Inkjet printing method and inkjet printing device

Abstract

To provide an ink jet printing method capable of suppressing printing unevenness of a substrate.SOLUTION: An ink jet printing method is such as to perform printing on a substrate while relatively moving the substrate and an ink jet head where a plurality of nozzles are disposed along a straight line. The ink jet printing method comprises: a process for dividing a coating region in a pixel bank on the substrate to a plurality of divided regions; a process for allocating a plurality of nozzles to the plurality of divided regions: a process for selecting nozzles discharging ink to the divided regions from the nozzles allocated to each of the divided regions at random; and a process for discharging the ink through the selected nozzle while relatively moving the substrate and the ink jet head.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an inkjet printing method and an inkjet printing apparatus. [Background technology]

[0002] In order to increase the display area, improve quality, and reduce costs, it is desirable to replace the semiconductor manufacturing process with a printing process for the manufacturing method of displays. Examples of displays whose manufacturing method can be replaced with a printing process include organic electroluminescence displays and quantum dot displays.

[0003] For example, an organic EL display usually has a functional layer containing an organic functional material disposed between an anode and a cathode. Depending on the function of the organic functional material, organic devices such as semiconductor elements (transistors), light-emitting elements, and liquid crystal elements can be obtained. The semiconductor element contains an organic semiconductor material that connects a source electrode and a drain electrode disposed on the substrate surface, for example. The organic EL element has a light-emitting layer containing an organic EL material laminated on an anode electrode disposed on the substrate, for example, and the light-emitting layer is further sandwiched between cathode electrodes.

[0004] In order to pattern a functional material on an electrode, a barrier (i.e., a bank) may be formed surrounding the electrode surface, and a composition containing the functional material may be printed in the area defined by the bank. The material of the bank may be a resin. When printing an ink containing a functional material in an area including the electrode surface defined by the bank, it is generally preferable that the wettability of the area to be printed (including the electrode surface) is high, and that the wettability of the upper surface of the bank is low. This is to prevent the ink from leaking out to areas other than the intended area. It is generally known that fluorine components reduce the energy of the surface of a material, thereby reducing wettability.

[0005] The printing area defined by the bank is hereinafter referred to as a subpixel. The subpixels are generally arranged in a matrix. Ink is discharged from a plurality of nozzles arranged in a row and landed on these subpixels. Then, the nozzles and the panel are moved relatively in a direction approximately perpendicular to the row of nozzles, and ink is repeatedly landed, so that all of the matrix-shaped subpixels can be filled with ink. In this process, if there is variation in the volume of the ink discharged between the nozzles, areas where the amount of ink filled in the subpixel is large and areas where it is small are formed in lines parallel to the printing direction. As a result, stripes of uneven light emission occur in the completed display device, and the display becomes a defective product. As a countermeasure against this, a method has been considered in which the nozzles used are randomly changed to distribute the variation in the ink discharge volume for each nozzle and land ink on each subpixel (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4984934 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the method described in Patent Document 1, the position of each subpixel and the position of the selected nozzle change for each pixel using a random number. If the position of the nozzle selected for the subpixel is biased, the ink thickness will be biased or an uncoated area will occur within the subpixel. This will cause variation in the amount of light emitted within the subpixel. Also, if the nozzle that is supposed to eject ink onto the subpixel has a problem such as a clogged nozzle, a streaky area of ​​poor light emission will occur.

[0008] In view of the above circumstances, an object of the present disclosure is to provide an inkjet printing method and inkjet printing apparatus that can suppress printing unevenness on a substrate. [Means for solving the problem]

[0009] The inkjet printing method disclosed herein is an inkjet printing method that prints on a substrate while moving a substrate and an inkjet head having a plurality of nozzles arranged in a straight line relative to each other, and includes the steps of dividing a coating area within a pixel bank on the substrate into a plurality of divided areas, assigning the plurality of nozzles to the plurality of divided areas, randomly selecting nozzles that eject ink into the divided areas from among the nozzles assigned to each of the divided areas, and ejecting ink from the selected nozzles into the plurality of divided areas while moving the substrate and the inkjet head relative to each other.

