Droplet discharge method

Abstract

The invention relates to a liquid droplet discharging method. In a droplet ejection method, a plurality of grids corresponding to a region of a substrate are provided. A discharge amount for each of the grids is determined based on a difference in discharge amount according to a change in temperature of ink to be discharged from nozzles designated for each of the plurality of grids. An ink droplet pattern for discharging ink is created having a discharge amount for each grid. Drops are discharged through nozzles according to the droplet pattern to form a thick film having a predetermined thickness on the substrate.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10 - 2023 - 0193897, filed with the Korean Intellectual Property Office (KIPO) on December 28, 2023, the content of which is incorporated herein by reference in its entirety. Technical field

[0003] Embodiments of the present disclosure relate to a droplet ejection device and a droplet ejection method, and more particularly, to a droplet ejection device for ejecting droplets using an ink - jet printing method and a droplet ejection method using the droplet ejection device. Background art

[0004] Before transporting a large panel for a large - area display device to equipment for a modular process, a protective film may be formed on the large panel. Instead of a conventional protective film, an ink - jet printing method may be used to print a resin - based material through a plurality of nozzles to form a thick film having a relatively large thickness on the entire surface of a large substrate. Since one or more heads have a limited width, the entire surface of the large substrate may be printed through a plurality of scans. In addition, since ink must be supplied to the heads during printing to form a thick film having a large thickness in a single printing, there is a problem in that the temperature of the ink in the reservoir supplying the ink to the nozzles decreases over time, and thus, the viscosity of the supplied ink increases, such that the amount of droplets ejected through the nozzles decreases, and thus, a thick film having a uniform thickness cannot be formed. Summary of the invention

[0005] An object of the present disclosure is to provide a droplet ejection method capable of forming a thick film having a uniform thickness.

[0006] Another object of the present disclosure is to provide a droplet ejection device for performing the droplet ejection method.

[0007] According to an exemplary embodiment, a droplet discharging method includes: determining a scanning order of nozzles of an inkjet head corresponding to a substrate; supplying ink from a reservoir to the nozzles of the inkjet head; and discharging droplets through the nozzles corresponding to a first region and a second region of the substrate according to the scanning order to form a thick film having a predetermined thickness on the substrate. In order to discharge droplets, a first temperature of the ink supplied to a first nozzle of the nozzles when discharging a first droplet on the first region of the substrate is compared with a second temperature of the ink supplied to a second nozzle of the nozzles when discharging a second droplet on the second region of the substrate, and when the second temperature is lower than the first temperature, a first control signal is output to the first nozzle for discharging the first droplet at a first discharge amount, and a second control signal is output to the second nozzle for discharging the second droplet at a second discharge amount greater than the first discharge amount.

[0008] In an exemplary embodiment, determining the scanning order of the nozzles may include: determining a plurality of grids corresponding to the entire region of the substrate; and designating the scanning order of the nozzles for each of the plurality of grids.

[0009] In an exemplary embodiment, comparing the first temperature and the second temperature may include: performing a temperature change from the first temperature to the second temperature on the entire grid to calculate a temporal temperature gradient of the ink for each grid; calculating a discharge amount for each grid based on a change in ink viscosity according to the temporal temperature gradient; and creating a droplet map for discharging ink having the discharge amount for each grid.

[0010] In an exemplary embodiment, the droplet map may have control signal data output to the nozzles designated for the grids respectively.

[0011] In an exemplary embodiment, outputting the first and second control signals may include: outputting the first control signal and the second control signal corresponding to the control signal data to the first nozzle and the second nozzle respectively.

[0012] In an exemplary embodiment, when the control signal data of the droplet map represents 2-bit data, four different control signals corresponding to the control signal data may be generated.

[0013] In an exemplary embodiment, comparing the first temperature and the second temperature may include: detecting the temperature of the ink in the reservoir.

[0014] In an exemplary embodiment, the discharge amount of the droplets discharged onto the substrate through the first nozzle according to the first control signal may be the same as the discharge amount of the droplets discharged onto the substrate through the second nozzle according to the second control signal.

[0015] In an exemplary embodiment, the thickness of the thick film may be in the range of 100 μm to 150 μm.

[0016] According to an exemplary embodiment, a droplet discharge method includes: setting a plurality of grids corresponding to regions of a substrate; determining a discharge amount for each grid based on a difference in discharge amounts according to temperature changes of ink to be discharged from nozzles respectively designated for the plurality of grids; creating a droplet map for discharging ink having the discharge amount for each grid; and discharging droplets through the nozzles according to the droplet map to form a thick film having a predetermined thickness on the substrate.

[0017] In an exemplary embodiment, setting a plurality of grids may include: dividing the substrate into a plurality of scan lines; and setting a plurality of sub-grid maps respectively corresponding to the plurality of scan lines.

[0018] In an exemplary embodiment, determining the discharge amount for each grid may include: detecting the temperature of the ink in a reservoir that supplies the ink to the nozzle.

[0019] In an exemplary embodiment, determining the discharge amount for each grid may include: when a first droplet is discharged in a first region of the substrate at a first time point according to a scan order of the nozzles and a second droplet is discharged in a second region of the substrate at a second time point after the first time, comparing a first temperature of the ink received in the nozzle when the first droplet is discharged in the first region and a second temperature of the ink received in the nozzle when the second droplet is discharged in the second region; performing a temperature change from the first temperature to the second temperature for the plurality of grids to calculate a temporal temperature gradient of the ink for each grid; and calculating the discharge amount for each grid based on a change in ink viscosity according to the temporal temperature gradient.

[0020] In an exemplary embodiment, the droplet map may have control signal data output to the nozzles respectively designated for the grids.

[0021] In an exemplary embodiment, discharging the droplets through the nozzles according to the droplet map may include: outputting at least two different control signals corresponding to the control signal data to the nozzles corresponding to the grids.

[0022] In an exemplary embodiment, the discharge amounts of the droplets respectively discharged on the substrate through the nozzles according to the droplet map are the same as each other.

