Inkjet printing method and inkjet printing apparatus

Abstract

Provided is an inkjet printing method and an inkjet printing apparatus, the inkjet printing method printing a substrate while relatively moving the substrate and an inkjet head having a plurality of nozzles arranged along a straight line, the inkjet printing method including: a step of dividing a coated region in a picture element dam on the substrate into a plurality of divided regions; a step of allocating the plurality of nozzles to the plurality of divided regions; a step of randomly selecting a nozzle that ejects ink to a divided region from the nozzles allocated to the divided region; and a step of relatively moving the substrate and the inkjet head while ejecting ink from the selected nozzle to the plurality of divided regions.

Description

Technical Field

[0001] This disclosure relates to inkjet printing methods and inkjet printing apparatus. Background Technology

[0002] To achieve large-area, high-quality, and low-cost displays, it is desirable to replace semiconductor manufacturing processes with printing processes. Examples of displays that can have their manufacturing methods replaced by printing processes include organic EL displays and quantum dot displays.

[0003] For example, organic EL displays typically have a functional layer containing organic functional materials disposed between the anode and cathode. Through the functionality of the organic functional materials, organic devices such as semiconductor elements (transistors), light-emitting elements, and liquid crystal elements can be obtained. Semiconductor elements, for example, include organic semiconductor materials that connect source and drain electrodes disposed on a substrate surface. Organic EL elements, for example, have a light-emitting layer containing organic EL material stacked on an anode electrode disposed on a substrate, and the light-emitting layer is sandwiched between a cathode electrode.

[0004] To pattern functional materials on electrodes, a barrier (i.e., a dam) is sometimes formed surrounding the electrode surface, and a composition containing the functional material is printed in the area defined by the dam. The dam can also be made of resin. When printing ink containing the functional material in the area containing the electrode surface defined by the dam, it is generally preferable that the area to be printed (including the electrode surface) has high wettability, and preferably that the surface of the dam has low wettability. This is to prevent ink leakage outside the intended area. It is known that, generally, fluorine components reduce the surface energy of a material, thus reducing wettability.

[0005] The printing area defined by the partition is referred to below as a sub-pixel. Sub-pixels are generally arranged in a matrix. Ink is ejected from multiple arranged nozzles and applied to these sub-pixels. Furthermore, the nozzles are moved relative to the panel in a direction approximately perpendicular to the nozzle array, and the ink is applied repeatedly, thereby filling all sub-pixels in the matrix with ink. In this process, if there is an uneven volume of ink ejected between the nozzles, areas with more ink and areas with less ink applied to the sub-pixels form lines parallel to the printing direction. As a result, striped luminous spots are produced on the finished display device, making the display a defective product. As a countermeasure, a method has been studied in which the nozzles used are randomly varied to distribute the uneven ink ejection volume of each nozzle to apply to each sub-pixel (for example, see Patent Document 1).

[0006] Prior technology literature

[0007] Patent Document 1: Japanese Patent No. 4984934 Summary of the Invention

[0008] The inkjet printing method disclosed herein involves printing on a substrate while moving it relative to an inkjet head having a plurality of nozzles arranged in a straight line. The inkjet printing method includes: dividing a coating area within a pixel partition on the substrate into a plurality of segmented regions; distributing the plurality of nozzles to the plurality of segmented regions; randomly selecting a nozzle from the nozzles distributed to each segmented region to eject ink into the segmented region; and ejecting ink from the selected nozzle into the plurality of segmented regions while moving the substrate relative to the inkjet head.

[0009] An inkjet printing apparatus according to one aspect of this disclosure 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 relative to the inkjet head; and a control unit that performs the following processes: dividing a coating area within a pixel partition on the substrate into a plurality of segmented regions; distributing the plurality of nozzles to the plurality of segmented regions; randomly selecting a nozzle from the nozzles distributed to each segmented region to eject ink into the segmented region; controlling the relative movement mechanism to move the substrate relative to the inkjet head, and controlling the inkjet head to eject ink from the selected nozzle into the plurality of segmented regions. Attached Figure Description

[0010] Figure 1 This is a schematic diagram illustrating an inkjet printing apparatus according to the first embodiment of the present disclosure.

[0011] Figure 2 This is a schematic diagram illustrating an inkjet printing apparatus according to a second embodiment of the present disclosure.

[0012] Figure 3 This is a schematic diagram illustrating an inkjet printing apparatus according to a third embodiment of the present disclosure.

[0013] Figure 4 This is a schematic diagram illustrating an inkjet printing apparatus according to the fourth embodiment of this disclosure.

[0014] Figure 5 This is a schematic diagram illustrating an inkjet printing apparatus according to the fifth embodiment of this disclosure.

[0015] Figure 6 This is a schematic diagram illustrating an inkjet printing apparatus during the implementation of a first non-ejection response process according to the fifth embodiment of this disclosure.

