder portion 141 and may be 80% or more of the inner diameter D2 of the internal space. In such a case, the ink present in the space surrounded by the inner wall of the cylinder portion 141 and the blade portion 142b of the screw portion 142b is pushed as the blade portion 142b rotates, and can move effectively in one direction.

[0053] From the viewpoint of transmitting force, it may be most effective if the outer diameter D1 of the screw portion 142 and the inner diameter D2 of the internal space are the same, but if the outer diameter D1 of the screw portion 142 and the inner diameter D2 of the internal space are the same, there is a risk that the rotating screw portion 142 will be pinched by the inner wall of the cylinder portion 141, and the screw portion 142 will not continue to rotate, or the cylinder portion 141 or the screw portion 142 will be damaged. On the other hand, if the outer diameter D1 of the screw portion 142 is smaller than 80% of the inner diameter D2 of the internal space, the ink pushed as the screw portion 142 rotates will not be supported by the inner wall of the cylinder portion 141, and some of the ink may stagnate along the inner wall of the cylinder portion 141 instead of moving in one direction, which may cause a problem of reduced circulation efficiency.

[0054] A separation space 145 may be provided between one end of the screw portion 142 and one end inside the internal space of the cylinder portion 141, and the third flow passage pipe 150 may be connected to the separation space 145.

[0055] The third flow path pipe 150 is disposed at one end of the screw part 142, and if ink moving along the blade part 142b of the rotating screw part 142 flows out through the third flow path pipe 150 as soon as it reaches one end of the screw part 142, the position of the blade part 142b changes as the screw part 142 rotates, and there is a risk that the ink will not flow out uniformly into the third flow path pipe 150. To solve this problem, one end of the screw part 142 does not abut or come close to one end inside the internal space of the cylinder part 141, and one end of the screw part 142 and one end inside the internal space of the cylinder part 141 are separated from each other to provide a separation space 145, so that the ink that reaches one end of the screw part 142 is stabilized through the separation space 145 and then pushed by the constant volume flow to flow out into the third flow path pipe 150. The separation distance between one end of the screw portion 142 and one end inside the internal space of the cylinder portion 141 may be larger than the inner diameter of the third flow path pipe 150 so as to ensure sufficient space for the ink to be separated from one end of the rotating screw portion 142 and stabilized in the separation space 145 to which the third flow path pipe 150 is connected.

[0056] The ink supply device 100 may further include a flow meter unit 160 that measures the flow rate of ink flowing inside the third flow path pipe 150, and a control unit 144 that controls at least one of the rotational speed, rotational amount, or rotational force of the motor unit 143 in accordance with the ink flow rate measured by the flow meter unit 160.

[0057] The flow meter unit 160 may measure the flow rate of the ink flowing out of the ink circulation unit 140 and flowing inside the third flow path pipe 150, and monitor the circulation state of the ink in the ink supply device by the ink circulation unit 140. If the flow rate of the circulating ink is too high, there is a risk that the components constituting the circulation flow path may wear out, and there is a risk that a sudden change in pressure may occur, making it difficult to control the meniscus state at the entrance of the nozzle unit. On the other hand, if the flow rate of the circulating ink is too low, sufficient effects cannot be obtained in removing air or stirring and homogenizing the ink by circulating the ink. Therefore, it is necessary to monitor whether the ink circulates at a preset flow rate in the ink supply device.

[0058] The flow meter unit 160 may also be arranged in other paths through which the ink circulates (e.g., the first flow path pipe 120, etc.), but by measuring the flow rate of the ink circulating downstream of the ink circulation unit 140, not only can the ink circulation state be confirmed by the ink circulatory unit 160 itself, but the flow meter unit 160 can also be maintained as is even when the flow path of the first flow path pipe 120, etc. is changed to accommodate multiple inkjet head units, as described below.

