Inkjet printing method and device

Abstract

The present invention provides an inkjet printing method for discharging ink onto a substrate using a nozzle formed with a plurality of nozzles, comprising: a grading step in which the grades of the nozzles are determined by measuring the discharge performance of the nozzles; a nozzle selecting step in which available nozzles that can participate in printing on the substrate are selected from the nozzles based on the grades determined in the grading step; and a printing step in which the ink is discharged onto the substrate using at least one of the available nozzles.

Description

Technical Field

[0001] Embodiments of the inventive concepts described herein relate to an inkjet printing method and an inkjet printing apparatus. Background Art

[0002] Recently, there has been a need to manufacture display devices, such as liquid crystal display devices and organic electroluminescent (EL) display devices, with high resolution. In order to manufacture display devices with high resolution, more pixels should be formed per unit area on a substrate (e.g., glass), and it is important to discharge ink droplets at precise positions on each densely arranged pixel. However, there is a deviation in discharge performance between nozzles of an ink droplet discharge head. This deviation in discharge performance makes it difficult to accurately control the landing position of ink droplets discharged from the nozzles.

[0003] In addition, if a plurality of ink droplets are discharged from the nozzle with low discharge performance (for example, the target position (i.e., the target point at which the nozzle is aimed for discharge) is significantly different from the actual landing position of the ink droplets), the plurality of ink droplets discharged onto the substrate are far from the target position. This reduces the quality of the display device. Summary of the invention

[0004] Embodiments of the inventive concept provide an inkjet printing method and an inkjet printing apparatus capable of efficiently performing a printing process on a substrate.

[0005] Embodiments of the inventive concept provide an inkjet printing method and an inkjet printing apparatus capable of appropriately discharging ink in the form of droplets at desired locations.

[0006] Embodiments of the inventive concept provide an inkjet printing method and an inkjet printing apparatus capable of improving the discharge quality of ink while preventing an increase in the time for performing a printing process on a substrate.

[0007] The technical objectives of the present invention are not limited to the above-mentioned technical objectives, and those skilled in the art will understand other technical objectives not mentioned according to the following description.

[0008] The present invention provides an inkjet printing method for discharging ink onto a substrate using a nozzle formed with a plurality of nozzles. The inkjet printing method includes: a grading step in which the grading of the nozzles is determined by measuring the discharge performance of the nozzles; a nozzle selecting step in which an available nozzle capable of participating in printing on the substrate is selected from among the nozzles based on the grading determined in the grading step; and a printing step in which the ink is discharged onto the substrate using at least one of the available nozzles.

[0009] In one embodiment, in the printing step, nozzles having high ranks determined in the grading step among the available nozzles are preferentially allowed to participate in printing.

[0010] In one embodiment, in the nozzle selection step, deactivated nozzles that are excluded from printing on the substrate are selected from among the nozzles based on the grades determined in the ranking step, and the remaining nozzles are selected as available nozzles.

[0011] In one embodiment, in order to select the deactivated nozzle in the nozzle selecting step, a nozzle having a grade lower than a reference grade is selected as the deactivated nozzle.

[0012] In one embodiment, the printing step is performed a plurality of times, and the grading step and the nozzle selecting step are performed between the printing steps.

[0013] In one embodiment, the classification step and the nozzle selection step are performed multiple times.

[0014] In one embodiment, in the nozzle selection step, if a set condition is satisfied, the nozzle selected as the deactivated nozzle is converted into the usable nozzle.

[0015] In one embodiment, the set condition is that if the deactivated nozzle participates in the printing step, a recovery probability that the deactivated nozzle will perform printing on the substrate with a quality of a reference level or higher is equal to or higher than a set probability.

[0016] In one embodiment, the restoration probability is obtained by comparing pre-acquired reference data and grade data of the nozzle selected as the deactivated nozzle, and the grade data is data about the grade determined for the nozzle selected as the deactivated nozzle by performing the classification step a plurality of times.

[0017] In one embodiment, the grading step further includes: a test discharge step, in which each of the nozzles discharges the ink onto the test component at least once; and an extraction step for extracting characteristic data of each of the nozzles based on the landing point of the ink discharged onto the test component.

[0018] In one embodiment, the extraction step is performed multiple times, and the extraction step further includes: a normalization step for normalizing the feature data extracted in the extraction step.

