Inkjet printing apparatus, device manufactured using the same, coating film formation unevenness detection method, and device manufacturing method

Abstract

To detect unevenness in coating film formation by an inkjet printing apparatus with high sensitivity by optical means.SOLUTION: An inkjet printing apparatus 1 prints to a substrate 10 where a plurality of cells 11 are provided on the surface by discharging ink P thereto. The inkjet printing apparatus 1 comprises: a printing head 20 for discharging a liquid ink P from a plurality of nozzles 21 to fill the ink P in each cell 11 and thereby forming a coating film on each cell 11; a stage 3 for moving the substrate 10 relatively to the printing head 20; and observation means 30 for observing by optical means the state of coating film on each cell 11 before the ink P filled in each cell 11 dries.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an inkjet printing apparatus, a device manufactured using the same, a method for detecting unevenness in coating film formation, and a method for manufacturing a device. [Background technology]

[0002] Inkjet printing is also used in the manufacture of various devices such as solar cells, displays, etc. For example, in the manufacture of organic electroluminescence displays, inkjet printing is used in the process of applying ink containing a functional material to the surface of a substrate.

[0003] A method is known in which a plurality of cells partitioned by banks are provided on the surface of a substrate to be printed, and ink is applied to each cell. Here, if the amount of ink filled in each of the plurality of cells is not uniform, the thickness of the coating film formed in each cell will differ, and uneven coating film formation may occur on the surface of the substrate. The uneven coating film formation may cause device defects. For example, in the case of an organic electroluminescence display, the uneven coating film formation appears as uneven color and uneven brightness, impairing the function of the display. Therefore, it is preferable that the amount of ink filled in each cell by inkjet printing is uniform.

[0004] For example, Patent Document 1 discloses an inspection method for inspecting unevenness in coating film formation by imaging a coated object with an angle of 70 to 80 degrees between a perpendicular line to the surface of the coated object and the imaging optical axis. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-205873 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the inspection by optical means as in the above-mentioned Patent Document 1, coating film formation unevenness is not detected, and coating film formation unevenness is sometimes detected for the first time in the lighting inspection carried out at the final stage of the manufacturing process. For example, in the case of an organic EL display, coating film formation unevenness can sometimes be detected for the first time as color unevenness or brightness unevenness by passing electricity through the functional material in the lighting inspection to cause the functional material to emit light.

[0007] If unevenness in the coating film formation is not detected until the final lighting inspection stage, the yield will decrease, which is undesirable.

[0008] The present disclosure has been made in view of the above points, and a main object of the present disclosure is to detect unevenness in coating film formation by inkjet printing with high sensitivity by optical means. [Means for solving the problem]

[0009] The inkjet printing apparatus according to the present disclosure is an inkjet printing apparatus that performs printing by ejecting ink onto a substrate having a plurality of cells on its surface, and includes a printing means that ejects liquid ink from a plurality of nozzles to fill each of the plurality of cells with ink, thereby forming a coating film in each of the cells, a moving means that moves the substrate relative to the printing means, and an observation means that observes the state of the coating film in each of the cells by optical means before the ink filled in each of the cells dries.

[0010] The device according to the present disclosure is manufactured by the inkjet printing apparatus described above.

[0011] The coating formation unevenness detection method according to the present disclosure is a method for detecting coating formation unevenness in a coating formed in each of a plurality of cells by filling each of the cells with ink in inkjet printing, which involves ejecting liquid ink onto a substrate having a plurality of cells on its surface, and observes the state of the coating in each of the cells before the ink filled in the cells dries.

[0012] The device manufacturing method according to the present disclosure is a device manufacturing method in which a coating film is formed in a plurality of cells provided on the surface of a substrate, and includes a printing process for forming a coating film in each of the plurality of cells by ejecting liquid ink into each of the cells to fill the cells, and an inspection process for observing the state of the coating film in each of the cells before the ink filled in the cells dries. Effect of the Invention