[0023] In an exemplary embodiment, the thickness of the thick film may be in the range of 100 μm to 150 μm.

[0024] According to an exemplary embodiment, a droplet discharge method includes: setting a plurality of grids corresponding to regions of a substrate; determining a scanning order of nozzles for the plurality of grids; obtaining a first temperature of ink received in a nozzle when a first droplet is discharged in a first region of the substrate at a first time point according to the scanning order of the nozzles, and a second temperature of ink received in the nozzle when a second droplet is discharged in a second region of the substrate at a second time point after the first time; performing a temperature change from the first temperature to the second temperature for the entire grid to calculate a temporal temperature gradient of the ink for each grid; calculating a discharge amount for each grid based on a change in ink viscosity according to the temporal temperature gradient; creating a droplet map for discharging ink having the discharge amount for each grid; and discharging droplets through the nozzles according to the droplet map to form a thick film having a predetermined thickness on the substrate.

[0025] In an exemplary embodiment, obtaining the first temperature and the second temperature may include: detecting a temperature of ink in a reservoir that supplies the ink to the nozzle.

[0026] In an exemplary embodiment, the discharge amounts of the droplets respectively discharged on the substrate through the nozzles according to the droplet map may be the same as each other.

[0027] According to an exemplary embodiment, when creating a droplet map for discharging droplets to a first region of a substrate through a nozzle of a head assembly and discharging droplets to a second region of the substrate after a first time, a first temperature of ink received in a first nozzle when discharging to the first region and a second temperature of ink received in a second nozzle when discharging to the second region may be compared. When the second temperature is determined to be lower than the first temperature, the waveform of a control signal may be adjusted such that, considering an increase in ink viscosity due to the temperature decrease, the amount of ink discharged in the second region is greater than the amount of ink discharged in the first region.

[0028] Therefore, even if the temperature of the ink in the reservoir for supplying ink to the nozzles cannot be raised to the desired temperature, the waveform of the control signal can be adjusted to eject droplets having a relatively large ejection amount. Accordingly, even if the temperature of the ink supplied to the first nozzle and the second nozzle gradually decreases as the printing time elapses, the ejection amounts of the droplets ejected sequentially from the first nozzle and the second nozzle onto the substrate can be kept constant, thereby forming a thick film having a uniform thickness over the entire area of the substrate.

[0029] However, the effects of the present disclosure are not limited to the above effects, and various extensions can be made without departing from the spirit and scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a perspective view showing a droplet ejection device according to an exemplary embodiment.

[0031] Figure 2 is a view showing Figure 1 a plan view of the droplet ejection device.

[0032] Figure 3 is a view showing Figure 1 a front view of the droplet ejection device.

[0033] Figure 4 is a view showing Figure 1 a side view of the droplet ejection device.

[0034] Figure 5 is a view showing Figure 1 a cross-sectional view of an inkjet head and a reservoir of an inkjet head unit.

[0035] Figure 6 is a view showing Figure 5 a plan view of a nozzle surface of an inkjet head unit.

[0036] Figure 7 is a view showing Figure 5 a cross-sectional view of a nozzle of an inkjet head.

[0037] Figure 8 is a view showing Figure 1 a block diagram of a control section of a droplet ejection device.

[0038] Figure 9 is a plan view showing a grid diagram corresponding to the entire area of a substrate and nozzles corresponding to the grids of the grid diagram.

[0039] Figure 10 is a view showing a droplet diagram for ejecting ink having an ejection amount for each grid.

[0040] Figure 11A 、 Figure 11B and Figure 11Care graphs showing voltage waveforms of control signals output from a control section according to Figure 10 a droplet pattern.

[0041] Figure 12 is a view showing a dot pattern discharged from a nozzle according to Figure 10 a droplet pattern.

[0042] Figure 13A is a view showing a stripe pattern discharged from a nozzle according to a droplet pattern of an exemplary embodiment.

[0043] Figure 13B is a view showing a thick film pattern formed by Figure 13A a stripe pattern.

[0044] Figure 14 is a view showing a stripe pattern discharged from a nozzle according to a droplet pattern of an exemplary embodiment.

[0045] Figure 15 is a flowchart showing a droplet discharging method of an exemplary embodiment. DETAILED DESCRIPTION

[0046] Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings.

[0047] Since various modifications can be made to the present disclosure and the present disclosure can have various forms, embodiments will be described in detail through a detailed description. However, this is by no means to limit the present disclosure to a specific disclosed form, and the present disclosure should be construed as including all modifications, equivalents, and alternatives included in the spirit and technical scope of the present disclosure.

[0048] The terms used herein are intended to describe only certain embodiments and should in no way limit the present disclosure. Unless the context clearly indicates otherwise, expressions in the singular form include the meaning of the plural form. In the present disclosure, terms such as "comprising" or "including" are intended to specify the presence of the features, numbers, steps, operations, elements, parts, or combinations thereof described in the present disclosure, and should not be construed as excluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, elements, parts, or combinations thereof.

[0049] When describing each drawing, like reference numerals will be used for like elements. Terms such as "first" and "second" may be used to describe various elements, but these elements are not limited by these terms, and these terms may be used only to distinguish one element from another.

[0050] Figure 1Is a perspective view showing a droplet ejection device according to an exemplary embodiment. Figure 2 Is a view showing Figure 1 Plan view of the droplet ejection device of. Figure 3 Is a view showing Figure 1 Front view of the droplet ejection device of. Figure 4 Is a view showing Figure 1 Side view of the droplet ejection device of. Figure 5 Is a view showing Figure 1 Cross-sectional view of the inkjet head and reservoir of the inkjet head unit of. Figure 6 Is a view showing Figure 5 Plan view of the nozzle surface of the inkjet head unit of. Figure 7 Is a view showing Figure 5 Cross-sectional view of the nozzle of the inkjet head of.

[0051] Reference Figures 1 to 7 , the droplet ejection device 10 may include a substrate support 100, a droplet ejection portion 200 configured to eject droplets onto a substrate S supported by the substrate support 100, and a control portion 300 configured to control the operations of the substrate support 100 and the droplet ejection portion 200.

