JP2010149028A - Coating method and coating machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for applying coating liquid that delays the drying of ink held in an ink jet nozzle tip even in a dry atmosphere, and never causes defect in delivering without deteriorating working efficiency in standing-by suspending coating operations using an ink jet nozzle and a coating machine therefor. <P>SOLUTION: The coating machine that relatively moves an ink jet head 12 having a plurality of ink jet nozzles 13 and coated objects and coats the ink onto the coated objects includes ink tanks 18, 19 that supply the ink to the ink jet nozzles 13, a pressure controlling means 17 that controls the negative pressure of the ink inside the ink jet nozzles 13, and a controlling means that commands the pressure controlling means 13 to generate the pressure of the ink into a negative pressure closer to the atmospheric pressure than the negative pressure in coating if a predetermined signal is inputted after the coating operations. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coating method and a coating apparatus that apply ink to a coating object by moving an inkjet head having a plurality of inkjet nozzles that apply ink to the coating object relative to the coating object.

  Recent progress in image display technology for information terminals has been remarkable, and large-screen image display devices (displays) or image display devices with very high definition even for small screens have been put into practical use and manufactured. . Under such circumstances, there is an increasing demand for an image display device that enables high-quality image display at low cost. There is a color filter as a key device of an image display device that meets such a requirement, and various devices have been incorporated into a manufacturing method and a manufacturing apparatus of the color filter.

  One of the conventional techniques developed in such a color filter manufacturing method and manufacturing apparatus is to form a matrix-shaped light-shielding portion on a substrate or the like with various materials having a light-shielding function, and coat the cells of this light-shielding portion. There is a technique for applying ink using this technique. However, in such a manufacturing method and manufacturing apparatus, the RGB three-color coloring processes are independent of each other, and each coloring process requires a shielding member (mask) that requires very high accuracy for light shielding. It was.

  Such a color filter manufacturing technique has a problem that the manufacturing cost is high both in terms of man-hours and in terms of equipment and members to be used. Therefore, recently, instead of such a technique, using an application device equipped with an inkjet head, ink is ejected and applied from an inkjet nozzle of the inkjet head onto a substrate or the like on which a light-shielding portion is formed in a matrix. A method for manufacturing a filter has been proposed.

  In such a coating apparatus, a state in which the coating operation using the ink jet nozzle is temporarily interrupted and is in a standby state, or a state in which the nozzle is abandoned by intermittent discharge at regular time intervals (hereinafter referred to as flushing). Then, the following problems occur. First, ink held by the action of negative pressure inside the inkjet nozzle at the tip of the inkjet nozzle by the dry air in the atmosphere is easy to dry. The viscosity of the ink at the tip of the nozzle increases (thickens) due to drying, and if ink sticks or thickens due to drying at the tip of the inkjet nozzle, ink is not ejected from this inkjet nozzle, so-called dot missing And the problem of missing nozzles is caused.

  Therefore, in order to prevent the ink from drying and clogging in the ink jet nozzle of the ink jet head, there has been proposed a coating apparatus having a structure in which the tip surface of the ink jet nozzle is sealed with a cap when the ink jet head is not used. (See Patent Document 1 and Patent Document 2).

  In the coating apparatus disclosed in Patent Document 1, the tip surface of the inkjet nozzle is sealed with a cap member in which a solution is stored, thereby being held by the negative pressure inside the inkjet nozzle at the tip. In addition to preventing the ink from drying, it prevents the ink from sticking and clogging.

Further, in the coating apparatus disclosed in Patent Document 2, the tip surface of the inkjet nozzle is sealed with a cap member in which a solution is stored, and the pressure inside the cap member is increased to fill the inkjet nozzle with the solution. By doing so, it is possible to prevent the ink held inside the inkjet nozzle inside the tip portion from being dried by the action of negative pressure and to prevent clogging due to adhering. Then, bubbles remaining in the ink jet nozzle are driven out and eliminated by the solution filled in the ink jet nozzle.
JP 2002-234174 A JP 2006-212500 A

  In the conventional coating apparatuses disclosed in Patent Documents 1 and 2, the inkjet head is sealed in a sealed environment by sealing the tip surface of the inkjet nozzle using a cap member in which a solution is stored. The inside of the ink jet is maintained in a wet state to prevent the ink inside the ink jet nozzle from drying, and to prevent clogging due to fixation.