[0019] In one embodiment, the grading step also includes a grade determination step for determining the grade of the nozzle, and obtaining evaluation data for evaluating the grade of each nozzle based on normalized feature data, and determining the grade of the nozzle based on a segment in which a rate of change of the obtained evaluation data exceeds a set value.

[0020] The present invention is conceived to provide an inkjet printing device. The inkjet printing device includes: a printing unit for performing printing by discharging ink onto a substrate; a maintenance unit positioned side by side with the printing unit; a nozzle configured to be movable between the printing unit and the maintenance unit and having a plurality of nozzles formed thereon; a measuring unit positioned at the maintenance unit and measuring the discharge performance of the nozzle; and a controller receiving measurement data measured by the measuring unit and controlling the nozzle based on the measurement data; and wherein the controller determines the discharge performance of the nozzle based on the measurement data, determines the grade of the nozzle, selects an available nozzle capable of participating in substrate printing in the printing unit based on the grade, and generates a control signal so that the nozzle can use at least one nozzle among the available nozzles to discharge the ink onto the substrate.

[0021] In one embodiment, the controller generates a control signal to preferentially allow nozzles having a high ranking among the available nozzles to participate in printing on the substrate.

[0022] In one embodiment, the controller selects deactivated nozzles to be excluded from printing on the substrate from among the nozzles based on the ranking, and selects the remaining nozzles as the available nozzles.

[0023] In one embodiment, the controller selects nozzles having a level lower than a reference level as the deactivated nozzles, and converts nozzles having a recovery probability equal to or greater than a set probability among the nozzles selected as the deactivated nozzles based on pre-stored reference data, wherein the recovery probability is the probability that the substrate will be printed with a quality equal to or higher than the reference level if the nozzle selected as the deactivated nozzle participates in printing the substrate.

[0024] In one embodiment, the reference data stored at the controller includes information of the level that varies according to a plurality of discharge processes of ink jets performed through the nozzles.

[0025] The present invention conceives to provide an inkjet printing method for discharging ink onto a substrate using a nozzle having a plurality of nozzles formed thereon, the inkjet printing method comprising: a grading step, wherein the grade of the nozzle is determined by measuring the discharge performance of the nozzle; a nozzle selection step, wherein available nozzles capable of participating in printing on the substrate are selected from among the nozzles based on the grade determined in the grading step; and a printing step, wherein the ink is discharged onto the substrate using at least one of the available nozzles, wherein the nozzles among the available nozzles with a high grade determined in the grading step are preferentially allowed to participate in printing.

[0026] In one embodiment, the grading step, the nozzle selecting step and the printing step are performed multiple times, and each time the grading step is performed, the grade of each nozzle is re-evaluated.

[0027] In one embodiment, the grading step, the nozzle selecting step and the printing step are performed multiple times, and the selection of the available nozzles is performed each time the nozzle selecting step is performed.

[0028] According to embodiments of the inventive concept, a printing process on a substrate can be efficiently performed.

[0029] According to embodiments of the inventive concept, ink in the form of droplets can be appropriately discharged at desired locations.

[0030] According to embodiments of the inventive concept, it is possible to improve the discharge quality of ink while preventing the time for performing a printing process on a substrate from increasing.

[0031] The effects of the present inventive concept are not limited to the effects described above, and other effects not mentioned will be apparent to those skilled in the art from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects will be apparent from the following description made with reference to the accompanying drawings, wherein like reference numerals refer to like parts throughout the various drawings unless otherwise specified, and wherein:

[0033] Figure 1 A substrate processing apparatus according to an embodiment of the inventive concept is illustrated.

[0034] Figure 2 Shown in Figure 1 An embodiment of a nozzle formed on a head is shown in FIG.

[0035] Figure 3 is a flowchart illustrating an inkjet printing method according to an embodiment of the inventive concept.

[0036] Figure 4 yes Figure 3 Detailed flow chart of the grading steps.

[0037] Figure 5 Shown in Figure 4 An embodiment of the feature data extracted in the extraction step.

[0038] Figure 6 Shown in Figure 4 Another embodiment of the feature data extracted in the extraction step.

[0039] Figure 7 Shown in Figure 4Another embodiment of the feature data extracted in the extraction step.

[0040] Figure 8 is used to describe Figure 4 A diagram of the method of determining nozzle grades in the grade determination step of FIG. DETAILED DESCRIPTION

[0041] The inventive concept may be modified in different ways and may have different forms, and specific embodiments thereof will be shown in the accompanying drawings and described in detail. However, the embodiments according to the inventive concept are not intended to limit the specific forms disclosed, and it should be understood that the inventive concept includes all variations, equivalents, and substitutions contained within the spirit of the technical scope of the inventive concept. In the description of the inventive concept, detailed descriptions of related known technologies are omitted when the substantive content of the inventive concept becomes unclear.