[0059] The flow meter unit 160 may be a non-contact type flow meter that is attached to the outer wall of the third flow tube 150 by a clamp-on method so as not to interfere with the flow of ink flowing inside the third flow tube 150 and that measures the flow rate. For example, the flow meter unit 160 may be a non-contact type ultrasonic flow meter that measures the flow rate by measuring the difference in arrival time of ultrasonic waves using ultrasonic sensors arranged at different positions along the flow direction of the fluid (ink), or may be a non-contact type temperature flow meter that measures the flow rate by measuring the temperature difference at two points using temperature sensors arranged at different positions along the flow direction of the fluid.

[0060] The control unit 144 may be connected to the flow meter unit 160 and the motor unit 143, monitor the ink flow rate measured by the flow meter unit 160, and control at least one of the rotational speed, rotational amount, or rotational force of the motor unit 143 in accordance with the ink flow rate measured by the flow meter unit 160.

[0061] The control unit 144 may include a flow rate determination unit 144a that compares a preset flow rate with the ink flow rate measured by the flow meter unit 160 to determine whether the flow rate of the circulating ink is within a normal range, and a drive control unit 144b that controls at least one of the rotation speed, rotation amount, or rotation force of the motor unit 143 if the flow rate determination unit 144a determines that the measured ink flow rate is outside the normal range. On the other hand, if the flow rate determination unit 144a determines that the measured ink flow rate is within the normal range, the drive control unit may maintain the current operating state of the motor unit 143.

[0062] The ink flowing out from the ink circulation section 140 is supplied to the ink reservoir 110 through the third flow pipe 150 so that the ink continues to circulate along the circulation path. The ink flowing in and collected through the third flow pipe 150 connected to a certain position of the ink reservoir 110 may be agitated while flowing from one position to another position of the ink reservoir 110 to flow out through the first flow pipe 120 connected to another position of the ink reservoir 110. In order to further enhance the agitation effect, a partition wall (e.g., vertical) that crosses the flow path between one position and another position may be disposed to continue mixing the ink while flowing. In this case, the partition wall may be disposed at least partially away from the inner wall of the ink reservoir 110 so that the ink can flow through the space between the partition wall and the inner wall of the ink reservoir 110. Furthermore, the air contained in the ink collected through the third flow path pipe 150 may be separated from the ink as the ink flows inside the ink reservoir 110 and removed by the negative pressure setting unit 173 connected to the ink reservoir 110. If a partition is provided inside the ink reservoir, the ink collides with the partition and the air contained in the ink can be separated more effectively while being detouring, and the ink can be exhausted very easily.

[0063] The ink supply device 100 may further include a capacity detection unit 171 that detects the volume of ink stored in the ink storage unit 110, and an ink refill unit 172 that is connected to the ink storage unit 110 and refills the missing ink if the volume of ink detected by the capacity detection unit 171 does not meet a standard volume.

[0064] The volume sensing unit 171 may sense the volume of ink stored in the ink reservoir 110 in order to check whether a certain level of ink is stored in the ink reservoir 110 so that ink can be stably discharged from the inkjet head unit 200. The volume of ink may be measured using a level sensor that measures the height of the surface of the ink stored in the ink reservoir 110, but the present invention is not limited thereto, and the volume of ink may be sensed by a variety of methods.

[0065] When the ink volume detected by the volume detection unit 171 is less than the reference volume, the ink refill unit 172 may supply ink to replenish the ink insufficiency in the ink reservoir 110. The ink refill unit 172 replenishes the ink that is being gradually reduced after being discharged from the inkjet head unit 200 for the inkjet printing operation, thereby maintaining a constant volume of ink stored in the ink reservoir 110. The ink refill unit 172 may be connected to an external storage tank that stores ink outside the device, and supply the ink stored in the external storage tank to the ink reservoir 110.

[0066] The ink supply device 100 may further include a buffer section 180 that is connected to the first flow path pipe 120, is disposed between the ink reservoir section 110 and the inkjet head section 200, and provides a buffer space having a cross-sectional area larger than that of the first flow path pipe 120.

