Printing apparatus and printing method

Abstract

To provide a printer suppressing light-emission unevenness of a display panel.SOLUTION: A printer such as to coat a plurality of cells of a display panel with ink, includes: an ink jet head having nozzles two or more of which are allocated to each of the cells; a camera observing a coating state of the ink in the plurality of cells; and a control device calculating the difference in an ink coating amount in the plurality of cells on the basis of the result of the observation by the camera, and adjusting the volume of droplet of each of the nozzles discharging droplets of the ink to the plurality of cells so that the different in the coating amount becomes smaller.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to a printing apparatus and a printing method.

Background Art

[0002] As a method for manufacturing a color filter of a liquid crystal display, a device such as an organic EL display, for example, a liquid containing a functional material is ejected as droplets from a plurality of nozzles by an inkjet method, and a film of the functional material is formed on a body to be ejected. A method is known. In this case, it is an important step to obtain the correspondence between the setting of the control device for controlling the ejection amount of the droplets and the actual ejection amount of the droplets, and to control the ejection amount to a constant value. This is because if the ejection amount becomes non-uniform, a difference will occur in the film thickness of the functional material, leading to defects in the device. For example, in the case of a color filter or an organic EL display, a difference in film thickness is observed as color unevenness or brightness unevenness.

[0003] As a method for examining the actual ejection amount, for example, a method of applying ink containing a polymer solute to a glass substrate in a predetermined number of droplets, drying the solvent, and then measuring the volume of the solute using a measuring instrument such as a white interference microscope is known (see, for example, Patent Document 1).

[0004] Also, as a method for examining the actual ejection amount, a method of measuring the height of droplets using a laser distance measuring instrument and calculating the volume of the droplets is known (see, for example, Patent Document 2).

[0005] Also, as a method for manufacturing an organic EL display by an inkjet method, after applying ink on a glass substrate, the shape of droplets after drying the solvent in the ink is measured with a confocal laser microscope to obtain the volume value of the droplets after drying. Then, based on the solid content concentration in the ink, the volume value of the droplets after solvent drying is converted into the volume of the droplets in the wet state before solvent drying (hereinafter sometimes referred to as "droplet volume") to obtain the droplet volume value ejected from each nozzle of the inkjet head. And a method is known in which printing with a uniform coating amount is realized by adjusting the droplet volume value in the wet state between nozzles (see, for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] When manufacturing an organic EL display by an inkjet method, the area where the ink is applied may be formed by a line-shaped bank (hereinafter sometimes referred to as "line bank"). In this case, as shown in FIG. 1A, the display panel 5006 is arranged so that the major axis direction of the line bank 1 formed on the display panel 5006 is parallel to the arrangement direction of the plurality of nozzles 101 of the inkjet head 30, and a plurality of nozzles 101 are assigned to the line bank 1 to eject ink to form a coating film. In this state, since ink is ejected onto a wide area formed in a line shape by many nozzles 101, the variation in the volume of the droplets 310 between the nozzles 101 is averaged. As a result, the variation in the film thickness of the coating film formed in the line bank 1 does not cause much of a problem.

[0008] In FIG. 1A, the case of printing with 14 nozzles 101 is illustrated. The variation in the droplet volume ejected from the 14 nozzles 101 is generally about 3%. However, since the droplets 310 from each nozzle 101 are mixed in the line bank 1, the originally existing variation in the droplet volume is averaged out.

[0009] The event in which the variation in the droplet volume is alleviated by coating from a plurality of nozzles will be described in detail. For example, when coating with 3 nozzles, if the standard deviation of the variation in the total droplet volume is σ mean , and the standard deviations of the variation in the droplet volumes of 3 different nozzles are σ1, σ2, and σ3, the following formula (1) holds. σ1 2 +σ2 2 +σ3 2 =σ mean 2 ···(1)

[0010] Assuming that the variation in the droplet volume of each nozzle is equal as shown in the following formula (2), formula (3) can be obtained from formulas (1) and (2). Further, formula (4) can be obtained from formula (3), and formula (5) can be obtained from formula (4). σ1=σ2=σ3···(2) 3σ1 2 =σ mean 2 ···(3) σ1 2 =σ mean 2 / 3···(4) σ1=σ mean / 3 1 / 2 ···(5)

[0011] Here, assuming that the variation in the average value of the standard deviation is n% (where n is 10 or less), the variation in the droplet volume at each nozzle is, from formula (5), σ1 = n / 3 1 / 2 and, for example, when n = 3%, σ1 = 1.7%. On the other hand, when coating with 14 different nozzles, σ1 = n / 14 1 / 2Thus, for example, when n = 3%, σ1 = 0.8%. That is, even if the droplet volume of the nozzle is adjusted to be the same, applying by a method with a larger number of nozzles can suppress the variation in droplet volume.

[0012] Here, as shown in FIG. 1B, when forming a coating film by discharging droplets 310 into a bank 2 partitioned in pixel form (hereinafter sometimes referred to as "pixel bank"), the number of nozzles 101 assigned to one cell 2A decreases. As a result, as described above, the variation in the droplet volume of the droplets 310 discharged into each cell 2A becomes large, and the influence of the variation in droplet volume on the variation in film thickness of the coating film increases.

[0013] FIG. 1C shows a cross-sectional view taken along line A-A of FIG. 1B before the solvent of the ink dries immediately after coating. The amount of ink in the coating films 311, 312, 313 formed by the droplets 310 discharged into each cell 2A changes according to the variation in the volume of the droplets 310 discharged from the inkjet head 30. In the example shown in FIG. 1B, since the number of nozzles 101 assigned to each cell 2A is three, the effect of averaging the variation in droplet volume becomes small, and the variation in the amount of ink applied for each cell 2A becomes prominent. This variation in the amount of ink is directly related to the variation in the film thickness of the coating film remaining after the solvent of the ink dries.

[0014] Therefore, the droplet volume is measured before drying. The variation in film thickness becomes, for example, the variation in emission luminance in an organic EL display, which has a great influence on the display quality of the display. In particular, the variation in emission luminance between adjacent cells 2A is visually significantly affected and appears as streak-like unevenness in emission. Therefore, when printing on the pixel bank 2, it is necessary to suppress the variation in droplet volume between the nozzles 101 more than ever. However, at present, the variation in droplet volume is suppressed to about 3%, and it is not easy to further reduce the variation in droplet volume.