[0013] According to the present disclosure, unevenness in coating film formation by inkjet printing can be detected with high sensitivity by optical means. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a schematic diagram of an inkjet printing apparatus according to an embodiment of the present disclosure. [Figure 2A] FIG. 2A is a schematic diagram illustrating a method of printing with an inkjet printing device. [Figure 2B] FIG. 2B is a schematic cross-sectional view taken along line IIB-IIB in FIG. 2A. [Figure 3A] FIG. 3A is a diagram showing a schematic diagram of a coating film formed in each cell in a state where no coating film formation unevenness occurs. [Figure 3B] FIG. 3A is a view equivalent to FIG. 3A in a state in which unevenness in coating film formation has occurred. [Figure 4A] FIG. 4A is a diagram showing a schematic diagram of a method for observing a coating film formed in each cell in a state where no coating film formation unevenness occurs. [Figure 4B] FIG. 4B is a view equivalent to FIG. 4A in a state in which unevenness in coating film formation has occurred. [Diagram 5] FIG. 5 is a diagram showing a schematic diagram of the change in shape of a coating film over time. [Figure 6] FIG. 6 is a graph showing the change in diameter of the coating over time in the examples. [Figure 7A] FIG. 7A is a photograph of a defect formed on the surface of a substrate in an example. [Figure 7B] FIG. 7B is a diagram showing defects formed on the surface of a substrate in an embodiment, which are highlighted by a predetermined algorithm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Before describing the present invention, the circumstances under which the present invention was conceived will be described.

[0016] There is a known method for manufacturing an organic electroluminescence display by inkjet printing, in which multiple cells are provided on the surface of a substrate and each cell is filled with ink containing a functional material to form a coating film in each cell.

[0017] Here, if the thickness of the coating film between the cells is not uniform, unevenness in the coating film formation occurs on the surface of the substrate. Unevenness in the coating film formation is undesirable because it impairs the quality of the product. In particular, in the case of an organic EL display, unevenness in the coating film formation causes a loss of image quality.

[0018] The final stage of the manufacturing process for OLED displays is usually a lighting test, in which electricity is passed through the functional material to actually light up the display. This allows unevenness in the coating film formation to be detected as uneven color and brightness.

[0019] In order to prevent a decrease in yield due to unevenness in the coating film formation, it is preferable to detect unevenness in the coating film formation as early as possible in the manufacturing process.

[0020] Here, a method is known in which coating unevenness is detected by observing the surface of the substrate by optical means during the manufacturing process. Examples of the coating unevenness detection method by optical means include a method that utilizes the difference in the amount of diffuse reflected light due to the difference in coating thickness, and a method that utilizes the difference in the directionality of transmitted light due to the difference in coating thickness.

[0021] However, in some cases, coating unevenness occurring on the surface of the substrate cannot be detected by optical inspection during the manufacturing process, resulting in poor yields because the coating unevenness is only detected during the lighting inspection at the final stage of the manufacturing process.

[0022] That is, in order to improve the yield, it is effective to detect unevenness in the coating film formation with high sensitivity by inspection using optical means carried out during the manufacturing process.

[0023] Therefore, the inventors of the present application conducted extensive research to improve the sensitivity of detecting unevenness in coating film formation by optical means. As a result, they discovered that there is a difference in the direction of ink shape change before and after drying of the ink ejected onto the substrate. They also found that the difference in the direction of ink shape change affects the sensitivity of detecting unevenness in coating film formation by optical means.

[0024] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its application, or its uses.

[0025] 1 is a schematic diagram of an inkjet printing apparatus 1 according to this embodiment. The inkjet printing apparatus 1 is an apparatus for manufacturing an organic EL display as a device, and performs printing by applying ink P to a substrate 10.

[0026] The inkjet printing device 1 includes a print head 20 as a printing means. The print head 20 is disposed above the substrate 10. The print head 20 is provided with a plurality of nozzles 21, 21, .... Liquid ink P is ejected from each nozzle 21 toward the surface of the substrate 10. The ink P contains at least a functional material that becomes a light-emitting element of the organic EL display, and a solvent. The ejection amount, ejection direction, etc. of each nozzle 21 in the print head 20 are controlled by a processing unit 2.

[0027] The inkjet printing apparatus 1 includes an observation unit 30 that observes the state of the surface of the substrate 10 by optical means. The observation unit 30 has an illumination 31 as a light source unit and a light sensor camera 32 as an imaging unit. The illumination 31 is disposed above the substrate 10 and irradiates the substrate 10 with illumination light L1. The light sensor camera 32 is disposed above the substrate 10. Specifically, the illumination 31 is disposed at a predetermined angle θ with respect to a perpendicular line to the surface of the substrate 10.