[0052] In an exemplary embodiment, the droplet ejection device 10 may be used to manufacture a large-area flat panel display (FPD) or the like. The droplet ejection device 10 may apply a chemical liquid onto the substrate S using an inkjet printing method. For example, the substrate may include a display panel such as a liquid crystal display (LCD), an organic light emitting diode (OLED) display, etc. The droplet ejection device 10 may print a resin-based material using an inkjet printing method through a plurality of nozzles to form a thick film having a large thickness on the entire surface of a large substrate, such as a protective film for protecting an OLED organic / inorganic film. The thickness of the thick film may be in the range of 100 μm to 150 μm. The chemical liquid may include an acrylic ultraviolet curable resin.

[0053] As Figures 1 to 4 shown, the substrate support 100 may include a transfer portion 110 on which the substrate S is placed and a suspension portion 130 that suspends the substrate S.

[0054] The transfer portion 110 may include a pair of holders 110a, 110b for adsorbing and supporting the substrate S. Each of the pair of holders 110a, 110b may extend in one direction to correspond to one side of the substrate S. The pair of holders 110a, 110b may be mounted to be movable along the guide rail 120 by a transfer mechanism. For example, the transfer mechanism may include a motor, gears, pulleys, belts, ball screws, linear motors, etc. Each of the guide rails 120 may extend in a first direction (X direction), and the guide rails 120 may be spaced apart from each other in a second direction (Y direction) perpendicular to the first direction.

[0055] The pair of holders 110a and 110b can hold the substrate S by a vacuum adsorption method. The upper surfaces of the pair of holders 110a and 110b may include adsorption portions in which adsorption holes 112 are formed. A vacuum pressure can be applied to the adsorption holes 112 so that both sides of the substrate S are adsorbed on the upper surfaces of the pair of holders 110a and 110b. Accordingly, the pair of holders 110a and 110b can fix the substrate S and reciprocally move the substrate S in the first direction (X direction).

[0056] The suspension part 130 can jet air to the lower part of the substrate S to suspend the substrate S. The suspension part 130 may be provided with a plurality of jet holes 132 for jetting air. The substrate S can be supported by an air-floating method in which the substrate floats by the air pressure jetted from the plurality of jet holes 132 therethrough.

[0057] The suspension part 130 can extend from a transport conveyor through which the substrate S is loaded and unloaded along the first direction (X direction) to pass through the droplet discharging part 200. When the substrate S is loaded onto the transport conveyor by a robot transfer device, the lift pins can rise to lift the substrate S, the pair of holders 110a and 110b can move below the substrate S, and then the lift pins can descend to transfer and place the substrate S onto the adsorption portions of the pair of holders 110a and 110b. The pair of holders 110a and 110b on which the substrate S is mounted can move along the guide rail 120 in the first direction (X direction) toward the droplet discharging part 200, and the droplet discharging part 200 can discharge liquid onto the substrate S adsorbed and supported by the pair of holders 110a and 110b.

[0058] In an exemplary embodiment, the droplet discharging device 10 may further include a droplet curing part configured to cure the droplets discharged onto the substrate S. The substrate S onto which the droplets are discharged can move to the droplet curing part, and the droplet curing part can cure the droplets discharged onto the substrate S. For example, the droplet curing part may include a light irradiation unit configured to irradiate the droplets with light. The light irradiation unit may include a heating lamp, an ultraviolet curing device, etc.

[0059] In an exemplary embodiment, the droplet discharging part 200 may include a head assembly 210 for jetting droplets in an inkjet manner, and a gantry 250 for supporting the head assembly 210. The head assembly 210 may be mounted and supported on the gantry 250 located above the substrate S.

[0060] The gantry 250 may have a support frame extending in a second direction (Y direction) above the pair of grippers 110a, 110b. The gantry 250 may be supported on frame support rods that extend in a third direction (Z direction) perpendicular to the first and second directions, respectively, and the frame support rods may be mounted to be movable along a guide extending in a first direction (X direction) by a transport mechanism. Accordingly, the gantry 250 may reciprocate in the first direction (X direction). The head assembly 210 may be mounted on the front side of the support frame of the gantry 250 by a carriage. A guide 252 may be mounted on the front side of the support frame and may extend in the second direction (Y direction), and the carriage of the head assembly 210 may be mounted to be movable along the guide 252 by a transport mechanism. Accordingly, the head assembly 210 may reciprocate in the second direction (Y direction).

[0061] In an exemplary embodiment, the head assembly 210 may include a head package assembly 220 having at least one inkjet head 230 mounted thereon. The head assembly 210 may include a reservoir 260 configured to hold ink IK and supply the ink IK to at least one inkjet head 230.

[0062] As Figure 5 and Figure 6 shown, the head package assembly 220 may include three inkjet heads 230. One reservoir 260 may supply ink IK to the three inkjet heads 230. Optionally, three reservoirs 260 may be provided to supply ink IK to the three inkjet heads 230, respectively. Each of the inkjet heads 230 may extend in one direction, and each of the inkjet heads 230 may include a plurality of nozzles 240 spaced apart at a predetermined interval. Each of the inkjet heads 230 may be arranged to be inclined so as to have a predetermined angle with respect to the first direction (X direction). Optionally, each of the inkjet heads 230 may be arranged such that the extending direction of the inkjet head 230 is parallel to the first direction (X direction). The inkjet heads 230 may be arranged to be spaced apart from each other in the second direction (Y direction). The inkjet heads 230 may be offset from each other in alignment in the first direction (X direction). When viewed in the second direction (Y direction), the inkjet heads 230 may be arranged to partially overlap each other. It will be understood that the number and arrangement of the inkjet heads 230, the number and arrangement of the nozzles 240, etc. are provided as examples, and the concept of the present invention is not limited thereto.