[0015] In view of such a situation, an object of the present disclosure is to provide a printing apparatus and a printing method capable of suppressing uneven light emission of a display panel.

Means for Solving the Problems

[0016] The printing apparatus of the present disclosure is a printing apparatus that applies ink to a plurality of cells of a display panel, and includes an inkjet head having nozzles assigned in plural for each of the cells, a camera that observes the application state of the ink in the plurality of cells, and a control device that calculates the difference in the amount of ink applied in the plurality of cells based on the observation result by the camera and adjusts the volume of droplets of the ink ejected from each nozzle so that the difference in the amount of ink applied becomes small.

[0017] The printing method of the present disclosure is a printing method in which a plurality of nozzles are assigned to each cell of a display panel to apply ink, observes the application state of the ink in the plurality of cells, calculates the difference in the amount of ink applied in the plurality of cells based on the result of the observation, and adjusts the volume of droplets of the ink ejected from each nozzle so that the difference in the amount of ink applied becomes small.

[0018] The printing method of the present disclosure is a printing method in which a plurality of nozzles are assigned to each cell of a display panel to apply ink, corrects the area of the droplets ejected into the plurality of cells as a function of the elapsed time from landing to observation, and adjusts the volume of droplets of each nozzle so that the area of the corrected droplets becomes uniform for each nozzle.

Advantages of the Invention

[0019] According to the printing method and the printing apparatus of the present disclosure, uneven light emission of a display panel can be suppressed.

Brief Description of the Drawings

[0020]

Figure 1A

Figure 1B

Figure 1C

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 7

Figure 8A

Figure 8B

Figure 8C

Figure 9

Figure 10A

Figure 10B

Figure 11A

Figure 11B

Figure 11C

Figure 12

Figure 13

Figure 14A

Figure 14B

Embodiments for Carrying Out the Invention

[0021] Hereinafter, an embodiment of the present disclosure will be described.

[0022] 〔Configuration of Printing Device〕 First, the configuration of the printing device will be described. FIG. 2 is a diagram showing the overall configuration of the printing device used in the present embodiment. FIG. 3 is a functional block diagram of the printing device.

[0023] As shown in FIGS. 2 and 3, the printing device 1000 includes a control device (PC) 15, an inkjet table 20, an inkjet head 30, a droplet observation device 40, and a coating unevenness observation device 50.

[0024] (Control Device) The control device 15 is composed of a CPU 150, a storage means 151 (including a large-capacity storage means such as an HDD), an input means 152, and a display means (display) 153. Specifically, a personal computer (PC) can be used as the control device 15. In the storage means 151, there are stored various control programs for driving the inkjet table 20, the inkjet head 30, the droplet observation device 40, and the coating unevenness observation device 50 connected to the control device 15, and the characteristic data of the inkjet head 30 (characteristic data regarding the applied voltage of the piezoelectric elements of all nozzles and the droplet volume). When the printing device 1000 is driven, the CPU 150 performs predetermined control based on the instructions input by the operator through the input means 152 and the various control programs stored in the storage means 151.

[0025] (Inkjet table) The inkjet table 20 is a so-called gantry type work table, on which two gantry parts (moving gantries) are arranged movably along a pair of guide shafts on the table of the base.

[0026] Specifically, on the plate-shaped base 200, columnar stands 201A, 201B, 202A, and 202B are arranged at the four corners of its upper surface. In the region surrounded by these stands 201A, 201B, 202A, and 202B, a fixed stage ST for placing the object to be coated and an ink pan (dish-shaped container) 60 used to stabilize the ejection of ink immediately before coating are respectively arranged.

[0027] Further, guide shafts 203A and 203B are supported in parallel by the stands 201A, 201B, 202A, and 202B along a pair of both side portions of the base 200 in its longitudinal direction (Y direction). Two linear motors 204A and 204B are inserted into one guide shaft 203A. Two linear motors 205A and 205B are inserted into the other guide shaft 203B. A gantry portion 210A is mounted on the linear motors 204A and 205A so as to cross the base 200. A gantry portion 210B is mounted on the linear motors 204B and 205B so as to cross the base 200. With such a configuration, when the printing apparatus 1000 is driven, the linear motors 204A, 205A, 204B, and 205B are driven, so that the two gantry portions 210A and 210B reciprocate independently along the longitudinal direction of the guide shafts 203A and 203B, respectively.

[0028] On each of the gantry portions 210A and 210B, moving bodies (carriages) 220A and 220B each consisting of an L-shaped pedestal are disposed. Servo motors (moving body motors) 221A and 221B are disposed on the moving bodies 220A and 220B. Gears (not shown) are arranged at the tips of the shafts of the servo motors 221A and 221B. The gears are fitted into guide grooves 211A and 211B formed along the longitudinal direction (X direction) of the gantry portions 210A and 210B. Fine racks (not shown) are formed along the longitudinal direction inside the guide grooves 211A and 211B. The racks are engaged with the gears. Therefore, when the servo motors 221A and 221B are driven, the moving bodies 220A and 220B move precisely and reciprocally along the X direction by a so-called pinion-rack mechanism. Here, the moving bodies 220A and 220B are each equipped with an inkjet head 30 and a coating unevenness observation device 50, and are driven independently of each other.

[0029] Note that the linear motors 204A, 205A, 204B, 205B and the servo motors 221A, 221B are each connected to a control unit 213 for controlling their drives. The control unit 213 is connected to the CPU 150 within the control device 15. When the printing device 1000 is driven, the drives of the linear motors 204A, 205A, 204B, 205B and the servo motors 221A, 221B are controlled via the control unit 213 by the CPU 150 that has loaded the control program (Fig. 3).

[0030] Also, the linear motors 204A, 205A, 204B, 205B and the servo motors 221A, 221B are merely examples of the moving means of the gantry units 210A, 210B and the moving bodies 220A, 220B, and the use of these is not essential. For example, at least one of the gantry unit or the moving body may be moved using a timing belt mechanism or a ball screw mechanism.

[0031] Note that in this embodiment, the inkjet head 30 moves with respect to the fixed stage ST. However, the present invention is not limited to this, and the inkjet head 30 may be fixed and the stage on which the object to be coated is placed may move, or both the inkjet head 30 and the stage may move. Note that the number of inkjet heads 30 mounted on the moving body 220A does not have to be one, and a plurality of inkjet heads 30 may be mounted, or a line head in which a plurality of inkjet heads 30 are unitized may be mounted.