  However, a coating apparatus using such a cap member inevitably requires an auxiliary facility for supplying a solution to the cap member or the cap member. In addition, when the cap member is installed in an external area of the coating work area, the inkjet apparatus Each time the coating operation using the nozzle is interrupted, the ink jet nozzle must be moved to the place where the cap member is installed, and this operation is incorporated in the takt time, which reduces work efficiency. .

  The present invention has been made in view of the above problems, and when the application operation using the inkjet nozzle is interrupted and waits, the ink held at the tip of the inkjet nozzle is unlikely to dry. An object is to provide a coating method and a coating apparatus.

  The application method of the present invention is a method of applying ink to the application object by relatively moving an ink jet head having a plurality of ink jet nozzles and the application object, and applying the ink to the ink jet nozzle. And applying a first negative pressure, and applying a second negative pressure closer to the atmospheric pressure than the negative pressure to wait for application.

That is, the present invention
An application method in which an inkjet head having a plurality of inkjet nozzles and an application target are moved relatively to apply ink to the application target,
Supplying ink to the inkjet nozzle;
Applying a first negative pressure to the ink to be applied to the application object;
And applying a second negative pressure closer to the atmospheric pressure than the first negative pressure to the ink and waiting for the application.

The present invention also provides
An application device that applies ink to the application object by relatively moving an inkjet head having a plurality of inkjet nozzles and the application object,
A sub tank for supplying ink to the inkjet nozzle;
Ink supply means for supplying ink to the sub tank;
A pressure sensor for measuring the pressure in the sub tank;
Pressure reducing means for reducing the pressure in the sub tank;
Having a control unit,
The controller is
An instruction command to cause the inkjet head to eject ink;
An instruction command to increase the pressure in the sub-tank;
An instruction command to lower the pressure in the sub-tank,
The present invention provides a coating apparatus that adjusts the pressure in the sub-tank to a first negative pressure when applying ink to the object to be applied, and to a second negative pressure when waiting for application.

  According to the coating method and the coating apparatus of the present invention, the ink in the inkjet nozzle is placed in a negative pressure state that is closer to the atmospheric pressure than the negative pressure during coating, although it is in a negative pressure state during the coating standby state. It is. For this reason, the meniscus formed in the ink jet nozzle has a small amount of air drawn from the mouth end of the ink jet nozzle, and accordingly, the surface area in contact with the air is reduced. Therefore, the evaporation amount of the solvent from the gas-liquid interface is reduced, and there is an effect that the drying of the ink can be prolonged.

  In the case of a batch-type coating apparatus such as the present invention, it takes a certain amount of time to replace a coating object (for example, a substrate). In the meantime, while operating as a coating apparatus, the ink jet head is in a standby state while being thrown away (flushing) by intermittent discharge at regular time intervals, or in a standby state without doing anything. . The present invention can suppress drying of the ink during these standby times, and can reduce the occurrence rate of clogging of the ink jet nozzle, that is, the missing dot of the coating in the next coating process.

  BEST MODE FOR CARRYING OUT THE INVENTION The best embodiment of a coating apparatus according to the present invention will be described in detail below with reference to the drawings. In the following, as a specific example of the coating apparatus, a color filter manufacturing apparatus that applies ink to a glass substrate as an application target will be described as an example.

  FIG. 1 is a perspective view showing an appearance of a color filter manufacturing apparatus as a coating apparatus 1 according to an embodiment of the present invention. In this color filter manufacturing apparatus, a suction table 3 (holding stage), a coating gantry 4 and a camera gantry 6 are supported on a machine base 20. The suction table 3 as a holding stage holds the glass substrate 2 by suction, and is driven to rotate around the Z axis by a drive mechanism and a guide mechanism (not shown) in order to position the glass substrate 2 at a predetermined position. .

  The application gantry 4 holds the inkjet head bar 5 and is driven in the main scanning direction (X direction) by a drive mechanism and a guide mechanism (not shown) in order to apply ink to a predetermined position of the glass substrate 2. . The inkjet head bar 5 is driven in the sub-scanning direction (Y direction) by a guide mechanism (not shown) of the coating gantry 4.