[0016] Figure 7 This is a schematic diagram illustrating an inkjet printing apparatus during the implementation of a second non-ejection response process according to the fifth embodiment of this disclosure.

[0017] Explanation of reference numerals in the attached figures:

[0018] Inkjet printing units 101, 201, 301, 401, 501

[0019] 102 Inkjet Head

[0020] 103 Workbench

[0021] 104 Relative Movement Mechanism

[0022] Control Units 105, 205, 305, 405, and 505

[0023] 106 nozzles

[0024] 110, 210, 310, 410, 510, 610 substrate

[0025] 111, 211, 311, 511 pixels

[0026] 112, 212, 312, 412, 512, 612 sub-pixels

[0027] 113, 213, 313, 413, 513, 613, 613A, 613B, 613C (Divided regions)

[0028] 114, 214, 414, 614 dividing lines

[0029] 314, 514 First dividing line

[0030] 315, 515 Second dividing line

[0031] 120 ink

[0032] 121, 121A, 121B, 531 hit the target location.

[0033] 506 Normal Nozzle

[0034] 506A First Normal Nozzle

[0035] 506B Second Normal Nozzle

[0036] 506C Third Normal Nozzle

[0037] 507 Abnormal Nozzle

[0038] 530 Inspect the substrate

[0039] 541 Waveform Generating Device

[0040] 542 camera

[0041] D1 Nozzle Arrangement Direction

[0042] D2 Printing direction. Detailed Implementation

[0043] In the method described in Patent Document 1, the positions of each sub-pixel and the selected nozzle are varied for each pixel by random numbers. If the position of the selected nozzle is off-center relative to the sub-pixel, an imbalance in ink thickness and uncoated areas occur within the sub-pixel. This results in uneven light emission within the sub-pixel. Furthermore, if the nozzle intended to eject ink into the sub-pixel experiences nozzle blockage or other defects, striped areas of poor light emission are produced.

[0044] In view of the present situation, the object of this disclosure is to provide an inkjet printing method and inkjet printing apparatus capable of suppressing printing spots on a substrate.

[0045] The following describes one embodiment of this disclosure. It should be noted that the configurations of the first to fifth embodiments shown below can be combined within a feasible range.

[0046] [First Implementation Method]

[0047] First, the first embodiment of this disclosure will be described. Figure 1 This is a schematic diagram illustrating an inkjet printing apparatus according to the first embodiment of the present disclosure.

[0048] like Figure 1 As shown, the inkjet printing apparatus 101 includes an inkjet head 102, a worktable 103, a relative movement mechanism 104, and a control unit 105.

[0049] On the inkjet head 102, a plurality of nozzles 106 are arranged in a row. Hereinafter, the arrangement direction of the plurality of nozzles 106 will sometimes be described as the nozzle arrangement direction D1. It should be noted that the plurality of nozzles 106 may also be arranged in two or more rows, in which case it may be a so-called staggered arrangement. In addition, the plurality of nozzles 106 may also be arranged in a direction inclined relative to the printing direction D2 described later.

[0050] The stage 103 holds the substrate 110 below the inkjet head 102 using a method such as vacuum adsorption. On the substrate 110, pixel cells 111 are arranged in a matrix. Each pixel cell 111 is composed of multiple sub-pixels 112, for example, with RGB three colors. Each sub-pixel 112 is a coating area within a pixel spacer, and is formed, for example, in an oblong shape. The length direction of the oblong shape of the sub-pixel 112 is parallel to the nozzle alignment direction D1. The three-color sub-pixels 112 are arranged in a direction orthogonal to the nozzle alignment direction D1. However, in the case of manufacturing a monochrome display panel, each pixel cell 111 is composed of a single sub-pixel 112.

[0051] The relative movement mechanism 104 moves the worktable 103 and the inkjet head 102 relative to each other in a direction orthogonal to the nozzle arrangement direction D1. In the first embodiment, the worktable 103 is moved relative to the inkjet head 102 in a direction... Figure 1 The inkjet head 102 can be moved in the printing direction D2 shown. It should be noted that the inkjet head 102 can also be moved relative to the worktable 103, and both the inkjet head 102 and the worktable 103 can be moved.

[0052] 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 worktable 103 along the printing direction D2, thereby allowing the substrate 110 to pass under the inkjet head 102. At this time, the control unit 105 controls the inkjet head 102 to hit the targeted sub-pixel 112, and adjusts the timing to eject the ink 120 from the nozzle 106.

[0053] To explain in more detail, the control unit 105 performs the segmentation process, the allocation process, the selection process, and the ejection process. Each process is described below.

[0054] In the segmentation process, the control unit 105 divides the sub-pixel 112 into multiple segmentation regions 113. Figure 1 In the configuration shown, the number of nozzles 106 that allow ink 120 to hit sub-pixels 112 is eight for each sub-pixel 112. The control unit 105 divides the sub-pixel 112 into, for example, four parts by dividing lines 114, and sets four dividing regions 113. When the printing direction D2 is set to forward, the control unit 105 divides the sub-pixel 112 left and right.