[0010] The inkjet printing apparatus disclosed herein includes a stage for holding a substrate, an inkjet head having a plurality of nozzles arranged in a row, a relative movement mechanism for moving the stage and the inkjet head relative to one another, and a control unit, wherein the control unit divides a coating area within a pixel bank on the substrate into a plurality of divided areas, assigns the plurality of nozzles to the plurality of divided areas, randomly selects a nozzle that ejects ink into the divided area from among the nozzles assigned to each divided area, controls the relative movement mechanism to move the substrate and the inkjet head relative to one another, and controls the inkjet head to eject ink from the selected nozzle into the plurality of divided areas. Effect of the Invention

[0011] According to the inkjet printing method and inkjet printing apparatus of the present disclosure, printing unevenness on a substrate can be suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an inkjet printing apparatus according to a first embodiment of the present disclosure; [Diagram 2] FIG. 1 is a schematic diagram showing an inkjet printing apparatus according to a second embodiment of the present disclosure; [Diagram 3] FIG. 13 is a schematic diagram showing an inkjet printing apparatus according to a third embodiment of the present disclosure. [Figure 4] FIG. 13 is a schematic diagram showing an inkjet printing apparatus according to a fourth embodiment of the present disclosure. [Diagram 5] FIG. 13 is a schematic diagram showing an inkjet printing apparatus according to a fifth embodiment of the present disclosure. [Figure 6] FIG. 13 is a schematic diagram showing an inkjet printing apparatus when a first ejection failure countermeasure process is being performed according to a fifth embodiment of the present disclosure; [Figure 7] FIG. 13 is a schematic diagram showing an inkjet printing apparatus when performing a second ejection failure countermeasure process according to a fifth embodiment of the present disclosure; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present disclosure will be described. Note that the configurations of the first to fifth embodiments described below can be combined within a feasible range.

[0014] [First embodiment] First, a first embodiment of the present disclosure will be described. Fig. 1 is a schematic diagram showing an inkjet printing apparatus according to the first embodiment of the present disclosure.

[0015] As shown in FIG. 1, an inkjet printing apparatus 101 includes an inkjet head 102, a stage 103, a relative movement mechanism 104, and a control unit 105.

[0016] The inkjet head 102 has a plurality of nozzles 106 arranged in a line. Hereinafter, the direction in which the plurality of nozzles 106 are arranged may be referred to as a nozzle arrangement direction D1. The plurality of nozzles 106 may be arranged in two or more lines, in which case they may be arranged in a so-called staggered arrangement. The plurality of nozzles 106 may also be arranged in a direction oblique to a printing direction D2, which will be described later.

[0017] The stage 103 holds the substrate 110 by vacuum suction or other methods at a position below the inkjet head 102. On the substrate 110, pixel pixels 111 are arranged in a matrix. Each pixel pixel 111 is composed of a plurality of sub-pixels 112 of three colors, for example, RGB. The sub-pixels 112 are coating areas in a pixel bank, and are formed, for example, in an elliptical shape. The sub-pixels 112 are formed so that the longitudinal direction of the elliptical shape is parallel to the nozzle arrangement direction D1. The three color sub-pixels 112 are aligned in a direction perpendicular to the nozzle arrangement direction D1. However, when manufacturing a black and white display panel, each pixel pixel 111 is composed of one sub-pixel 112.

[0018] The relative movement mechanism 104 moves the stage 103 and the inkjet head 102 relatively in a direction perpendicular to the nozzle arrangement direction D1. In the first embodiment, the stage 103 moves relative to the inkjet head 102 in the printing direction D2 shown in Fig. 1. Note that the inkjet head 102 may be moved relative to the stage 103, or both the inkjet head 102 and the stage 103 may be moved.

[0019] The control unit 105 performs overall control of the inkjet printing apparatus 101. The control unit 105 controls the relative movement mechanism 104 to move the stage 103 in the printing direction D2, thereby causing the substrate 110 to pass under the inkjet head 102. At this time, the control unit 105 controls the inkjet head 102 to eject the ink 120 from the nozzle 106 in a timed manner so that the ink 120 lands within the target subpixel 112.

[0020] More specifically, the control unit 105 executes a division process, an allocation process, a selection process, and a discharge process. Each process will be described below.

[0021] 1, the number of nozzles 106 capable of depositing ink 120 on each subpixel 112 is eight per subpixel 112. The control unit 105 divides the subpixel 112, for example, into four by dividing lines 114, and sets four divided regions 113. When the printing direction D2 is the forward direction, the control unit 105 divides the subpixel 112 into left and right.

[0022] In the allocation step, the control unit 105 allocates the nozzles 106 constituting the inkjet head 102 to the multiple divided regions 113. The control unit 105 allocates, for example, two nozzles 106 each of the eight nozzles 106 capable of landing ink 120 on one subpixel 112 to each divided region 113.

[0023] In the selection step, the control unit 105 uses random numbers to randomly select nozzles 106 that will eject ink 120 into each divided region 113 from among the nozzles 106 assigned to each divided region 113. The control unit 105 selects nozzles 106 in a number that is 50% or more of the total number of nozzles 106 assigned to one divided region 113. In the first embodiment, one nozzle 106 is selected for each divided region 113. Note that the control unit 105 does not need to use random numbers when randomly selecting the nozzles 106.