  The camera gantry 6 holds alignment cameras 7 and 8 for alignment of the glass substrate 2, and also holds a scan camera 9 that is a measuring unit for detecting ink supplied to the glass substrate 2. In order to detect ink, the ink is driven in the X direction by a drive mechanism and a guide mechanism (not shown). The alignment cameras 7 and 8 and the scan camera 9 are driven in the Y direction by a drive mechanism and a guide mechanism (not shown). The alignment cameras 7 and 8 detect marks (not shown) on the glass substrate 2, rotate the suction table 3 based on the mark detection results by the alignment cameras 7 and 8, and / or move in the Y direction. By doing so, alignment to the glass substrate 2 can be executed.

  Here, the X axis and the Y axis are orthogonal axes set so as to define a plane parallel to the upper surface of the glass substrate 2 sucked and held by the suction table 3, and the Z axis is the X axis and the Y axis. Is an axis orthogonal to the plane defined by.

  The ink jet head bar 5 is configured by arranging and arranging ink jet heads 12 each having a plurality of ink jet nozzles 13 that eject ink of each color tone. The ink jet head bar 5 is driven in the main scanning direction (X direction), the sub scanning direction (Y direction), and the Z direction while being held by the coating gantry 4, and ejects ink of each color tone from the plurality of ink jet nozzles 13. Then, it is applied to a predetermined position of the glass substrate 2.

  FIG. 2 shows a configuration relating to control of ink supply and coating operation of the coating apparatus of the present invention. In addition to the configuration of the coating apparatus shown in FIG. 1, the coating apparatus of the present invention is added with the control of the ink supply and coating operation of FIG.

  The ink supply and application operation control system of the application apparatus of the present invention includes a sub tank 62 that supplies ink to the inkjet head 12 attached to the application gantry 4, an ink supply system that supplies ink to the sub tank 62, and a sub tank 62. A pressure adjustment system for adjusting the pressure, a position sensor 102 for obtaining position information of the coating gantry 4, and a control unit 100 for controlling the whole are included. The sub tank has a pressure and quantity sensor 105 (hereinafter simply referred to as “sensor 105”). The sensor 105 knows the pressure in the sub tank and the ink amount.

  The ink supply system includes an electromagnetic valve 114 that adjusts the amount of ink supplied to the sub-tank 62, a main tank 60 that accumulates ink supplied via the electromagnetic valve 114, and a pressure pump that applies pressure to the main tank 60. 74 and a switching valve 116 for selecting either high-pressure air applied by the pressurizing pump 74 or atmospheric pressure. The main tank 60 has a pressure sensor 107.

  The pressure adjustment system includes a pressurizing pump 72, a switching valve 112 that selects the pressurizing pump 72 and atmospheric pressure, a decompression pump 70, and a switching valve 110 that switches between the decompression pump 70 and the switching valve 112.

  The control unit 100 is connected to the inkjet head 12, the position sensor 102, the switching valves 110, 112, 116, the sensor 105, the pressure sensor 107, and the timer 106.

  The control unit 100 sends an ink discharge instruction Cik to the inkjet head 12. By this signal, ink is ejected from the inkjet nozzles of the inkjet head. Further, the control unit 100 obtains the position information Dxy of the inkjet head from the position sensor 102. Ink is ejected based on the position information Dxy.

  Further, the control unit 100 obtains pressure information Dps and ink amount Dqs in the sub tank from the sensor 105. When the amount of ink in the sub tank 62 is small, ink is supplied to the sub tank from the ink supply system.

  In the ink supply system, the inside of the main tank 60 can be pressurized by the pressurizing pump 74 and the switching valve 116. Specifically, the control unit 100 transmits a switching valve drive instruction command Css to the switching valve 116 and introduces high-pressure air into the main tank 60 until the pressure in the main tank 60 reaches a predetermined pressure. The pressure in the main tank is known from the pressure information Dpm from the pressure sensor 107.

  Next, the electromagnetic valve 114 is opened to inject ink into the sub tank. The electromagnetic valve 114 is performed by an electromagnetic valve drive instruction Cvm from the control unit 100.