[0042] The terms used herein are only used to describe specific embodiments and are not intended to limit the inventive concept. As used herein, when no quantity is specified, it is intended to also include a plurality of cases, unless the context clearly indicates otherwise. It should also be understood that the use of the words "include" and / or "comprise" in this specification indicates the presence of the recorded features, wholes, steps, operations, elements and / or parts, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, parts and / or combinations thereof. As used herein, the word "and / or" includes any or all combinations of one or more of the associated enumerated items. Hedgehog, the word "example" is intended to indicate an example or illustration.

[0043] It should be understood that although the words "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections are not limited by these words. These words are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Therefore, the first element, component, region, layer or section discussed below may also be referred to as the second element, component, region, layer or section without departing from the teachings of the present inventive concept.

[0044] It should be understood that when an element or layer is referred to as being "connected," "coupled," or "covering" another element or layer or "on it," it may be directly connected, coupled, or covering the other element or layer or on it, or there may be intermediate elements or layers. Conversely, when an element or layer is referred to as being "directly connected," "directly coupled," or "directly on it," there are no intermediate elements or layers. Other terms such as "between," "adjacent," "near," etc. should be understood in the same manner.

[0045] All terms used herein, including technical or scientific terms, have the same meaning as those generally understood by those skilled in the art to which the inventive concept belongs, unless they are defined differently. Terms, such as those defined in commonly used dictionaries, should be interpreted as being consistent with the context of the relevant technology, and should not be interpreted as ideal or overly formal meanings unless they are clearly defined in this application.

[0046] In the following, reference will be made to Figures 1 to 8 Embodiments of the inventive concept are described.

[0047] Figure 1 A substrate processing apparatus according to an embodiment of the inventive concept is illustrated.

[0048] refer to Figure 1 , a substrate processing device according to an embodiment of the inventive concept may be an inkjet printing device that processes a substrate S by supplying ink in the form of droplets onto the substrate. The substrate S may be glass. The substrate S may be a glass substrate for manufacturing a display device. However, the type of the substrate S is not limited thereto, and may be modified in various forms to be a known object to be processed that requires supply of droplet-type ink.

[0049] The inkjet printing device may include a printing unit 10 , a maintenance unit 30 , an ink supply unit 50 , and a controller 70 .

[0050] The printing unit 10 may perform a printing process on the substrate S. In the printing unit 10, the ink supply unit 50 described below may be an area for performing a printing process by supplying ink in the form of droplets to the top surface of the substrate S. The printing unit 10 may include a printing table 100 and a moving member 110. The printing table 100 may define an area in which the substrate S is processed. In addition, the printing table 100 may be provided with an air supply pipe (not shown) that supplies air to the bottom surface of the substrate S to float the substrate S, and an exhaust pipe (not shown) that absorbs a portion of the air supplied by the air supply pipe. The printing table 100 may be used as a floating table for floating the substrate S.

[0051] The substrate S floated by the air supplied at the printing table 100 may be gripped by the moving member 110. The moving member 110 may grip one side and / or the other side of the substrate S. The moving member 110 may grip one side and / or the other side of the substrate S in a vacuum adsorption manner. The moving member 110 may move the substrate S in a direction in which the printing table 100 extends. The moving member 110 may be referred to as a clamp.

[0052] When viewed from above, the maintenance unit 30 may be arranged side by side with the printing unit 10. The maintenance unit 30 may perform maintenance on the nozzle unit 510 of the inkjet unit 50 to be described below. In addition, the maintenance unit 30 may measure the state of the nozzle unit 510. Furthermore, in the maintenance unit 30, a test discharge of the nozzle H included in the nozzle unit 510 may be performed to measure the discharge performance of the nozzle N.

[0053] Since the nozzle unit 510 may discharge ink for correcting a landing position of the discharged ink, adjusting a volume of ink, controlling an ink discharge amount, etc., the maintenance unit 30 may have the same or similar process environment as the printing unit 10 .

[0054] The maintenance unit 30 may include a maintenance station 300 and a measuring unit 310. The maintenance station 300 may have the same or similar structure as the printing station 100 described above, and, although not shown, may also be provided with a moving member having the same or similar structure as the moving member 110.