[0028] The licenser camera 32 is positioned on a line perpendicular to the surface of the substrate 10. That is, the imaging axis T2 of the licenser camera 32 has a predetermined angle θ with respect to the irradiation axis T1 of the illumination light L1. The data of the image captured by the licenser camera 32 is input to the processing unit 2.

[0029] The illumination axis T1 refers to the central axis of the light emitted from the illumination 31. The imaging axis T2 refers to the direction in which the lens of the image sensor camera 32 faces (the central axis of the lens).

[0030] The inkjet printing apparatus 1 includes a stage 3 as a moving means. The stage 3 moves the substrate 10 relative to the print head 20. Specifically, the stage 3 places the substrate 10 on its upper surface and transports the substrate 10 from the print head 20 to the observation means 30. In the figure, X indicates the transport direction of the substrate 10 (stage 3) and indicates the relative movement direction of the substrate 10 with respect to the print head 20 (hereinafter simply referred to as the "transport direction X"). The observation means 30 is disposed at a position in the transport direction X where the surface of the substrate 10 is observed immediately after the ink P is applied from the nozzle 21 of the print head 20 to the surface of the substrate 10.

[0031] FIG. 2A is a schematic diagram showing a method of printing with the inkjet printing apparatus 1. FIG. 2B is a schematic diagram showing a cross section taken along line IIB-IIB in FIG. 2A. A plurality of cells 11, 11, ... are provided on the surface of the substrate 10. The cells 11 are arranged in the transport direction X and in a direction perpendicular to the transport direction X. Here, a plurality of banks 12, 12, ... are provided on the surface of the substrate 10. Each bank 12 in the plurality of banks 12, 12, ... is a wall protruding upward from the surface of the substrate 10. Each bank 12 extends in a direction perpendicular to the transport direction X and is parallel to the transport direction X. The cells 11, 11 adjacent to each other in the transport direction X are partitioned by the bank 12.

[0032] Here, the multiple nozzles 21 in the print head 20 are arranged in the transport direction X and in a direction perpendicular to the transport direction X. In addition, a plurality of license sensor cameras 32 are arranged in a direction perpendicular to the transport direction X (not shown).

[0033] 2B, the ink P is filled into each cell 11. As a result, a coating film is formed in each cell 11.

[0034] In this embodiment, red, green and blue inks Pa, Pb and Pc in the RGB color system are prepared as the ink P. One of the inks Pa, Pb and Pc is filled into each cell 11. Cells 11a, 11b and 11c corresponding to the inks Pa, Pb and Pc are provided on the surface of the substrate 10 and are arranged in the transport direction X.

[0035] Here, it is preferable that the thicknesses of the coatings of the inks Pa, Pb, and Pc filled in the cells 11a, 11b, and 11c are equal to each other, because non-uniformity in the coating thicknesses causes uneven coating formation on the surface of the substrate 10. In order to equalize the thicknesses of the coatings of the inks Pa, Pb, and Pc filled in the cells 11a, 11b, and 11c, the discharge amount, discharge direction, and the like of each nozzle 21 are controlled by the processing unit 2.

[0036] FIG. 3A shows a schematic diagram of the coating film formed in each cell 11 in a state where no unevenness in coating film formation occurs (hereinafter referred to as a normal state). FIG. 3B shows a schematic diagram of the coating film formed in each cell 11 in a state where unevenness in coating film formation occurs (hereinafter referred to as an abnormal state). As shown in FIG. 3A, in a normal state, ink Pc is ejected directly downward from each nozzle 21. Therefore, ink Pc is not filled into cell 11b adjacent to cell 11c, and is entirely filled into cell 11c. The same thing happens with cells 11a and 11b.

[0037] In this case, the thicknesses of the coatings of the inks Pa, Pb, and Pc filled in the cells 11a, 11b, and 11c are approximately equal to each other, so that no coating unevenness occurs on the surface of the substrate 10.

[0038] As shown in FIG. 3B, in an abnormal state, due to clogging of the nozzle 21, manufacturing errors, etc., some of the ink Pc may be ejected from the nozzle 21 toward the cell 11b side instead of being ejected directly downward. As a result, some of the ink Pc fills the cell 11b instead of the cell 11c. As a result, the amount of ink Pc filled in the cell 11c decreases, and the thickness of the coating in the cell 11c decreases. On the other hand, the cell 11b is filled with the ink Pb and some of the ink Pc, and the thickness of the coating in the cell 11b increases.