[0024] In the ejection step, the control unit 105 controls the relative movement mechanism 104 to move the stage 103, and also controls the inkjet head 102 to eject the ink 120 from the nozzle 106 selected in the selection step. At this time, the control unit 105 controls the inkjet head 102 so that the volume of ink ejected for each divided region 113 is within ±50% of the average volume of ink ejected into these divided regions 113, and ejects the ink 120 from the nozzle 106 in the selection step. In other words, the control unit 105 controls the inkjet head 102 so as to satisfy the following formula (1).

[0025]

number

[0026] FIG. 1 shows the ink 120 discharged to each divided region 113 and the target landing position 121 of the nozzle 106 from which the ink 120 was not discharged. In FIG. 1, the ink 120 is shown as a circle filled with gray, and the target landing position 121 is shown as a circle with a dashed line. The ink 120 spreads from the target landing position in a substantially concentric manner. The number of divisions of the subpixel 112 in the division process, the selection probability of the nozzle 106 discharging the ink 120 in the selection process, and the discharge volume and number of droplets of the ink 120 controlled in the discharge process are set so that this spreading fills the entire divided region 113. It is ideal to increase the randomness of the film thickness, that is, the variation of the combination of the nozzles 106 while satisfying the necessary condition for the volume of the ink 120 based on the above formula (1). This combination K is expressed by the following formula (2), where the number of nozzles 106 assigned to each divided region 113 is n and the number of nozzles 106 discharging the ink 120 is r. Furthermore, as shown in the following formula (3), by setting r to about half of n, the number of combinations of the nozzles 106 can be maximized. K= n C r (2) r ≒ n / 2 (3)

[0027] As described above, the control unit 105 divides the subpixel 112 into a plurality of divided regions 113, and assigns a plurality of nozzles 106 of the inkjet head 102 to the plurality of divided regions 113. The control unit 105 randomly selects a nozzle 106 that ejects ink into the divided region 113 from among the nozzles 106 assigned to each divided region 113, and ejects the ink 120 from the selected nozzle 106 into the plurality of divided regions 113. As a result, the ink 120 is ejected into each divided region 113, and it is possible to randomly change the film thickness of the ink 120 for each divided region 113 while preventing the occurrence of a region in the subpixel 112 that is not covered with the ink 120. Therefore, it is possible to reduce the deviation in the film thickness of the ink 120 parallel to the printing direction D2, and it is possible to suppress the occurrence of streaky printing unevenness on the substrate 110. As a result, it is possible to suppress uneven light emission on the substrate.

[0028] [Second embodiment] Next, a second embodiment of the present disclosure will be described. Fig. 2 is a schematic diagram showing an inkjet printing apparatus according to the second embodiment of the present disclosure. Note that the same components as those in the inkjet printing apparatus 101 of the first embodiment are given the same names and symbols, and descriptions thereof will be omitted.

[0029] In the second embodiment, a plurality of pixels 211 are arranged on a substrate 210. Each pixel 211 is composed of three color sub-pixels 212. The sub-pixels 212 are coated areas within a pixel bank, and are formed, for example, in a substantially square shape with curved corners.

[0030] The control unit 205 of the inkjet printing apparatus 201 executes a division process, an allocation process, a selection process, and a discharge process.

[0031] 2, the number of nozzles 106 capable of depositing ink 120 on each subpixel 212 is three per subpixel 212. The control unit 205 divides the subpixel 212, for example, into three by dividing lines 214, and sets three divided regions 213. When the printing direction D2 is the forward direction, the control unit 205 divides the subpixel 212 into front and rear.

[0032] In the allocation step, the control unit 205 allocates all of the three nozzles 106 capable of landing the ink 120 on one subpixel 212 to one divided region 213. In other words, the control unit 205 allows the ink 120 to land from each of the three nozzles 106 on the three divided regions 213 that make up one subpixel 212.

[0033] In the selection process, the control unit 205 uses random numbers to randomly select the nozzles 106 that will eject the ink 120 into the divided regions 213. The control unit 205 selects nozzles 106 in a number that is 50% or more of the total number of nozzles 106 assigned to one divided region 213. In the second embodiment, two nozzles 106 are selected for each divided region 213.

[0034] In the ejection step, the control unit 205 performs printing by ejecting the ink 120 from the nozzles 106 selected in the selection step so as to satisfy the above formula (1).