[0055] In addition, the measuring unit 310 may be arranged in the maintenance unit 30. The measuring unit 310 may be arranged to measure the discharge performance of the nozzle N described below. The discharge performance of the nozzle N to be measured by the measuring unit 310 may be, for example, the accuracy of the drop position of the ink discharged from the nozzle N. The accuracy of the drop position increases as the distance from the target position of the ink discharged by each nozzle N decreases. The measuring unit 310 may be a JOF unit capable of supplying a test member TW (e.g., a test film). The measuring unit 310 may supply the test member TW by winding or rolling the test member TW in a roller manner. In addition, the measuring unit 310 may include an image acquisition member such as a camera to acquire an image I associated with the ink discharged to the test member TW, and a light source. The measurement data (e.g., an image I associated with the ink discharged to the test member TW) acquired and measured by the measuring unit 310 may be transmitted to the controller 70 described below.

[0056] The ink supply unit 50 may discharge ink onto the substrate S. The ink supply unit 50 may include a hanger 500 and a nozzle unit 510. The hanger 500 may be installed to span the printing table 100 and the maintenance table 300 when viewed from above. The hanger 500 may provide a moving path through which the nozzle unit 510 may move back and forth between the printing table 100 of the printing unit 10 and the maintenance table 300 of the maintenance unit 30. That is, the nozzle unit 510 may be configured to be able to move between the printing unit 10 and the maintenance unit 30.

[0057] The spray head unit 510 may include a plurality of spray heads H, and a plurality of nozzles N may be formed in each spray head H. Figure 2 Although Figure 2A total of 10 nozzles N from the first nozzle N1 to the tenth nozzle N10 are shown, but the inventive concept is not limited thereto, and the number of nozzles N formed in each nozzle H may be variously changed as needed. For example, the nozzle unit 510 may have about 30,000 nozzles N per color R (red), G (green), and B (blue), thereby having a total of about 90,000 nozzles N.

[0058] Reference again Figure 1 , the controller 70 may control the substrate processing apparatus. The controller 70 may generate a control signal so that the substrate processing apparatus may perform the inkjet printing method described below. The controller 70 may receive measurement data measured by the measurement unit 310, and generate a control signal for controlling the nozzle H of the nozzle unit 510 based on the measurement data.

[0059] In addition, the controller 70 may include one or more processors for performing control of the substrate processing device and a computer program stored in a computer readable medium, which includes instructions for the processor to perform operations to control the substrate processing device. In addition, the controller 70 may include a user interface, including: a keyboard for performing command input operations, etc. to manage the substrate processing device by an operator; or a display for visually displaying the operating status of the substrate processing device. In addition, the user interface and the storage unit may be connected to the processor.

[0060] Figure 3 is a flow chart illustrating an inkjet printing method according to an embodiment of the inventive concept. Figure 3 The inkjet printing method according to an embodiment of the inventive concept may include a presetting step S00, a printing step S10, a grading step S20, and a nozzle selecting step S30. Furthermore, the printing step S10, the grading step S20, and the nozzle selecting step S30 may be repeatedly performed based on the number of substrates S to be processed.

[0061] In the presetting step S00, a setting value for controlling the nozzle unit 510 in the first printing step S10 of the nozzle unit 510 may be input. In the presetting step S00, the nozzle unit 510 may perform multiple test discharges of the nozzle N to correct the ink discharge timing, ink volume, and ink drop position of the nozzle N, and the discharge performance of each nozzle N may be measured in advance, and the level of each nozzle N may be input to the controller 70.

[0062] For example, the level of each nozzle N input in the presetting step S00 may be as follows:

[0063] [Table 1]

[0064] Nozzle No. grade 1 C 2 A 3 B 4 C 5 B 6 A 7 A 8 A 9 B 10 B

[0065] Hereinafter, a high level of the nozzle N may mean that the drop position of the ink discharged from the nozzle N is more accurate. In addition, a high level of the nozzle N may mean that when the ink is discharged from the nozzle N multiple times, the drop position of the ink is relatively more concentrated at the target position. In addition, a high level of the nozzle N may mean that the level of the nozzle N is closer to level A among levels A, B, and C. The classification described above as A, B, and C is only an example and may be modified to various ways capable of expressing the discharge performance of the nozzle N. In addition, in the presetting step S00, based on the level of the nozzle N previously input, available nozzles that can participate in the printing of the substrate S and deactivated nozzles that cannot participate in the printing of the substrate S can be distinguished.