[0063] Since the primary scan width covered by the nozzle 240 of the head assembly 210 is smaller than the width of the substrate S, the head assembly 210 can print the entire surface of the substrate S through multiple scans. That is, when the head assembly 210 is at the first position, the substrate S can move in the first direction (X direction), and the head assembly 210 can eject droplets DR to form a first dot pattern along the first scan line. Then, when the head assembly 210 moves a preset distance in the second direction (Y direction) and is at the second position, the substrate S can move in the first direction (X direction), and the head assembly 210 can eject droplets DR to form a second dot pattern along the second scan line. Then, while the head assembly 210 sequentially moves a preset distance in the second direction (Y direction), the droplets DR can be repeatedly ejected until a thick film is formed on the entire surface of the substrate S.

[0064] As Figure 7 shown, the inkjet head 230 can eject ink IK in a piezoelectric manner. Each of the nozzles 240 can include a piezoelectric element 242, an ink chamber 246 adjacent to the piezoelectric element 242, an ejection port 248 opening to the outside from the ink chamber 246, and a diaphragm 244 disposed between the piezoelectric element 242 and the ink chamber 246. The piezoelectric element 242 can control the volume of the ink chamber 246. The piezoelectric element 242 can include a piezoelectric body. The piezoelectric body can include a material whose shape changes when an electrical signal is applied. When an electrical signal as a control signal CS from the control section 300 is applied to the piezoelectric element 242 of the nozzle 240, the shape of the piezoelectric element 242 can change to apply pressure to the ink chamber 246 through the diaphragm 244, and thus, the ink IK accommodated inside the ink chamber 246 can be ejected toward the substrate S through the ejection port 248 to perform an inkjet printing process.

[0065] The ink chamber 246 can accommodate the ink IK therein. For example, the volume of the ink IK accommodated in the ink chamber 246 can be in the range of 4 cubic centimeters to 8 cubic centimeters. As the printing process is continuously performed on the substrate S, the ink IK in the ink chamber 246 can be consumed, and the ink chamber 246 can receive the ink IK from the reservoir 260 through the flow path tube 264 to maintain a certain amount of the ink IK.

[0066] The diaphragm 244 may be disposed between the piezoelectric element 242 and the ink chamber 246. The diaphragm 244 may be made of an elastic material, and when a control signal CS is applied to the piezoelectric element 242, its shape may change and bend according to the deformation of the piezoelectric element 242, thereby changing the volume of the ink chamber 246. For example, the control signal CS may be a voltage pulse signal having a preset waveform. When a voltage signal including pulses of positive (+) and negative (-) waveforms is applied, the diaphragm 244 may be deformed such that the nozzle 240 can eject droplets DR having a discharge amount corresponding to the waveform.

[0067] In an exemplary embodiment, the head assembly 210 may further include a temperature sensor 262 for measuring the temperature of the ink IK in the reservoir 260. The temperature sensor 262 may be mounted on one side wall of the reservoir 260 and may measure the temperature of the ink IK contained in the reservoir 260. The temperature sensor 262 may be connected to the control section 300, and the control section 300 may receive the ink temperature data T measured by the temperature sensor 262. The temperature sensor 262 may measure the temperature change of the ink IK supplied to the nozzle 240 during the entire printing process on the substrate S. The control section 300 may calculate a temporal temperature gradient (i.e., the time-series temperature change of the entire area) of the ink IK supplied to the nozzle 240 when ejecting droplets DR along the scan lines of the substrate S during the printing process based on the temperature change data.

[0068] For example, in order to form a thick film having a large thickness on the entire surface of the substrate S, one nozzle 240 may eject 10 cubic centimeters or more of the ink IK. Therefore, since the amount of ink in the ink chamber 246 of the nozzle 240 is insufficient during the printing of the substrate S, the reservoir 260 may supply the ink IK to the ink chamber 246 of the nozzle 240. A heater may be installed in the reservoir 260 to maintain the temperature of the ink IK inside the reservoir 260 at a constant temperature. For example, the temperature of the ink IK inside the reservoir 260 may be maintained at 36°C. However, as the printing progresses, the temperature of the ink IK inside the reservoir 260 may gradually decrease to 35°C or lower. As the temperature of the ink IK gradually decreases, the viscosity of the ink IK may increase, such that even when a voltage signal of the same waveform is applied to the piezoelectric element 242 of the nozzle 240, the discharge amount of the droplets ejected from the nozzle 240 may decrease. That is, although the diaphragm 244 is deformed to the same size by a preset voltage signal, the discharge amount of the droplets DR ejected through the ejection port 248 of the ink chamber 246 may decrease due to the increase in viscosity. Therefore, as the printing progresses, the thickness of the thick film formed on the substrate S may gradually decrease.

[0069] The control section 300 can determine the discharge amount for each of the grids corresponding to the entire area of the substrate S based on the discharge amount difference according to the time-series temperature change of the ink IK inside the liquid reservoir 260, create a droplet map based on the discharge amount for each grid, and adjust the control signal CS for controlling the nozzle 240 according to the droplet map.

[0070] Hereinafter, the operation of the control section for adjusting the control signal for controlling the discharge amount of the nozzle will be described.

[0071] Figure 8 is a diagram showing Figure 1 a block diagram of the control section of the droplet discharge device. Figure 9 is a plan view showing a grid map corresponding to the entire area of the substrate and nozzles corresponding to the grids of the grid map. Figure 10 is a view showing a droplet map for discharging ink having a discharge amount for each grid. Figure 11A 、 Figure 11B and Figure 11C are respectively graphs showing the voltage waveforms of the control signals output from the control section according to the Figure 10 droplet map. Figure 12 is a view showing a dot pattern discharged from the nozzle according to the Figure 10 droplet map.

[0072] Referring to Figures 8 to 12 , the control section 300 of the droplet discharge device 10 can include a grid map determination section 310, a droplet map determination section 320, and an ejection driver 330.

[0073] Specifically, the grid map determination section 310 can create a grid map BM having a plurality of grids G corresponding to the entire area of the substrate S. The substrate S can be divided into rectangular regions (i.e., grids G) having two sides parallel to the row direction and two sides parallel to the column direction. At this time, the position of each grid can be represented by unique coordinates according to the order in the row direction and the column direction.