[0032] (Inkjet head) The inkjet head 30 is a head that adopts the piezo method, and is composed of a head portion 301 and a main body portion 302 shown in FIG. 2, and a control portion 300 shown in FIG. 3. A servo motor 304 is built in the main body portion 302. The inkjet head 30 is fixed to the moving body 220A via the main body portion 302. As shown in FIG. 2, the head portion 301 has a rectangular parallelepiped external shape, and is suspended from the tip of the shaft of the servo motor 304 of the main body portion 302 near the center of the upper surface thereof. Thereby, a plurality of nozzles 3030 (see FIG. 4) formed on the bottom surface of the head portion 301 rotate above the fixed stage ST according to the rotation of the shaft of the servo motor 304.

[0033] FIG. 4 is a cross-sectional view showing the internal configuration of the head portion of the inkjet head. In FIG. 4, three ink ejection mechanism portions formed adjacent to each other in the head portion 301 are partially shown.

[0034] As shown in FIG. 4, a plurality of ink ejection mechanism portions for ejecting ink are arranged in the head portion 301 along the longitudinal direction. The ink ejection mechanism portions are arranged side by side in a row at regular intervals. Each ink ejection mechanism portion is composed of a piezoelectric element 3010 (3010a, 3010b, 3010c), a liquid chamber 3020 (3020a, 3020b, 3020c), a nozzle 3030 (3030a, 3030b, 3030c), and a diaphragm 3040.

[0035] The diaphragm 3040 is disposed so as to cover the liquid chamber 3020. A piezoelectric element 3010 is laminated on the diaphragm 3040. By applying a voltage to each of the piezoelectric elements 3010a, 3010b, 3010c, the ink ejection mechanism portions are driven independently.

[0036] The liquid chamber 3020 and the nozzle 3030 are made of a metal material such as SUS or a ceramic material. The liquid chamber 3020 and the nozzle 3030 are respectively formed by machining, etching, or electrical discharge machining. The liquid chamber 3020 is a space for storing the ink immediately before ejection, and its volume is reversibly reduced and restored by the driving of the piezoelectric element 3010. The nozzles 3030 are formed in a row at a constant pitch so as to communicate with the liquid chamber 3020. Here, the pitch of each nozzle 3030 is constitutionally constant, but by adjusting the rotation angle of the shaft of the servo motor 304, the application pitch of the ink on the object to be coated can be adjusted. Note that the arrangement of the nozzles 3030 is not limited to the above-mentioned single row. For example, the nozzles 3030 can be formed in multiple rows, or the nozzles 3030 can be formed in multiple rows and in a staggered pattern, so as to narrow the pitch between the nozzles 3030.

[0037] The diaphragm 3040 is a thin plate made of stainless steel or nickel, and is disposed so as to be deformable together with the piezoelectric element 3010 laminated thereon. The piezoelectric element 3010 is a known piezo element, and has a structure of a laminate in which a plate-like piezoelectric body made of, for example, lead zirconate titanate is sandwiched between one or more pairs of electrodes. The energization of the electrodes is managed by the CPU 150 via the control unit 300 as shown in FIG. 3. Based on a predetermined control program stored in the storage means 151, a rectangular pulse voltage with a width of several tens of μs is continuously applied to the electrodes at a driving frequency of several hundred Hz to several tens of kHz when the ink is ejected. The piezoelectric element 3010 deforms in accordance with the rise of each of these rectangular pulse voltages, and the diaphragm 3040 deforms so that the volume of the liquid chamber 3020 decreases or is restored as the piezoelectric element 3010 deforms. When the volume of the liquid chamber 3020 decreases, the ink is ejected from the nozzle 3030. Note that the pulse voltage is not limited to a rectangular shape, and may be a waveform incorporating a stepped shape or a partially curved shape.

[0038] When driving each piezoelectric element 3010, the CPU 150 reads a predetermined control program from the storage means 151 and instructs the control unit 300 to apply a predetermined voltage to the target piezoelectric element 3010. In the printing apparatus 1000, as will be described later, when unevenness is confirmed in the state of printing on the object to be coated, control is performed so as to correct the droplet volume for each nozzle 3030. Note that, in the present embodiment, an example in which one inkjet head 30 is provided has been shown, but the number of inkjet heads 30 to be arranged is not limited, and a plurality of inkjet heads 30 can also be arranged.

[0039] (Droplet observation device 40) The droplet observation device 40 is configured using a camera for ink ejection confirmation. As shown in FIG. 2, the droplet observation device 40 includes a droplet observation camera (CCD camera) 402 having a built-in light-emitting light, a zoom lens 403 attached to the tip of the droplet observation camera in the objective direction, and a control unit 400 for controlling the driving of the droplet observation camera and the zoom lens 403. In the configuration shown in FIG. 2, a state where the droplet observation camera is fixed to the fixed base 401 is shown, but the fixing method is not limited to this, and the droplet observation camera may be directly fixed to the base 200. The droplet observation camera is connected to the control unit 400 by a cable 404. The control unit 400 is connected to the CPU 150 as shown in FIG. 3.

[0040] In the printing apparatus 1000, as shown in FIG. 2, the droplet observation camera is directed to a position where it can image the state of droplets ejected from each nozzle 3030 of the head unit 301. With such a configuration, at the time of imaging, image data of still images and moving images can be continuously obtained in synchronization with the strobe light emission of the light-emitting light built in the droplet observation camera. The CPU 150 of the control device 15 stores the captured image data in the storage means 151 and displays it on the display means 153 based on a predetermined control program.

[0041] Incidentally, the droplet observation device 40 measures the velocity of droplets (hereinafter sometimes referred to as "droplet velocity"). If the droplet velocity is too high, satellite droplets called satellites are generated. If the droplet velocity is too low, the landing position accuracy deteriorates due to air resistance during flight. Therefore, it is necessary to confirm that the droplets are flying at an appropriate droplet velocity. In addition, the droplet observation device 40 can measure the droplet volume for each nozzle 3030. Assuming that the flying droplets are spherical, the volume is estimated from the diameter of the droplets observed two-dimensionally. The measurement of the droplet volume can be performed by coating and measuring on the droplet volume adjustment substrate as described later, but it is also possible to measure using the droplet observation device 40.

[0042] (Method for obtaining droplet volume data for each nozzle) In order to adjust the droplet volume for each nozzle 3030, data for voltage determination showing the correlation between the applied voltage of the piezoelectric element 3010 and the droplet volume is used. To obtain the voltage determination data, a droplet volume adjustment substrate is used. As the droplet volume adjustment substrate, at least one having a surface area for applying ink that is water-repellent processed by fluorine coating, plasma treatment, or the like is used. Such water-repellent processing is a device for accurately measuring the droplet volume of the dropped ink.