[0067] In general, an inkjet printing system includes a plurality of inkjet head units, and requires a plurality of first flow tubes 120 for supplying ink to the inkjet head units 200, respectively. If the plurality of first flow tubes 120 are connected to the ink reservoir unit 110, respectively, and ink circulates along a circulation path, the flow rate of ink moving through the plurality of first flow tubes 120 may differ depending on the connection position of the ink reservoir unit 110, etc. Also, if negative pressure is set in the ink reservoir unit 110 to control the meniscus state at the entrance of the nozzle unit of the inkjet head unit 200, the negative pressure is transmitted through the plurality of first flow tubes 120, but the magnitude of the negative pressure transmitted through each of the plurality of first flow tubes 120 may differ. If the flow rate of ink moving through the plurality of first flow tubes 120 or the magnitude of the negative pressure differs, the state of the ink discharged from the plurality of inkjet head units 200 may also differ depending on the position, and there is a risk that uniform print quality cannot be ensured.

[0068] The buffer unit 180, which is connected to the first flow path pipe 120 and provides a buffer space having a larger cross section than the first flow path pipe 120, is disposed between the ink reservoir 110 and the inkjet head unit 200, so that when the ink flowing through the first flow path pipe 120 flows into the buffer space, which is a larger space than the first flow path pipe 120, the inks are mixed and homogenized, and the negative pressure applied to the first flow path pipe 120 is also made constant. That is, the buffer unit 180 may be connected to a plurality of first flow path pipes 120 to provide a common buffer space to homogenize the inks, and then supply the ink to a plurality of inkjet head units 200 via a plurality of downstream first flow path pipes 120. The first flow path pipe 120 is divided into an upstream first flow path pipe 120A and a downstream first flow path pipe 120B centered on the buffer section 180, and homogenized ink flows in the downstream first flow path pipe 120B, allowing a uniform negative pressure to be transmitted to each inkjet head section 200.

[0069] On the other hand, the first flow passage tubes 120 may be provided in a plurality of tubes, and the inner diameter of the third flow passage tube 150 may be larger than that of the first flow passage tube 120. Even if the ink is collected from a plurality of ink-jet head units 200, it accumulates in the ink circulation unit 140 and then flows out and is supplied to the ink storage unit 110 via the third flow passage tube 150. Therefore, if the ink is not consumed by being discharged from the ink-jet head unit 200, the ink can be supplied to the ink-jet head unit 200 via the first flow passage tube 120 at the same flow rate as the collected ink. Since the ink moving via the third flow passage tube 150 forming a single flow passage circulates to each of the plurality of first flow passage tubes 120, the inner diameter of the third flow passage tube 150 may be larger than that of each of the plurality of first flow passage tubes 120 so that the first flow passage tube 120 and the third flow passage tube 150 constituting the circulation path do not interfere with the circulation of the ink. For accurate comparison, the inner diameter of the third flow path pipe 150 and the inner diameters of the plurality of first flow path pipes 120 that correspond to the same height may be used.

[0070] In the present invention, the ink may contain solids.

[0071] In an industrial inkjet printing system used in the manufacture of electronic products such as display devices, an ink containing a substance necessary for manufacturing parts may be used together with or instead of a pigment. Various solids may be included in the ink to provide a required functionality to a part of an electric / electronic component such as a display panel. For example, an ink containing quantum dot materials or nanorods exhibiting various optical properties, polymer resins as insulating materials, and metallic copper for conductivity may be used. In this way, since ink for inkjet printing systems used in the industrial field contains various components including solids with different specific gravities from the liquid components, simply adding a dispersant together may make it difficult to maintain the dispersibility of various substances contained in the ink for a long period of time. Therefore, by allowing the ink to continue to circulate through an ink circulation path including an inkjet head unit 200 for printing in an inkjet printing system using the ink supply device according to the present invention, not only can air present in the ink be removed, but various components including solids present in the ink can be mixed and maintained uniformly.

