Inkjet head inspection device and inkjet recording device, inkjet head inspection method and inkjet recording method, and program

Abstract

To inspect defects of each nozzle arranged on an ink discharge surface of an inkjet head, and prevent a shortage of a liquid amount of ink and color mixture in a discharge destination by deviated discharge and ink non-discharge.SOLUTION: An inkjet head inspection device for inspecting an inkjet head includes a nozzle inspection part for inspecting presence / absence of failure on the basis of the shape of droplets of ink formed on a discharge surface of the inkjet head corresponding to a plurality of nozzles arranged on the discharge surface, for each of the nozzles.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to an inkjet head inspection device, an inkjet recording device, an inkjet head inspection method, an inkjet recording method, and a program. [Background technology]

[0002] Inkjet recording devices are sometimes used to form organic EL elements used in light-emitting elements of displays and quantum dot color conversion layers used for color conversion. The inkjet head of an inkjet recording device has a nozzle row on the ink ejection surface, and ejects ink from each nozzle included in the nozzle row. For such applications, inkjet recording devices are required to have extremely high landing accuracy and stability. For example, when ejecting functional ink containing quantum dots onto a substrate having multiple banks arranged in a matrix shape, it is required to land the same ink in the target bank without excess or deficiency. However, if there is a nozzle defect, defects such as a shortage of liquid in the bank due to ink failure and ink color mixing due to ejection distortion occur. In the case of ink failure, these defects can be compensated for by adding the required amount of ink from another nozzle, but it is difficult to compensate for color mixing due to ejection distortion. In order to suppress such ejection distortion and ink failure, an inspection means for identifying defective nozzles is required. For example, an inspection means using a vibration waveform in the ink flow path can detect a non-ejecting nozzle where a nozzle blockage has occurred. However, the inspection accuracy is low because it is not possible to detect foreign matter on the nozzle that leads to ejection distortion or the ink wetting state around the nozzle based on the vibration waveform. Patent Document 1 discloses a method for directly observing nozzles. In the method disclosed in Patent Document 1, ink droplets are formed on the nozzles, and a minute vibration of the meniscus is applied to the droplets, and the behavior of the droplets at that time is observed from the side of the nozzle to detect defective nozzles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-206686 A [Patent Document 2] U.S. Patent Publication 2018 / 0361735 [Patent Document 3] U.S. Patent Publication 2020 / 0189266 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the method disclosed in Patent Document 1, although it is possible to detect as a defective nozzle a nozzle where the droplets on the nozzle are fluctuating significantly, there is an issue in that it is not possible to detect the cause of minute ejection deviations caused by a decrease in the water repellency of the nozzle, etc. In addition, the state of ink adhesion near the nozzle on the ink ejection surface cannot be confirmed from the side of the nozzle, so it is not possible to observe the state of ink adhesion that leads to ejection deviations.

[0005] The present disclosure has been made in consideration of the above points, and aims to inspect each nozzle arranged on the ink ejection surface of an inkjet head for defects and to prevent ink liquid shortages and color mixing at the ejection destination due to ejection deviations or ink non-ejection. [Means for solving the problem]

[0006] The present disclosure relates to an inkjet head inspection device for inspecting an inkjet head, the inkjet head inspection device including a nozzle inspection unit that inspects each of a plurality of nozzles arranged on the ejection surface of the inkjet head for defects based on the shape of ink droplets formed on the ejection surface in correspondence with the nozzle. Effect of the Invention

[0007] According to the present disclosure, it is possible to inspect each nozzle arranged on the ink ejection surface of an inkjet head for defects, and to prevent ink shortages or color mixing at the ejection destination due to ejection deviations or ink non-ejection. [Brief description of the drawings]

[0008] [Figure 1] 1A and 1B are a plan view and a side view, respectively, illustrating an overview of a recording apparatus according to an embodiment; [Diagram 2] FIG. 2A is a conceptual diagram of an inkjet head and a cap unit according to an embodiment, and FIG. 2B is a conceptual diagram showing an outline of a supply recovery system. [Diagram 3] FIG. 1 is a conceptual diagram showing nozzles arranged on a discharge surface according to an embodiment; [Figure 4] FIG. 1 is a functional block diagram showing an overview of a control system for a recording apparatus according to an embodiment; [Diagram 5] FIG. 1 is a block diagram of a functional unit related to nozzle inspection and nozzle complementation according to an embodiment; [Figure 6] 1A to 1E are plan views showing the shape of ink droplets along the ejection surface. [Figure 7] FIG. 2 is a plan view showing the distribution of droplets in the peripheral area of ​​the nozzles on the discharge surface; [Figure 8] 1 is a flowchart showing a nozzle complementing method executed by a defective nozzle complementing unit according to an embodiment. [Figure 9] A flowchart showing details of the complementation process shown in FIG. 8. [Figure 10] FIG. 1A is a conceptual diagram for explaining S911, showing nozzles arranged on an ejection surface according to an embodiment; FIG. 1B is a conceptual diagram for explaining S914, showing nozzles arranged on an ejection surface according to an embodiment; [Figure 11] 1A and 1B are conceptual diagrams for explaining S916, showing nozzles arranged on an ejection surface according to an embodiment; [Figure 12] FIG. 9 is a schematic side view of S916 showing an inkjet head and a substrate to which functional inks are applied according to an embodiment; [Figure 13]FIG. 13 is a conceptual diagram for explaining S919, showing nozzles arranged on an ejection surface according to an embodiment; [Figure 14] FIG. 9 is a schematic side view of an inkjet head according to an embodiment and a substrate to which functional ink is applied, for illustrating S919. [Figure 15] FIG. 1 is a conceptual diagram showing an outline of an ink circulation system of a recording apparatus according to an embodiment; [Figure 16] FIG. 1 is a perspective view showing an outline of a substrate to which a functional ink according to an embodiment is applied; [Figure 17] Table showing nozzle inspection results and complementary nozzle assignments DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0010] <Configuration of Inkjet Printing Apparatus> FIG. 1 is a conceptual diagram showing the configuration of a recording device 100 in the present disclosure. Note that FIG. 1(a) is a top view, and FIG. 1(b) is a side view, and for convenience of illustration, only some of the elements of the recording device are shown. In addition, the ink supply system and the recovery system mechanism will be described in detail later, so detailed explanations will be omitted here. A substrate 111 to which a functional ink is applied from an inkjet head 102 is set at a predetermined position on a stage 110, and the stage 110 is fixed to a base 109 of the device. The substrate 111 has a thickness of 0.7 mm to 1.1 mm, and a bank material is arranged on the substrate 111. The bank material is a partition wall for preventing ink from flowing and mixing between banks, and has a thickness of about 2 to 30 um. The inkjet head 102 has four head chips 201 (see FIG. 2(a)), and a plurality of nozzle rows (four in the example of FIG. 2(a)) are arranged on an ink ejection surface 301 (see FIG. 3) of each head chip 201 in a direction facing the substrate 111. A plurality of nozzles 202 (see FIG. 2(a)) are arranged in each nozzle row. Therefore, the nozzles 202 are arranged in a matrix on the ink ejection surface 301 of each head chip 201. The nozzles 202 are connected to pressure chambers (not shown) driven by pressure generating means (not shown), and ink in the pressure chambers can be ejected from the nozzles 202. The pressure generating means may be one that uses the deformation of a piezoelectric element such as a piezo element, or one that uses film boiling of a heating element. The inkjet head 102 is supported by a scanning mechanism, and is configured to scan the nozzles 202 in a plane parallel to the XY plane at a height spaced a predetermined distance from the substrate 111 in the Z direction. That is, a main scanning guide rail 105 extending along the main scanning direction (Y direction) is supported by a sub-scanning guide rail 107 extending along the sub-scanning direction (X direction), and the sub-scanning guide rail 107 is supported by a support member 108. A main scanner 104 is provided on the main scanning guide rail 105, and the inkjet head 102 is fixed to the main scanner 104. Therefore, the inkjet head 102 can freely scan within a plane parallel to the XY plane. Note that it is sufficient that the inkjet head 102 and the substrate 111 are capable of moving relative to each other, and the inkjet head 102 may be fixed and the substrate 111 may move.It should be noted that the dashed lines conceptually represent the paths of the ink supply system and do not represent physical connections.

[0011] <System control configuration> FIG. 4 is a control block diagram showing a simplified control system of the recording device 100. For convenience of illustration, only a part of the elements controlled by the control unit is shown. The CPU 401 reads out a program for system control stored in the ROM 402, executes it, and controls the entire system according to the program. At this time, the program is loaded into the RAM 405, and the RAM 405 is used as a working area. That is, the RAM 405 temporarily stores data required for processing executed by the CPU 401, input data, and the like. The CPU 401 also controls the operation of the cleaning unit 404, the transport unit 403, and the like. Furthermore, the CPU 401 also controls the recording operation by the inkjet head 102 through the drive circuit 406.

[0012] The camera 113 is fixed on the base 109 with the lens facing upward as shown in FIG. 1, and captures the ink ejection surface 301 of the inkjet head 102 from below to obtain image data. The binarization circuit 410 binarizes the image data. The vibration sensor 407 is used when the pressure generating means of the inkjet head 102 utilizes the deformation of a piezoelectric element, and measures the residual vibration for each nozzle 202 after a pressure wave is generated in the piezoelectric element corresponding to the nozzle 202. When the pressure generating means of the inkjet head 102 utilizes film boiling, a temperature sensor 408 is used instead of the vibration sensor 407. The temperature sensor 408 measures the temperature in the ink in the pressure chamber after film boiling. The CPU 401 inputs the binarized image data from the binarization circuit 410. The CPU 401 also inputs a signal indicating the residual vibration from the vibration sensor 407, or inputs a signal indicating the temperature from the temperature sensor 408. The binarization circuit 410 may be omitted, and the binarization process of the image data may be performed by the CPU 401.