  The coating apparatus of the present invention has a pressure adjustment system in order to adjust the pressure in the sub tank. The pressure adjustment system includes a decompression pump 70 that is a negative pressure source, a pressurization pump 72 that is a pressure source, and switching valves 112 and 110 that switch between them. When depressurizing the inside of the sub tank, the control unit 100 sends a valve operation instruction Cvs to the switching valve 110 to extract air from the sub tank. Further, when it is desired to pressurize the sub tank, valve operation instructions Cvs and Cva are sent to the switching valves 110 and 112, respectively.

  In the switching valves 112 and 116, reference numeral 79 is an air inlet. By using the switching valves 112 and 116 as the air introduction port 79, the pressure in the main tank and the sub tank returns to the atmospheric pressure and avoids the pressure exceeding a predetermined level.

  The air compressed by the pressurizing pump 74 is introduced into the main tank 60 by opening the switching valve 116. The main tank 60 has a positive pressure with respect to the atmosphere. The pressure in the main tank at this time is detected by the pressure sensor 107 and sent to the control unit 100 as pressure information Dpm. The control unit 100 can open and close the switching valve 116 according to the operation instruction Css to keep the inside of the main tank 60 at a predetermined pressure.

  When the electromagnetic valve 114 is opened by the operation instruction Cvm, the ink in the main tank 60 is injected into the sub tank 62. At this time, if the switching valve 110 to which the decompression pump 70 is connected is opened by the operation instruction Cvs and the inside of the sub tank 62 is set to a negative pressure with respect to the atmospheric pressure, the ink can be introduced more smoothly.

  The control unit 100 knows the amount of ink in the sub tank 62 from the ink amount information Dqs of the sensor 105. Therefore, when the ink amount in the sub tank 62 becomes an appropriate amount, the electromagnetic valve 114 is closed.

  Next, application using an inkjet head will be described. FIG. 3 shows a cross section of the inkjet head nozzle 13. Referring to FIG. 3A, when coating is performed with a normal inkjet head, a slight negative pressure is applied to the ink in the inkjet nozzle 13 to create a meniscus 63 at the gas-liquid interface between the ink and the atmosphere. This is because ink droplets are ejected from minute nozzles.

  Refer to FIG. 2 again. Therefore, it is necessary to keep the inside of the sub tank 62 at a predetermined negative pressure with respect to the atmospheric pressure. When the pressure is higher than a predetermined value while monitoring the pressure information Dps from the sensor 105, the control unit 100 reduces the pressure in the sub tank by connecting the switching valve 110 to the pressure reducing pump side. If the pressure in the sub tank is too low, the switching valve 110 is set to the switching valve 112 side, and the atmospheric pressure port 79 or the pressurizing pump 72 is selected to increase the pressure in the sub tank.

  Referring to FIG. 3 again, in the applied inkjet nozzle, it is necessary to create a predetermined meniscus at the gas-liquid interface between the ink and the atmosphere. However, since this meniscus is at a negative pressure from the atmospheric pressure, the pull-in amount 65 from the inkjet nozzle port is large, and the surface area of the gas-liquid interface is large. Therefore, if left as it is, the solvent in the ink evaporates and the nozzle is clogged.

  Therefore, when the application is put into a standby state, the second negative pressure close to the atmospheric pressure is set in the sub tank even if flushing is performed. As a result, the amount of meniscus drawing 66 at the gas-liquid interface of the ink jet nozzle is reduced, the surface area of the gas-liquid interface is reduced, and evaporation of the solvent in the ink can be reduced. That is, it becomes more difficult to dry. Therefore, it is possible to reduce the occurrence of a defective state such as nozzle clogging.

  Here, the pressure in the sub-tank is maintained in a negative pressure state with respect to the atmospheric pressure. That is, the application is not waited for in the atmospheric state. When the pressure in the nozzle reaches atmospheric pressure, the ink may droop from the inkjet nozzle due to its own weight, and the pressure applied to the ink in the sub-tank in the standby state is about 40 to 90% of the negative pressure set at the time of application. Preferably, a pressure of 60 to 80% is more preferable.