[0066] For example, the deactivated nozzles may be selected as nozzles N having a level lower than a preset reference level. For example, when the reference level is level B, nozzles N having a level C lower than level B are excluded from printing on the substrate S. For example, the first nozzle N1 and the fourth nozzle N4 in Table 1 may be selected as deactivated nozzles. In addition, the second nozzle N2, the third nozzle N3, and the fifth nozzle N5 to the tenth nozzle N10 may be selected as available nozzles.

[0067] When the presetting step S00 is completed, the head unit 510 may perform the first printing step S10. In the printing step S10, the head unit 510 may discharge ink to the substrate S. In the printing step S10, the nozzles N selected as available nozzles among the nozzles N of the head unit 510 may participate in the printing operation on the substrate S.

[0068] In addition, the number of nozzles N participating in the printing operation may be changed according to the process time set by the user at the controller 70. For example, if the user wants to complete the printing step S10 on the substrate S in a shorter time, the number of nozzles N participating in the printing operation may be increased, and if the user wants to complete the printing step S10 on the substrate S in a longer time, the number of nozzles N participating in the printing operation may be reduced. That is, the number of nozzles N participating in the printing operation may be changed according to the user's setting.

[0069] When the number of nozzles N classified as available nozzles is greater than the number of nozzles N actually participating in the printing operation, the controller 70 may first select a high-level nozzle N among the available nozzles to participate in the printing of the substrate S. For example, when the number of nozzles N participating in the actual printing operation is 4, the nozzles N participating in the printing step S10 in Table 1 may be the second nozzle N2, the sixth nozzle N6, the seventh nozzle N7, and the eighth nozzle N8. Therefore, the printing quality of the substrate S can be further improved. In addition, one printing step S10 cannot perform a printing operation on multiple substrates S, but can perform a printing operation on a single substrate S.

[0070] When the printing step S10 is completed, the grading step S20 may be performed. In the grading step S20, the nozzle unit 510 may be moved above the measuring unit 310 to measure the discharge performance of the nozzle N, and then the grading of the nozzle N may be determined again.

[0071] For example, in the ranking step S20, the ranking of the nozzle N input in the presetting step S00 may be updated. The ranking of the nozzle N after the update may be as follows:

[0072] [Table 2]

[0073] Nozzle No. grade 1 C 2 A 3 C 4 B 5 B 6 A 7 A 8 A 9 B 10 A

[0074] Hereinafter, the classification step S20 will be described in more detail. Figure 4 yes Figure 3 A detailed flow chart of the grading steps. Figure 4 , the grading step S20 may include a test emission step S21, an extraction step S22, a normalization step S23, and a grade determination step S24. The test emission step S21, the extraction step S22, the normalization step S23, and the grade determination step S24 may be performed sequentially.

[0075] The test discharge step S21 may be a step in which each nozzle N (ie, all nozzles N) discharges ink onto the test member TW at least once. In the test discharge step S21, each nozzle N may discharge ink onto the test member multiple times (eg, five times or more).

[0076] When the nozzles N all discharge ink onto the test member TW in the test discharge step S21 , the measurement unit 310 may acquire an image I (an example of measurement data) of the test member TW, and may transmit the image to the controller 70 .

[0077] In the extraction step S22 , feature data of each nozzle N may be extracted based on the landing position of the ink discharged onto the test member TW.

[0078] In an embodiment, Figure 5 As shown in , in order to rate the nozzle N in consideration of changes over time, five points P1 to P5 may be measured according to a plurality of discharge periods during which ink is discharged, and a distance F11 from P1 to P2, a distance F12 from P2 to P3, a distance F13 from P3 to P4, and a distance F14 from P4 to P5 may be calculated. Then, an F1 value (an embodiment of characteristic data) obtained by summing all values ​​F11 to F14 may be calculated. This process may be performed for each nozzle N.

[0079] In this case, regarding each nozzle N, since the nozzle N having a smaller F1 value has a smaller magnitude of change over time in the ink jet landing position, it can be determined as a nozzle N having a relatively high discharge performance.

[0080] As another example, Figure 6 As shown in , in order to rank the nozzles N based on the distribution of the landing positions of the ink jets, the distances F11, F12, F13, F14, and F15 between the five points P1 to P5 and the center point RP of the set area RA can be calculated, and the maximum value among these distances (an embodiment of the pitch data) can be extracted. This process can be performed for each nozzle N.