[0013] Fig. 5 is a block diagram of functional units related to nozzle inspection and nozzle complementation that function as a result of the CPU 401 executing a program. Note that each functional block in the CPU 401 shown in Fig. 5 may be realized by hardware other than the CPU 401.

[0014] When ink is ejected from the nozzles 202 toward the bank, ink droplets are formed in the nozzle holes and the surrounding area of ​​the ink ejection surface 301. A circularity calculation unit 501 calculates the circularity, which is an index of the shape of the ink droplets formed on the ink ejection surface 301 corresponding to each nozzle 202 along the ink ejection surface 301, based on the binary image data. A nozzle surrounding droplet occupancy calculation unit 502 calculates the occupancy of the ink droplets in the surrounding area of ​​the nozzle 202 for each nozzle 202, based on the binary image data.

[0015] The nozzle internal inspection unit 503 evaluates each nozzle 202 based on the residual vibration measured by the vibration sensor 407 or the temperature measured by the temperature sensor 408, and outputs the evaluation result. When the pressure generating means of the inkjet head 102 uses the deformation of a piezoelectric element, for example, as shown in Patent Document 2 or Patent Document 3, a means for evaluating the residual vibration after generating a pressure wave using a piezoelectric element to the extent that ink is not ejected can be mentioned. The nozzle internal inspection unit 503 is a means for analyzing a defective nozzle by detecting the state inside the nozzle. The nozzle internal inspection unit 503 is good at detecting clogging of the nozzle outlet, clogging of the flow path, settling and retention of insoluble particles in the ink, etc., and is widely used because it is an inspection method that can be performed in a short time without ejecting ink.

[0016] The defective nozzle detection unit 504 inputs the circularity calculated by the circularity calculation unit 501, the occupancy rate calculated by the nozzle periphery droplet occupancy rate calculation unit 502, and the evaluation results output by the nozzle inside inspection unit 503, and based on these, inspects each nozzle 202 for defects.

[0017] The roundness calculation unit 501, the nozzle peripheral droplet occupancy calculation unit 502, the nozzle internal inspection unit 503, and the defective nozzle detection unit 504 collectively function as a nozzle inspection unit 500. The nozzle inspection unit 500 corresponds to the inkjet head inspection device of the present invention, and the process performed by the nozzle inspection unit 500 corresponds to the inkjet head inspection method of the present invention. The defective nozzle detection unit 504 may inspect the presence or absence of defects for each nozzle 202 based on the roundness calculated by the roundness calculation unit 501, the occupancy calculated by the nozzle peripheral droplet occupancy calculation unit 502, and part of the evaluation result output by the nozzle internal inspection unit 503. For example, the defective nozzle detection unit 504 may inspect the presence or absence of defects for each nozzle 202 based on the roundness calculated by the roundness calculation unit 501, and the occupancy calculated by the nozzle peripheral droplet occupancy calculation unit 502. Also, for example, defective nozzle detection unit 504 may inspect each nozzle 202 for the presence or absence of defects based on the circularity calculated by circularity calculation unit 501.

[0018] The inspection by the nozzle inspection unit 500 is performed every time a batch job is started in which ink is ejected from each of the multiple substrates 111 in turn.

[0019] The nozzle allocation unit 505 allocates, to each bank, one or more nozzles 202 to be used for ink ejection among the multiple nozzles 202 arranged on the ink ejection surface 301. The nozzle allocation unit 505 also writes allocation data regarding which nozzles are allocated to which banks and in which scans in an allocation table 509. For example, as shown in FIG. 2(a), the inkjet head 102 is provided with four head chips 201, and as shown in FIG. 3, 1024 (=256×4) nozzles 202 are arranged on the ink ejection surface 301 of one head chip 201. Therefore, 4,096 nozzles 202 are arranged on the inkjet head 102. For example, the ink capacity of one bank is about 65 pl, and 5 pl of ink is ejected from one nozzle 202 per ejection. Therefore, a total of 13 ejections are required. Therefore, a total of 13 nozzles 202 are required for one bank. Also, for example, in order to eject a required amount of ink to all the banks of one substrate 111, the inkjet head 102 scans the substrate 111 three times. Therefore, for example, for each bank, five nozzles 202 are assigned for ink ejection in the first scan, four nozzles 202 in the second scan, and four nozzles in the third scan. Therefore, the nozzles 202 assigned for ink ejection simultaneously or within a short period of time to multiple banks are a portion of the 4,096 nozzles 202. Therefore, when focusing on each bank, there are some nozzles 202 that do not eject ink to that bank even if they are capable of ejecting ink to that bank.

[0020] The defect determination unit 506 determines whether or not each of one or more nozzles assigned to each bank in any scan is defective, based on the assignment data written in the assignment table 509 and the inspection results for defective nozzles by the nozzle inspection unit 500.

[0021] The defective nozzle complementing unit 507 complements defective nozzles determined to be defective by the defect determination unit 506 for each bank with complementary nozzles. The method of complementing defective nozzles performed by the defective nozzle complementing unit 507 will be described later. The content of complementation is then reflected in the allocation data written in the allocation table 509. That is, in the allocation data, the allocation of the defective nozzle to the corresponding bank is released, and the allocation of the complementary nozzle is added.

[0022] The drive circuit 406 drives the inkjet head 102 under the control of a drive circuit control unit 508 of the CPU 401. At this time, the drive circuit 406 controls whether or not each nozzle ejects ink for each bank, based on the assignment data written in an assignment table 509. Note that, in order to control whether or not ink is ejected, the drive circuit 406 also refers to the current coordinates of the inkjet head 102, the coordinates of the bank, and the current number of scans, in addition to the assignment data.

[0023] <Nozzle inspection based on the shape of the ink droplets along the ejection surface> Inspection of the nozzles based on the shape of the ink droplets along the ejection surface is performed by observing the ink ejection surface 301 (see FIG. 3) of the head chip 201 (see FIG. 2(a)) having a plurality of nozzle rows. Here, a plurality of nozzles 202 (256 nozzles in the example of FIG. 3) are arranged in each nozzle row (rows a to d in the example of FIG. 3). A commercially available general-purpose camera can be used as the camera 113 (see FIG. 1(b)) for observing the ink ejection surface 301 of the head chip 201. The camera 113 takes a still image of the droplets formed on the ink ejection surface 301 corresponding to each nozzle 202, and the image data obtained by this is binarized by the binarization circuit 410, and the binarized image data is input to the CPU 401. In order to form the droplets for inspection on the ink ejection surface 301 corresponding to the nozzles 202, the volume of the pressure chamber is changed by deforming the piezoelectric element. The piezoelectric element is deformed so that the amount of deformation of the piezoelectric element at this time is, for example, one order of magnitude smaller than the amount of deformation when ink is ejected onto the bank.

[0024] FIG. 6(a) shows a perfectly circular droplet 600 formed near the nozzle hole when the nozzle 202 is normal. FIG. 6(b) to FIG. 6(e) show the shape of droplets for each type of nozzle defect. Nozzle defects can be detected by observing the vicinity of the nozzle hole with the camera 113. FIG. 6(b) shows an area 601 near the nozzle hole when the nozzle hole is clogged with a solid or foreign matter and no droplets are formed at all. FIG. 6(c) shows an irregular droplet 602 formed near the nozzle hole when a foreign matter adheres to the nozzle hole and the droplet is dragged by the foreign matter. The droplet 602 has a shape such that a protrusion is added to a perfect circle. FIG. 6(d) shows an irregular droplet 603 formed near the nozzle hole when the nozzle hole is damaged. The droplet 603 has a shape such that a part of the perfect circle is missing. Figure 6(e) shows a droplet 604 that is not perfectly round and is formed near the nozzle hole when the water repellency of the nozzle hole decreases (deterioration of nozzle water repellency occurs) and the droplet spreads out. The droplet 604 has a shape that is like a perfect circle with a protrusion added. However, compared to the droplet 602, the protrusion has a wider range. By checking the circularity of the droplet based on image data obtained by photographing with a camera, it is possible to determine whether the nozzle is normal or defective.

[0025] The shape of the droplets formed near the nozzle hole varies depending on the shape of foreign matter or scratches, and also on the degree of deterioration of water repellency. Therefore, the droplet shapes shown in Figures 6(a) to 6(e) are only examples. However, in any case, it is possible to determine whether the nozzle is normal or defective based on the circularity of the droplets.

[0026] In this embodiment, normal nozzles and defective nozzles are classified based on the circularity of droplets when a circular nozzle is used as the nozzle. However, the shape of the nozzle does not limit the scope of this disclosure, and for example, nozzles with a square shape, a diamond shape, an I-shape, and the like are also included in the scope of this disclosure. What is important in this disclosure is the extent to which the shape of the droplets corresponding to the defective nozzle deviates from the shape of the droplets corresponding to the normal nozzle for each nozzle shape. In this embodiment, a circular nozzle is taken up as an example. This is because circular nozzles are most commonly used as inkjet heads for organic EL element-containing inks and quantum dot-containing inks, since the accuracy of the amount of droplets discharged from a circular nozzle, the discharge angle, and the like are highly stable.