[0055] In the dispensing process, the control unit 105 distributes the nozzles 106 constituting the inkjet head 102 to multiple segmented regions 113. For example, the control unit 105 distributes two nozzles to each segmented region 113, which are capable of directing ink 120 to hit one sub-pixel 112.

[0056] In the selection process, the control unit 105 randomly selects a nozzle 106 from the nozzles 106 allocated to each segmented region 113 to eject ink 120 into the segmented region 113 using a random number. The control unit 105 selects nozzles 106 that account for more than 50% of the total number of nozzles 106 allocated to one segmented region 113. In the first embodiment, one nozzle 106 is selected for each segmented region 113. It should be noted that the control unit 105 may also select nozzles 106 without using a random number.

[0057] In the ejection process, the control unit 105 controls the relative movement mechanism 104 to move the worktable 103 and controls the inkjet head 102 to eject ink 120 from the nozzle 106 selected in the selection process. At this time, the control unit 105 controls the inkjet head 102 to make the volume of ink ejected for each segmented region 113 within ±50% of the average volume of ink ejected to these segmented regions 113, and causes the ink 120 to be ejected from the nozzle 106 in the ejection process. That is, the control unit 105 controls the inkjet head 102 to satisfy the following formula (1).

[0058]

[0059] b: Number of sub-pixel segments

[0060] V i : The volume of ink ejected into the i-th segmented region

[0061] exist Figure 1 The image shows the ink 120 ejected into each segmented area 113, and the target position 121 of the nozzle 106 that did not eject ink 120. Figure 1 In the diagram, the ink 120 is represented by a gray circle, and the target location 121 is represented by a dashed circle. The ink 120 spreads in a roughly concentric circle shape from the target location. The number of sub-pixels 112 in the segmentation process, the selection probability of the nozzles 106 that eject the ink 120 in the selection process, and the ejection volume and number of droplets of the ink 120 controlled in the ejection process are set so that the spreading fills the entire segmented region 113. Ideally, the randomness of the film thickness, i.e., the variation of the combination of nozzles 106, should be increased to satisfy the necessary condition of the volume of ink 120 based on the above equation (1). When the number of nozzles 106 allocated to each segmented region 113 is set to n, and the number of nozzles 106 that eject the ink 120 is set to r, the combination K is represented by the following equation (2). In addition, as shown in the following equation (3), the combination of nozzles 106 can be maximized by setting r to about half of n.

[0062]

[0063] r≈n / 2 ···(3)

[0064] As described above, the control unit 105 divides the sub-pixel 112 into multiple segmented regions 113 and distributes the multiple nozzles 106 of the inkjet head 102 to the multiple segmented regions 113. The control unit 105 randomly selects a nozzle 106 from the nozzles 106 distributed to each segmented region 113 to eject ink into the segmented region 113, and ejects ink 120 from the selected nozzle 106 into the multiple segmented regions 113. Therefore, by ejecting ink 120 into each segmented region 113, it is possible to prevent the generation of areas within the sub-pixel 112 that are not covered by ink 120, while also allowing the film thickness of ink 120 to vary randomly according to each segmented region 113. Therefore, it is possible to reduce the bias in the film thickness of ink 120 parallel to the printing direction D2, and to suppress the generation of striped printing spots on the substrate 110. As a result, it is possible to suppress the light-emitting spots on the substrate.

[0065] [Second Implementation]

[0066] Next, the second embodiment of this disclosure will be described. Figure 2 This is a schematic diagram illustrating an inkjet printing apparatus according to the second embodiment of this disclosure. It should be noted that structures identical to those in the inkjet printing apparatus 101 of the first embodiment are labeled with the same names and reference numerals, and descriptions are omitted.

[0067] In the second embodiment, a plurality of pixel cells 211 are arranged on the substrate 210. Each pixel cell 211 is composed of three-color sub-pixels 212. Each sub-pixel 212 is a coating area within a pixel partition, for example, a roughly square shape with a curved corner.

[0068] The control unit 205 of the inkjet printing apparatus 201 performs the segmentation process, the allocation process, the selection process, and the ejection process.

[0069] The control unit 205 divides the sub-pixel 212 into multiple segmentation regions 213 during the segmentation process. Figure 2 In the configuration shown, the number of nozzles 106 that allow ink 120 to hit sub-pixels 212 is three for each sub-pixel 212. The control unit 205 divides the sub-pixel 212 into, for example, three parts by dividing lines 214, setting three division regions 213. When the printing direction D2 is set to forward, the control unit 205 divides the sub-pixel 212 forward and backward.