  FIG. 4 shows a flow of coating processing of the coating apparatus of the present invention that operates in this way. When the coating apparatus of the present invention is started (S100), preparation before coating (S102) is performed. Preparation before application is an operation of injecting ink from the main tank into the sub tank or adjusting the pressure in the main tank or the sub tank to a predetermined pressure.

  When the pre-application operation is completed, the head standby state is entered (S104). The head standby state is a state in which processing determination relating to the standby state of the inkjet head is performed, and the entire coating apparatus proceeds regardless of the head standby state. The processing in the head standby state will be described later with reference to FIG.

  Next, the application object is set on the stage (S106). This process is not particularly limited, and may be performed by the coating apparatus itself, by a human hand, or by another robot. When the application object is set on the stage, the head preparation state is entered (S108).

  The head preparation state (S108) is a state in which application may be started when the ink jet head is ready for application. In this state, an ink jet head start command is input to the control unit 100.

  This command may be issued when the coating apparatus itself detects the state of the object to be coated, or may be input to the control unit 100 by pressing a switch or the like with a human hand.

  When an inkjet head start command is input, the control unit 100 makes the inkjet head ready for application and starts application processing (S110). In the application process, ink is applied to the object to be applied according to a predetermined procedure. Here, it is determined whether or not the coating process is ended by the coating end determination (112). However, the application may be ended when the determined process is ended.

  Next, it is determined whether or not the coating apparatus itself is terminated (S116). This may be determined based on the presence / absence of an object to be applied, or may be determined based on whether the number of times of application has been determined in advance. Further, it may be determined by a person whether or not the process is ended. If not finished (N branch of S114), the process returns to the head standby state (S104).

  FIG. 5 shows an example of processing in the head standby state (S104). When the inkjet head enters a standby state (S200), the current time is first recorded from the clock (S202). This is because the waiting time is integrated. This can be realized by the control unit 100 obtaining time information from the clock 106 in FIG.

  Next, it is determined whether or not the ink jet head is installed at a predetermined position (S204). The ink-jet head is disposed in the coating gantry 4 and can be moved to any position within the movable range by movement of the coating gantry in the X and Y directions. Therefore, there is a case where a standby area for the inkjet head is provided in advance in the coating apparatus. The determination in step S204 means that if the ink jet head is placed at such a position, the processing in step S210 and subsequent steps is immediately performed. Note that the control unit 100 determines whether or not the inkjet head has come to a predetermined position based on the position information Dxy from the position sensor 102.

  Step S210 is a process of increasing the pressure in the sub tank. Due to the pressure increase at this time, the second negative pressure is set closer to the atmospheric pressure than the pressure during application (negative pressure). Specifically, the pressure in the sub tank 105 is known from the pressure information Dps from the sensor 105, and the switching valve 110 and the switching valve 112 are switched by operation instructions Cvs and Cva to set the pressure in the sub tank 105 to a predetermined pressure.

  When the pressure in the sub tank 105 reaches a predetermined value, flushing is started and the command is waited, or the command is waited without doing anything. (S212). Here, the command is a command for starting the inkjet head. When this command is input (Y branch of S212), the pressure in the sub tank is reduced to the pressure at the time of application (S214), and the process returns to the main routine (S216).

  Further, the pressure increase (S210) in the standby state may be changed not only by the ink jet head moving to a predetermined position but also by other factors (events). Step S206 is one example of such an event. Here, it is determined whether or not a predetermined time has elapsed. If a predetermined time elapses after entering the standby process starting from step S104, the process may proceed to the sub tank pressure increase process (S210) regardless of the position of the inkjet head (Y branch of S206).

  If the predetermined time has not elapsed (N branch of S206), it is determined whether to wait for a command (S208). If no command has been received (N branch of S208), the process returns to step S204. If a command is received (Y branch of S208), the pressure in the sub-tank is lowered and the process returns to the main routine (S216).

  Depending on whether the inkjet head has been moved to a predetermined location or a predetermined time has elapsed while waiting for application by the above processing, the pressure in the sub-tank is more negative than atmospheric pressure, but negative pressure during application The negative pressure state closer to the atmospheric pressure is reset. As a result, the occurrence rate of clogging of the inkjet nozzles can be reduced.