[0027] The circularity of the droplets can be confirmed by binarizing the image data including the obtained nozzle information, and calculating the circularity of the binary image data obtained by this process using image processing software. The binarization process and circularity calculation used here can be performed using general-purpose image processing software. For example, in this embodiment, the binarization process was performed using a small general-purpose image processing analysis system LUSEX-AP (manufactured by Nireco Corporation), and the circularity calculation was performed using image analysis software ImageJ. The formula for calculating circularity is as follows: (Circularity)=4π×(Droplet area) / (Perimeter^2) was used.

[0028] The resolution required to detect nozzle defects will be described. For example, this is applied when the diameter of a droplet having a circular shape is 15 um, and if the droplet is represented by 25 pixels or more, it is possible to perform a roundness calculation with a precision that enables the detection of nozzle defects. In order to improve the accuracy of the roundness calculation, the droplet is preferably represented by 100 pixels, more preferably 225 pixels or more.

[0029] As shown in Figure 6(a), when the droplet shape is a perfect circle, the circularity is 1.00. As the droplet shape deviates from a perfect circle, as shown in Figures 6(c) to 6(e), the circularity decreases. In Figure 6(c), the circularity is 0.93, in Figure 6(d), the circularity is 0.90, and in Figure 6(e), the circularity is 0.88. For example, when the circularity is outside the range of 0.95 to 1.00, the nozzle is determined to be defective.

[0030] As a method for improving the accuracy of the nozzle inspection based on the shape of the ink droplet along the ejection surface, there is a method for observing the difference in the state of the ink droplet when the size of the ink droplet is changed (i.e., when the ink droplet is expanded or contracted). In order to change the size of the ink droplet attached to the periphery of the nozzle 202 on the ink ejection surface 301, for example, the volume of the pressure chamber may be changed by deforming a piezoelectric element. For example, when the roundness of a droplet with a diameter of 15 um is a threshold value of 0.95, the diameter of the droplet is expanded from 16 um to 17 um, and then contracted until it returns to 15 um. Then, it is confirmed that the roundness does not vary significantly from 0.95 at any diameter, which improves the reliability of the nozzle inspection result. Therefore, for nozzles with a roundness close to the threshold value of 0.95, it is preferable to perform a droplet expansion and contraction inspection in order to increase the inspection accuracy and reduce the probability of occurrence of ejection distortion. It is also possible to perform a droplet expansion and contraction inspection when the roundness has a value close to the threshold value. For example, if the threshold is 0.95, then a droplet expansion / contraction test may be performed when the circularity is in the range of 0.94 to 0.96.

[0031] <Inside nozzle inspection> In order to improve the accuracy of detecting non-ejecting nozzles, it is preferable to perform nozzle evaluation in combination with an internal nozzle inspection that evaluates residual vibrations after generating a pressure wave using the aforementioned piezoelectric element to the extent that it does not eject ink.

[0032] <Nozzle inspection based on the occupancy rate of ink droplets in the area surrounding the nozzle> By repeating the ejection of ink onto the bank on a number of substrates, the presence or absence of a nozzle defect can also be determined based on the occupancy rate of ink droplets in a predetermined range adhering to the periphery of the nozzle 302 on the ink ejection surface 301. The nozzle inspection based on the occupancy rate of ink droplets in the peripheral region of the nozzle can be performed using the binary image data of the ink ejection surface 301, similar to the nozzle inspection based on the shape of the ink droplets along the ejection surface. In addition, the nozzle inspection based on the occupancy rate of ink droplets in the peripheral region of the nozzle is performed based on the adhesion state of the droplets adhering to the periphery of the nozzle. The nozzle peripheral droplet occupancy calculation unit 502 calculates the droplet occupancy rate in a 30 um square range centered on the nozzle based on the binary image data. The higher the droplet occupancy rate, the more likely it is that the ink droplets will get caught on the nozzle in the next ink recording sequence, causing ejection distortion or non-ejection. It is preferable that the threshold value of the droplet occupancy rate used to determine the presence or absence of a nozzle defect is determined by deep learning in each recording device.

[0033] The resolution threshold of the captured still image can be appropriately determined by the above-mentioned deep learning. In this embodiment, it is preferable that the 30 μm square field of view around the nozzle is expressed by 50 pixels or more, and it is more preferable that the field of view is expressed by 300 pixels or more, because this allows for a high-precision prediction of defective nozzles in advance.

[0034] Deep learning can be performed using general-purpose software. In this embodiment, the open source platform TensorFlow and the network library Keras that can be executed on TensorFlow were used. The relationship between the droplet occupancy rate around the nozzle and the ejection distortion and ejection failure was calculated based on 5000 times of binarized image data. Based on this, it was found that if the droplet occupancy rate is 40% or less, the probability of ejection distortion and ejection failure can be suppressed to 5% or less. Therefore, 40% was set as the threshold value of the droplet occupancy rate used to determine whether or not the nozzle is defective. If the droplet occupancy rate exceeds the threshold value, it is determined that the nozzle is defective.

[0035] FIG. 7 is a schematic diagram for explaining the droplet occupancy rate around the nozzle. The nozzle peripheral area surrounded by a dotted frame occupies a 30 um square range centered on the nozzle. The nozzle peripheral area 701 on the left has a droplet occupancy rate of 5%, so it can be determined that it does not need to be supplemented. On the other hand, the nozzle peripheral area 702 in the center has a droplet occupancy rate of 45%, so it can be determined that it needs to be supplemented. In the example of the peripheral area 702, there is no foreign matter or scratch on the nozzle, and the nozzle is not detected as defective in particular by the nozzle inspection based on the shape along the ink droplet ejection surface. However, since the droplet occupancy rate of 45% exceeds the threshold value of 40%, it is highly likely that it will become defective during the next ink recording sequence, and therefore a supplement process is performed. The nozzle peripheral area 703 on the right has a droplet occupancy rate of 30%, so it can be determined that it does not need to be supplemented. However, since it is close to the threshold value of 40% in this embodiment, it may be necessary to supplement in the next inspection.

[0036] <Detection of defective nozzles> The defective nozzle detection unit 504 inputs the circularity calculated by the circularity calculation unit 501, the occupancy rate calculated by the nozzle peripheral droplet occupancy calculation unit 502, and the evaluation results output by the nozzle inside inspection unit 503, and inspects each nozzle 202 for defects based on these. Basically, the defective nozzle detection unit 504 determines that a nozzle is defective if any one of the circularity, occupancy rate, and evaluation results for each nozzle 202 indicates a defect. The defective nozzle detection unit 504 performs this determination for all nozzles 202 provided in the inkjet head 102.

[0037] <Identifying defective nozzles for each bank> The defect determination unit 506 inputs the identification information of all nozzles used for ejecting ink for each bank from the used nozzle allocation unit 505. The defect determination unit 506 also inputs the identification information of defective nozzles from the defective nozzle detection unit 504. Then, based on the identification numbers input from both units, the defect determination unit 506 determines the identification information of defective nozzles included in all nozzles used for ejecting ink for each bank (nozzles assigned to that bank). In this way, the defect determination unit 506 can determine the defective nozzles included in all nozzles used for ejecting ink (assigned nozzles) for each bank.

[0038] <Pre-nozzle complementation processing> As described above, the defective nozzle is complemented by other nozzles by the defective nozzle complement unit 507. Hereinafter, the nozzle that complements the defective nozzle is referred to as the complementary nozzle. Complement of the defective nozzle by the complementary nozzle may be performed within the same head chip 201, or may be performed across different head chips 201. That is, a nozzle arranged in the same head chip 201 as the head chip 201 in which the defective nozzle is arranged may be used as the complementary nozzle. Also, a nozzle arranged in a head chip 201 different from the head chip 201 in which the defective nozzle is arranged may be used as the complementary nozzle. Note that, when focusing on a certain bank, if it is determined that a certain nozzle originally assigned to that bank is a defective nozzle, a complementary nozzle is selected from nozzles other than the other nozzles originally assigned to that bank. That is, one nozzle that can be used as a complementary nozzle is selected as the complementary nozzle from nozzles other than the other nozzles originally assigned to that bank. In this case, a nozzle in the same head chip 201 as the defective nozzle may be selected as the complementary nozzle, or a nozzle in a head chip 201 different from the defective nozzle may be selected as the complementary nozzle. Since continuous ink ejection is not required for such compensation, there is no need to slow down the scan speed, and therefore such compensation has a high priority.

[0039] Also, as described above, by scanning one substrate 111 multiple times (for example, three times), it is possible to eject the necessary amount of ink to all the banks arranged on the substrate 111. The complement of the defective nozzle by the complementary nozzle may be performed within the same scan, or across different scans. That is, a nozzle capable of complementing a defective nozzle used in a certain scan in the same scan may be searched for as a complementary nozzle, and the certain nozzle may be complemented by the complementary nozzle searched for in the certain scan. Also, a nozzle capable of complementing a defective nozzle used in a certain scan in another scan may be searched for as a complementary nozzle, and the certain nozzle may be complemented by the complementary nozzle searched for in the other scan. Note that, similarly to the above, when a certain bank is focused on, if it is determined that a certain nozzle originally assigned to that bank is a defective nozzle, a complementary nozzle is selected from nozzles other than the other nozzles originally assigned to that bank. That is, one nozzle that can be used as a complementary nozzle is selected as a complementary nozzle from nozzles other than the other nozzles originally assigned to that bank. In this case, a nozzle that ejects ink into the same bank as the defective nozzle in the same scan as the defective nozzle may be selected as a complementary nozzle, or a nozzle that ejects ink into the same bank as the defective nozzle in a different scan as the defective nozzle may be selected as a complementary nozzle. Since continuous ink ejection is not required for such a complement, there is no need to reduce the scan speed. Therefore, this type of complement has a high priority.