[0070] In the dispensing process, the control unit 205 dispenses all three nozzles 106 that enable the ink 120 to hit one sub-pixel 212 into one segmented region 213. That is, the control unit 205 can make the ink 120 hit one sub-pixel 212 from the three nozzles 106 respectively for the three segmented regions 213 constituting one sub-pixel 212.

[0071] In the selection process, the control unit 205 randomly selects nozzles 106 that eject ink 120 into the segmented area 213 using a random number. The control unit 205 selects nozzles 106 that account for more than 50% of the total number of nozzles 106 assigned to one segmented area 213. In the second embodiment, two nozzles 106 are selected for each segmented area 213.

[0072] In the ejection process, the control unit 205 ejects ink 120 from the nozzle 106 selected in the selection process in a manner that satisfies the above formula (1), thereby performing printing.

[0073] exist Figure 2 The diagram shows the target positions 121 of ink 120 ejected into each segmented region 213 and the nozzles 106 that did not eject ink 120. In the second embodiment, there is a concern about producing sub-pixels 212 with misaligned coating positions. For example, in Figure 2 In the second column from the left, starting from the second sub-pixel 212 from the bottom, the target positions 121 of the nozzles 106 that did not eject ink 120 are arranged in a row, with the ink 120 coating position shifted to the left of the center. Therefore, in order to ensure that the ink 120 can spread and wet the entire sub-pixel 212 even under such conditions, the number of nozzles 106 ejecting ink 120 needs to be determined by considering the wetting spread of ink 120 into the sub-pixel 212 and the shape of the sub-pixel 212. For example, if the diameter of the nozzle 106 is 20 μm, the diameter of the ejected droplet is approximately 20 μm. The wetting spread of the hit droplet is greatly influenced by the wettability of the sub-pixel 212. The hit droplet may start wetting from a state with a contact angle greater than 10 degrees and a droplet diameter of approximately 20 μm, and then spread to a contact angle of 0 degrees, which is called extended wetting. For example, when the nozzle spacing of 106 is 20 μm, the size of sub-pixel 212 in the nozzle arrangement direction D1 is 60 μm, and the droplet diameter of ink 120 after wetting and spreading on sub-pixel 212 is 60 μm, even if the sub-pixel 212 is misaligned, the ink 120 can still be wetted and spread within the sub-pixel 212. The inkjet printing method of the second embodiment is effective when the ejection spacing in the printing direction D2 can be shortened, and the shape of sub-pixel 212 is long in the printing direction D2 and short in the nozzle arrangement direction D1.

[0074] [Third Implementation Method]

[0075] Next, the third embodiment of this disclosure will be described. Figure 3 This is a schematic diagram illustrating an inkjet printing apparatus according to the third embodiment of this disclosure. It should be noted that components identical to those in the inkjet printing apparatus 101 of the first embodiment are labeled with the same names and reference numerals, and descriptions are omitted.

[0076] In the third embodiment, a plurality of pixel cells 311 are arranged on the substrate 310. Each pixel cell 311 is composed of three-color sub-pixels 312 arranged in the printing direction D2. The sub-pixel 312 is a coating area within a pixel partition and is formed into the same elongated oval shape as the sub-pixel 112 in the first embodiment.

[0077] The control unit 305 of the inkjet printing apparatus 301 performs the segmentation process, the allocation process, the selection process, and the ejection process.

[0078] In the segmentation process, the control unit 305 divides the sub-pixel 312 into multiple segmentation regions 313. Figure 3 In the configuration shown, the number of nozzles 106 that allow ink 120 to hit sub-pixels 312 is 8 for each sub-pixel 312. The control unit 305 divides the sub-pixel 312 into 4 parts 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, setting 4 division regions 313. When the printing direction D2 is set to forward, the control unit 305 divides the sub-pixel 312 front-back and left-right.

[0079] In the dispensing process, the control unit 305 dispenses ink 120 from eight nozzles 106 that are capable of hitting one sub-pixel 312, for example, dispensing four nozzles to each of the two left-right arranged segmented regions 313. That is, the control unit 305 can make ink 120 hit from four nozzles 106 respectively for the four segmented regions 313 that constitute one sub-pixel 312.

[0080] In the selection process, the control unit 305 randomly selects nozzles 106 that eject ink 120 into the segmented area 313 using a random number. The control unit 305 selects nozzles 106 that account for more than 50% of the total number of nozzles 106 allocated to one segmented area 313. In the third embodiment, two nozzles 106 are selected for each segmented area 313.

[0081] In the ejection process, the control unit 305 ejects ink 120 from the nozzle 106 selected in the selection process in a manner that satisfies the above formula (1), thereby performing printing.