[0074] As Figure 9 shown, each of the nozzles 240 in the head assembly 210 can be assigned to each of the grids G arranged in a row in the grid map BM. When the head assembly 210 is at a predetermined position above the substrate S, the plurality of nozzles 240 can correspond to predetermined coordinates on the grid map BM. When the head assembly 210 moves along the scan line on the substrate S, the nozzles 240 can independently (e.g., sequentially or simultaneously) discharge droplets DR onto the areas of the substrate S, which areas of the substrate S respectively correspond to the grids G arranged in a row. The column direction can correspond to the scan direction, and when the head assembly 210 moves along a plurality of scan lines, the grid map BM can include a plurality of sub-grid maps corresponding to each of the plurality of scan lines.

[0075] The droplet pattern determination unit 320 can determine the discharge amount for each grid based on the discharge amount difference according to the temperature change of the ink IK to be supplied to the nozzle 240, and create a droplet pattern for discharging the ink with the discharge amount for each grid. The droplet pattern determination unit 320 can receive the temperature data T of the ink IK inside the reservoir 260 from the temperature sensor 262, and calculate the sequential temperature gradient of the ink IK supplied to the nozzle 240 during the entire printing process of the substrate S. The droplet pattern determination unit 320 can calculate the ink discharge amount difference of the nozzle 240 according to the sequential temperature gradient of the ink IK inside the reservoir 260, determine the discharge amount for each grid based on the calculated ink discharge amount difference, and create a droplet pattern according to the discharge amount for each grid.

[0076] According to the scanning order of the nozzle 240 in accordance with the grid map BM, the head assembly 210 can discharge the first droplet in the first region of the substrate S at the first time point, and discharge the second droplet in the second region of the substrate S at the second time point after the first time. The droplet pattern determination unit 320 can compare the first temperature of the ink IK received in the nozzle 240 when the first droplet is ejected in the first region and the second temperature of the ink IK received in the nozzle 240 when the second droplet is ejected in the second region. The droplet pattern determination unit 320 can perform the temperature change from the first temperature to the second temperature for the entire grid map BM to calculate the sequential temperature gradient of the ink IK for each grid. When the second temperature is determined to be lower than the first temperature, the droplet pattern determination unit 320 can determine the discharge amount for the grid by considering the increase in the ink viscosity due to the temperature decrease, such that the ink discharge amount in the second region is greater than the ink discharge amount in the first region, and can create a droplet pattern according to the discharge amount for each grid.

[0077] As Figure 10 shown, the droplet pattern can indicate the discharge timing and the ink discharge amount of each designated nozzle 240 in the grid. The droplet pattern can be a grayscale bitmap indicating the control signal corresponding to each grid output to the nozzle 240. In the droplet pattern, each grid can indicate the data of the control signal to be output to the corresponding nozzle 240. For example, when the data of the control signal has 2-bit data, "1" can be output as the signal for outputting the first control signal, "2 (binary 10)" can be output as the signal for outputting the second control signal, and "3 (binary 11)" can be output as the signal for outputting the third control signal. That is, when the output data has 2-bit data, 4 control signals can be generated. When the data of the control signal has 3-bit data, 8 control signals can be generated.

[0078] The ejection driver 330 may output a control signal CS to the piezoelectric element 242 of the nozzle 240 corresponding to each grid according to the droplet pattern.

[0079] As Figure 11A , Figure 11B and Figure 11C shown in, the ejection driver 330 may output a first control signal, a second control signal, and a third control signal corresponding to 2-bit control signal data. As Figure 11A shown in, the first control signal may be a unit pulse of one cycle including alternating pulses of a positive (+) waveform and a negative (-) waveform. As Figure 11B shown in, the second control signal may include two different unit pulses. As Figure 11C shown in, the third control signal may include three different unit pulses. It will be understood that the voltage waveforms of the first control signal to the third control signal are not limited thereto.

[0080] The nozzle 240 may form a dot pattern by ejecting droplets DR onto a corresponding area of the substrate S corresponding to each grid G in response to the control signal CS from the ejection driver 330.

[0081] As Figure 12 shown in, the nozzle 240 may eject droplets DR having a first discharge amount in response to the first control signal to form a first dot pattern DP1 on the substrate S, eject droplets DR having a second discharge amount in response to the second control signal to form a second dot pattern DP2 on the substrate S, and eject droplets DR having a third discharge amount in response to the third control signal to form a third dot pattern DP3 on the substrate S.

[0082] When the temperature of the ink IK in the reservoir 260 remains constant as the printing time of the substrate S elapses, the second discharge amount may be greater than the first discharge amount, and the third discharge amount may be greater than the second discharge amount. In this case, the thickness of the second dot pattern DP2 may be greater than the thickness of the first dot pattern DP1, and the thickness of the third dot pattern DP3 may be greater than the thickness of the second dot pattern DP2.

[0083] In other words, when the temperature of the ink IK in the reservoir 260 gradually decreases as the printing time of the substrate S elapses, the viscosity of the ink IK may gradually increase, so that the first discharge amount actually ejected from the nozzle 240 in response to the first control signal may be equal to the second discharge amount actually ejected from the nozzle 240 in response to the second control signal, and the third discharge amount actually ejected from the nozzle 240 in response to the third control signal may be equal to the second discharge amount. In this case, the thickness of the second dot pattern DP2 may be equal to the thickness of the first dot pattern DP1, and the thickness of the third dot pattern DP3 may be equal to the thickness of the second dot pattern DP2.

[0084] As described above, when creating a droplet map for discharging droplets DR to a first region of a substrate S through a nozzle 240 of a head assembly 210 and for discharging droplets DR to a second region of the substrate S after a first time has elapsed, a first temperature of ink IK received in the nozzle 240 when discharging to the first region and a second temperature of ink IK received in the nozzle 240 when discharging to the second region can be compared. When the second temperature is determined to be lower than the first temperature, considering an increase in the viscosity of the ink due to the temperature decrease, the waveform of a control signal can be adjusted such that the amount of ink discharged in the second region is greater than the amount of ink discharged in the first region.