[0081] In this case, as the distance of each extracted nozzle N increases, since the landing position of the ink jet is relatively unconcentrated, it can be determined as a nozzle N having a relatively low discharge performance.

[0082] As another example, Figure 7 As shown, basic statistics can be used to rank the nozzles N. For example, Figure 7 As shown, the five points related to the landing position of the inkjet include all information about the X-axis and the Y-axis, that is, multi-dimensional information. In this case, it is difficult to compare the quality between the nozzles N. For example, it is difficult to compare the landing position regardless of the poor discharge performance of the nozzle N elongated in the X-axis direction or the poor discharge performance of the nozzle N elongated in the Y-axis direction.

[0083] Therefore, a hyperplane (HP) can be obtained using a principal component analysis (PCA) algorithm, and five points P1 to P5 can be projected onto the hyperplane. In this case, a dispersion value (an embodiment of feature data) can be obtained to know how dispersed the projected five points P1' to P5' are.

[0084] In this case, as the dispersion value increases, since the landing positions of the ejected ink are relatively unconcentrated, it can be determined that the nozzle N has a relatively low discharge performance.

[0085] The feature data extracted in the extraction step S22 is only an example, and various feature data may be used to determine the level of the nozzle N using data (eg, image I) about the ink discharged to the test member TW in the test discharge step S21.

[0086] As described above, the extraction step S22 may be performed multiple times. In this case, the levels of the feature data extracted in the extraction step S22 may be different from each other. In this case, some feature data may occupy a portion that is too large when determining the level of the nozzle N, while other feature data may occupy a portion that is too small when determining the level of the nozzle N. Therefore, according to an embodiment of the inventive concept, a normalization step S23 of normalizing the extracted feature data and matching the levels equally or similarly between the feature data is performed.

[0087] After the normalization step S23, a level determination step S24 of determining the level of the nozzle N may be performed. In the level determination step S24, the feature data subjected to the normalization step S23 may be used in a statistical manner (e.g., a method such as addition, but not limited thereto, and various statistical methods may be used) to obtain an evaluation data value E for evaluating the level of each nozzle.

[0088] In this case, when the grade of each nozzle N is determined based on the evaluation data value E, a specific value that is usually adopted (i.e., a threshold value for classifying the grades of the nozzles N at a specific ratio) is not set as a standard, and as shown in FIG. Figure 8 As shown in , the levels of the nozzles N can be classified based on the sections where the change rate of the evaluation data value E exceeds the preset value (ie, the sections where the magnitude of the evaluation data value E changes relatively greatly).

[0089] In this case, as shown in Table 2, the first nozzle N1 and the third nozzle N3 may be determined as level C, the fourth nozzle N4, the fifth nozzle N5 and the ninth nozzle N9 may be determined as level B, and the seventh nozzle N10, the sixth nozzle N6 and the eighth nozzle N8 may be determined as level A.

[0090] Reference again Figure 3 , after performing the grading step S20 , a nozzle selecting step S30 of selecting a nozzle N to participate in the printing step S10 may be performed.

[0091] In the nozzle selection step S30 , available nozzles that can participate in printing on the substrate S and disabled nozzles that are excluded from printing on the substrate S may be distinguished based on the rankings of the nozzles N updated in the ranking step S20 .

[0092] For example, the deactivated nozzles may be selected as nozzles N having a level lower than a preset reference level. For example, when the reference level is level B, nozzles N having a level C lower than level B may be excluded from printing on the substrate S. For example, the first nozzle N1 and the third nozzle N3 in Table 2 may be selected as deactivated nozzles. In addition, the fourth nozzle N4, the fifth nozzle N5, the ninth nozzle N9, the seventh nozzle N7, the tenth nozzle N10, the sixth nozzle N6, the eighth nozzle N8, and the second nozzle N2 may be selected as available nozzles.

[0093] When the nozzle selection step S30 is completed, the nozzle unit 510 may perform the second printing step S10. In the second printing step S10, the nozzle unit 510 may discharge ink onto the substrate S. In this printing step S10, the nozzles N selected as available nozzles among the nozzles N of the nozzle unit 510 may participate in the printing operation on the substrate S.