[0040] Furthermore, when focusing on a certain bank, if it is determined that a certain nozzle originally assigned to that bank is a defective nozzle, another nozzle originally assigned to that bank may be used as a complementary nozzle. In that case, the nozzle to be used as the complementary nozzle ejects ink twice consecutively at the timing originally specified for ejecting ink. The scan speed may be reduced so that the nozzle can eject ink twice consecutively. Note that the other nozzle originally assigned to that bank may or may not be located on the same head chip 201 as the defective nozzle. Also, the other nozzle originally assigned to that bank may or may not be a nozzle that was specified to eject ink in the same scan as the defective nozzle.

[0041] Furthermore, when n scans are originally specified for one substrate 111, scans for ejecting ink from complementary nozzles may be added, so that the number of scans exceeds n.

[0042] The flow of the nozzle complementation method executed by the CPU 401 is shown in Figure 8. The complementation nozzle is selected from the nozzles that pass over the bank from which the defective nozzle was scheduled to eject ink. In the following explanation, "Step S" will be abbreviated to "S".

[0043] 8 is executed before starting a batch job by the defective nozzle complementing unit 507. The scan in the following description is not an actual scan but a virtual scan performed in advance.

[0044] 8, the CPU 401 repeats the process from S801S to S801E n times. That is, the CPU 401 repeats the sub-scanning n times, thereby repeating the scanning of the entire substrate 111 n times.

[0045] The CPU 401 repeats the process from S802S to S802E s times in each sub-scan. That is, the CPU 401 repeats the main scan s times while moving the sub-scan position in each sub-scan.

[0046] In each main scan, the CPU 401 repeats the processes from S803S to S803E for all banks at the same sub-scanning position.

[0047] For each bank, the CPU 401 repeats the process between S804S and S804E (ie, S805) for all defective nozzles corresponding to the bank.

[0048] In S805, the CPU 401 executes the complementation process.

[0049] FIG. 9 shows a flow of the complementation process executed by the CPU 401.

[0050] In S911, the CPU 401 checks whether a complementary nozzle can be found in the same row (see FIG. 10(a)). That is, the CPU 401 checks whether there is an available nozzle in the current bank that can eject ink in the same row as the defective nozzle on the ink ejection surface 301 during the current scan (current repetition of S801S to S801E) of the entire substrate 111. Note that the nozzle originally assigned to the current bank is excluded.

[0051] If the CPU 401 confirms in S911 that a complementary nozzle capable of complementing in the current scan can be found in the same row (YES), the process proceeds to S912, where the CPU 401 selects a complementary nozzle from the same row. In other words, the CPU 401 selects one of the nozzles found in S911 as a complementary nozzle.

[0052] Next, in S913, the CPU 401 executes a process for complementing in the current scan. That is, the CPU 401 executes a process for using the complementary nozzle selected in S912 in place of the defective nozzle in the current scan. Specifically, the CPU 401 changes the contents of the allocation table 509.

[0053] If the CPU 401 cannot confirm in S911 that a complementary nozzle can be found in the same row (NO), it proceeds to S914 and checks whether a complementary nozzle can be found in the same column (see FIG. 10(b)). In other words, the CPU 401 checks whether there is an available nozzle in the current bank that can eject ink in the same column as the defective nozzle on the ink ejection surface 301 during the current scan (current repetition of S801S to S801E) of the entire substrate 111. Note that the nozzle originally assigned to the current bank is excluded.

[0054] If the CPU 401 confirms in S914 that a complementary nozzle that can be complemented in the current scan can be found in the same column (YES), the process proceeds to S915, where the CPU 401 selects a complementary nozzle from the same column, i.e., selects one of the nozzles found in S914 as a complementary nozzle.

[0055] Next, in S913, the CPU 401 executes a process for complementing in the current scan. That is, the CPU 401 executes a process for using the complementary nozzle selected in S915 in place of the defective nozzle in the current scan. Specifically, the CPU 401 changes the contents of the allocation table 509.

[0056] If the CPU 401 is unable to confirm in S914 that a complementary nozzle can be found in the same row (NO), the process proceeds to S916, where it checks whether a complementary nozzle can be found in the next scan or a subsequent scan (see FIGS. 11(a) and 11(b)). In other words, the CPU 401 checks whether there are any free nozzles in the current bank that can eject ink in the next scan or a subsequent scan of the entire substrate 111. Here, the next scan of the entire substrate 111 refers to the next repetition from S801S to S801E, and the subsequent scan refers to the next and subsequent repetitions from S801S to S801E. Note that nozzles originally assigned to the current bank are excluded.

[0057] 10(a) and 11(b), in the example of Fig. 10(a), the 255th nozzle in row d is used for complementation in the current scan, and in the example of Fig. 11(b), the 255th nozzle in row d is used for complementation in the next scan, because nozzle allocation differs depending on the bank.

[0058] If the CPU 401 confirms in S916 that it can find a nozzle capable of ejecting ink into the current bank in the next scan or a scan thereafter (YES), the process proceeds to S917. Then, in S917, the CPU 401 selects one of the nozzles found in S916 as a complementary nozzle. In other words, the CPU 401 selects one of the nozzles found in S914 as a complementary nozzle.

[0059] Next, in S918, the CPU 401 executes a process for complementing in the next scan or a scan thereafter (see FIG. 12). That is, the CPU 401 executes a process for using the complementary nozzle selected in S917 in place of the defective nozzle in the next scan or a scan thereafter. Specifically, the CPU 401 changes the contents of the allocation table 509.

[0060] If the CPU 401 cannot confirm in S916 that it can find nozzles capable of ejecting ink into the current bank in the next scan (NO), the process proceeds to S919 to confirm whether the scheduled nozzles can eject ink continuously (see FIG. 13). In other words, the CPU 401 confirms whether any nozzles originally assigned to the current bank can eject ink continuously in any scan of the entire substrate 111 (any repetition of S801S to S801E).

[0061] If the CPU 401 confirms in S919 that any of the nozzles originally assigned to the current bank can continuously eject ink (YES), the process proceeds to S920. Then, in S920, the CPU 401 selects any of the nozzles originally assigned to the current bank that can continuously eject ink as a complementary nozzle. In other words, the CPU 401 selects any of the nozzles found in S919 as a complementary nozzle.

[0062] Next, in S921, the CPU 401 executes a process for complementing in any of the scheduled scans (see FIG. 14). That is, the CPU 401 executes a process for continuously ejecting ink in any of the scheduled scans using the complementary nozzle selected in S920 in place of the defective nozzle. Note that the scan speed may be reduced in order to continuously eject ink.

[0063] If the complementary processing shown in FIG. 9 cannot be performed, that is, if the results are NO in S911, S914, S916, and S919, a cleaning process or a wiping process is performed on the inkjet head 102.

[0064] It is possible to delete some of the steps shown in Fig. 9. For example, steps S916 to S921 may be deleted, or steps S919 to S921 may be deleted.

[0065] <Ink circulation system> 2(a) and 2(b) are conceptual diagrams showing the relationship between the inkjet head 102 and a supply and recovery system. FIG. 2(a) is a top view, and FIG. 2(b) is a side view. As described above, a plurality of nozzle rows are arranged in the head chip 201, and a plurality of nozzles 202 are arranged in each nozzle row. For example, the chip 201 has four nozzle rows, and each nozzle row has 256 nozzles. As described above, the inkjet head 102 has four chips 201, which are arranged in a staggered pattern. FIG. 15 is a conceptual diagram of the ink circulation and ink function detection system.

[0066] A flow path 1504 for supplying ink is connected to the inkjet head 102. The cap unit 114 is a unit for receiving waste ink discharged from the inkjet head 102. By appropriately combining and operating the solenoid valve 1507 and the suction pump 204, the waste ink discharged into the cap unit 114 can be discharged downstream. The inkjet head 102 uses the same type (same color) of ink, and when multiple types of ink are used, multiple similar configurations are prepared. Although only one inkjet head 102 is shown in FIG. 15, multiple inkjet heads may be used. The following description will be given assuming that a single type (same color) of ink is used.

[0067] 15 shows a configuration including a flow path 1504, a sub-tank 1505, a negative pressure adjustment unit 1506, the inkjet head 102, the cap unit 114, and a suction pump 204. However, the sub-tank 1505, the negative pressure adjustment unit 1506, the suction pump 204, etc. are not necessarily required components.

[0068] A method of filling the ink into the inkjet head 102 will be described. The cleaning unit 404, which receives an instruction from the CPU 401, drives the pressurizing pump 1502 to supply ink from the main tank 101 to each flow path 1504. At that time, minute foreign matter is filtered through a filter 1503. Note that degassing may be performed appropriately using a degassing unit (not shown). Note that by providing a sub-tank 1505, even if the main tank 101 becomes empty, it is possible to replace the main tank 101 while continuing the recording operation. Also, the negative pressure applied to the nozzle 202 of each inkjet head unit of the inkjet head 102 is appropriately maintained by the negative pressure adjustment unit 1506. Note that if the negative pressure can be appropriately managed by a head difference supply method or the like, the negative pressure adjustment unit 1506 is not necessary. As described above, the ink can be filled up to the inkjet head 102. Although the ink filling by the pressurizing method has been described, ink filling by a decompression method such as suction with a cap is also possible.