[0082] exist Figure 3The diagram shows the ink 120 ejected into each segmented area 313 and the target position 121 of the nozzles 106 that did not eject ink 120. In the third embodiment, the sub-pixel 312 can be arbitrarily divided in the printing direction D2, so even if the sub-pixel 312 is large, it can effectively prevent the sub-pixel 312 from being unfilled with ink 120. In addition, in the third embodiment, when multiple first dividing lines 314 are set, that is, when the sub-pixel 312 is divided into three or more segments, the inkjet head 102 needs to cope with high-frequency ejection or reduce the relative movement speed between the inkjet head 102 and the worktable 103 to print at a low speed. For high-resolution display production, the inkjet head 102 reduces the orifice diameter of the nozzles 106 and narrows the spacing. The third embodiment is effective when using such an inkjet head 102 to manufacture low-resolution large-screen displays or when manufacturing multiple varieties on a single production line.

[0083] [Fourth Implementation Method]

[0084] Next, the fourth embodiment of this disclosure will be described. Figure 4 This is a schematic diagram illustrating the inkjet printing apparatus according to the fourth embodiment of this disclosure. It should be noted that components identical to those in the inkjet printing apparatus 101 of the first embodiment are labeled with the same names and reference numerals, and descriptions are omitted.

[0085] In the fourth embodiment, sub-pixels 412 constituting pixel pixels are arranged on the substrate 410. Sub-pixels 412 are coating areas within pixel partitions and are formed into the same elongated oval shape as sub-pixels 112 in the first embodiment.

[0086] The control unit 405 of the inkjet printing apparatus 401 performs the segmentation process, the allocation process, the selection process, and the ejection process.

[0087] In the segmentation process, the control unit 405 divides the sub-pixel 412 into multiple segmentation regions 413. When the printing direction D2 is set to forward, the control unit 405 divides the sub-pixel 412 into two parts, left and right. Figure 4In the configuration shown, the number of nozzles 106 capable of striking the ink 120 against the sub-pixel 412 is an odd number of 7 for each sub-pixel 412. When the number of nozzles 106 capable of striking one sub-pixel 412 is odd, the number of nozzles 106 cannot be evenly distributed to each segmented region 413 in a number other than 1, as in the case of an even number. In the fourth embodiment, the control unit 405 randomly determines the segmentation position in the sub-pixel 412, for example, using a random number. In this case, the control unit 405 can also make the segmentation position different for each sub-pixel 412 based on the bent segmentation line 414. In the fourth embodiment, an example is shown where the number of nozzles 106 allocated to the left and right segmented regions 413 is 2 and 5, 3 and 4, or 4 and 3 respectively, but the sub-pixels 412 can also be segmented in a manner such as 1 and 6.

[0088] In the dispensing process, the control unit 405 allocates a number of nozzles 106, which enable ink 120 to hit a sub-pixel 412, to two left-right arranged segmented regions 413, respectively, according to the size of each segmented region 413.

[0089] In the selection process, the control unit 405 randomly selects the nozzles 106 that eject ink 120 into the segmented area 413 using a random number. In the fourth embodiment, an example is the selection of 2 or 1 nozzles 106 out of 3 nozzles 106 allocated to each segmented area 413, 3 or 2 or 1 nozzles 106 out of 4 nozzles 106, or 3 or 2 or 1 nozzles 106 out of 5 nozzles 106. However, the selection can also be as follows: Alternatively, if the control unit 405 has 1 and 6 nozzles 106 allocated to the left and right segmented areas 413 respectively, it must select 1 nozzle 106 for the left segmented area 413 and 4 nozzles 106 out of 6 nozzles 106 for the right segmented area 413. Furthermore, the control unit 405 may select nozzles 106 that are 50% or more of the total number of nozzles 106 allocated to one segmented area 413.

[0090] In the ejection process, the control unit 405 ejects ink 120 from the nozzle 106 selected in the selection process in a manner that satisfies the above formula (1), thereby performing printing.

[0091] exist Figure 4The diagram shows the target positions 121 of the ink 120 ejected into each segmented region 413 and the nozzles 106 that did not eject ink 120. Preferably, the number of nozzles 106 ejecting ink 120 in each sub-pixel 412 is the same. However, this is not a limitation if the volume variation of ink 120 in each sub-pixel 412 is within the range required for a complete display. For example, it is acceptable as long as the variation in ink thickness (film thickness) of each sub-pixel 412 does not exceed ±50% of the average ink thickness of all sub-pixels 412. When the above description is generalized, it becomes the following equations (4) and (5).

[0092]

[0093] L: The number of nozzles that can direct ink towards sub-pixels.

[0094] n i The number of nozzles assigned to the segmented region.

[0095] b: Number of sub-pixel segments

[0096]

[0097] Z[j]: The number of nozzles that caused the ink to hit the sub-pixel.

[0098] j: The index of any sub-pixel

[0099] r i The number of nozzles that caused the ink to hit the segmented area.

[0100] [Fifth Implementation Method]

[0101] Next, the fifth embodiment of this disclosure will be described. Figure 5 This is a schematic diagram illustrating an inkjet printing apparatus according to the fifth embodiment of this disclosure. Figure 6 This is a schematic diagram of an inkjet printing apparatus during the implementation of a response to the first non-ejection. Figure 7 This is a schematic diagram illustrating the inkjet printing apparatus when the second non-ejection response is implemented. It should be noted that components identical to the inkjet printing apparatus 101 of the first embodiment are labeled with the same names and reference numerals, and descriptions are omitted.