[0039] Fig. 4A shows a schematic diagram of a method for observing the coating film formed on each cell 11 in a normal state. Fig. 4B shows a schematic diagram of a method for observing the coating film formed on each cell 11 in an abnormal state. As shown in Fig. 4A, in a normal state, illumination light L1 irradiated from an illumination 31 becomes specularly reflected light L2 from the surface of the substrate 10.

[0040] 4B, in an abnormal state, the illumination light L1 emitted from the illumination 31 is diffusely reflected by the side surface of the raised portion P1 of the coating film in the cell 11b, and is input to the light sensor camera 32 as diffused light L3 from the substrate 10. That is, the light sensor camera 32 receives the diffusely reflected light L3 of the illumination light L1 from the substrate 10. By receiving a larger amount of the diffusely reflected light L3 by the light sensor camera 32, the detection sensitivity of coating film formation unevenness is improved.

[0041] Here, if the predetermined angle θ is too small, specifically, if it is smaller than 70 degrees, the light sensor camera 32 also receives the specular reflected light L2, making it difficult to detect the minute diffuse reflected light L3, and the detection sensitivity of the coating film unevenness decreases. On the other hand, if the predetermined angle θ is too large, specifically, if it is larger than 80 degrees, the illumination 31 interferes with the stage 3, making installation difficult. Therefore, the predetermined angle θ is preferably 70 degrees or more and 80 degrees or less.

[0042] The image data captured by the line sensor camera 32 is input to the processing unit 2. Here, as shown in FIG. 2A, the substrate 10 placed on the stage 3 moves in the transport direction X relative to the nozzles 21 of the print head 20. Therefore, if the unevenness of the coating thickness between the cells 11 (uneven coating formation) is caused by a defect in any one of the multiple nozzles 21, 21, ..., a linear defect extending in the transport direction X is formed on the surface of the substrate 10 (see FIGS. 7A and 7B). Note that examples of the defect in the nozzle 21 include a decrease in the discharge amount due to clogging of the nozzle 21, and a mismatch in the discharge direction due to a manufacturing error of the nozzle 21. When the observation means 30 observes the linear defect, the processing unit 2 detects the linear defect as the unevenness of the coating thickness between the cells 11 (uneven coating formation) caused by a defect in any one of the multiple nozzles 21, 21, ....

[0043] Furthermore, the processing unit 2 highlights the linear defect in comparison to other defects, making it easier to distinguish between defects caused by uneven coating film formation due to a malfunction of the nozzle 21 and other defects (e.g., defects caused by the surface condition of the substrate 10, etc.).

[0044] The change in shape of the coating of ink P that has been discharged onto the surface of the substrate 10 and filled into each cell will be described with reference to FIG. 5. FIG. 5 shows a schematic diagram of the change in shape of the coating over time. The ink P discharged onto the surface of the substrate 10 from the nozzle 21 of the print head 20 fills each cell 11. The solvent in the ink P starts to evaporate immediately after it is discharged from the nozzle 21. In other words, the ink P starts to dry immediately after it is discharged from the nozzle 21.

[0045] Here, the ink P ejected from the nozzle 21 onto the surface of the substrate 10 first becomes thinner in thickness over time. At this time, the diameter of the ink P film hardly changes. Then, after a certain time has passed, the ink P dries and the thickness of the ink P film becomes sufficiently small. After that, the diameter of the ink P film starts to become smaller. At this time, the thickness of the ink P film hardly changes.

[0046] That is, after a certain time has passed since the ink P was discharged from the nozzle 21, and the ink P filled in each cell 11 has dried and the thickness of the coating film has become sufficiently small, there is almost no difference in the thickness of the coating film between each cell 11. Therefore, it becomes difficult to detect unevenness in the thickness of the coating film between each cell 11 (unevenness in coating film formation) by optical means. Therefore, in this embodiment, the state of the coating film in each cell 11 is observed by the observation means 30 before the ink P filled in each cell 11 dries (before the thickness of the coating film becomes sufficiently small).

[0047] As described above, in this embodiment, by observing the state of the coating film in each cell 11 before the ink P filled in each cell 11 dries (before the thickness of the coating film becomes sufficiently small), unevenness in the coating film formed by inkjet printing can be detected with high sensitivity by the observation means 30, which is an optical means. This makes it possible to detect unevenness in the coating film formation before the lighting inspection performed in the final stage, thereby improving the yield.