[0069] <Inkjet head recovery configuration> Next, a case where the nozzle 202 of the inkjet head 102 needs to be restored will be described. For example, when the inkjet head 102 has not been used for a long period of time, the ink may thicken inside or near the nozzle 202 due to the volatilization of the components in the ink. Alternatively, when the inkjet head 102 is continuously used for a recording operation, ink deposits or foreign matter may adhere to the vicinity of the nozzle 202 of the inkjet head 102. In the above case, it is necessary to perform a light recovery operation such as flushing or wiping to forcibly discharge the nozzle from the nozzle 202 of the inkjet head 102. If the ink thickens or the mist adheres to the vicinity of the nozzle 202, the light recovery operation may not be sufficient to restore the ink, and a heavy recovery operation may be required. An example of a heavy recovery operation is a pressurized recovery operation. In the pressurized recovery operation, the pressurized pump 1502, the electromagnetic three-way valve 1501 of each flow path 1504, the suction pump 204, and the electromagnetic valves 1507 and 205 are appropriately operated to pressurize the vicinity of the nozzle 202 of the inkjet head 102. Then, the ink is discharged onto the cap unit 114 via the nozzles 202 of the inkjet head 102. As another heavy recovery operation, there is a method in which the cap unit 114 is brought into contact with the inkjet head 102, the suction pump 204 and the solenoid valve 205 are appropriately operated, and a suction recovery operation is performed in which the ink is sucked through the nozzles 202, and the ink is recovered in the ink recovery unit 140.

[0070] <Patterning using an inkjet recording device> In this embodiment, an inkjet recording device is used to apply ink to form a pattern of the functional element material. Patterning using an inkjet recording device has the advantages of high material usage efficiency because on-demand patterning is possible, and the manufacturing equipment is relatively small because it is a non-vacuum process. Examples of functional elements include organic EL elements and quantum dot color conversion elements, and color filters, which are functional components of displays, are obtained by patterning the elements.

[0071] The color filter pattern varies depending on the arrangement of the pixel shape, but an example is a stripe pattern obtained by repeating a pattern in which functional materials for three colors, red, green, and blue, are arranged in a straight line.

[0072] In the field of functional elements such as organic electroluminescence elements, a very large number of functional elements are often formed on a large-area substrate, and therefore high uniformity is required in the amount of functional element applied to each pixel.

[0073] An example of a substrate 111 to be printed on is shown in Fig. 16. Fig. 16 is a schematic perspective view for explaining the substrate 111, where 111 is the substrate, 1601 is the base surface which is the surface of the substrate 111 on which pixels are formed, and 1602 is each pixel. Since this is a schematic view, only 5 x 7 pixels 1602 are shown on the base surface 1601, but in reality a very large number of pixels can be formed.

[0074] Assume that the substrate surface 1601 is parallel to the XY plane. The inkjet head 102 is spaced a predetermined distance in the Z direction from the substrate surface 1601 and maintained at this distance. First, the inkjet head 102 is moved in the plus direction along a track 1603 parallel to the X direction, which is the main scanning direction, while discharging ink to the pixels 1602 arranged in row A (A-1 to A-7). Next, when the inkjet head 102 has moved to the outside of the area where the pixels 1602 are arranged, i.e., the application area, the inkjet head 102 is moved a predetermined distance along a track 1604 parallel to the Y direction, which is the sub-scanning direction. Next, the inkjet head 102 is moved in the minus direction along a track 1605 parallel to the X direction, which is the main scanning direction, while discharging ink to the pixels 1602 arranged in row A (A-1 to A-7) and the pixels 1602 arranged in row B (B-1 to B-7). Next, when the inkjet head 102 has moved to the outside of the area where the pixels 1602 are lined up, i.e., the coating area, the inkjet head 102 is moved a predetermined distance along a track 1604 parallel to the Y direction, which is the sub-scanning direction. Next, while moving the inkjet head 102 in the plus direction along a track 1605 parallel to the X direction, which is the main scanning direction, ink is ejected onto the pixels 1602 lined up in row B (A-1 to A-7) and the pixels 1602 lined up in row C (C-1 to C-7). In this way, ink is ejected onto each pixel while performing two scans.

[0075] By repeating this movement, the inkjet head 102 scans by reciprocating in the main scanning direction. In the first scan, ink is ejected onto the banks in row A in the order A-1 → A-2 → A-3 →...A-7. In the second scan, ink is ejected onto two rows simultaneously in the order A-7 → A-6 →...A-1 and B-7 → B-6 →...B-1 onto the banks in row A and row B.

[0076] By performing two or more scans on the same pixel, even if there is a discharge defect in the first scan, it is possible to improve the uniformity of the ink amount between pixels by controlling the amount of ink discharged in the second or subsequent scans.

[0077] For the sake of simplicity, the inkjet head 102 has been described as having nozzles for two rows of pixels, but if the inkjet head has wider nozzles, it is possible to eject material onto more rows of pixels in a single main scan. EXAMPLES

[0078] The present disclosure will be described in detail below using examples and comparative examples. The present disclosure is not limited to the following examples without departing from the gist of the present disclosure.

[0079] [Example 1] In this example, quantum dot ink was ejected onto each bank using the recording device shown in Figures 1 and 4. The ink used was a commercially available core-shell type quantum dot ink 776785 (manufactured by Merck), and the inkjet head 102 used had a pressure generating means that utilized the deformation of a piezoelectric element.

[0080] The nozzle hole of the inkjet head 102 used in this embodiment is a circle with a diameter of 15 um, and in the case of a normal nozzle, a perfectly circular droplet with a diameter of 16 um is formed on the nozzle by deforming the piezoelectric element. A digital microscope HRX-01 (manufactured by HIROX) was used as the camera 113 for observing the droplets, and a high-resolution telecentric electric zoom lens HR-1020E was used as the lens. In the nozzle observation, the inkjet head 102 was moved to directly above the camera 113, and then the inkjet head 102 was moved in the direction of the main scanning guide rail 105 at 30 mm / s to observe the entire ink discharge surface 301 of the inkjet head 102. The circularity was calculated using image data with a resolution of 100 pixels representing a nozzle hole with a diameter of 15 um.

[0081] The acquired image data was binarized using a small general-purpose image processing and analysis system LUSEX-AP (manufactured by Nireco Corporation), and the roundness was calculated using the image analysis software ImageJ based on the binarized image data obtained. (Circularity)=4π×(Droplet area) / (Perimeter^2) The calculation was performed using the formula. In the present embodiment, when the circularity was in the range of 0.96 to 1.00 with 1 / 100 accuracy, the nozzle was determined to be normal, and when it was 0.94 or less, the nozzle was determined to be defective. However, when the circularity was 0.95, the circularity was checked during expansion and contraction. The threshold value can be changed as appropriate depending on the allowable range of the ejection deviation in each recording device. In this embodiment, under the condition that the distance between the inkjet head 102 and the bank material to be landed is 500 um, the allowable range of the ejection deviation is set to a range of 89.6° to 90.4° when 90° is considered to be no ejection deviation.

[0082] The nozzle inspection based on the occupancy rate of the ink droplets in the peripheral area of ​​the nozzle was carried out using a binarized image obtained in the same manner as the nozzle inspection based on the shape of the ink droplets along the ejection surface. Image data was obtained by taking still images of the state around the nozzle using a digital microscope HRX-01 (manufactured by HIROX Co., Ltd.) and a high-resolution telecentric electric zoom lens HR-1020E. The image data was transferred to the nozzle peripheral droplet occupancy calculation unit 5502 to calculate the droplet occupancy rate in a 30 um square range centered on the nozzle. The droplet occupancy rate was calculated based on binarized image data obtained by binarizing the image data obtained by photographing with a small general-purpose image processing analysis system LUSEX-AP (manufactured by NIRECO Co., Ltd.). The droplet occupancy rate was calculated based on the occupancy rate of the ink droplets within a 30 um square. The image data used in this embodiment was a 30 um square consisting of 100 pixels. The threshold value of the droplet occupancy rate was calculated by deep learning. Deep learning was performed using the open source platform TensorFlow and Keras, a network library that can be executed on TensorFlow. In deep learning, the relationship between the droplet occupancy rate around the nozzle and the ejection distortion and non-ejection was obtained from 5,000 binary image data, and it was possible to determine that the droplet occupancy rate should not exceed a threshold of 40% as a condition for keeping the probability of ejection distortion and non-ejection occurrence below 5%.

[0083] FIG. 3 also shows the number assignment of nozzles. The table shown in FIG. 17 is a table regarding the inspection results of defective nozzles and the assignment of complementary nozzles. FIG. 3 shows the numbers 1 to 256 assigned to the 256 nozzles × 4 rows arranged on the ink ejection surface 301 of the head chip 201, and the column names a to d. In the table shown in FIG. 17, "on the nozzle" in the inspection classification indicates the above-mentioned <inspection of the nozzle based on the shape along the ink droplet ejection surface>. "Around the nozzle" indicates the above-mentioned <inspection of the nozzle based on the occupancy rate of the ink droplet in the peripheral area of ​​the nozzle>. "Inside the nozzle" indicates the above-mentioned <inspection inside the nozzle using the vibration sensor 407 or the temperature sensor 408>. In this head chip 201, the nozzles that were detected as having clogged flow paths in the nozzle internal inspection were "b-81", "d-204", and "d-233". In the on-nozzle inspection, three nozzles were detected as non-compliant with nozzle roundness or above the threshold: "a-17", "b-36", and "c-73". Even after the droplet expansion / contraction inspection, one nozzle, "c-73", was detected as a defective nozzle because it was above the threshold. In the nozzle periphery inspection, three nozzles, "a-58" and "a-59", were determined to be non-compliant with the droplet occupancy rate.