[0035] FIG. 2 shows the ink 120 discharged to each divided region 213 and the landing target positions 121 of the nozzles 106 to which the ink 120 was not discharged. In the second embodiment, there is a concern that the application position of the subpixel 212 may be biased. For example, in the subpixel 212 second from the bottom in the second row from the left in FIG. 2, the landing target positions 121 of the nozzles 106 to which the ink 120 was not discharged are lined up in a row, and the application position of the ink 120 is biased to the left of the center. Therefore, even in such a case, it is necessary to determine the number of nozzles 106 that discharge the ink 120 in consideration of the wetting and spreading of the ink 120 to the subpixel 212 and the shape of the subpixel 212 so that the ink 120 can be spread over the entire subpixel 212. For example, when the diameter of the nozzle 106 is 20 μm, the diameter of the discharged droplet is approximately 20 μm. The way in which the droplet spreads after landing is greatly influenced by the wettability of the subpixel 212. The droplets that land may spread from a state in which the contact angle exceeds 10 degrees and the droplet diameter is approximately 20 μm until the contact angle, called expanded wetting, reaches 0 degrees. For example, if the arrangement pitch of the nozzles 106 is 20 μm, the dimension of the subpixel 212 in the nozzle arrangement direction D1 is 60 μm, and the droplet diameter of the ink 120 that spreads onto the subpixel 212 is 60 μm, the ink 120 can be made to spread into the subpixel 212 even if the application position of the subpixel 212 is biased. The inkjet printing method of the second embodiment is effective when the discharge pitch in the printing direction D2 can be shortened or when the shape of the subpixel 212 is long in the printing direction D2 and short in the nozzle arrangement direction D1.

[0036] [Third embodiment] Next, a third embodiment of the present disclosure will be described. Fig. 3 is a schematic diagram showing an inkjet printing apparatus according to the third embodiment of the present disclosure. Note that the same components as those of the inkjet printing apparatus 101 of the first embodiment are given the same names and symbols, and descriptions thereof will be omitted.

[0037] In the third embodiment, a plurality of pixels 311 are arranged on a substrate 310. Each pixel 311 is composed of three color sub-pixels 312 aligned in a printing direction D2. The sub-pixels 312 are coating areas within a pixel bank, and are formed in an oval shape similar to the sub-pixels 112 in the first embodiment.

[0038] The control unit 305 of the inkjet printing apparatus 301 executes a division process, an allocation process, a selection process, and a discharge process.

[0039] In the dividing step, the control unit 305 divides the subpixel 312 into a plurality of divided regions 313. In the configuration shown in Fig. 3, the number of nozzles 106 capable of depositing ink 120 on each subpixel 312 is eight per subpixel 312. The control unit 305 divides the subpixel 312 into four by a first dividing line 314 parallel to the nozzle arrangement direction D1 and a second dividing line 315 parallel to the printing direction D2, and sets the four divided regions 313. When the printing direction D2 is defined as the forward direction, the control unit 305 divides the subpixel 312 into front-rear and left-right.

[0040] In the allocation step, the control unit 305 allocates, for example, four nozzles 106 each of two divided regions 313 arranged side by side from left to right out of the eight nozzles 106 capable of landing ink 120 on one subpixel 312. In other words, the control unit 305 allows ink 120 to land from four nozzles 106 on each of the four divided regions 313 that make up one subpixel 312.

[0041] In the selection process, the control unit 305 uses random numbers to randomly select nozzles 106 that will eject ink 120 into the divided regions 313. The control unit 305 selects nozzles 106 in a number that is 50% or more of the total number of nozzles 106 assigned to one divided region 313. In the third embodiment, two nozzles 106 are selected for each divided region 313.

[0042] In the ejection step, the control unit 305 performs printing by ejecting the ink 120 from the nozzles 106 selected in the selection step so as to satisfy the above formula (1).

[0043] FIG. 3 shows the ink 120 discharged to each divided region 313 and the target landing position 121 of the nozzle 106 where the ink 120 was not discharged. In the third embodiment, the subpixel 312 can be arbitrarily divided in the front-rear and left-right directions with the printing direction D2 as the forward direction. Therefore, even if the subpixel 312 is large, the ink 120 can be effectively prevented from being left unfilled in the subpixel 312. In addition, in the third embodiment, when the first division lines 314 are set many times, that is, when the subpixel 312 is divided into three or more parts in the front-rear direction, it is necessary to perform printing at a low speed by making the inkjet head 102 compatible with high frequency discharge or by reducing the relative movement speed between the inkjet head 102 and the stage 103. For the production of high-definition displays, the inkjet head 102 has a small hole diameter and a narrow pitch for the nozzle 106. The third embodiment is effective in the case of manufacturing a plurality of types of displays on a single production line, such as when manufacturing a large-screen display with low definition using such an inkjet head 102.