[0048] The observation means 30 utilizes diffuse reflected light from the surface of the substrate 10, and therefore, unlike the case where transmitted light is used, it is possible to detect coating formation unevenness formed on the surface of the substrate 10 even if the substrate 10 is opaque.

[0049] By setting the predetermined angle θ to be 70 degrees or more and 80 degrees or less, the light sensor camera 32 can receive only the diffuse reflected light L3 without receiving much of the regular reflected light L2. This allows the coating film formation unevenness to be detected with high accuracy. In addition, the interference between the illumination 31 and the stage 3 can be suppressed.

[0050] When a linear defect is observed on the surface of the substrate 10, the processing unit 2 identifies it as uneven coating formation caused by a defective nozzle 21, so that the cause of the defect can be found at an early stage.

[0051] Although the present invention has been described above with reference to the preferred embodiments, such description is not limiting and various modifications are possible.

[0052] For example, the inkjet printing apparatus 1 may include a landing camera. The landing camera captures an image of the ink P ejected from the nozzles 21. As described above, when a linear defect is found on the surface of the substrate 10, the cause of the linear defect is identified as a defect in one of the nozzles 21, 21, .... At this time, by checking the image captured by the landing camera, it is possible to further identify which nozzle 21, 21, ... is causing the defect.

[0053] The observation means 30 is not limited to one that uses the diffuse reflected light L3, and may be one that uses, for example, transmitted light.

[0054] The device manufactured by the inkjet printing apparatus 1 is not limited to an organic EL display, but may be, for example, a solar cell.

[0055] The coating formation unevenness detection method of the present disclosure is a coating formation unevenness detection method for a coating formed in each of a plurality of cells 11, 11, ... by filling each of the cells 11 with ink P in ink jet printing, which performs printing by ejecting liquid ink P onto a substrate 10 having a plurality of cells 11 on its surface, and observes the condition of the coating in each cell 11 before the ink P filled in each cell 11 dries.

[0056] The method for manufacturing a device according to the present disclosure is a method for manufacturing a device in which a coating film is formed in a plurality of cells 11 provided on the surface of a substrate 10, and includes a printing process for forming a coating film in each of the plurality of cells 11, 11, ... by ejecting liquid ink P into each of the cells 11 to fill them, and an inspection process for observing the state of the coating film in each of the cells 11 before the ink P filled in each of the cells 11 dries. EXAMPLES

[0057] Next, specific examples will be described.

[0058] The ink was dropped onto a glass substrate. The amount of ink dropped was the amount that filled the cell. The change in diameter of the coating film due to the evaporation of the solvent contained in the ink after dropping was measured. Figure 6 is a graph showing the change in diameter of the coating film over time. As shown in Figure 6, no significant change in diameter was observed for about 60 seconds after dropping, but a significant change was observed after 60 seconds. From the time of dropping to about 60 seconds, the reduction in the liquid volume due to the evaporation of the solvent changes in the height direction of the coating film. Then, after about 60 seconds, when the thickness of the coating film becomes sufficiently small, the diameter of the coating film begins to decrease. Therefore, it was found that it is necessary to observe the coating film within 60 seconds after the ink measured this time is discharged from the nozzle.

[0059] The observation means used was a line sensor camera (model number: VT-9K7C-H80, manufactured by ViewWorks, Inc.) The number of line sensor cameras was four, arranged in a direction perpendicular to the conveying direction X of the substrate.

[0060] A bar light (model number: PDL-T-1500-1, manufactured by Nippon Pi) and an LED light source (model number: SLG-150V-R, manufactured by REVOX) were prepared as the lighting section. A personal computer (model number: LR-41S49, manufactured by Logitec) was prepared as the processing section. An image input board (model number: APX-3800, manufactured by Aval Data) was installed in the personal computer and connected to a line sensor camera. The specified angle θ was set to 70 degrees.