[0043] First, droplets are applied from all the nozzles 3030 onto the droplet volume adjustment substrate in a predetermined number of droplets. After drying the solvent contained in the applied droplets by vacuum drying or the like, the volume of the remaining solute is measured. The volume measurement is performed using a confocal laser microscope, a white interference microscope, or the like. Here, generally, in a confocal laser microscope or a white interference microscope, an image of only the focal part can be obtained. Therefore, by changing the focal distance, the area of the image at the height of each focal distance can be measured. Since the ink droplets to be measured are hemispherical, the shape seen from above is almost circular. Therefore, the shape of each droplet part divided at a predetermined fine constant height h interval is regarded as a disk shape, and from the radius r of the disk at the constant height h, the partial volume of the disk shape (πr 2 ×h) is obtained. The partial volume of this disk shape is calculated up to the total height H of the droplet. Then, by summing up the previously obtained partial volumes, the droplet volume V of the ink can be calculated as an approximate value.

[0044] Since the volume of a single droplet is extremely small, in the above calculation, it is calculated based on the volume Vsum of a large droplet formed by combining a certain number of droplets (for example, the droplet volume of 4 droplets). That is, four drops of ink are dropped from each nozzle 3030 onto the same position on the droplet volume adjustment substrate to form a large droplet. By dividing the volume Vsum of this large droplet by the number of droplets (4 drops), the ink volume Vdr per drop (=Vsum / 4) can be calculated.

[0045] By measuring the droplet volume for each nozzle 3030 by changing the voltage in the above method, data for voltage determination as shown in FIG. 5 can be obtained. This voltage determination data is stored in the storage means 151 as a table for each nozzle 3030. Thereby, the voltage adjustment value at the time of droplet volume adjustment can be known. Specifically, it can be known that in order to change the droplet volume by 0.1 pL, the applied voltage of the piezoelectric element 3010 may be adjusted by 0.24 V.

[0046] (Coating unevenness observation device 50) The coating unevenness observation device 50 is one of the main characteristic parts of the printing device 1000, and is a means for observing the unevenness of the coating film on the display panel which is the object to be coated placed on the fixed stage ST. FIG. 6A is a diagram showing the configuration of the coating unevenness observation device. FIG. 6B is a diagram showing the arrangement of the optical system of the coating unevenness observation device.

[0047] As shown in Fig. 3, the coating unevenness observation device 50 is composed of a photographing unit 501 and a control unit 500. As shown in Fig. 6A, the photographing unit 501 is composed of a lighting 5001, a camera 5002, a lens 5003, a cylindrical lens 5004, and a rod lighting 5005. The cylindrical lens 5004 is provided with a lens function only in one direction. The cylindrical lens 5004 can uniformly apply light in a straight line while condensing the light. As shown in Fig. 6B, the illumination light from the rod lighting 5005 is irradiated obliquely onto the coating film 5008 applied in the bank pattern 5007 (cell 5007A) on the display panel 5006. Depending on the coating liquid amount of the coating film 5008, reflected light is generated on the surface of the coating film 5008, and the reflected light is received by the camera 5002 arranged in a direction perpendicular to the display panel 5006 through the lens 5003. By irradiating the illumination light obliquely, total reflection occurs on the surface of the coating film 5008, eliminating the loss of reflected light and improving the observation sensitivity. The camera and the lighting are not limited to the above, as long as the coating film 5008 can be observed.

[0048] The reason for using such a coating unevenness observation device 50 is as follows. The volume of the droplets ejected from the nozzle 3030 is adjusted in advance to a predetermined volume. However, even when printing is performed in the adjusted state, depending on the position and number of the nozzles 3030 assigned to the cells, there may be a difference in the droplet volume between adjacent cells, resulting in coating unevenness. In such a case, by directly observing the coating unevenness, it is for adjusting the droplet volume ejected from the nozzle 3030 to an optimal state.

[0049] (Adjustment of Droplet Volume by Measuring the Area of the Landing Droplet) It is possible to observe the droplets landing on the workpiece from above with a camera, measure the area of the droplets, and adjust the volume of the droplets. The method will be described. The workpiece may be a part other than the cells of the display panel, or may be a glass substrate whose surface area for landing at least the droplets has been subjected to liquid-repellent processing such as fluororesin coating or plasma treatment.

[0050] FIG. 10A shows a state where droplets 321 are printed on a substrate 5010. The surface of the substrate 5010 is coated with a water-repellent material. Note that the surface of the display panel 5006 is also coated with a water-repellent material. The substrate 5010 has the property of repelling ink. If the ink spreads on the substrate 5010, adjacent droplets may connect to each other. In order to prevent such connection of adjacent droplets, it is necessary to prevent the ink from spreading on the substrate 5010. The contact angle of the ink with respect to the substrate 5010 is about 30° to 70°.

[0051] First, before landing the droplet 321 on the substrate 5010, in order to make the drying states of the droplet 321 to be landed first and the droplet 321 to be landed later as equivalent as possible, dummy droplets 320 are printed. The dummy droplets 320 are formed by landing several to dozens of droplets from each nozzle 3030.

[0052] After printing the dummy droplets 320, the droplets 321 are printed. If the density on the substrate 5010 between the droplets 321 is too high, it is likely to be affected by drying, and adjacent droplets 321 may connect to each other. In order to eliminate the influence of such drying or prevent adjacent droplets 321 from connecting to each other, the droplets 321 are printed while ensuring a certain distance between them. For example, the CPU 150 of the control device 15 prints the droplets 321 by moving the inkjet head 30 in the printing direction and discharging the droplets 321 from adjacent nozzles 3030 at staggered times. The droplets 321 are applied in an isotropic manner, spreading more than the actual positional relationship between a plurality of nozzles 3030. In the present embodiment, when the direction orthogonal to the printing direction is defined as the row direction, the droplets 321 discharged from adjacent nozzles 3030 are printed in different rows on the substrate 5010.

[0053] FIG. 10B is an explanatory diagram of a method for measuring the area of the droplet 321 on the substrate 5010. As shown in FIG. 10B, the area of the droplet 321 is measured by observing the droplet 321 that has landed on the substrate 5010 from above with the camera 5011. Here, the area refers to the area of the shadow (the projected area of the droplet 321 on the substrate 5010) when the droplet 321 is viewed from above, rather than the surface area.