[0084] The identification information of the defective nozzles detected by these inspection means is integrated by defective nozzle detection unit 504. Specifically, defective nozzle detection unit 504 integrates "a-17", "a-58", "a-59", "b-81", "c-73", "d-204", and "d-233" as identification information of defective nozzles. The result of this integration is shown in the "Good / Bad" row of FIG.

[0085] A defect determination unit 506 determines whether each nozzle assigned to each bank is a defective nozzle, and if it is a defective nozzle, a complementary nozzle for complementing the defective nozzle is searched for, and a scan for complementing the defective nozzle is specified.

[0086] If a defective nozzle "d-254" (see Figure 17) is assigned to a certain bank #b1 and it is specified that nozzle "d-254" will eject ink into bank #b1 during the first scan, for example, the following process is executed.

[0087] 10A, if it is determined in S911 that the nozzle "d-255" can be used for complementation in the first scan, then in S912 the nozzle "d-255" is selected as the complementary nozzle. Then, in S913, processing is performed to complement the nozzle "d-255" in the first scan.

[0088] If a defective nozzle "d-254" (see Figure 17) is assigned to a certain bank #b2, and it is specified that nozzle "d-254" will eject ink into bank #b1 during the first scan, for example, the following process is executed.

[0089] 10B, if it is determined in S914 that the nozzle "c-254" can be used for complementation in the first scan, then in S915 the nozzle "c-254" is selected as the complementary nozzle. Then, in S913, processing is executed to complement the nozzle "c-254" in the first scan.

[0090] If a defective nozzle "d-254" (see Figure 17) is assigned to a certain bank #b3, and it is specified that nozzle "d-254" will eject ink into bank #b1 during the first scan, for example, the following process is executed.

[0091] 11(a) and 11(b), if it is determined in S916 that the nozzle "d-255" can be used for complementation in the second scan, then in S917 the nozzle "d-255" is selected as the complementary nozzle. Then, in S918, processing is performed to complement the nozzle "d-255" in the second scan.

[0092] Fig. 12 is an explanatory diagram of a case where the nozzle "d-255" is used for complementation in the nth scan. In Fig. 12, setting n=1 corresponds to this example.

[0093] If a defective nozzle "d-254" (see Figure 17) is assigned to a certain bank #b4, and it is specified that nozzle "d-254" will eject ink into bank #b1 during the first scan, for example, the following process is executed.

[0094] 13, if it is determined in S919 that the nozzle "d-2" can be used for complementation in the nth (e.g., first) scan, then in S920 the nozzle "d-2" is selected as the complementary nozzle. Then, in S921, processing is executed to complement the nozzle "d-2" in the nth (e.g., first) scan.

[0095] Fig. 14 is an explanatory diagram of the case where the nozzle "d-2" is used for complementation in the nth scan. In the example of Fig. 14, the scan speed is reduced and two drops of ink are continuously ejected from the nozzle "d-2" onto the target bank #4. If n=1 in Fig. 14, this corresponds to this example.

[0096] <Evaluation> The volume of each bank of the color filter was approximately 65 pl, and droplets of approximately 5 pl were ejected from the inkjet head 102 per ejection. Each bank was scanned three times, with five droplets of ink being applied in the first scan, and four droplets each in the second and third scans. The arrangement of each pixel (corresponding to each bank) in the color filter differs depending on the design of the display, but in this embodiment, the same ink was dropped in the same row parallel to the main scanning direction.

[0097] In order to evaluate the luminance unevenness of the color filter after the printing was completed, the ink was cured by irradiating it with UV of 400 nm wavelength. FUSION LIGHT HAMMER (manufactured by Alpha UV Systems) was used for UV curing. When color mixing occurs in the bank, the mixed color area emits light with a different color from the original luminance color. For example, a mixed color area where red ink and green ink are mixed emits yellow light, so it is possible to distinguish the mixed color bank by visual evaluation under a microscope. No mixed color bank was observed in the bank on the color filter created in this embodiment. In addition, the emission intensity was measured to evaluate the presence or absence of non-discharge. When the amount of liquid in the bank changes, the luminance unevenness occurs in the color filter after ultraviolet curing in proportion to the change. A photometric evaluation spectroscopic measurement system (manufactured by Hamamatsu Photonics) was used as the emission intensity measurement means. The emission wavelength of the quantum dots used was about 660 nm, and the integrated intensity of this wavelength was calculated.

[0098] The target variation range of luminance unevenness was set to ±5% for evaluation. In this embodiment, the luminance unevenness was within the target value of ±3.5% on average, and no significant luminance unevenness that could cause discharge failure occurred.

[0099] As described above, by detecting and complementing defective nozzles before printing, a color filter for display can be obtained without causing color mixing within a bank or a shortage of ink within a bank.

[0100] A comparative example will be used to clarify the effects of Example 1. In order to avoid duplication of explanation, only the differences between Comparative Example 1, Example 2, and Example 3 and Example 1 will be described.

[0101] [Comparative Example 1] In the head chip 201 in which 256 nozzles are arranged in 4 rows, three nozzles were found to have clogged flow paths in the <inspection of the nozzle using the vibration sensor 407 or the temperature sensor 408>. In addition, two nozzles were found to have nozzle roundness non-conformity in the <inspection of the nozzle based on the shape along the ejection surface of the ink droplets>. Furthermore, three nozzles were found to have droplet occupancy non-conformity in the <inspection of the nozzle based on the occupancy rate of the ink droplets in the peripheral area of ​​the nozzle>. Unlike the first embodiment, only nozzles that were found to be defective in the generally confirmed <inspection of the nozzle using the vibration sensor 407 or the temperature sensor 408> were subjected to a supplementary process using other nozzles, and printing, UV curing, and subsequent color mixing and non-ejection evaluation were performed in the same manner as in the first embodiment. As a result, one mixed color bank was generated that was not used for the nozzles that were found to be defective in the nozzle internal inspection for ink application. The brightness unevenness was ±5.5% on average, exceeding the target value of 5%, and the effect of non-ejection was confirmed. From this result, it is understood that color mixing and non-ejection within a bank cannot be sufficiently suppressed by only performing complementary processing based on <intra-nozzle inspection using the vibration sensor 407 or temperature sensor 408>.

[0102] [Example 2] In the head chip 201 in which 256 nozzles are arranged in 4 rows, two nozzles were found to have clogged flow paths in the <inspection inside the nozzle using the vibration sensor 407 or the temperature sensor 408>. In addition, 13 nozzles were found to have nozzle roundness non-conformity in the <inspection of the nozzle based on the shape along the ink droplet ejection surface>. Furthermore, two nozzles were found to have droplet occupancy non-conformity in the <inspection of the nozzle based on the occupancy rate of the ink droplets in the peripheral area of ​​the nozzle>. It was difficult to complement the 13 nozzles found to be defective in the <inspection of the nozzle based on the shape along the ink droplet ejection surface> with other nozzles. Therefore, a command was issued from the CPU 401 to the cleaning unit 404 to perform recovery processing by nozzle suction in order to clean the nozzle hole, and the command was executed. After that, each nozzle was inspected again, and it was found that 0 nozzles were found to have clogged flow paths in the nozzle inside inspection, 1 nozzle was found to have nozzle roundness non-conformity in the on-nozzle inspection, and 2 nozzles were found to have droplet occupancy non-conformity in the nozzle peripheral inspection. This recovery process allowed the nozzles in other rows in the same head chip 201 to be compensated for, as in Example 1. Thereafter, evaluation was performed in the same manner as in Example 1, and it was confirmed that no color mixing within the bank due to deflected ejection or uneven brightness due to non-ejection had occurred.

[0103] [Example 3] In the head chip 201 in which 256 nozzles are arranged in 4 rows, two nozzles were found to have clogged flow paths in the <inspection inside the nozzle using the vibration sensor 407 or the temperature sensor 408>. In addition, one nozzle was found to have non-conforming nozzle roundness in the <inspection of the nozzle based on the shape along the ejection surface of the ink droplets>. Furthermore, seven nozzles were found to have non-conforming droplet occupancy in the <inspection of the nozzle based on the occupancy rate of the ink droplets in the peripheral area of ​​the nozzle>. It was difficult to compensate for the seven nozzles found to be defective in the <inspection of the nozzle based on the occupancy rate of the ink droplets in the peripheral area of ​​the nozzle> with other nozzles. Therefore, a command was issued from the CPU 401 to the cleaning unit 404 to perform a recovery process by wiping in order to remove the droplets around the nozzle, and the command was executed. After that, each inspection was performed again, and it was confirmed that one nozzle was found to have clogged flow paths in the nozzle inside inspection, one nozzle was found to have non-conforming nozzle roundness in the on-nozzle inspection, and no nozzles were found to have non-conforming droplet occupancy in the nozzle peripheral inspection. This recovery process allowed the nozzles in other rows in the same head chip 201 to be compensated for, as in Example 1. Thereafter, evaluation was performed in the same manner as in Example 1, and it was confirmed that no color mixing within the bank due to deflected ejection or uneven brightness due to non-ejection had occurred.