[0044] [Fourth embodiment] Next, a fourth embodiment of the present disclosure will be described. Fig. 4 is a schematic diagram showing an inkjet printing apparatus according to the fourth embodiment of the present disclosure. Note that the same components as those of the inkjet printing apparatus 101 of the first embodiment are given the same names and symbols, and descriptions thereof will be omitted.

[0045] Sub-pixels 412 constituting a pixel are arranged on a substrate 410 in the fourth embodiment. The sub-pixels 412 are coated areas in a pixel bank, and are formed in an elliptical shape similar to the sub-pixels 112 in the first embodiment.

[0046] The control unit 405 of the inkjet printing apparatus 401 executes a division process, an allocation process, a selection process, and a discharge process.

[0047] In the division step, the control unit 405 divides the subpixel 412 into a plurality of division regions 413. When the print direction D2 is the forward direction, the control unit 405 divides the subpixel 412 into two, left and right. In the configuration shown in FIG. 4, the number of nozzles 106 capable of landing the ink 120 on one subpixel 412 is 7 per subpixel 412, that is, an odd number. When the number of nozzles 106 capable of landing the ink 120 on one subpixel 412 is an odd number, the nozzles 106 cannot be assigned to each division region 413 in the same number other than 1, as in the case of an even number. In the fourth embodiment, the control unit 405 randomly determines the division position in the subpixel 412, for example, by using a random number. At this time, the control unit 405 may make the division position different for each subpixel 412 based on the curved division line 414. In the fourth embodiment, a configuration is illustrated in which each subpixel 412 is divided so that the numbers of nozzles 106 assigned to the left and right divided areas 413 are 2 and 5, 3 and 4, and 4 and 3, respectively, but the subpixel 412 may also be divided so that the numbers of nozzles 106 assigned to the left and right divided areas 413 are 1 and 6.

[0048] In the allocation process, the control unit 405 allocates seven nozzles 106 capable of depositing ink 120 on one subpixel 412 to, for example, two divided areas 413 arranged side by side, in a number according to the size of each divided area 413.

[0049] In the selection step, the control unit 405 randomly selects the nozzles 106 that eject the ink 120 into the divided region 413 using random numbers. In the fourth embodiment, a configuration is illustrated in which two or one nozzle 106 out of three nozzles 106 assigned to each divided region 413, three, two or one nozzle 106 out of four nozzles 106, or three, two or one nozzle 106 out of five nozzles 106 are selected, but the selection may be made as follows, for example. When the number of nozzles 106 assigned to the left and right divided regions 413 is one and six, respectively, the control unit 405 always selects one nozzle 106 in the left divided region 413, and may select four nozzles 106 out of six nozzles 106 in the right divided region 413. The control unit 405 may also select nozzles 106 that are 50% or more of the total number of nozzles 106 assigned to one divided region 413.

[0050] In the ejection step, the control unit 405 performs printing by ejecting the ink 120 from the nozzles 106 selected in the selection step so as to satisfy the above formula (1).

[0051] 4 shows the ink 120 ejected into each divided region 413 and the target landing positions 121 of the nozzles 106 from which the ink 120 was not ejected. It is desirable that the number of nozzles 106 from which the ink 120 is ejected for each subpixel 412 is the same. However, this does not apply if the variation in the volume of the ink 120 for each subpixel 412 is within the range required for the completed display. For example, it is sufficient that the variation in the ink thickness (film thickness) for each subpixel 412 does not exceed ±50% of the average ink thickness for all subpixels 412. The above explanation can be generalized to the following formulas (4) and (5).

[0052]

number

[0053]

number

[0054] [Fifth embodiment] Next, a fifth embodiment of the present disclosure will be described. Fig. 5 is a schematic diagram showing an inkjet printing apparatus according to the fifth embodiment of the present disclosure. Fig. 6 is a schematic diagram showing an inkjet printing apparatus when a first non-ejection countermeasure process is being carried out. Fig. 7 is a schematic diagram showing an inkjet printing apparatus when a second non-ejection countermeasure process is being carried out. Note that the same names and symbols are used for the same configurations as those of the inkjet printing apparatus 101 of the first embodiment, and description thereof will be omitted.

[0055] As shown in FIGS. 5 and 6, the inkjet printing apparatus 501 includes an inkjet head 102, a stage 103, a relative movement mechanism 104, a control unit 505 configured by a computer, a waveform generating device 541, and a camera 542.

[0056] As shown in Fig. 6, a plurality of pixel elements 511 are arranged on a substrate 510 of the fifth embodiment. Each pixel element 511 is composed of sub-pixels 512 of three colors arranged in a printing direction D2. As shown in Fig. 7, a plurality of sub-pixels 612 are arranged on a substrate 610 of the fifth embodiment. The sub-pixels 512, 612 are coated areas in a pixel bank, and are formed in an oval shape similar to the sub-pixel 112 of the first embodiment.