[0094] In addition, when the number of nozzles N classified as available nozzles is greater than the number of nozzles N participating in the actual printing operation, the controller 70 may first select a high-level nozzle N among the available nozzles to participate in printing on the substrate S. For example, when the number of nozzles N participating in the actual printing operation is 4, as the nozzles N participating in the printing step S10 in Table 2, four nozzles may be selected from the seventh nozzle N7, the tenth nozzle N10, the sixth nozzle N6, the eighth nozzle N8, and the second nozzle N2 to perform printing on the substrate.

[0095] That is, according to an embodiment of the inventive concept, when a printing process is completed for one substrate S, the ranks of the nozzles N are updated, and nozzles N having high discharge performance according to the ranks are preferentially discharged, thereby improving processing efficiency for the substrate S.

[0096] Meanwhile, as described above, the user can change the processing conditions such as the processing time in various ways, and in some cases, it is necessary to reduce the time for performing the printing step S10 as much as possible. That is, for the processing efficiency of the substrate S, it is advantageous to ensure that there are as many available nozzles as possible that can participate in the printing of the substrate S in the printing step S10.

[0097] Therefore, according to an embodiment of the inventive concept, if the nozzle selected as the deactivated nozzle in the nozzle selection step S30 satisfies the set condition, it may be switched to an available nozzle. Hereinafter, an example in which the nozzle N selected as the deactivated nozzle is converted to an available nozzle is described.

[0098] As described above, the ranking step S20 may be performed multiple times. In this case, as shown in Table 3, the change in the ranking of each nozzle N determined in the ranking step S20 may be accumulated.

[0099] [Table 3]

[0100]

[0101] Referring to Table 3, the first nozzle, the second nozzle, the third nozzle, and the fifth nozzle having the grade C (below the reference grade) measured in the fourth classification step S20 are first selected as the disabled nozzles. However, if the first nozzle, the second nozzle, the third nozzle, and the fifth nozzle selected as the disabled nozzles are all classified as disabled nozzles, the number of available nozzles that can actually participate in the printing of the substrate S will be relatively small, which is disadvantageous for the processing performance. However, in some cases, even if the first nozzle, the second nozzle, the third nozzle, and the fifth nozzle are determined to be at the grade C (even for nozzles classified as disabled nozzles), there is a possibility of printing at a quality higher than or equal to the reference grade (e.g., grade B) in the printing step S10. For a nozzle having a recovery probability greater than or equal to the set probability, even if the nozzle is selected as a disabled nozzle due to being given the grade C in the classification step S20, the nozzle may be converted into an available nozzle.

[0102] The restoration probability may be determined by previously obtained reference data. The reference data may be previously stored in the controller 70. The following is an example of reference data.

[0103] [Table 4]

[0104]

[0105] When confirmation is performed based on the reference data of Table 4 and the probability is set to 0.7, the nozzles converted from the deactivated nozzles to the usable nozzles in Table 3 may be the second nozzle N2 and the fifth nozzle N5.

[0106] Effects of the inventive concept are not limited to the above-mentioned effects, and those skilled in the art to which the inventive concept pertains can clearly understand unmentioned effects based on the present specification and the accompanying drawings.

[0107] Although preferred embodiments of the inventive concept have been illustrated and described so far, the inventive concept is not limited to the specific embodiments described above, and it should be noted that a person skilled in the art to which the inventive concept belongs may implement the inventive concept in various ways without departing from the essence of the inventive concept as claimed in the claims, and modifications to the invention should not be understood separately from the technical idea or expectation of the inventive concept.

Claims

1. An inkjet printing method for discharging ink onto a substrate using a nozzle having a plurality of nozzles, the inkjet printing method comprising: a grading step, wherein the grade of the nozzle is determined by measuring the discharge performance of the nozzle; a nozzle selection step of selecting, from among the nozzles, available nozzles capable of participating in printing on the substrate based on the grades determined in the grading step; as well as a printing step, wherein the ink is discharged onto the substrate using at least one of the available nozzles, Wherein, in the nozzle selection step, based on the grade determined in the grading step, a deactivated nozzle that is excluded from printing on the substrate is selected from among the nozzles, and the remaining nozzles are selected as the available nozzles, wherein nozzles having a grade lower than a reference grade are selected as the deactivated nozzles, and nozzles having a recovery probability equal to or higher than a set probability among the nozzles selected as the deactivated nozzles are converted into the available nozzles, wherein the recovery probability is the probability that the substrate will be printed with a quality equal to or higher than the reference grade if the nozzle selected as the deactivated nozzle participates in printing on the substrate, and the recovery probability is determined based on pre-stored reference data, the reference data including data on the grade of the nozzle selected as the deactivated nozzle determined by previously performing the grading step multiple times.