[0085] Accordingly, even if the temperature of the ink IK in a reservoir 260 for supplying the ink IK to the nozzle 240 cannot be increased to a desired temperature, the waveform of the control signal can be adjusted to discharge droplets having a relatively large discharge amount. Accordingly, even if the temperature of the ink IK supplied to the nozzle 240 gradually decreases as printing time elapses, the discharge amounts of the droplets DR sequentially discharged from the nozzle 240 onto the substrate S can be kept constant, thereby forming a thick film having a uniform thickness over the entire region of the substrate S.

[0086] Figure 13A is a view showing a stripe pattern discharged from a nozzle according to a droplet map according to an exemplary embodiment. Figure 13B is a view showing a Figure 13A thick film pattern formed by the stripe pattern.

[0087] Referring to Figure 13A and Figure 13B , in a case where the head assembly 210 sequentially moves along a first scan line SL1, a second scan line SL2, and a third scan line SL3, a first stripe pattern SW1 can be discharged to a first region of the substrate S along the first scan line SL1 through the nozzle 240 of the head assembly 210, and after a first time has elapsed, a second stripe pattern SW2 can be discharged to a second region of the substrate S along the second scan line SL2, and after a second time has elapsed, a third stripe pattern SW3 can be discharged to a third region of the substrate S along the third scan line SL3.

[0088] In this case, the grid diagram may include a first sub-grid diagram, a second sub-grid diagram, and a third sub-grid diagram corresponding to the first scan line SL1, the second scan line SL2, and the third scan line SL3 respectively, and the ink droplet diagram may include a first sub-ink droplet diagram, a second sub-ink droplet diagram, and a third sub-ink droplet diagram corresponding to the first sub-grid diagram, the second sub-grid diagram, and the third sub-grid diagram respectively. The nozzles 240 of the head assembly 210 may eject a first stripe pattern SW1 according to the first sub-ink droplet diagram, a second stripe pattern SW2 according to the second sub-ink droplet diagram, and a third stripe pattern SW3 according to the third sub-ink droplet diagram.

[0089] The first temperature of the ink IK contained in the nozzle 240 when ejected in the first region, the second temperature of the ink IK contained in the nozzle 240 when ejected in the second region, and the third temperature of the ink IK contained in the nozzle 240 when ejected in the third region may be compared with each other.

[0090] When it is determined that the second temperature is lower than the first temperature and the third temperature is lower than the second temperature, the grids in the first sub-ink droplet diagram may have first control signal data for ejecting a first ink ejection amount, the grids in the second sub-ink droplet diagram may have second control signal data for ejecting a second ink ejection amount greater than the first ink ejection amount, and the grids in the third sub-ink droplet diagram may have third control signal data for ejecting a third ink ejection amount greater than the second ink ejection amount.

[0091] Due to the increase in the viscosity of the ink caused by the decrease in temperature, the thickness of each of the second dot patterns DP2 in the second stripe pattern SW2 ejected according to the second sub-ink droplet diagram may be the same as the thickness of each of the first dot patterns DP1 in the first stripe pattern SW1 ejected according to the first sub-ink droplet diagram, and the thickness of each of the third dot patterns DP3 in the third stripe pattern SW3 ejected according to the third sub-ink droplet diagram may be the same as the thickness of each of the second dot patterns DP2 in the second stripe pattern SW2 ejected according to the second sub-ink droplet diagram.

[0092] Therefore, the thickness of the first thick film pattern PT1 formed by the first stripe pattern SW1, the thickness of the second thick film pattern PT2 formed by the second stripe pattern SW2, and the thickness of the third thick film pattern PT3 formed by the third stripe pattern SW3 may be the same as each other.

[0093] In other words, even if it is determined that the second temperature is lower than the first temperature and the third temperature is lower than the second temperature, when all the grids in the grid of the first sub-droplet pattern, the grid of the second sub-droplet pattern, and the grid of the third sub-droplet pattern have the same first control signal data, due to the increase in the ink viscosity according to the decrease in temperature, the thickness of the second thick film pattern PT2' formed by the second strip pattern SW2 may be smaller than the thickness of the first thick film pattern PT1' formed by the first strip pattern SW1, and the thickness of the third thick film pattern PT3' formed by the third strip pattern SW3 may be smaller than the thickness of the second thick film pattern PT2' formed by the second strip pattern SW2.

[0094] Figure 14 is a view showing a strip pattern discharged from a nozzle according to a droplet pattern according to an exemplary embodiment.

[0095] Reference Figure 14 , when the head assembly 210 moves along a scan line SL, a strip pattern can be ejected through the nozzles 240 of the head assembly 210 according to the droplet pattern. Droplets DR can be discharged to a first area of the substrate S through the nozzles 240 of the head assembly 210, and after a first time, droplets DR can be discharged to a second area of the substrate S, and after a second time, droplets DR can be ejected to a third area of the substrate S.

[0096] In this case, the grid map can include a first set of grids corresponding to the first area, a second set of grids corresponding to the second area, and a third set of grids corresponding to the third area.

[0097] When it is determined that the second temperature of the ink IK accommodated in the nozzle 240 when discharged in the second area is lower than the first temperature of the ink IK accommodated in the nozzle 240 when discharged in the first area, and the third temperature of the ink IK accommodated in the nozzle 240 when discharged in the third area is lower than the second temperature, the first set of grids in the droplet pattern can have first control signal data for discharging a first ink discharge amount, the second set of grids can have second control signal data for discharging a second ink discharge amount greater than the first ink discharge amount, and the third set of grids can have third control signal data for discharging a third ink discharge amount greater than the second ink discharge amount.

[0098] Due to the increase in the ink viscosity caused by the decrease in temperature, the dot patterns of the strip pattern ejected according to the droplet pattern can have the same thickness. Therefore, the thick film pattern formed by the strip pattern can have a uniform thickness.