[0054] First, the camera 5011 is scanned, and the droplets 321 in each row are observed in order from the droplet 321 at the end of each row. After the observation of the droplets 321 in the first row is completed, the observations of the droplets 321 in the second row and the droplets 321 in the third row are performed in order. The CPU 150 of the control device 15 measures the area of the droplet 321 before the landed droplet 321 dries. The ink contains about 0.5 to 10% of solid content such as the light-emitting material of the organic EL. After the solvent of the ink dries, the solid content remains, but the amount of the solid content is very small, so the area of the droplet 321 becomes small. When the area of the droplet 321 becomes small, it becomes difficult to distinguish the difference in the volume of the droplet 321 for each nozzle 3030. Therefore, the area of the droplet 321 is measured before the droplet 321 dries.

[0055] An experiment using the above method was performed to measure the area of the droplet 321. The measurement results of the area of the droplet 321 are shown in FIG. 11A. The horizontal axis of the graph in FIG. 11A indicates the measurement order of the droplet 321, and the vertical axis indicates the area of the droplet 321. FIG. 11B shows the result of correcting the horizontal axis of the result shown in FIG. 11A to the elapsed time from when the droplet 321 lands until the observation is performed. From the relationship shown in FIG. 11B, it can be seen that the longer the elapsed time from when the droplet 321 lands, the smaller the area of the droplet 321 becomes. On the other hand, the area of the landed droplet 321 also changes according to the volume of the droplet 321 ejected from the nozzle 3030. In order to obtain the correct area corresponding to the volume of the droplet 321 ejected from the nozzle 3030, it is necessary to correct the value in consideration of the fact that the droplet 321 becomes small due to drying and the area changes.

[0056] Therefore, the drying of the droplet 321 on the substrate 5010 was considered using the model shown in FIG. 12. The initial stage is a mode called the CCR (Constant Contact Radius) mode, where the diameter of the droplet 321 remains constant at D0, and the contact angle decreases from θ shown in the upper left figure of FIG. 12 to θ1 shown in the upper middle figure. C After that, it transitions to the CCA (Constant Contact Angle) mode, where the contact angle remains constant at θ1, and the diameter of the droplet 321 decreases from D0 shown in the upper middle figure of FIG. 12 to D2 shown in the upper right figure.

[0057] Also, the droplet 321 that landed on the substrate 5010 was considered as a spherical cap (a part of a sphere cut by a plane) shown in the lower figure of FIG. 12. Let the radius of the sphere be r, the radius of the spherical cap be a (i.e., the radius of the circle when observing the droplet 321 from above), and the polar angle between the line from the center of the sphere to the apex (pole) of the spherical cap and the end of the bottom surface of the spherical cap be θ. Here, θ is equal to the contact angle θ of the landed droplet 321 with respect to the substrate 5010. C The surface area of the spherical cap is expressed by the following formula (1), and the volume of the spherical cap is expressed by the following formula (2). Surface area A of the spherical cap = 2πr 2 (1 - cosθ) … (1) Volume V of the spherical cap = (πr 2 / 3)×(2 + cosθ)(1 - cosθ) 2 … (2)

[0058] In this experiment, the volume of the droplet 321 ejected from the nozzle 3030 was 4100 μm 3 , and the contact angle θ CIt is 61°. When calculated using Formula (1), Formula (2), and the experimental values, the relationship between the elapsed time since the droplet 321 landed and the area of the droplet 321 as viewed from above is represented as shown in FIG. 13. From FIG. 13, it can be seen that in the region where the elapsed time is short, the area of the droplet 321 is represented as a linear function with respect to the elapsed time. Therefore, it can be understood that the CPU 150 of the control device 15 can correct the area of the droplet 321 using a linear equation of the elapsed time since landing. The result shown in FIG. 11B is corrected using the above linear equation, and the result is shown in FIG. 11C. The CPU 150 of the control device 15 changes the conditions (for example, drive voltage) for discharging ink by the inkjet head 30 so that the difference in the area values of each nozzle 3030 becomes small (becomes uniform) using the area value shown in FIG. 11C, thereby reducing the variation in the volume of the droplet 321 for each nozzle 3030.

[0059] Also, it is desirable to correct the area of the droplet 321 for each row to be printed. For example, in FIG. 10B, the correction is performed separately for the first row, the second row, and the third row. Although dummy droplets 320 are arranged first to equalize the drying conditions of the droplet 321, there is still a possibility that the drying state may differ slightly for each row. Therefore, correcting for each row enables more accurate area correction.

[0060] Also, in order to equalize the drying state, as shown in FIG. 14A, dummy droplets 320 may be arranged at both ends of each row. The nozzle 3030 corresponding to the droplet 321 at the end of each row may be treated as a dummy nozzle and operated as a nozzle 3030 for which volume adjustment is not performed. Also, as shown in FIG. 14B, the dummy droplets 320 may be arranged before and after the printing direction with respect to the droplet 321 printed for each row. By doing so, the drying state of the droplet 321 becomes substantially uniform within the plane.

[0061] Also, it is desirable to perform area correction for each type of ink. This is because the drying state changes depending on the solvent of the ink, and the area correction formula changes. Even if the solvents are the same, the correction formula may change only due to differences in the type or concentration of the solid content, so it is desirable to perform correction for each ink. Also, the droplets 321 ejected from one nozzle 3030 may be landed in several droplets over multiple rows, and the average value may be used as the droplet area to be corrected. By averaging the area values of multiple droplets, it becomes possible to mitigate the influence on the droplet area to be corrected due to variations in the repeatability of ejection or variations in wettability depending on the location of the substrate 5010.

[0062] 〔Coating unevenness adjustment method〕 Next, a coating unevenness adjustment method using the printing apparatus 1000 will be described. FIG. 7 is a diagram showing a process flow of the coating unevenness adjustment method. FIG. 8A is a diagram showing a state in which printing is performed on the display panel in the coating unevenness adjustment flow. FIG. 8B is a diagram showing a state in which the ink applied in the cell spreads within the cell. FIG. 8C is a cross-sectional view taken along line A-A of FIG. 8B. FIG. 9 is a diagram showing a state in which two patterns with different coating amounts are printed in the cell.