[0104] As described above, from the results of the examples, it is clear that by using the present disclosure, it is possible to prevent defects due to ejection errors and non-ejection that could not be detected by conventional internal nozzle inspections.

[0105] In the above embodiment, the circularity is used when inspecting the shape of the ink droplet along the ink ejection surface, but this is not limited to this. For example, the ratio of the area of ​​an ellipse that approximates the shape to the area of ​​a perfect circle when the nozzle is normal may be used. In order to obtain the ellipse that approximates the shape, for example, the least squares method is used based on multiple points included in the outline of the droplet. In this case, since the ratio increases and decreases around 1, an upper threshold and a lower threshold are used as thresholds. For example, 1.05 is set as the upper threshold and 0.95 is set as the lower threshold, and if the ratio is not within the range between these thresholds, it is determined that the nozzle is defective.

[0106] As mentioned above, the nozzle shape may be a square, diamond, or I-shape, but even in such cases, it is possible to determine whether the nozzle is defective based on the shape of the ink droplet along the ink ejection surface. For example, when using a square nozzle, the shape of the ink droplet can be evaluated based on the shape of the ink droplet when the square nozzle is normal. If the shape of the ink droplet when the square nozzle is normal is a square, a square that approximates the shape of the droplet is found using the least squares method or the like, and a defective nozzle is determined in the same manner as above.

[0107] In the above embodiment, <inspection of nozzles based on the shape of ink droplets along the ejection surface> is performed, but the present disclosure is not limited thereto. In the present disclosure, <inspection of nozzles based on the shape of ink droplets along the ejection surface> may be changed to inspection of nozzles based on other ink droplet shapes. For example, taking into consideration the focal depth of the optical system that photographs the droplets, the nozzle may be inspected based on the three-dimensional ink shape, not just the ink shape along the ejection surface, or the nozzle may be inspected based on the shape of a portion away from the ink ejection surface.

[0108] 9, if the answer is NO in S914, a nozzle (excluding nozzles in the same row or column) that can complement the defective nozzle in the same scan may be searched for before proceeding to S916. Then, if a nozzle is found, that nozzle may be selected as a complementary nozzle, and a process for complementing the defective nozzle in the same scan may be performed.

[0109] 9, in steps S916 to S918, a nozzle that can be complemented in a scan prior to the current scan may be set as a complementary nozzle. For example, if the current scan is the second scan, a nozzle that can be complemented in the first scan may be set as a complementary nozzle.

[0110] The multiple banks arranged on the substrate may be formed so as to be arranged in a matrix, or may be formed so as to be arranged according to another pattern.

[0111] According to the present disclosure, it is possible to detect a decrease in water repellency or scratches on the nozzles, and to detect defects that lead to minute ejection deviations. Also, by observing the state of ink adhesion near the nozzles, it is possible to pre-complement nozzles with other nozzles instead of using nozzles that are likely to cause defects in the next job. Furthermore, the above means can prevent color mixing caused by minute ejection deviations and a shortage of liquid in the bank due to non-ejection without involving ink ejection. If no allocation is made by the complementation process, it becomes possible to perform a pre-recovery process as necessary.

[0112] The above-mentioned embodiment can also be realized by executing the following process. That is, software (programs) that realize the functions of the above-mentioned embodiment are supplied to a system or device via a network or various storage media, and a computer (CPU, MPU, etc.) of the system or device reads and executes the program. The program may be executed by one computer, or may be executed by multiple computers in cooperation with each other. It is not necessary to realize all of the above-mentioned processes by software, and some or all of the processes may be realized by hardware such as ASIC. The CPU is not limited to one that performs all the processes by one CPU, and multiple CPUs may perform processes while appropriately coordinating with each other. The functions of the above-mentioned embodiment are not only realized by executing the program code read by the computer. It also includes a case where an OS running on a computer performs some or all of the actual processes based on the instructions of the program code, and the functions of the above-mentioned embodiment are realized by the processes.

[0113] <Technical Features of the Present Disclosure> The present disclosure includes the following configurations, methods, and programs.

[0114] [Configuration 1] An inkjet head inspection device for inspecting an inkjet head, comprising: a nozzle inspection unit that inspects each of a plurality of nozzles arranged on the ejection surface of the inkjet head for the presence or absence of defects based on the shape of ink droplets formed on the ejection surface in correspondence with the nozzle; Inkjet head inspection device.

[0115] [Configuration 2] the nozzle inspection unit determines a circularity of the ink droplet based on a shape of the ink droplet along the ejection surface, and inspects for the presence or absence of defects based on the circularity. 2. An inkjet head inspection device according to configuration 1.

[0116] [Configuration 3] the nozzle inspection unit determines that there is a defect when the circularity is outside a predetermined range. 3. An inkjet head inspection device according to configuration 2.

[0117] [Configuration 4] the nozzle inspection unit inspects for defects based on the shape of the ink droplets when the size of the ink droplets is changed; 4. An inkjet head inspection device according to any one of configurations 1 to 3.

[0118] [Configuration 5] the nozzle inspection unit inspects each of the plurality of nozzles for the presence or absence of a defect based on whether or not ink droplets are formed on the ejection surface corresponding to the nozzle; 5. An inkjet head inspection device according to any one of configurations 1 to 4.

[0119] [Configuration 6] the nozzle inspection unit inspects each of the plurality of nozzles for the presence or absence of defects based on an occupancy rate of ink droplets in a peripheral area of ​​the nozzle; 6. An inkjet head inspection device according to any one of configurations 1 to 5.

[0120] [Configuration 7] the nozzle inspection unit determines that there is a defect when the occupancy rate exceeds a threshold value. 7. An inkjet head inspection device according to configuration 6.

[0121] [Configuration 8] The threshold is a threshold determined by deep learning. 8. An inkjet head inspection device according to configuration 7.

[0122] [Configuration 9] The pressure generating means corresponding to the nozzle utilizes a piezoelectric element, the nozzle inspection unit inspects each of the plurality of nozzles for the presence or absence of a defect based on an evaluation result of a residual vibration after a pressure wave is generated in a piezoelectric element corresponding to the nozzle. 9. An inkjet head inspection device according to any one of configurations 1 to 8.

[0123] [Configuration 10] The pressure generating means corresponding to the nozzle utilizes film boiling, the nozzle inspection unit inspects each of the plurality of nozzles for the presence or absence of a defect based on an evaluation result of a temperature in the ink after film boiling in a pressure chamber corresponding to the nozzle; 9. An inkjet head inspection device according to any one of configurations 1 to 8.

[0124] [Configuration 11] An inkjet recording apparatus that ejects ink from an inkjet head onto a plurality of banks arranged on a substrate, a nozzle allocation unit that allocates, to each bank, one or more nozzles to be used for ejecting ink from among a plurality of nozzles arranged on an ejection surface of the inkjet head; a nozzle inspection unit that inspects each of a plurality of nozzles arranged on an ejection surface of the inkjet head for the presence or absence of defects; a defect determination unit that determines whether or not each of one or more nozzles used for each bank is defective based on the allocation by the used nozzle allocation unit and the inspection results by the nozzle inspection unit; a nozzle complementing section for complementing a defective nozzle determined to be defective by the defect determining section for each bank with a complementary nozzle; Equipped with Inkjet recording device.

[0125] [Configuration 12] the nozzle complementing unit adopts, as the complementary nozzle, any nozzle capable of ejecting ink to the bank to which the defective nozzle is to be ejected; 12. The inkjet recording apparatus according to configuration 11.

[0126] [Configuration 13] the nozzle complementing unit adopts, as the complementary nozzle, any nozzle capable of ejecting ink to the bank that is the ejection destination of the defective nozzle in the same scan as a scan in which the defective nozzle is designated to eject ink to the bank; 13. The inkjet recording apparatus according to configuration 12.

[0127] [Configuration 14] the nozzle complementing unit adopts, as the complementary nozzle, any nozzle capable of ejecting ink to the bank that is the ejection destination of the defective nozzle in a scan different from a scan in which the defective nozzle is designated to eject ink to the bank; 13. The inkjet recording apparatus according to configuration 12.

[0128] [Configuration 15] The nozzles are arranged in a matrix on the ejection surface of the inkjet head, the nozzle complementing unit is capable of ejecting ink to the bank to which the defective nozzle is to be ejected, and employs any nozzle in the same row or column as the defective nozzle as the complementary nozzle; 13. The inkjet recording apparatus according to configuration 12.

[0129] [Configuration 16] the nozzle complementing unit adopts, as the complementary nozzle, any of the nozzles assigned by the active nozzle assignment unit to the bank to which the defective nozzle is assigned, excluding the defective nozzle; 12. The inkjet recording apparatus according to configuration 11.

[0130] [Configuration 17] 17. The inkjet recording apparatus according to any one of configurations 11 to 16, The nozzle inspection unit includes the inkjet head inspection device according to any one of configurations 1 to 10. Inkjet recording device.

[0131] [Method 1] An inkjet head inspection method for inspecting an inkjet head, comprising: a nozzle inspection step of inspecting each of a plurality of nozzles arranged on the ejection surface of the inkjet head for the presence or absence of defects based on the shape of ink droplets formed on the ejection surface in correspondence with the nozzle; Inkjet head inspection method.