[0072] The ink supplying device 100 may include a flow path pipe including the first flow path pipe 120 to the third flow path pipe 150 through which the ink flows, and a plurality of valves 190; 191, 192, 193, 194 that are disposed in an exhaust pipe connected between the ink reservoir 110 and the negative pressure setting unit 173 and can control the flow rate or exhaust amount of the ink as necessary. The control unit 144 may be connected to the capacitance sensing unit 171, the flow meter unit 160, the plurality of valves 191 to 194, etc., and may turn on / off the plurality of valves 191 to 194 or adjust the flow rate by generating and transmitting control signals for controlling the plurality of valves 191 to 194 using measurement signals measured by the capacitance sensing unit 171, etc.

[0073] For example, in the process of filling the ink reservoir 110 with an appropriate volume, the valve 193 disposed between the ink refill unit 172 and the ink reservoir 110 may be opened, and the valves 191, 192 disposed in the first flow path pipe 120 to the third flow path pipe 150 may be closed. When the ink stored in the ink reservoir 110 reaches an appropriate volume, the valve 193 may be closed, and then the valve 194 disposed between the ink reservoir 110 and the negative pressure setting unit 173 and the valves 191, 192 disposed in the first flow path pipe 120 to the third flow path pipe 150 may be opened.

[0074] Referring to Figures 1 and 2, an inkjet printing system according to another embodiment of the present invention may include an inkjet head unit 200 having a plurality of nozzle units that eject ink onto a substrate, and an ink supply device 100 according to an embodiment of the present invention that supplies ink to the inkjet head unit 200.

[0075] In describing the inkjet printing system according to another embodiment of the present invention, a description of the same matters as those described above in relation to the ink supply device 100 according to the embodiment of the present invention will be omitted.

[0076] The inkjet printing system may form and print a coating layer by spraying ink in a solution state containing various functional materials onto a substrate through a plurality of nozzles arranged in the inkjet head unit 200.

[0077] In the case of a large-area substrate, it is difficult to fabricate a head unit equipped with a plurality of nozzle portions corresponding to the area of ​​the substrate, and forming a working space for performing inkjet printing work by spraying ink through a plurality of nozzle portions requires the provision of a large chamber, which may be cumbersome from various aspects.

[0078] The multiple nozzle units arranged on the inkjet head unit 200 may be aligned along a first direction, but by moving the inkjet head unit 200 or the substrate in a second direction intersecting the first direction, it is possible to form a uniform coating layer over a large area even on a large-area substrate or using a small-scale inkjet printing system.

[0079] Inkjet printing systems manufactured for industrial use in the manufacture of electronic components and displays use a large amount of ink to accommodate large-area substrates, and therefore may have a structure in which an ink supply device 100 that stores and stably supplies ink and an inkjet head unit 200 are separated.

[0080] The inkjet head unit 200 may include a plurality of nozzles that eject ink onto a substrate for printing. The inkjet head unit 200 may be operated in a thermal manner, in which ink is heated using fine heat rays to increase its volume and eject ink in an amount commensurate with the increased volume, or in a piezoelectric manner, in which pressure is applied to the inside of the head using a piezoelectric element that deforms when a voltage is applied to eject ink, but the present invention is not limited thereto.

[0081] The ink supply device 100 may include an ink storage section 110 that stores ink at least temporarily, a first flow path pipe 120 that supplies the ink stored in the ink storage section 110 to an inkjet head section 200, a second flow path pipe 130 that recovers ink from the inkjet head 200, an ink circulation section 140 that moves the ink flowing in through the second flow path pipe 130 in one direction, and a third flow path pipe 150 that supplies the ink flowing out from the ink circulation section 140 to the ink storage section 110.