[0063] First, as shown in FIG. 7, the display panel before printing is observed (step S1). Specifically, the display panel before printing is observed with the coating unevenness observation apparatus 50, and image information is acquired from the panel before printing the ink to acquire the background information, and the background noise of the coating unevenness observation apparatus 50 in the subsequent cell observation is removed.

[0064] Next, the printing apparatus 1000 performs printing on the display panel observed in step S1 (step S2). Specifically, as shown in FIG. 8A, ink is applied in the cell 2A formed by the bank 2 and in locations other than the cell 2A.

[0065] Next, the CPU 150 of the control device 15 calculates the volume of the droplets for each nozzle 3030 (step S3). When the droplet 310 is applied into the cell 2A as shown in FIG. 8A, the droplet 310 immediately spreads, and coating films 311, 312, 313 that fill the inside of the cell 2A as shown in FIG. 8B are formed. Based on such coating films 311, 312, 313 inside the cell 2A, the volume of the droplet 310 for each nozzle 3030 cannot be calculated. Therefore, the CPU 150 calculates the volume of the droplets for each nozzle 3030 applied at a location other than the cell 2A. As shown in FIG. 8C, it is desirable that the location of the droplet 315 applied outside the cell 2A is above the bank 2. This is because the area above the bank 2 has high liquid repellency with respect to the droplet 315, and the applied droplet 315 is likely to be stably formed in a hemispherical shape. By making the shape of the droplet 315 such a hemispherical shape, the diameter and height of the droplet 315 are likely to change regularly according to the droplet volume of the droplet 315, and when the droplet 315 is observed from above by the camera 5002, the droplet volume can be accurately measured. The intensity of the reflected light is correlated with the height of the droplet 315. Therefore, the CPU 150 calculates the volume of the droplet 315 as follows.

[0066] First, in advance, data for calculating the droplet height showing the relationship between the reflected light intensity from the droplets applied at locations other than cell 2A and the height of the droplets is stored in a database and accumulated in the storage means 151. The coating unevenness observation device 50 observes the droplets 315 on the bank 2 and outputs image data indicating the observation results to the control device 15. By observing with the coating unevenness observation device 50, image data of a 256 - gradation gray scale from 0 to 255 is obtained. Note that the image data may be not limited to gray scale but may be color. The CPU 150 of the control device 15 calculates the area of the droplet 315 (the area of the orthographic projection onto the coating surface of the droplet, that is, the cross - sectional area of the droplet, in other words, the circular area visible to the observer) and the reflected light intensity from the droplet 315 based on the image data. The CPU 150 calculates the volume of the droplet 315 based on the area and the reflected light intensity of the droplet 315 calculated based on the image data and the data for calculating the droplet height. As a simple measurement method for the droplet 315, it is also possible to estimate the volume only from the area of the droplet 315 described above. This is because the height of the droplet is determined by the contact angle of the droplet 315 on the bank 2 and is considered to be almost constant regardless of the size of the droplet volume.

[0067] With reference to the droplet volume for each nozzle 3030 measured by the above method, the nozzle 3030 to be adjusted when adjusting the droplet volume for each cell 2A is determined. This is because it is difficult to further increase the volume of droplets that are originally large or to further decrease the volume of droplets that are originally small.

[0068] Next, the coating unevenness observation device 50 observes the printed cell 2A (step S4). It is desirable to observe the printed cell 2A before the solvent of the ink dries. This is because if the cell 2A is observed after the solvent of the ink has dried, the volume of the droplets ejected from the nozzle 3030 cannot be accurately calculated.

[0069] Next, the CPU 150 of the control device 15 calculates the volume of the droplets applied by dividing them into areas for each cell 2A based on the image data obtained in step S4 (step S5). When the cell 2A is observed from above by the camera 5002 of the coating unevenness observation device 50, the area of the droplets displayed in the image data (the area of the orthographic projection onto the coating surface of the droplets, that is, the cross-sectional area of the droplets, in other words, the area of the circle visible to the observer) is determined by the size of the cell 2A and is constant. Therefore, it is possible to estimate the droplet volume based on the difference in the intensity of the reflected light that varies depending on the height of the applied droplets. The intensity of the reflected light can be obtained from the image data obtained in step S4. By using the method as described above, in advance, the data for calculating the cell coating amount representing the relationship between the reflected light intensity (image data) from the coating film in the cell 2A and the droplet volume is made into a database and stored in the storage means 151, so that the droplet volume can be calculated. Note that the database creation of the droplet volume may use supervised machine learning with the input information being cell image data and the output information being volume numerical data for each cell.

[0070] The leftmost figure in FIG. 9 shows the cell 2A before printing, and the central and rightmost figures in FIG. 9 show the state where the coating film 316 is printed with inks of different coating amounts on the cell 2A. As shown in the central and rightmost figures in FIG. 9, from the shapes of the four corners of the coating area within the cell 2A, which is the area surrounded by the dashed-dotted line, the width and height measurements of the coating area, and the contrast of the grayscale image data, it is also possible to estimate the shape of the coating film 316 and calculate the droplet volume. In this case, the data for calculating the cell coating amount representing the relationship between the shapes of the four corners, the width and height measurements of the coating area, the contrast, and the droplet volume, each obtained from the image data, can be made into a database and stored in the storage means 151.

[0071] The CPU 150 of the control device 15 calculates the value of the droplet volume to be adjusted for each cell 2A so that the droplet volume for each cell 2A becomes uniform, based on the calculated value of the droplet volume for each cell 2A described above (step S6). At this time, in order to prevent streaks from occurring, that is, to eliminate (reduce) the difference in the droplet volume for each cell 2A calculated in step S5, the volume for each cell 2A is determined. In particular, since the variation in droplet volume between adjacent cells 2A leads to streaks, it is necessary to adjust with high precision.

[0072] The CPU 150 of the control device 15 determines the value of the adjusted droplet volume for each nozzle 3030 from the position information of the nozzle 3030 assigned to each cell 2A, the droplet volume value for each nozzle 3030 calculated in step S3, the droplet volume value to be adjusted for each cell 2A calculated in step S6, and the voltage determination data shown in FIG. 5 (step S7). Although the droplet volume can be adjusted by voltage, increasing the applied voltage increases the droplet velocity. When the droplet velocity becomes faster than a certain level, secondary droplets called satellites are generated in addition to the main droplet. Since satellites may reduce the landing position accuracy of the droplets, it is necessary to eject the droplets without generating satellites. Also, decreasing the voltage decreases the droplet velocity. When the droplet velocity becomes slower than a certain level, the droplets may fluctuate due to air resistance during flight, which may reduce the landing position accuracy. Therefore, although the droplet volume can be adjusted by the applied voltage, the adjustment range is limited from the perspective of the droplet velocity. Thus, it is difficult to make adjustments such as increasing the volume of droplets with a high velocity or decreasing the volume of droplets with a low velocity. For this reason, the CPU 150 of the control device 15 needs to select a nozzle 3030 that is appropriate from the perspective of droplet velocity as the nozzle 3030 for adjusting the droplet volume. That is, it is necessary to select a nozzle 3030 that can adjust the droplet volume within the adjustable range of the droplet volume excluding the range where the above volume adjustment is difficult.