[0132] [Method 2] An inkjet recording method for ejecting ink from an inkjet head onto a plurality of banks arranged on a substrate, comprising the steps of: a nozzle allocation step of allocating, to each bank, one or more nozzles to be used for ejecting ink from among a plurality of nozzles arranged on an ejection surface of the inkjet head; a nozzle inspection step of inspecting each of a plurality of nozzles arranged on an ejection surface of the inkjet head for the presence or absence of defects; a determining step of determining whether or not each of one or more nozzles to be used for each bank is defective based on the allocation in the used nozzle allocation step and the test results in the nozzle test step; a nozzle complementing step of complementing a defective nozzle determined to be defective in the determining step for each bank with a complementary nozzle; having Inkjet recording method.

[0133] [Program 1] A program for causing a computer to execute an inkjet head inspection method for inspecting an inkjet head, The inkjet head inspection method includes: a nozzle inspection step of inspecting each of a plurality of nozzles arranged on the ejection surface of the inkjet head for the presence or absence of defects based on the shape of ink droplets formed on the ejection surface in correspondence with the nozzle; program.

[0134] [Program 2] A program for causing a computer to execute an inkjet recording method for ejecting ink from an inkjet head onto a plurality of banks arranged on a substrate, the program comprising: The inkjet recording method includes a nozzle allocation step of allocating, to each bank, one or more nozzles to be used for ejecting ink from among a plurality of nozzles arranged on an ejection surface of the inkjet head; a nozzle inspection step of inspecting each of a plurality of nozzles arranged on an ejection surface of the inkjet head for the presence or absence of defects; a determining step of determining whether or not each of one or more nozzles to be used for each bank is defective based on the allocation in the used nozzle allocation step and the test results in the nozzle test step; a nozzle complementing step of complementing a defective nozzle determined to be defective in the determining step for each bank with a complementary nozzle; having program. [Explanation of symbols]

[0135] 111 Substrate 113 Camera 500 Nozzle Inspection Unit 501 Roundness Calculation Section 502 Nozzle Surrounding Droplet Occupancy Rate Calculation Unit 503 Nozzle Inspection Section 504 Defective nozzle detector 507 Defective nozzle replacement part

Claims

1. An inkjet head inspection device for inspecting an inkjet head, a nozzle inspection unit that inspects each of a plurality of nozzles arranged on the ejection surface of the inkjet head for defects based on the shape of ink droplets formed on the ejection surface in correspondence with the nozzle; The inkjet head inspection device is characterized in that the nozzle inspection unit determines the circularity of the ink droplets based on the shape of the ink droplets along the ejection surface, and inspects for defects based on the circularity.

2. the nozzle inspection unit determines that there is a defect when the circularity is outside a predetermined range; The inkjet head inspection device according to claim 1 .

3. the nozzle inspection unit inspects for defects based on the shape of the ink droplets when the size of the ink droplets is changed; The inkjet head inspection device according to claim 1 .

4. the nozzle inspection unit inspects each of the plurality of nozzles for the presence or absence of a defect based on whether or not ink droplets are formed on the ejection surface corresponding to the nozzle. The inkjet head inspection device according to claim 1 .

5. the nozzle inspection unit inspects each of the plurality of nozzles for defects based on the occupancy rate of ink droplets in a peripheral area of ​​the nozzle; The inkjet head inspection device according to claim 1 .

6. the nozzle inspection unit determines that there is a defect when the occupancy rate exceeds a threshold value; The inkjet head inspection device according to claim 5 .

7. The threshold is a threshold determined by deep learning.

7. The inkjet head inspection device according to claim 6.

8. The pressure generating means corresponding to the nozzle utilizes a piezoelectric element, the nozzle inspection unit inspects each of the plurality of nozzles for defects based on an evaluation result of residual vibration after a pressure wave is generated in a piezoelectric element corresponding to the nozzle. The inkjet head inspection device according to claim 1 .

9. The pressure generating means corresponding to the nozzle utilizes film boiling, the nozzle inspection unit inspects each of the plurality of nozzles for the presence or absence of defects based on an evaluation result of the temperature of the ink after film boiling in the pressure chamber corresponding to the nozzle. The inkjet head inspection device according to claim 1 .

10. An inkjet recording apparatus that ejects ink onto a plurality of banks arranged on a substrate using an inkjet head, a nozzle allocation unit that allocates, to each bank, one or more nozzles to be used for ejecting ink from among a plurality of nozzles arranged on an ejection surface of the inkjet head; a nozzle inspection unit that inspects each of a plurality of nozzles arranged on the ejection surface of the inkjet head for defects; a defect determination unit that determines whether or not each of the one or more nozzles to be used for each bank is defective based on the allocation by the used nozzle allocation unit and the test results by the nozzle test unit; a nozzle complementing section for complementing a defective nozzle determined to be defective by the defect determining section for each bank with a complementary nozzle; Equipped with The inkjet recording apparatus is characterized in that the nozzle inspection unit determines the roundness of the ink droplets based on the shape of the ink droplets along the discharge surface, and inspects for defects based on the roundness.

11. the nozzle complementing unit adopts, as the complementary nozzle, any nozzle that can eject ink to the bank that is the ejection destination of the defective nozzle; The inkjet recording apparatus according to claim 10.

12. the nozzle complementing unit adopts, as the complementary nozzle, any nozzle that can eject ink to the bank that is the ejection destination of the defective nozzle in the same scan as a scan in which the defective nozzle is designated to eject ink to the bank; The inkjet recording apparatus according to claim 11.

13. the nozzle complementing unit adopts, as the complementary nozzle, any nozzle that can eject ink to the bank that is the ejection destination of the defective nozzle in a scan different from a scan in which the defective nozzle is designated to eject ink to the bank; The inkjet recording apparatus according to claim 11.

14. The plurality of nozzles are arranged in a matrix on the ejection surface of the inkjet head, the nozzle complementing unit is capable of ejecting ink to the bank to which the defective nozzle is directed, and employs any nozzle in the same row or column as the defective nozzle as the complementary nozzle; The inkjet recording apparatus according to claim 11.

15. the nozzle complementing unit adopts, as the complementary nozzle, any nozzle assigned by the active nozzle assigning unit to the bank to which the defective nozzle is assigned, excluding the defective nozzle; The inkjet recording apparatus according to claim 10.

16. An inkjet recording apparatus that ejects ink onto a plurality of banks arranged on a substrate using an inkjet head, a nozzle allocation unit that allocates, to each bank, one or more nozzles to be used for ejecting ink from among a plurality of nozzles arranged on an ejection surface of the inkjet head; a nozzle inspection unit that inspects each of a plurality of nozzles arranged on the ejection surface of the inkjet head for defects; a defect determination unit that determines whether or not each of the one or more nozzles to be used for each bank is defective based on the allocation by the used nozzle allocation unit and the test results by the nozzle test unit; a nozzle complementing section for complementing a defective nozzle determined to be defective by the defect determining section for each bank with a complementary nozzle; Equipped with An inkjet recording apparatus, The nozzle inspection unit is provided with the inkjet head inspection device according to any one of claims 1 to 9. Inkjet recording device.

17. An inkjet head inspection method for inspecting an inkjet head, comprising: a nozzle inspection step of inspecting each of a plurality of nozzles arranged on the ejection surface of the inkjet head for defects based on the shape of ink droplets formed on the ejection surface in correspondence with the nozzle; the nozzle inspection step is characterized in that the circularity of the ink droplet is determined based on the shape of the ink droplet along the ejection surface, and the presence or absence of defects is inspected based on the circularity. Inkjet head inspection method.

18. An inkjet recording method in which ink is ejected by an inkjet head onto a plurality of banks arranged on a substrate, comprising: a nozzle allocation step of allocating, to each bank, one or more nozzles to be used for ejecting ink from among a plurality of nozzles arranged on the ejection surface of the inkjet head; a nozzle inspection step of inspecting each of a plurality of nozzles arranged on the ejection surface of the inkjet head for defects; a determining step of determining whether or not each of the one or more nozzles to be used for each bank is defective based on the allocation made in the used nozzle allocation step and the test results made in the nozzle test step; a nozzle complementing step of complementing, for each bank, a defective nozzle determined to be defective in the determining step with a complementary nozzle; and the nozzle inspection step is characterized in that the circularity of the ink droplet is determined based on the shape of the ink droplet along the ejection surface, and the presence or absence of defects is inspected based on the circularity. Inkjet recording method.

19. A program for causing a computer to execute an inkjet head inspection method for inspecting an inkjet head, The inkjet head inspection method includes: a nozzle inspection step of inspecting each of a plurality of nozzles arranged on the ejection surface of the inkjet head for defects based on the shape of ink droplets formed on the ejection surface in correspondence with the nozzle; the nozzle inspection step is characterized in that the circularity of the ink droplet is determined based on the shape of the ink droplet along the ejection surface, and the presence or absence of defects is inspected based on the circularity. program.

20. A program for causing a computer to execute an inkjet recording method in which ink is ejected from an inkjet head onto a plurality of banks arranged on a substrate, the program comprising: The inkjet recording method is a nozzle allocation step of allocating, to each bank, one or more nozzles to be used for ejecting ink from among a plurality of nozzles arranged on the ejection surface of the inkjet head; a nozzle inspection step of inspecting each of a plurality of nozzles arranged on the ejection surface of the inkjet head for defects; a determining step of determining whether or not each of the one or more nozzles to be used for each bank is defective based on the allocation made in the used nozzle allocation step and the test results made in the nozzle test step; a nozzle complementing step of complementing, for each bank, a defective nozzle determined to be defective in the determining step with a complementary nozzle; and the nozzle inspection step is characterized in that the circularity of the ink droplet is determined based on the shape of the ink droplet along the ejection surface, and the presence or absence of defects is inspected based on the circularity. program.

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