  Using an actual ink jet head, the degree of clogging of the ink jet head due to the pressure in the sub tank was confirmed. The ink jet head used was a head provided with 256 ink jet nozzles having a width of 34 mm. The sub-tank, the control unit, and the like described in the above embodiment are coupled to the inkjet head.

  The confirmation was performed as follows.

  First, a large amount of ink was ejected from the inkjet nozzles of the inkjet head, and ink droplets remaining on the surface were wiped off with a cloth dipped in a solvent. This is because the piping from the sub tank to the inkjet head is filled with ink.

  Next, the inside of the sub tank was set to a negative pressure up to the pressure at the time of application. This pressure is -1.4 kPa with respect to atmospheric pressure. And ink was discharged from all the inkjet nozzles for 1 minute.

  Next, after the ink discharge was stopped, the inside of the sub tank was brought to a predetermined pressure. This pressure is the standby pressure. Then, after a predetermined time had elapsed, ink was again ejected from all the inkjet heads, and the time until no ink was ejected from any of the 256 inkjet nozzles (nozzle missing occurrence time) was examined.

  FIG. 6 shows the relationship between the standby pressure (horizontal axis) and the missing nozzle occurrence time (vertical axis). At the time of application (-1.4 kPa), the nozzle missing occurrence time was 180 seconds, but at about 40% of the pressure (-0.6 Pa), it was 290 seconds. This indicates that ink is ejected from all of the inkjet nozzles during the next application even if the application is on standby for 290 seconds.

It is a perspective view which shows the external appearance of the coating device which concerns on this invention. It is a figure which shows the structure regarding control of the coating device which concerns on this invention. It is a figure which shows the state of the gas-liquid interface of the ink in an inkjet head nozzle, and air | atmosphere. It is a figure which shows the processing flow of the coating device which concerns on this invention. It is a figure which shows the flow of the standby state of the inkjet head which concerns on this invention. It is a graph which shows the relationship between the negative pressure which shows the drying suppression and prevention effect of the ink by the pressure adjustment means of a coating device, and the time until discharge defect generation.

Explanation of symbols

1 Coating device 2 Glass substrate (Coating object)
3 Suction table (holding stage)
4 Coating gantry 5 Inkjet head bar 6 Camera gantry 7, 8 Alignment camera 9 Scan camera (measuring means)
DESCRIPTION OF SYMBOLS 10 Inkjet head unit 11 Inkjet head module 12 Inkjet head 13 Inkjet nozzle 15 Discharge position control part 16 Discharge pressure control part 17 Pressure control part 20 Machine stand 60 Main tank 62 Sub tank 70 Decompression pump 72, 74 Pressure pump 100 Control part 102 Position Sensor 105 Pressure and ink amount sensor 110 Switching valve 112 Switching valve 116 Switching valve

Claims (6)

An application method in which an inkjet head having a plurality of inkjet nozzles and an application target are moved relatively to apply ink to the application target,
Supplying ink to the inkjet nozzle;
Applying a first negative pressure to the ink to be applied to the application object;
Applying the second negative pressure closer to the atmospheric pressure than the first negative pressure and waiting for the application.   The coating method according to claim 1, wherein the second negative pressure is a value in a range of 40% to 90% of the first negative pressure. The coating method according to claim 1, wherein the step of waiting for the coating is a step of intermittently discharging ink from the inkjet nozzles at regular time intervals. An application device that applies ink to the application object by relatively moving an inkjet head having a plurality of inkjet nozzles and the application object,
A sub tank for supplying ink to the inkjet nozzle;
Ink supply means for supplying ink to the sub tank;
A pressure sensor for measuring the pressure in the sub tank;
Pressure reducing means for reducing the pressure in the sub tank;
Having a control unit,
The controller is
An instruction command to cause the inkjet head to eject ink;
An instruction command to increase the pressure in the sub-tank;
An instruction command to lower the pressure in the sub-tank,
An application device that adjusts the pressure in the sub-tank to a first negative pressure when applying ink to the application object, and to a second negative pressure when waiting for application.   The coating apparatus according to claim 4, wherein the second negative pressure is in a range of 40% to 90% of the first negative pressure. 5. The coating apparatus according to claim 4, wherein in the standby for coating, ink is intermittently ejected from the nozzle at regular time intervals.

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