[0057] The waveform generating device 541 outputs an ejection waveform to the inkjet head 102 based on an output command from the control unit 505. The inkjet head 102 ejects ink 120 from a predetermined nozzle 106 at a predetermined timing based on the ejection waveform. The camera 542 acquires an image for inspecting the ink 120 that has landed on the inspection substrate 530 shown in FIG.

[0058] The control unit 505 of the inkjet printing apparatus 501 executes an inspection process, a division process, an allocation process, a selection process, and a discharge process.

[0059] In the inspection process, the control unit 505 controls the relative movement mechanism 104 and the inkjet head 102 to cause ink 120 to land from all of the nozzles 106 of the inkjet head 102 on an inspection substrate 530 held on the stage 103. The camera 542 outputs an image of the inspection substrate 530 to the control unit 505. The control unit 505 determines the position of the ink 120 that has landed on the inspection substrate 530, the size of the droplets, and whether or not the ink has been ejected. If the ink 120 is not present at a target landing position on the inspection substrate 530 where the ink 120 should be, the control unit 505 identifies the nozzle 106 that was supposed to eject the ink 120 at that target landing position as an abnormal nozzle 507. For example, when ink 120 is not present at target landing position 531 shown by a dashed circle in Fig. 5, control unit 505 identifies nozzle 106 that was supposed to eject ink 120 to target landing position 531 as abnormal nozzle 507, for example, based on the relationship between the preset target landing position and the position of nozzle 106. Note that hereinafter, nozzle 106 that can eject ink 120 may be referred to as normal nozzle 506. In Figs. 5 to 7, normal nozzle 506 is shown as a simple circle, and abnormal nozzle 507 is shown as a circle hatched with diagonal lines.

[0060] If no abnormal nozzle 507 is found in the inspection process, the control unit 505 executes the same division process, allocation process, selection process, and discharge process as in the first to fourth embodiments. In the discharge process, the control unit 505 causes the waveform generating device 541 to output a discharge waveform that is based on the assumption that no abnormal nozzle 507 exists. On the other hand, if an abnormal nozzle 507 is found in the inspection process, the control unit 505 executes the following first non-discharge handling process or second non-discharge handling process.

[0061] [First Non-ejection Countermeasure Processing] 6, the number of nozzles 106 capable of depositing ink 120 on each subpixel 512 is seven per subpixel 512. In the division step, the control unit 505 uses random numbers to divide the subpixel 512 into a plurality of divided regions 513, as in the fourth embodiment. The control unit 505 divides the subpixel 512 into two divided regions 513 via a bent first division line 514.

[0062] The control unit 505 does not change the size of the divided region 513 defined by the first division line 514 for a subpixel 512 in which there is no abnormal nozzle 507 among the nozzles 106 capable of landing the ink 120. The control unit 505 changes the bent first division line 514 to a straight second division line 515 for a subpixel 512 in which there is an abnormal nozzle 507 among the nozzles 106 capable of landing the ink 120, and changes the size of the divided region 513. At this time, it is desirable for the control unit 505 to set the divided region 513 such that at least two normal nozzles 506 are assigned to the divided region 513 to which the abnormal nozzle 507 is assigned.

[0063] In the allocating step, for divided regions 513 divided via a first division line 514, the control unit 505 allocates normal nozzles 506 in a number corresponding to the sizes of the two divided regions 513. In the allocating step, for divided regions 513 divided via a second division line 515, the control unit 505 allocates abnormal nozzles 507 and normal nozzles 506 in a number corresponding to the sizes of the divided regions 513.

[0064] In the selection step, the control unit 505 uses random numbers to randomly select normal nozzles 506 that eject ink 120 into the divided region 513. The control unit 505 selects normal nozzles 506 in a number that is 50% or more of the total number of normal nozzles 506 assigned to one divided region 513. In other words, for a divided region 513 to which an abnormal nozzle 507 is assigned, the control unit 505 selects nozzles 106 in a number that is 50% or more of the total number of nozzles 106 excluding the abnormal nozzle 507 (in the example of FIG. 6, two normal nozzles 506 out of the three normal nozzles 506).

[0065] In the ejection step, the control unit 505 performs printing by ejecting the ink 120 from the normal nozzles 506 selected in the selection step so as to satisfy the above formula (1). At this time, the control unit 505 causes the waveform generating device 541 to output an ejection waveform that is premised on the presence of the abnormal nozzle 507. The inkjet head 102 ejects the ink 120 only from the normal nozzles 506 based on the ejection waveform from the waveform generating device 541. Note that, if the abnormal nozzle 507 is present, it is assumed that the arrangement ranges of the remaining six normal nozzles 506 are biased to the right or left side (the right side in the example of FIG. 6) within the subpixel 512. In this case, the relative position of the inkjet head 102 with respect to the substrate 510 can be corrected within a range in which the printing positions of the other subpixels 512 are acceptable, and the arrangement ranges of the six normal nozzles 506 can be positioned in the center of the subpixel 512.