[0102] like Figure 5 and Figure 6 As shown, the inkjet printing apparatus 501 includes an inkjet head 102, a worktable 103, a relative movement mechanism 104, a control unit 505 composed of a computer, a waveform generation device 541, and a camera 542.

[0103] like Figure 6As shown, a plurality of pixel cells 511 are arranged on the substrate 510 of the fifth embodiment. Each pixel cell 511 is composed of three-color sub-pixels 512 arranged in the printing direction D2. Figure 7 As shown, a plurality of sub-pixels 612 are arranged on the substrate 610 of the fifth embodiment. Sub-pixels 512 and 612 are coating areas within the pixel partition and are formed into the same elongated oval shape as sub-pixel 112 in the first embodiment.

[0104] The waveform generation 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, based on the ejection waveform, ejects ink 120 from a predetermined nozzle 106 at predetermined timings. The camera 542 acquires data for checking for ink penetration. Figure 5 The image of the ink 120 on the substrate 530 is shown, and the image is output to the control unit 505.

[0105] The control unit 505 of the inkjet printing apparatus 501 performs inspection, division, allocation, selection and ejection processes.

[0106] During the inspection process, the control unit 505 controls the relative movement mechanism 104 and the inkjet head 102 to ensure that ink 120 is ejected from all nozzles 106 of the inkjet head 102 and strikes the inspection substrate 530 held on the worktable 103. The camera 542 outputs an image of the inspection substrate 530 to the control unit 505. The control unit 505 determines the location of the ink 120 that strikes the inspection substrate 530, the size of the droplet, and whether it has been ejected. If ink 120 is absent at the target location on the inspection substrate 530 where it should be present, the control unit 505 identifies the nozzle 106 that should have ejected ink 120 at that target location as an abnormal nozzle 507. For example, in Figure 5 If there is no ink 120 at the target location 531 indicated by the dashed circle, the control unit 505, for example, based on a preset relationship between the target location and the nozzle 106 position, identifies the nozzle 106, which should be ejecting ink 120 to the target location 531, as an abnormal nozzle 507. It should be noted that, hereinafter, the nozzle 106 capable of ejecting ink 120 may sometimes be referred to as a normal nozzle 506. Figures 5-7 In the diagram, a normal nozzle 506 is represented by a simple circle, while an abnormal nozzle 507 is represented by a circle with a shading line drawn across it.

[0107] If no abnormal nozzle 507 is found during the inspection process, the control unit 505 performs the same segmentation, allocation, selection, and ejection processes as in the first to fourth embodiments. During the ejection process, the control unit 505 causes the waveform generation device 541 to output an ejection waveform assuming the absence of the abnormal nozzle 507. Conversely, if an abnormal nozzle 507 is found during the inspection process, the control unit 505 performs either a first non-ejection response or a second non-ejection response.

[0108] [Handling the first instance of non-spraying]

[0109] exist Figure 6 In the configuration shown, the number of nozzles 106 capable of directing ink 120 towards sub-pixels 512 is seven for each sub-pixel 512. In the segmentation process, the control unit 505, similar to the fourth embodiment, uses random numbers to segment the sub-pixel 512 into multiple segmented regions 513. The control unit 505 segments the sub-pixel 512 into two segmented regions 513 via a bent first segmentation line 514.

[0110] The control unit 505 does not change the size of the segmented region 513 divided by the first dividing line 514 for sub-pixels 512 in which there are no abnormal nozzles 507 among the nozzles 106 capable of hitting the ink 120. For sub-pixels 512 in which there are abnormal nozzles 507 among the nozzles 106 capable of hitting the ink 120, the control unit 505 changes the size of the segmented region 513 by changing the bent first dividing line 514 to a straight second dividing line 515. In this case, it is preferable that the control unit 505 sets the segmented region 513 such that at least two normal nozzles 506 are allocated to the segmented region 513 where abnormal nozzles 507 are located.

[0111] In the dispensing process, the control unit 505 dispenses a number of normal nozzles 506 corresponding to the size of the two dividing regions 513, which are divided by the first dividing line 514. In the dispensing process, the control unit 505 also dispenses abnormal nozzles 507 and a number of normal nozzles 506 corresponding to the size of the dividing regions 513, which are divided by the second dividing line 515.

[0112] In the selection process, the control unit 505 randomly selects normal nozzles 506 that eject ink 120 into the segmented area 513 using a random number. The control unit 505 selects at least 50% of the total number of normal nozzles 506 assigned to one segmented area 513. That is, for a segmented area 513 assigned an abnormal nozzle 507, the control unit 505 selects at least 50% of the total number of nozzles 106 other than the abnormal nozzle 507. Figure 6In the example, two of the three normal nozzles 506 are normal nozzles 506.