[0073] In addition, the CPU 150 of the control device 15 determines the nozzle 3030 for adjusting the droplet volume, taking into account the arrangement of the nozzles 3030 assigned to the cell 2A and the balance of the droplet volumes ejected from each nozzle 3030. For example, in FIG. 8A, the CPU 150 of the control device 15 determines the nozzle 3030 for adjusting the volume so that the total volume of the droplets 310 ejected from the three nozzles 3030 assigned to one cell 2A becomes as uniform as possible. Which nozzle 3030's volume is adjusted is determined by the original droplet volume value (predetermined set value of the droplet volume) of each nozzle 3030 assigned to the cell 2A. Specifically, for the volumes of the three droplets 310 arranged in one cell 2A, the CPU 150 of the control device 15 (Pattern 1) Make the left droplet volume smaller Make the central droplet volume smaller Make the right droplet volume larger Rather than (Pattern 2) Make the left droplet volume smaller Make the central droplet volume larger Make the right droplet volume smaller It is conceivable to select the nozzle 3030 for adjusting the droplet volume so as to do so. However, in the case of the conditions of Pattern 1, the droplet volume printed from the center to the left in the cell 2A becomes smaller, and conversely, the droplet volume printed to the right becomes larger, which may result in an asymmetric shape in the cell 2A. On the other hand, under the conditions of Pattern 2, the distribution of the droplet volumes in the cell 2A is symmetric left and right. From the viewpoint of the distribution of the film shape formed in the cell 2A, it is desirable to select the nozzle 3030 for adjusting the droplet volume as in Pattern 2. The CPU 150 of the control device 15 determines the adjusted droplet volume of the selected nozzle 3030.

[0074] The CPU 150 of the control device 15 rewrites the applied voltage data for each nozzle 3030 (step S8). Specifically, the CPU 150 of the control device 15 determines the adjusted applied voltage for each nozzle 3030 based on the adjusted droplet volume of the nozzle 3030 determined in step S7 and the voltage determination data shown in FIG. 5. The CPU 150 of the control device 15 transmits the determined value of the applied voltage to the control unit 300 of the inkjet head 30 to rewrite the applied voltage data in real time. The rewriting of the applied voltage data is performed by directly rewriting the memory (RAM) mounted on the head control board of the control unit 300.

[0075] After the display panel on the fixed stage ST is replaced with a new display panel, the printing apparatus 1000 performs printing on the cells of the display panel based on the rewritten applied voltage data. The coating unevenness observation device 50 observes the coating unevenness of the display panel. When the CPU 150 of the control device 15 determines that there is coating unevenness based on the observation result of the coating unevenness observation device 50 (step S9: YES), it performs the process of step S1. When it determines that there is no coating unevenness (step S9: NO), it ends the coating unevenness adjustment.

[0076] As described above, the coating unevenness observation device 50 observes the coating state of the ink in the cell 2A (the formation state of the coating film). Based on the observation result of the coating unevenness observation device 50, the CPU 150 of the control device 15 adjusts the droplet volume of each nozzle 3030 that discharges ink to the cell 2A so that the difference in droplet volume between each cell 2A becomes small. In this way, by adjusting the droplet volume of each nozzle 3030 based on the observation result of the droplet volume of each actually coated cell 2A, the variation in droplet volume between the cells 2A can be suppressed. As a result, the emission unevenness of the display panel can be suppressed.

Industrial Applicability

[0077] The printing apparatus and printing method of the present disclosure can suppress emission unevenness even when printing on a pixel bank to manufacture a display panel, and can be applied to the manufacture of display panels.

Explanation of reference numerals

[0078] 1 Line bank 2 Pixel bank 2A, 5007A Cells 15 Control device 20 Inkjet table 30 Inkjet head 40 Droplet observation device 50 Coating unevenness observation device 60 Ink pan (dish-shaped container) 101 Nozzle 150 CPU 151 Storage means 152 Input means 153 Display means (display) 200 Base 201A, 201B, 202A, 202B Stands 203A, 203B Guide shafts 204A, 204B Linear motors 204A, 204B, 205A, 205B Linear motors 210A, 210B Gantry parts 211A, 211B Guide grooves 213 Control unit 220A, 220B Moving bodies 221A, 221B Servo motors 300 Control unit 301 Head part 302 Main body part 304 Servo motor 310, 315 Droplets 311, 312, 313, 316 Coating films 320 Dummy droplet 321 Droplet 400 Control unit 401 Fixed table 402 Droplet Observation Camera (CCD Camera) 403 Zoom Lens 404 Cable 500 Control Unit 501 Shooting Unit 1000 Printing Device 3010, 3010a, 3010b, 3010c Piezoelectric Element 3020, 3020a, 3020b, 3020c Liquid Chamber 3030, 3030a, 3030b, 3030c Nozzle 3040 Diaphragm 5001 Lighting 5002 Camera 5003 Lens 5004 Cylindrical Lens 5005 Rod Lighting 5006 Display Panel 5007 Bank Pattern 5008 Coating Film 5010 Substrate 5011 Camera ST Fixed Stage

Claims

1. A printing apparatus for applying ink to a plurality of cells of a display panel, comprising: an inkjet head having a plurality of nozzles assigned to each of the cells; a camera for observing the application state of the ink in the plurality of cells; a control device that calculates a difference in the amount of ink applied to the plurality of cells based on the observation result by the camera, and adjusts the volume of droplets for each nozzle that discharges ink droplets to the plurality of cells so that the difference in the amount of ink applied becomes small.

2. The printing apparatus according to claim 1, wherein the camera observes the application state before the solvent of the ink in the cell dries.