[0061] The observation means was disposed immediately after the print head in the transport direction X. This made it possible to observe the surface of the substrate by the observation means immediately after ink was ejected from the nozzles. (Ink application) A 730 mm x 920 mm glass substrate (model number: AN100, manufactured by AGC) was prepared as the substrate. The glass substrate was placed on the stage of an inkjet printing device. Then, ink was applied to the surface of the glass substrate from the nozzle of the print head. The application time was 27 seconds. (Method for detecting unevenness in coating film formation) After the ink was applied to the surface of the glass substrate, the glass substrate was transported to the observation means at 150 mm / s by the stage. The total transport time and observation preparation time was 15 seconds. Then, the surface of the glass substrate was imaged by four line sensor cameras. The image capture time was 10 seconds. As a result, image data was obtained 25 to 52 seconds after application, and the surface of the substrate could be observed within 60 seconds after the ink was applied. The captured image data was sent to a processing unit, and coating film formation unevenness was detected.

[0062] (Confirmation of effectiveness) Fig. 7A is a photograph of a defect formed on the surface of a substrate taken by an observation camera (model number: HS-80-04K40 / manufactured by DALSA). Fig. 7B is a diagram showing the defect formed on the surface of the substrate photographed by a licenser camera, which is highlighted by a predetermined algorithm in the processing unit.

[0063] The observation camera is installed perpendicular to the surface of the stage (not shown). The observation camera irradiates light from directly above the surface of the glass substrate and observes the specularly reflected light from the glass substrate. As a result, as shown in Figure 7A, in the image captured by the observation camera, defective areas (uneven coating film formation) are captured in black compared to normal areas.

[0064] In addition, in the image captured by the licenser camera, a large amount of diffuse reflected light from defective parts (uneven coating film formation) is detected, so the defective parts are captured in white compared to normal parts, as shown in Fig. 7B. Note that, as shown in Fig. 7B, the processing unit uses a predetermined algorithm to highlight defects that are formed linearly in the conveying direction X. When the image captured by the observation camera shown in Fig. 7A and the image in which the defective parts are highlighted by the processing unit shown in Fig. 7B are compared, it was confirmed that the positions of the defective parts matched. [Explanation of symbols]

[0065] P Ink X conveying direction L1 illumination light L2 Specular reflection light L3 Diffuse T1 Irradiation axis T2 imaging axis 1 Inkjet printing device 2 Processing section 3 Stage (Transportation) 10 Substrate 11 Cell 20 Print head (printing means) 21 Nozzle 30 Observation methods 31 Lighting (light source section) 32 Licensed camera (imaging unit)

Claims

1. An inkjet printing apparatus that performs printing by ejecting ink onto a substrate having a plurality of cells on its surface, a printing means for ejecting liquid ink from a plurality of nozzles to fill each of the plurality of cells with ink, thereby forming a coating film in each of the cells; a moving means for moving the substrate relative to the printing means; and an observation means for observing a state of the coating film in each of the cells by an optical means before the ink filled in each of the cells dries, The observation means is a light source unit that irradiates the substrate with illumination light; an imaging unit that receives diffuse reflected light of the illumination light from the substrate, an imaging axis of the imaging unit has a predetermined angle with respect to an irradiation axis of the illumination light; The predetermined angle is equal to or greater than 70 degrees and equal to or less than 80 degrees, The substrate is provided with a plurality of banks, Each of the plurality of banks protrudes from the substrate, extends in a direction perpendicular to a relative movement direction of the substrate with respect to the printing means, and is aligned in the relative movement direction; the cells adjacent to each other in the moving direction are partitioned by the bank, An inkjet printing apparatus, wherein the imaging axis is along a normal to the substrate.

2. In claim 1, An inkjet printing device, wherein the imaging unit receives the diffuse reflected light from the substrate when the ink runs over the bank, and does not receive the specular reflected light from the substrate when the ink does not run over the bank.

3. In claim 1 or 2, An inkjet printing apparatus, wherein the imaging units are arranged in a direction perpendicular to the direction of movement of the substrate relative to the printing means.

4. In any one of claims 1 to 3, the light source unit is disposed above the substrate, The inkjet printing apparatus, wherein the imaging unit is disposed above the substrate.

5. In any one of claims 1 to 4, The inkjet printing device further includes a processing unit that, when the observation means observes a linear defect on the surface of the substrate extending in the relative movement direction of the substrate with respect to the printing means, detects the defect as an unevenness in the thickness of the coating film between the cells caused by any one of the multiple nozzles.

6. A device manufactured by an inkjet printing apparatus according to any one of claims 1 to 5.

7. In claim 6, A solar cell,device.

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