[0113] In the ejection process, the control unit 505 ejects ink 120 from the normal nozzle 506 selected in the selection process in a manner that satisfies the above formula (1), thereby performing printing. At this time, the control unit 505 causes the waveform generation device 541 to output an ejection waveform assuming the presence of an abnormal nozzle 507. Based on the ejection waveform from the waveform generation device 541, the inkjet head 102 ejects ink 120 only from the normal nozzle 506. It should be noted that, assuming that when an abnormal nozzle 507 is present, the arrangement range of the remaining 6 normal nozzles 506 is biased towards the right or left side within the sub-pixel 512 (in Figure 6 (The example shown is the right side). In this case, the relative position of the inkjet head 102 with respect to the substrate 510 can also be adjusted within the allowable range of the printing position of other sub-pixels 512, so that the configuration range of the above-mentioned six normal nozzles 506 is located in the center of the sub-pixel 512.

[0114] [Second, handling situations where spraying doesn't occur]

[0115] exist Figure 7 In the configuration shown, the number of nozzles 106 capable of directing ink 120 towards sub-pixels 612 is eight for each sub-pixel 612. During the segmentation process, the control unit 505 divides the sub-pixels 612 into multiple sub-pixels 612 via straight segmentation lines 614 (in...). Figure 7 In the example, there are 2) segmented regions 613.

[0116] In the allocation process, the control unit 505 allocates a number of partitions 613 corresponding to the size of each partition 613. Figure 7 In the example, there are 4 nozzles (106 in total). For example, in... Figure 7 In this example, the control unit 505 assigns four nozzles 106 to the four leftmost segmented regions 613 arranged in the printing direction D2. The four nozzles 106 are arranged from left to right in the order of first normal nozzle 506A, abnormal nozzle 507, second normal nozzle 506B, and third normal nozzle 506C.

[0117] In the selection process, the control unit 505 randomly selects nozzles 106 that eject ink 120 into the segmented area 613 using a random number. The control unit 505 selects a number of nozzles 106 that represent more than 50% of the total number of nozzles 106 assigned to one segmented area 613. Figure 7 In the example, there are 3 out of 4 nozzles 106. If the selected nozzles 106 include an abnormal nozzle 507, the control unit 505 performs at least one of the following first reselection process and second reselection process.

[0118] First, the first reselection process will be explained. If, in the selection process, the first normal nozzle 506A, the abnormal nozzle 507, and the third normal nozzle 506C are selected for the lowermost segment 613A among the four leftmost segmented segments 613, the control unit 505, in the first reselection process, replaces the abnormal nozzle 507 and reselects the second normal nozzle 506B, which was not selected in the selection process. Then, in the ejection process, the control unit 505 ejects ink 120 from the first to third normal nozzles 506A to 506C onto the segmented segment 613A in a manner satisfying the above formula (1), thereby performing printing. That is, regarding the target position 121A, the ink 120 from the abnormal nozzle 507 should have hit it, but the ink 120 cannot be ejected from the abnormal nozzle 507; therefore, the ink 120 from the second normal nozzle 506B hits the target position 121B, which was originally not intended to be hit.

[0119] Next, the second reselection process will be explained. For segment 613B, the second segment from the bottom among the four leftmost segmented segments 613, if the first normal nozzle 506A, the abnormal nozzle 507, and the second normal nozzle 506B were selected in the selection process, the control unit 505, in the second reselection process, replaces the abnormal nozzle 507 with the first normal nozzle 506A selected in the selection process, and uses it as the normal nozzle 506 to eject ink 120. Then, in the ejection process, the control unit 505 ejects ink 120 from the first normal nozzle 506A and the second normal nozzle 506B to segment 613B in a manner satisfying the above formula (1), thereby performing printing. At this time, the control unit 505 ejects ink 120 twice from the first normal nozzle 506A at different times for segment 613B.

[0120] It should be noted that, alternatively, if the control unit 505 selects the abnormal nozzle 507, the second normal nozzle 506B, and the third normal nozzle 506C in the selection process for the second segment 613C (one of the four leftmost segmented segments 613 from the top), in the second reselection process, it may select the second normal nozzle 506B again instead of the abnormal nozzle 507 as the normal nozzle 506 that ejects ink 120 in place of the abnormal nozzle 507. In this case, during the ejection process, ink 120 is ejected from the second normal nozzle 506B and the third normal nozzle 506C onto the segmented segment 613C in a manner that satisfies the above formula (1). At this time, ink 120 is ejected twice from the second normal nozzle 506B at different times for the segmented segment 613C.