2. The inkjet printing method according to claim 1, wherein the printing step is performed a plurality of times, and the grading step and the nozzle selecting step are performed between the printing steps.

3. The inkjet printing method according to claim 2, wherein the grading step and the nozzle selecting step are performed a plurality of times.

4. The inkjet printing method according to any one of claims 1 to 3, wherein the classification step further comprises: a test discharge step, wherein each of the nozzles discharges the ink onto a test member at least once; as well as An extraction step for extracting characteristic data of each of the nozzles based on a landing point of the ink discharged onto the test member.

5. The inkjet printing method according to claim 4, wherein the extracting step is performed multiple times, and The extracting step further comprises: A normalization step for normalizing the feature data extracted in the extraction step.

6. The inkjet printing method according to claim 5, wherein the grading step further comprises a grade determination step for determining the grade of the nozzle, and Evaluation data for evaluating the grade of each nozzle is obtained based on the normalized feature data, and the grade of the nozzle is determined based on a section in which a change rate of the obtained evaluation data exceeds a set value.

7. An inkjet printing device, comprising: a printing unit for performing printing by discharging ink onto a substrate; a maintenance unit positioned side by side with the printing unit; a nozzle configured to be movable between the printing unit and the maintenance unit and having a plurality of nozzles formed thereon; a measuring unit that is positioned at the maintenance unit and measures a discharge performance of the nozzle; as well as a controller that receives measurement data measured by the measurement unit and controls the nozzle based on the measurement data; and wherein the controller determines the discharge performance of the nozzle based on the measurement data, determines the grade of the nozzle, selects available nozzles that can participate in the printing of the substrate in the printing unit based on the grade, and generates a control signal so that the nozzle head can use at least one nozzle among the available nozzles to discharge the ink onto the substrate, wherein the controller selects deactivated nozzles from among the nozzles to be excluded from printing on the substrate based on the level, and selects the remaining nozzles as the available nozzles, wherein the controller selects nozzles having a level lower than a reference level as the deactivated nozzles, and converts nozzles having a recovery probability equal to or greater than a set probability among the nozzles selected as the deactivated nozzles into the available nozzles, wherein the recovery probability is the probability that the substrate will be printed with a quality equal to or higher than the reference level if the nozzle selected as the deactivated nozzle participates in printing on the substrate, and the recovery probability is determined based on pre-stored reference data, the reference data including data on the level of the nozzle selected as the deactivated nozzle determined by a previous plurality of emission performance measurements. 8 . The inkjet printing apparatus according to claim 7 , wherein the controller generates a control signal to preferentially allow a nozzle having a high rank among the available nozzles to participate in printing on the substrate.

9. An inkjet printing method for discharging ink onto a substrate using a nozzle having a plurality of nozzles formed thereon, the inkjet printing method comprising: a grading step, wherein the grade of the nozzle is determined by measuring the discharge performance of the nozzle; a nozzle selection step of selecting, from among the nozzles, available nozzles capable of participating in printing on the substrate based on the grades determined in the grading step; as well as a printing step, wherein the ink is discharged onto the substrate using at least one of the available nozzles, wherein the nozzles having a high grade determined in the ranking step among the available nozzles are preferentially involved in printing, Wherein, in the nozzle selection step, based on the grade determined in the grading step, a deactivated nozzle that is excluded from printing on the substrate is selected from among the nozzles, and the remaining nozzles are selected as the available nozzles, wherein nozzles having a grade lower than a reference grade are selected as the deactivated nozzles, and nozzles having a recovery probability equal to or higher than a set probability among the nozzles selected as the deactivated nozzles are converted into the available nozzles, wherein the recovery probability is the probability that the substrate will be printed with a quality equal to or higher than the reference grade if the nozzle selected as the deactivated nozzle participates in printing on the substrate, and the recovery probability is determined based on pre-stored reference data, the reference data including data on the grade of the nozzle selected as the deactivated nozzle determined by previously performing the grading step multiple times.

10. The inkjet printing method according to claim 9, wherein the grading step, the nozzle selecting step, and the printing step are performed a plurality of times, and Each time the ranking step is performed, the ranking of each of the nozzles is re-evaluated.

11. The inkjet printing method according to claim 9, wherein the grading step, the nozzle selecting step, and the printing step are performed a plurality of times, and Each time the nozzle selection step is performed, the selection of the available nozzles is performed.

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