[0099] Hereinafter, a method of discharging droplets onto a substrate using Figure 1 the droplet discharging device will be described.

[0100] Figure 15 is a flowchart showing a droplet ejection method according to an exemplary embodiment.

[0101] Referring Figures 1 to 15 , first, the substrate S may be divided into a plurality of meshes (S10), and the nozzles 240 of the head assembly 210 may be designated to correspond to the plurality of meshes, respectively (S20).

[0102] In an exemplary embodiment, in order to perform an inkjet printing process, the substrate S may be placed on the pair of holders 110a, 110b, and the substrate S may be moved to an initial position below the stage 250 of the droplet ejection section 200. Then, the head assembly 210 may be moved to the initial position along the guide 252 of the stage 250.

[0103] Since the scanning width covered by the nozzles 240 of the head assembly 210 is smaller than the width of the substrate S, the head assembly 210 may be controlled to move along a plurality of scan lines in order to print the entire surface of the substrate S.

[0104] As Figure 8 and Figure 9 shown, the mesh map determination section 310 of the control section 300 may create a mesh map BM having a plurality of meshes G corresponding to a region (i.e., the entire region of the substrate S). Each of the nozzles 240 of the head assembly 210 may be assigned to each of the meshes G arranged in a row in the mesh map BM. When the head assembly 210 is at a predetermined position above the substrate S, the plurality of nozzles 240 may correspond to predetermined coordinates on the mesh map BM. When the head assembly 210 moves along the scan line on the substrate S, the nozzles 240 may independently (sequentially or simultaneously) eject droplets DR onto the regions of the substrate S that correspond to the meshes G arranged in a row, respectively.

[0105] Then, the ejection amount for each mesh may be determined based on the difference in the ejection amount caused by the temperature change of the ink IK to be ejected from the nozzles 240 (S30), and a droplet map for ejecting the ink IK having the ejection amount for each mesh may be created (S40).

[0106] In an exemplary embodiment, the droplet pattern determination part 320 of the control part 300 may receive the temperature data T of the ink IK inside the reservoir 260 from the temperature sensor 262, and may calculate the sequential temperature gradient of the ink IK supplied to the nozzle 240 during the entire printing process of the substrate S. The droplet pattern determination part 320 may calculate the difference in the ink discharge amount of the nozzle 240 based on the sequential temperature gradient of the ink IK inside the reservoir 260, determine the discharge amount for each grid based on the calculated difference in the ink discharge amount, and may create a droplet pattern according to the discharge amount for each grid.

[0107] According to the scanning order of the nozzle 240 in accordance with the grid map BM, the head assembly 210 may discharge droplets DR to the first area of the substrate S, and after a first period of time, discharge droplets DR to the second area of the substrate S. The droplet pattern determination part 320 may compare the first temperature of the ink IK received in the first nozzle when discharging droplets DR to the first area and the second temperature of the ink IK received in the second nozzle when discharging droplets DR to the second area. The second nozzle may be the same as or different from the first nozzle. The droplet pattern determination part 320 may perform the temperature change from the first temperature to the second temperature for the entire grid map BM to calculate the sequential temperature gradient of the ink IK for each grid. When the droplet pattern determination part 320 determines that the second temperature is lower than the first temperature, the droplet pattern determination part 320 may determine the discharge amount for each grid by considering the increase in the ink viscosity caused by the temperature decrease, such that the ink discharge amount in the second area is greater than the ink discharge amount in the first area, and may create a droplet pattern according to the discharge amount for each grid.

[0108] The droplet pattern may be represented by the ink discharge amount of each designated nozzle 240 in the grid. The droplet pattern may be a grayscale bitmap representing the control signal corresponding to each grid output to the nozzle 240. In the droplet pattern, each grid may represent the data of the control signal output to the corresponding nozzle 240. For example, if the data of the control signal has 2-bit data, "1" may be output as the signal for outputting the first control signal, "2 (binary 10)" may be output as the signal for outputting the second control signal, and "3 (binary 11)" may be output as the signal for outputting the third control signal. That is, if the output data represents 2-bit data, four control signals may be generated.

[0109] Then, the ink IK may be discharged through the nozzle 240 of the head assembly 210 according to the droplet pattern (S50).

[0110] In an exemplary embodiment, the ejection driver 330 of the control part 300 may output a control signal CS to the piezoelectric element 242 corresponding to each grid of the nozzle 240 according to the droplet pattern.

[0111] For example, the nozzle 240 may eject droplets DR having a first ejection amount in response to a first control signal to form a first dot pattern DP1 on the substrate S, eject droplets DR having a second ejection amount in response to a second control signal to form a second dot pattern DP2 on the substrate S, and eject droplets DR having a third ejection amount in response to a third control signal to form a third dot pattern DP3 on the substrate S. As the printing process time of the substrate S elapses and the temperature of the ink IK in the reservoir 260 gradually decreases, the viscosity of the ink IK may gradually increase, such that the first ejection amount actually ejected from the nozzle 240 in response to the first control signal may be equal to the second ejection amount actually ejected from the nozzle 240 in response to the second control signal, and the third ejection amount actually ejected from the nozzle 240 in response to the third control signal may be equal to the second ejection amount. In this case, the thickness of the second dot pattern DP2 may be equal to the thickness of the first dot pattern DP1, and the thickness of the third dot pattern DP3 may be equal to the thickness of the second dot pattern DP2.

[0112] Accordingly, even during a single printing over the entire area of the substrate S, even if the temperature of the ink IK in the reservoir 260 that supplies the ink IK to the nozzle 240 cannot be raised to a desired temperature, the waveform of the control signal can be adjusted to eject droplets having a relatively large ejection amount. Accordingly, a thick film having a uniform thickness can be formed over the entire area of the substrate S.

[0113] Then, the substrate S on which the droplets are ejected may be moved to a droplet curing section, and the droplet curing section may cure the droplets ejected onto the substrate S. For example, the droplet curing section may include a light irradiation unit configured to irradiate the droplets with light.