[0066] [Second Non-ejection Countermeasure Processing] 7, the number of nozzles 106 capable of depositing ink 120 on each subpixel 612 is eight per subpixel 612. In the division step, the control unit 505 divides the subpixel 612 into a plurality of divided regions 613 (two in the example of FIG. 7) via straight division lines 614.

[0067] In the allocation step, the control unit 505 allocates to each divided area 613 the number of nozzles 106 (four for each divided area in the example of FIG. 7) according to the size of the divided area 613. For example, in the example of FIG. 7, the control unit 505 allocates four nozzles 106 to the four divided areas 613 on the leftmost side aligned in the printing direction D2. These four nozzles 106 are aligned from the left in the order of the first normal nozzle 506A, the abnormal nozzle 507, the second normal nozzle 506B, and the third normal nozzle 506C.

[0068] In the selection step, the control unit 505 uses random numbers to randomly select nozzles 106 that will eject ink 120 into the divided region 613. The control unit 505 selects nozzles 106 that are 50% or more of the total number of nozzles 106 assigned to one divided region 613 (three out of the four nozzles 106 in the example of FIG. 7). If an abnormal nozzle 507 is included among the selected nozzles 106, the control unit 505 performs at least one of the following first reselection step and second reselection step.

[0069] First, the first reselection step will be described. When the first normal nozzle 506A, the abnormal nozzle 507, and the third normal nozzle 506C are selected in the selection step for the divided area 613A located at the bottom of the four divided areas 613 on the left side, the control unit 505 reselects the second normal nozzle 506B, which was not selected in the selection step, in place of the abnormal nozzle 507 in the first reselection step. After that, in the ejection step, the control unit 505 performs printing by ejecting ink 120 from the first to third normal nozzles 506A to 506C onto the divided area 613A so as to satisfy the above formula (1). That is, the ink 120 from the abnormal nozzle 507 was originally supposed to land at the landing target position 121A, but since the ink 120 cannot be ejected from the abnormal nozzle 507, the ink 120 from the second normal nozzle 506B is caused to land at the landing target position 121B, which was not originally supposed to land.

[0070] Next, the second reselection process will be described. When the first normal nozzle 506A, the abnormal nozzle 507, and the second normal nozzle 506B are selected in the selection process for the divided region 613B located second from the bottom among the four divided regions 613 on the leftmost side, the control unit 505 reselects the first normal nozzle 506A selected in the selection process as the normal nozzle 506 that ejects the ink 120 in place of the abnormal nozzle 507 in the second reselection process. After that, in the ejection process, the control unit 505 ejects the ink 120 from the first and second normal nozzles 506A and 506B into the divided region 613B so as to satisfy the above formula (1), thereby performing printing. At this time, the control unit 505 ejects the ink 120 twice from the first normal nozzle 506A into the divided region 613B at different timings.

[0071] In addition, when the abnormal nozzle 507, the second normal nozzle 506B, and the third normal nozzle 506C are selected in the selection step for the divided region 613C located second from the top among the four divided regions 613 on the leftmost side, the control unit 505 may reselect the second normal nozzle 506B as the normal nozzle 506 that ejects the ink 120 instead of the abnormal nozzle 507 in the second reselection step. In this case, in the ejection step, the ink 120 is ejected from the second and third normal nozzles 506B and 506C to the divided region 613C so as to satisfy the above formula (1). At this time, the ink 120 is ejected twice from the second normal nozzle 506B to the divided region 613C at different timings.

[0072] According to the second non-ejection handling process described above, when an abnormal nozzle 507 is present, it is possible to prevent the ejecting normal nozzle 506 from becoming fixed, even in the area along the printing direction D2 where the normal nozzle 506 adjacent to the abnormal nozzle 507 prints, and it is possible to randomly change the film thickness of the ink 120 for each divided area 613 while preventing the occurrence of areas within the subpixel 612 that are not covered by ink 120. [Industrial Applicability]

[0073] The inkjet printing method and inkjet printing device according to the present disclosure are capable of producing displays, which are an example of a substrate, with high quality even if volume variations occur between nozzles during production. Furthermore, the inkjet printing method and inkjet printing device according to the present disclosure are applicable not only to displays but also to devices formed by printing on a substrate, such as lighting, sensors, and solar cells, and are therefore extremely useful and highly applicable industrially. [Explanation of symbols]