[0082] According to the ink supply device 100, without distinguishing between an ink circulation path for printing and an ink circulation path for stirring during standby, the ink can be circulated using the same circulation path to remove any air bubbles present in the ink, and ink can be supplied to the inkjet head unit 200 while maintaining a homogeneous and stable ink state.This means that ink can be ejected from the inkjet head unit 200 very stably and accurately, improving print quality.

[0083] The inkjet printing system of the present invention may include a plurality of inkjet head units 200. The plurality of inkjet head units 200 may be arranged in various arrangements according to various purposes. When printing on a large-area substrate, since one inkjet head unit 200 cannot cover such a large area, the plurality of inkjet head units 200 may be arranged in a first direction, and the inkjet head unit 200 or the substrate may be moved relatively. Alternatively, since the interval between the plurality of nozzle units of the inkjet head unit 200 is fixed, when it is necessary to eject ink at intervals narrower than this (i.e., when it is necessary to perform printing at a high resolution), the plurality of inkjet head units 200 may be spaced apart in a second direction intersecting the first direction, and the plurality of nozzle units may be arranged so as not to overlap each other, and the inkjet head unit 200 or the substrate may be moved relatively to perform printing.

[0084] A plurality of first flow passage pipes 120 for supplying ink to the inkjet head units 200 and a plurality of second flow passage pipes 130 for recovering ink from the inkjet head units 200 may be provided corresponding to the plurality of inkjet head units 200. Each of the first flow passage pipes 120 may be connected to one side of the corresponding inkjet head unit 200, and each of the second flow passage pipes 130 may be connected to the other side of the corresponding inkjet head unit 200. In order to make the flow of ink uniform within the inkjet head unit 200, the one side and the other side to which the first flow passage pipe 120 and the second flow passage pipe 130 are connected may be provided at the same position of the inkjet head unit 200.

[0085] The ink supply device of the present invention and the inkjet printing system equipped with the same can remove air bubbles present in the ink or on the ink flow path, making it possible to stably supply ink to the inkjet head without interrupting the ink flow.

[0086] In order to provide various functions to the applied coating layer, in the case of inks that contain various solids mixed in or that clump together, harden, or gel when the flow is interrupted or stagnated, the ink can be uniformly agitated by continuously circulating between the inkjet head and the ink reservoir, and the ink state can be maintained. Furthermore, the precipitation of solids contained in the ink, the phenomenon of ink clumping, and localized hardening or gelling of the ink can be suppressed, and damage to the inkjet head due to clogging of the nozzle caused by these factors can be prevented.

[0087] Furthermore, air bubbles can be removed from the ink and the ink flow path, and sudden pressure changes or pulsation phenomena in the ink reservoir and ink flow path can be suppressed, allowing for the formation and maintenance of an accurate meniscus, thereby effectively improving the stability of ink ejection and the accuracy of the ink landing position.

[0088] Furthermore, in the inkjet printing system, the ink is continuously circulated using an ink circulation path that includes the inkjet head, which is the object to which ink is supplied for printing. This makes it possible to remove air bubbles that may be present in the inkjet head and also effectively prevents the solid matter from clumping together, thereby enabling smooth ink circulation and improving print quality.

[0089] The phrase "on" used in the above description encompasses a case where there is direct contact and a case where there is no direct contact but is located opposite the upper or lower surface, and it means that it can be located opposite the entire upper or lower surface, or it can be located partially opposite, and it means that it faces the upper or lower surface at a distance or directly contacts the upper or lower surface. Furthermore, the phrases "upper", "lower", "front end", "rear end", "upper", "lower", "top end", "bottom end", etc. used in the above description are defined based on the drawings for ease of explanation, and these phrases do not limit the shape and position of each component in any way.