[0114] Although the exemplary embodiments of the present disclosure have been described above, those of ordinary skill in the art will understand that various modifications and changes can be made to the present disclosure without departing from the spirit and scope of the present disclosure set forth in the appended claims.

Claims

1. A droplet discharge method comprising: determining a scanning order of nozzles of the inkjet head to correspond to the substrate; supplying ink from a reservoir to the nozzles of the inkjet head; as well as discharging droplets through the nozzles corresponding to the first and second regions of the substrate according to the scanning sequence to form a film having a predetermined thickness on the substrate, Wherein, discharging the droplets comprises: comparing a first temperature of ink supplied to a first nozzle of the nozzles when a first droplet is discharged on the first area of ​​the substrate and a second temperature of ink supplied to a second nozzle of the nozzles when a second droplet is discharged on the second area of ​​the substrate; and When the second temperature is lower than the first temperature, a first control signal is output to the first nozzle for discharging the first liquid droplet at a first discharge amount, and a second control signal is output to the second nozzle for discharging the second liquid droplet at a second discharge amount greater than the first discharge amount.

2. The liquid droplet discharge method according to claim 1, wherein: Determining the scanning order of the nozzles includes: determining a plurality of grids corresponding to the entire area of ​​the substrate; and The scanning order of the nozzles is specified for each of the plurality of grids.

3. The liquid droplet discharge method according to claim 2, wherein: Comparing the first temperature and the second temperature includes: performing a temperature change from the first temperature to the second temperature on the entire grid to calculate a temporal temperature gradient of the ink for each grid; Calculating the discharge amount for each grid based on the change in ink viscosity according to the time-series temperature gradient; and An ink drop map for discharging ink having the discharge amount for each mesh is created.

4. The liquid droplet discharge method according to claim 3, wherein: The ink drop map has control signal data output to the nozzles respectively designated for the grids.

5. The droplet discharge method according to claim 4, wherein: Outputting the first control signal and the second control signal includes outputting the first control signal and the second control signal corresponding to the control signal data to the first nozzle and the second nozzle, respectively.

6. The liquid droplet discharge method according to claim 4, wherein: When the control signal data of the ink droplet pattern represents 2-bit data, four different control signals corresponding to the control signal data are generated.

7. The liquid droplet discharge method according to claim 1, wherein: Comparing the first temperature and the second temperature includes detecting a temperature of ink in the reservoir.

8. The liquid droplet discharge method according to claim 1, wherein: The discharge amount of the droplets discharged on the substrate through the first nozzle according to the first control signal is the same as the discharge amount of the droplets discharged on the substrate through the second nozzle according to the second control signal.

9. The liquid droplet discharge method according to claim 1, wherein: The thickness of the film is in the range of 100 μm to 150 μm.

10. A droplet discharge method comprising: providing a plurality of grids corresponding to regions of the substrate; determining a discharge amount for each mesh based on a difference in discharge amount according to a change in temperature of ink to be discharged from nozzles respectively designated for the plurality of meshes; creating an ink drop map for discharging ink having the discharge amount for each grid; as well as Liquid droplets are discharged through the nozzles according to the ink drop pattern to form a film having a predetermined thickness on the substrate.

11. The liquid droplet discharge method according to claim 10, wherein: Setting the plurality of grids comprises: dividing the substrate into a plurality of scan lines; and A plurality of sub-grid images are set corresponding to the plurality of scan lines respectively.

12. The liquid droplet discharge method according to claim 10, wherein: Determining the discharge amount for each grid includes detecting a temperature of ink in a reservoir that supplies the ink to the nozzles.

13. The liquid droplet discharge method according to claim 10, wherein: Determining the discharge amount for each grid includes: When a first droplet is discharged in a first region of the substrate at a first time point according to a scanning order of the nozzle, and a second droplet is discharged in a second region of the substrate at a second time point after a first time has passed, comparing a first temperature of the ink received in the nozzle when the first droplet is discharged in the first region and a second temperature of the ink received in the nozzle when the second droplet is discharged in the second region; performing a temperature change from the first temperature to the second temperature on the plurality of grids to calculate a temporal temperature gradient of the ink for each grid; and The discharge amount for each mesh is calculated based on the change in ink viscosity according to the time-series temperature gradient.

14. The liquid droplet discharge method according to claim 10, wherein: The ink drop map has control signal data output to the nozzles respectively designated for the grids.

15. The liquid droplet discharge method according to claim 14, wherein: Discharging the droplets through the nozzles according to the droplet map includes outputting at least two different control signals corresponding to the control signal data to the nozzles corresponding to the grid.

16. The liquid droplet discharge method according to claim 10, wherein: The discharge amounts of the droplets respectively discharged on the substrate through the nozzles according to the droplet pattern are identical to each other.

17. The liquid droplet discharge method according to claim 10, wherein: The thickness of the film is in the range of 100 μm to 150 μm.

18. A method for discharging a droplet, comprising: providing a plurality of grids corresponding to regions of the substrate; determining a scanning order of nozzles for the plurality of grids; obtaining a first temperature of the ink received in the nozzle when a first droplet is discharged in a first region of the substrate at a first time point according to the scanning order of the nozzle, and a second temperature of the ink received in the nozzle when a second droplet is discharged in a second region of the substrate at a second time point after the first time has passed; performing a temperature change from the first temperature to the second temperature on the entire grid to calculate a temporal temperature gradient of the ink for each grid; Calculating the discharge amount for each grid based on the change in ink viscosity according to the time series temperature gradient; creating an ink drop map for discharging ink having the discharge amount for each grid; as well as Liquid droplets are discharged through the nozzles according to the ink drop pattern to form a film having a predetermined thickness on the substrate.

19. The liquid droplet discharge method according to claim 18, wherein: Obtaining the first temperature and the second temperature includes detecting a temperature of ink in a reservoir that supplies the ink to the nozzle.

20. The liquid droplet discharge method according to claim 18, wherein: The discharge amounts of the droplets respectively discharged on the substrate through the nozzles according to the droplet pattern are identical to each other.

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