[0074] 101,201,301,401,501 Inkjet printing device 102 Inkjet head 103 Stage 104 Relative movement mechanism 105,205,305,405,505 Control section 106 Nozzle 110,210,310,410,510,610 Board 111,211,311,511 pixels 112,212,312,412,512,612 subpixels 113,213,313,413,513,613,613A,613B,613C divided area 114,214,414,614 Dividing line 314,514 First dividing line 315,515 Second dividing line 120 Ink 121, 121A, 121B, 531 Target position 506 Normal nozzle 506A First normal nozzle 506B Second normal nozzle 506C 3rd normal nozzle 507 Abnormal nozzle 530 Inspection Board 541 Waveform generator 542 Camera D1 Nozzle arrangement direction D2 Printing direction

Claims

1. 1. An inkjet printing method for performing printing on a substrate while moving a substrate and an inkjet head having a plurality of nozzles arranged in a straight line relative to the substrate, comprising: Dividing a coating area within a pixel bank on the substrate into a plurality of divided areas; allocating the plurality of nozzles to the plurality of divided regions; a step of randomly selecting nozzles that eject ink into each divided region from among the nozzles assigned to each divided region; ejecting ink from the selected nozzles onto the plurality of divided regions while moving the substrate and the inkjet head relative to one another.

2. 2. The inkjet printing method according to claim 1, wherein the step of ejecting ink includes a step of ejecting ink from the selected nozzles so that a volume of ink ejected onto each of the plurality of divided regions is within ±50% of an average volume of ink ejected onto the plurality of divided regions.

3. The inkjet printing method according to claim 1 , wherein the step of selecting nozzles includes the step of selecting nozzles in a number equal to or greater than 50% of a total number of nozzles allocated to the divided regions.

4. 4. The inkjet printing method according to claim 1, wherein the step of dividing the coating area into a plurality of divided areas includes a step of dividing the coating area into left and right halves when a moving direction of the substrate relative to the inkjet head is defined as a forward direction.

5. The inkjet printing method according to claim 1 , wherein the step of dividing the coating area into a plurality of divided areas includes a step of dividing the coating area into front and rear areas when a moving direction of the substrate relative to the inkjet head is defined as a forward direction.

6. 4. The inkjet printing method according to claim 1, wherein the step of dividing the coating area into a plurality of divided areas includes a step of dividing the coating area into front-rear and left-right areas when a moving direction of the substrate relative to the inkjet head is defined as a forward direction.

7. A plurality of the coating regions are formed on the substrate, The inkjet printing method according to claim 1 , wherein dividing the coating area into a plurality of divided areas includes making a division position of at least one of the coating areas different from division positions of the other coating areas.

8. 8. The inkjet printing method according to claim 1, wherein the step of allocating the plurality of nozzles to the plurality of divided regions includes a step of making a number of nozzles allocated to at least one of the divided regions different from a number of nozzles allocated to the other divided regions.

9. a step of determining whether or not there is an abnormal nozzle that cannot eject ink among the plurality of nozzles, 9. The inkjet printing method according to claim 1, wherein, when an abnormal nozzle is present, the step of selecting the nozzle includes a step of selecting a nozzle to eject ink into the divided region from among the nozzles assigned to the divided region, excluding the abnormal nozzle.

10. a step of determining whether or not there is an abnormal nozzle that cannot eject ink among the plurality of nozzles, 9. The inkjet printing method according to claim 1, wherein, when an abnormal nozzle is present, the step of ejecting ink includes a step of ejecting ink in place of the abnormal nozzle from a nozzle that is assigned to the application region together with the abnormal nozzle and that has not been selected as a nozzle for ejecting ink into the divided region.

11. a step of determining whether or not there is an abnormal nozzle that cannot eject ink among the plurality of nozzles, 9. The inkjet printing method according to claim 1, wherein, when an abnormal nozzle is present, the step of ejecting ink includes a step of ejecting ink in place of the abnormal nozzle from a nozzle selected as a nozzle for ejecting ink into the divided region from among nozzles assigned to the application region together with the abnormal nozzle.

12. A stage for holding the substrate; An inkjet head having a plurality of nozzles arranged in a row; a relative movement mechanism for moving the stage and the inkjet head relative to each other; A control unit, The control unit is Dividing a coating area in a pixel bank on the substrate into a plurality of divided areas; Allocating the plurality of nozzles to the plurality of divided regions; Randomly selecting nozzles that will eject ink into each divided region from among the nozzles assigned to each divided region; an inkjet printing apparatus that controls the relative movement mechanism to move the substrate and the inkjet head relative to each other, and controls the inkjet head to eject ink from the selected nozzles onto the plurality of divided regions.

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