[0121] Based on the above-described second non-ejection handling, in the presence of an abnormal nozzle 507, the normal nozzle 506 printed along the printing direction D2 in the area printed by the normal nozzle 506 adjacent to the abnormal nozzle 507 can also prevent the normal nozzle 506 from being fixed, can prevent the generation of areas not covered by ink 120 in the sub-pixel 612, and can randomly vary the film thickness of ink 120 according to each segmented area 613.

[0122] According to the inkjet printing method and inkjet printing apparatus disclosed herein, it is possible to suppress printing spots on the substrate.

[0123] [Industry Applicability]

[0124] Even when uneven volume of each nozzle occurs during production, the inkjet printing method and apparatus disclosed herein can produce displays, for example, with high quality as a substrate. Furthermore, the inkjet printing method and apparatus disclosed herein can be applied not only to displays, but also to devices formed on substrates by printing, such as lighting, sensors, and solar cells, making them extremely useful and highly industrially applicable.

Claims

1. An inkjet printing method, wherein printing is performed on a substrate while moving it relative to an inkjet head having a plurality of nozzles arranged in a straight line, wherein... The inkjet printing method comprises: The process of dividing the coating area within the pixel partition on the substrate into multiple segmented areas. The process of distributing the plurality of nozzles to the plurality of segmented regions; The process of randomly selecting a nozzle from the nozzles allocated to each segmented region to eject ink into the segmented region; as well as A process of ejecting ink from the selected nozzles into the plurality of segmented regions while moving the substrate relative to the inkjet head.

2. The inkjet printing method according to claim 1, wherein, The process of ejecting the ink includes the process of ejecting ink from the selected nozzle in such a way that the volume of ink ejected to each of the plurality of segmented regions is within ±50% of the average volume of ink ejected to the plurality of segmented regions.

3. The inkjet printing method according to claim 1 or 2, wherein, The process of selecting the nozzles includes selecting a number of nozzles that accounts for more than 50% of the total number of nozzles allocated to the segmented area.

4. The inkjet printing method according to claim 1 or 2, wherein, The process of dividing the coating area into multiple segments includes: dividing the coating area into left and right segments when the moving direction of the substrate relative to the inkjet head is set to forward.

5. The inkjet printing method according to claim 1 or 2, wherein, The process of dividing the coating area into multiple segments includes: dividing the coating area front to back when the moving direction of the substrate relative to the inkjet head is set to forward.

6. The inkjet printing method according to claim 1 or 2, wherein, The process of dividing the coating area into multiple segments includes: dividing the coating area front-to-back and left-to-right when the moving direction of the substrate relative to the inkjet head is set to forward.

7. The inkjet printing method according to claim 1 or 2, wherein, A plurality of coating areas are formed on the substrate. The process of dividing the coating area into multiple segments includes: making the segmentation position in at least one coating area different from the segmentation positions in other coating areas.

8. The inkjet printing method according to claim 1 or 2, wherein, The process of allocating the plurality of nozzles to the plurality of segmented regions includes the process of making the number of nozzles allocated to at least one segmented region different from the number of nozzles allocated to the other segmented regions.

9. The inkjet printing method according to claim 1 or 2, wherein, The inkjet printing method further includes the step of determining whether there are any abnormal nozzles among the plurality of nozzles that cannot eject ink. In the presence of the abnormal nozzle, the process of selecting the nozzle includes the process of selecting a nozzle that ejects ink into the segmented area from among the nozzles allocated to the segmented area, excluding the abnormal nozzle.

10. The inkjet printing method according to claim 1 or 2, wherein, The inkjet printing method further includes the step of determining whether there are any abnormal nozzles among the plurality of nozzles that cannot eject ink. In the presence of the malfunctioning nozzle, the process of ejecting the ink includes: ejecting ink from a nozzle that was not selected as a nozzle for ejecting ink to the segmented area, which was assigned to the coating area along with the malfunctioning nozzle, in place of the malfunctioning nozzle.

11. The inkjet printing method according to claim 1 or 2, wherein, The inkjet printing method further includes the step of determining whether there are any abnormal nozzles among the plurality of nozzles that cannot eject ink. In the presence of the malfunctioning nozzle, the process of ejecting the ink includes: ejecting ink from a nozzle selected as a nozzle for ejecting ink into the segmented area, which is assigned to the coating area along with the malfunctioning nozzle, in place of the malfunctioning nozzle.

12. An inkjet printing apparatus, wherein, The inkjet printing apparatus includes: The worktable holds the substrate. An inkjet head consists of multiple nozzles arranged in a row; A relative movement mechanism that moves the worktable relative to the inkjet head; and Control Department The control unit performs the following processing: The coating area within the pixel partition on the substrate is divided into multiple segmented areas. Distribute the plurality of nozzles to the plurality of segmented regions; A nozzle is randomly selected from the nozzles assigned to each segmented region to eject ink into the segmented region; The relative movement mechanism is controlled to move the substrate relative to the inkjet head, and the inkjet head is controlled to eject ink from the selected nozzles into the plurality of segmented regions.

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