[0090] Although the preferred embodiment of the present invention has been illustrated and described above, the present invention is not limited to the above embodiment, and it should be understood by those skilled in the art that various modifications can be made thereto and equivalent embodiments can be adopted without departing from the gist of the present invention as claimed in the claims. Therefore, the technical scope of protection of the present invention should be determined by the following claims. [Explanation of symbols]

[0091] 100 Ink supply device 110 Ink storage section 120 First flow pipe 130 Second flow pipe 140 Ink Circulation Section 141 Cylinder section 142 Screw section 143 Motor section 144 Control Unit 145 Separate space 150 Third flow pipe 160 Flow meter section 171 Capacitance sensing section 172 Ink refill section 173 Negative pressure setting section 200 Inkjet head unit

Claims

1. an ink reservoir for at least temporarily storing ink; a first flow path pipe for supplying the ink stored in the ink storage portion to an inkjet head portion; a second flow passage pipe for recovering ink from the inkjet head; an ink circulation section that moves the ink flowing in through the second flow path pipe in one direction; a third flow path pipe that supplies the ink flowing out from the ink circulation section to the ink reservoir section; An ink supply device comprising:

2. The ink circulation unit includes: A cylinder portion providing a hollow internal space extending in the one direction; a screw portion extending in the one direction and fitted into the internal space so as to be rotatable; A motor unit that selectively rotates the screw unit; The ink supply apparatus of claim 1 , comprising:

3. The internal space is cylindrical and has a uniform inner diameter along the one direction, The ink supply device according to claim 2 , wherein the screw portion has a uniform outer diameter along the one direction.

4. 4. The ink supply device according to claim 3, wherein an outer diameter of the screw portion is smaller than an inner diameter of the internal space and is 80% or more of the inner diameter of the internal space.

5. The screw portion is A shaft portion extending in the one direction; A blade portion is arranged in a spiral shape along an outer wall of the shaft portion; Equipped with The ink supply device according to claim 2 , wherein the outer diameter and pitch of the blade portion are uniform along the one direction.

6. A separation space is provided between one end of the screw portion and one end inside the internal space, The ink supply device according to claim 2 , wherein the third flow pipe is connected to the isolated space.

7. a flow meter unit that measures a flow rate of ink flowing inside the third flow tube; a control unit that controls at least one of a rotation speed, a rotation amount, and a rotation force of the motor unit in response to a flow rate of the ink measured by the flow meter unit; The ink supply apparatus of claim 2 further comprising:

8. a volume sensing unit that senses the volume of ink stored in the ink storage unit; an ink refill unit connected to the ink reservoir for refilling the ink when the ink volume detected by the volume detection unit is less than a reference volume; The ink supply apparatus of claim 1 further comprising:

9. 2. The ink supply device according to claim 1, further comprising a negative pressure setting unit connected to the ink reservoir unit and setting an internal space of the ink reservoir unit at a pressure lower than atmospheric pressure.

10. 2. The ink supply device according to claim 1, further comprising a buffer section communicating with the first flow tube, disposed between the ink reservoir section and the inkjet head section, and providing a buffer space having a cross-sectional area larger than that of the first flow tube.

11. The first flow path pipe is arranged in a plurality of pieces, 2. The ink supply device according to claim 1, wherein an inner diameter of the third flow tube is greater than an inner diameter of the first flow tube.

12. The ink supply apparatus of claim 1 , wherein the ink includes solids.

13. an inkjet head unit having a plurality of nozzles that eject ink onto a substrate; The ink supply device according to claim 1 , which supplies ink to the inkjet head unit; An inkjet printing system comprising:

14. The inkjet printing system according to claim 13 , wherein the inkjet head unit is arranged in a plurality of units.

15. a plurality of the first flow path pipes to a plurality of the second flow path pipes are provided corresponding to the plurality of the inkjet head units; Each of the first flow passages is connected to one side of a corresponding ink-jet head unit, The inkjet printing system of claim 14 , wherein each of the second flow conduits is connected to the other side of a corresponding inkjet head portion.

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