3. A printing apparatus for applying ink to a plurality of cells of a display panel, comprising: an inkjet head having a plurality of nozzles assigned to each of the cells; a camera for observing the application state of the ink in the plurality of cells; a control device that calculates a difference in the amount of ink applied to the plurality of cells based on the observation result by the camera, and adjusts the volume of droplets for each nozzle that discharges ink droplets to the plurality of cells so that the difference in the amount of ink applied becomes small. The control device has data for calculating the cell application amount that represents the relationship between the image data indicating the observation result in the camera and the amount of ink applied in the cell, and based on the image data indicating the observation result acquired from the camera and the data for calculating the cell application amount, calculates the difference in the amount of ink applied to the plurality of cells.

4. The cell is quadrilateral. The data for calculating the cell application amount represents the relationship between at least any one of the shape, horizontal width, vertical width, and contrast of the corner of the ink application region in the cell obtained from the image data and the amount of ink applied in the cell.

5. The camera observes, from a position facing the display panel, droplets discharged to a region other than the plurality of cells in the display panel by the nozzles that discharge droplets to the plurality of cells. The printing apparatus according to any one of claims 1 to 4, wherein the control device calculates the volume of each droplet based on the area of each droplet observed from a position facing the display panel, and adjusts the volume of each droplet of the nozzles so that the difference in the amount of ink applied in the plurality of cells becomes small based on the calculated volume of the droplets.

6. A printing apparatus for applying ink to a plurality of cells of a display panel, comprising: an inkjet head having a plurality of nozzles assigned to each of the cells; a camera for observing the application state of the ink in the plurality of cells; a control device that calculates the difference in the amount of ink applied in the plurality of cells based on the observation result by the camera, and adjusts the volume of each droplet of the nozzles that eject ink droplets to the plurality of cells so that the difference in the amount of application becomes small; the camera observes, from a position facing the display panel, droplets ejected to an area other than the plurality of cells in the display panel by nozzles that eject droplets to the plurality of cells; the control device calculates the volume of each droplet based on the area of each droplet observed from a position facing the display panel, and adjusts the volume of each droplet of the nozzles so that the difference in the amount of ink applied in the plurality of cells becomes small based on the calculated volume of the droplets; the printing apparatus, wherein the control device corrects the area of the droplet by a function of the elapsed time from landing to observation.

7. The printing apparatus according to claim 6, wherein the control device corrects the area of the droplet by a linear function of the elapsed time from landing to observation.

8. When the control device ejects the droplets from the nozzles while moving the inkjet head in one direction with respect to the display panel, and when the direction orthogonal to the one direction is the row direction, the control device applies the droplets to the display panel by dividing them into two or more rows. The printing apparatus according to any one of claims 5 to 7.

9. The printing apparatus according to claim 8, wherein the control device applies droplets ejected from adjacent nozzles to different rows.

10. A printing apparatus for applying ink to a plurality of cells of a display panel, comprising: an inkjet head having a plurality of nozzles assigned to each of the cells; a camera for observing the application state of the ink in the plurality of cells; Based on the observation results by the camera, calculate the difference in the amount of ink applied in the plurality of cells, and a control device that adjusts the volume of droplets for each nozzle that discharges ink droplets to the plurality of cells so that the difference in the amount of application becomes small, and The camera observes, from a position facing the display panel, droplets discharged to an area other than the plurality of cells in the display panel by nozzles that discharge droplets to the plurality of cells, The control device calculates the volume of the droplet based on the area of the droplet for each nozzle observed from a position facing the display panel, and based on the calculated volume of the droplet, the difference in the amount of ink applied in the plurality of cells is reduced. The volume of the droplet for each nozzle is adjusted so that When the control device discharges the droplets from the nozzles while moving the inkjet head in one direction with respect to the display panel, when the direction orthogonal to the one direction is the row direction, the droplets are divided into two or more rows and applied to the display panel. The control device applies droplets discharged from adjacent nozzles to different rows. The control device is a printing device that corrects the area of the droplet for each row.

11. The printing device according to any one of claims 5 to 10, wherein the control device measures the area of the droplet before the solvent of the ink dries.

12. The substrate on which the droplet lands to obtain a function of the elapsed time from landing to observation of the area of the droplet is a substrate having a liquid-repellent surface, according to any one of claims 6 to 11. Printing device.

13. The inkjet head has the same number of piezoelectric elements for driving each of the plurality of nozzles as the number of the nozzles, The control device has voltage determination data representing the relationship between the applied voltage of the piezoelectric element and the volume of the droplet discharged from the nozzle, and the volume of the droplet calculated based on the area of the droplet and the voltage determination data. Based on this, the voltage applied to the piezoelectric element when adjusting the volume of the droplet for each nozzle is determined, and the determined voltage is applied to the piezoelectric element. The printing device according to any one of claims 5 to 12.

14. The printing device according to claim 13, wherein the control device writes data of the voltage applied to the piezoelectric element for each nozzle into a memory disposed in the control unit of the inkjet head.

15. The control device calculates an adjustment value for the ink application amount in the plurality of cells based on the difference in the ink application amount in the plurality of cells, and determines a nozzle for adjusting the volume of the droplets ejected from the nozzle based on the calculated adjustment value and the adjustable range of the volume of the droplets ejected from the nozzle. The printing apparatus according to any one of claims 1 to 14.

16. Based on the arrangement of the plurality of nozzles assigned to each cell and the set value of the volume of the droplets ejected from each nozzle, a nozzle for adjusting the volume of the droplets is determined. The printing apparatus according to any one of claims 1 to 15.

17. The camera observes the droplets ejected into the region other than the plurality of cells in the display panel by the nozzles that eject the droplets into the plurality of cells. The control device measures the volume of the droplets based on the observation result by the camera. Based on the measured volume of the droplets, a nozzle to be adjusted in droplet volume adjustment is determined, and the volume of the droplets of the determined nozzle is adjusted. The printing apparatus according to any one of claims 1 to 4.

18. A printing method of applying ink by assigning a plurality of nozzles to each cell of a display panel, observing the ink application state in the plurality of cells, Based on the result of the observation, the difference in the ink application amount in the plurality of cells is calculated, and the volume of the droplets of each nozzle that ejects the ink droplets into the plurality of cells is adjusted so that the difference in the application amount becomes small. Printing method.

19. A printing method of applying ink by assigning a plurality of nozzles to each cell of a display panel, correcting the area of the droplets ejected into the plurality of cells as a function of the elapsed time from landing to observation, Adjusting the volume of the droplets for each nozzle so that the area of the droplets after correction becomes uniform for each nozzle. Printing method.

Images