JP2013202609A - Coating liquid coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity by maintaining an appropriate negative pressure in an application head while suppressing an increase in cost.
As a means for detecting a pressure in a space in a supply tank for storing a coating liquid supplied to a coating head, a storage tank for storing a liquid and one end of the tank are immersed in the liquid stored in the storage tank, The other end portion is provided with a liquid level pipe that communicates with the supply tank, and the amount of immersion in the liquid in the storage tank at the lower end of the liquid level pipe is determined so that the negative pressure in the space in the supply tank has a predetermined magnitude. The liquid level of the liquid in the storage tank was set lower than the lower end of the liquid level pipe.
[Selection] Figure 1

Description

  The present invention relates to a coating liquid coating apparatus that coats a coating liquid.

  In the manufacturing process of a liquid crystal display panel and the manufacturing process of a semiconductor device, a technique for forming a film by applying a coating solution in which a film forming material is dissolved or mixed onto the surface of an object to be coated such as a glass substrate or a semiconductor wafer is known. It has been.

  In such a coating liquid coating technique, a coating liquid coating apparatus including an inkjet coating head is used (see, for example, Patent Document 1).

  By the way, in the ink jet type coating head, in order to ensure the droplet ejection stability and to prevent the coating liquid from leaking from the nozzle of the coating head even during non-ejection, a predetermined chamber is provided in the liquid chamber of the coating head. The negative pressure is maintained.

  That is, a predetermined negative pressure is applied to the space in the supply tank of the coating liquid provided above the coating head, thereby applying a predetermined negative pressure to the liquid chamber of the coating head.

  And control of the pressure of the space in a supply tank is performed by changing the magnitude | size of the negative pressure made to act in a supply tank based on the detection signal of the pressure sensor provided in the supply tank.

JP 2009-125656 A

  However, it is generally difficult to quickly and accurately adjust the magnitude of the negative pressure acting in the supply tank.

  Therefore, when the magnitude of the negative pressure in the supply tank suddenly increases unexpectedly, the control for returning the magnitude of the negative pressure in the supply tank to the predetermined magnitude is not in time. In some cases, the pressure in the space in the supply tank may drop too much.

  In such a case, the coating liquid in the nozzle is drawn into the coating head, causing a problem that air enters the coating head through the nozzle.

  In such a case, it is necessary to discharge the air that has entered from the inside of the coating head, and it takes a long time to perform the work. During this time, the coating liquid cannot be applied, and the productivity is significantly reduced. Occurs.

  An object of the present invention is to provide a coating liquid coating apparatus that can maintain the pressure applied in the coating head at an appropriate negative pressure and improve productivity.

A coating liquid coating apparatus according to an embodiment of the present invention includes a coating head having a nozzle that discharges the coating liquid as droplets, a supply tank that stores the coating liquid supplied to the coating head, Pressure adjusting means for adjusting the pressure of the space to a negative pressure, and in a coating liquid coating apparatus for spraying the droplets from the nozzles of the coating head and coating the coating target object,
The pressure adjusting means is
A storage tank for storing liquid;
A liquid level pipe having one end immersed in the liquid stored in the storage tank and the other end communicating with the supply tank;
Have
The level of the liquid stored in the storage tank is lower than the lower end of the level pipe when the negative pressure in the space in the supply tank reaches a predetermined level. The amount of immersion in the liquid is set so as to be low.

  According to the present invention, the pressure applied in the coating head can be maintained at an appropriate negative pressure while suppressing an increase in cost, and thereby productivity can be improved.

FIG. 1 is a front view showing an overall configuration of a coating liquid coating apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a control configuration of the coating liquid coating apparatus according to the embodiment of the present invention. FIG. 3 is an enlarged view of a main part of the coating liquid coating apparatus according to the embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the displacement of the position of the liquid surface of the coating liquid in the nozzle of the coating head.

  A first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the coating liquid coating apparatus 1 has a gantry 2. A Y-axis moving table 4 is movably provided on the gantry 2 via a pair of guide rails 3 arranged along the Y-axis direction.

  The Y-axis moving table 4 includes a drive device (not shown), and is moved along the guide rail 3 by this drive device. A substrate stage 5 is fixed on the Y-axis moving table 4. In addition, as a drive mechanism of the Y-axis moving table 4, for example, a linear motor drive device using a linear motor as a drive source or a ball screw drive device using a servo motor as a drive source can be used. The substrate stage 5 can be reciprocated along the Y-axis direction by the movement of the Y-axis moving table 4, and passes under the coating head 6 described later during this movement.

  On the upper surface of the substrate stage 5, a substrate W as an application target is attracted and held by a suction means such as vacuum suction or an electrostatic chuck. Here, as the substrate W, for example, a silicon substrate such as a semiconductor wafer, a rectangular glass substrate used for manufacturing a display panel, or the like is used.

  In addition, a plurality of, in this embodiment, three coating heads 6 are arranged on the gantry 2 along the X-axis direction (the arrow X direction in the drawing) orthogonal to the Y-axis direction. These coating heads 6 are not shown so that the nozzle 6a (see FIG. 4) faces downward above the movement path of the substrate stage 5, that is, the nozzle forming surface 6b faces the mounting surface 5a of the substrate stage 5. It is supported by the support member. In FIG. 1, the three coating heads 6 are shown at intervals for convenience, but in actuality, the positions of the coating heads 6 are alternately shifted in the Y-axis direction between the adjacent coating heads 6. They are arranged in a staggered arrangement so that the parts overlap.

  Here, the coating head 6 is an inkjet-type coating head, and a plurality of nozzles 6a are provided on the nozzle forming surface 6b at a predetermined pitch along the X-axis direction. The coating head 6 includes a liquid chamber 6c (see FIG. 4) as a pressure chamber for storing the coating liquid and a piezoelectric element (not shown) that causes a volume change in the liquid chamber 6c corresponding to each nozzle 6a. By applying a driving voltage to the piezoelectric element, the piezoelectric element expands and contracts, whereby a volume change occurs in the liquid chamber, and a predetermined amount of coating liquid is ejected as droplets from the nozzle 6a.

  According to such a coating head 6, the amount of the coating liquid discharged from the nozzle 6 a can be adjusted by changing the magnitude of the driving voltage applied to the piezoelectric element, and the driving voltage application interval is changed. Thus, the discharge frequency (discharge time interval) can be adjusted.

  The coating liquid is supplied to the coating head 6 by the coating liquid supply system 10.

  The coating liquid supply system 10 includes a supply tank 11 that stores the coating liquid supplied to the coating head 6, a supply tank 12 that replenishes the supply tank 11 with the coating liquid, and a storage tank 13 that stores the coating liquid discharged from the coating head 6. A disposal tank 14 for storing the coating liquid to be discarded, and a pipe 15 for connecting the tanks 11 to 14 and the coating head 6.

  In the coating liquid supply system 10, individual liquid supply pipes 15 </ b> A are connected to the coating liquid inlets of the respective coating heads 6. The other ends of these individual liquid supply pipes 15 </ b> A are connected to a common liquid supply pipe 15 </ b> B connected to the bottom of the supply tank 11. The individual liquid supply pipe 15A is provided with an opening / closing valve 16 for opening and closing the flow path of the individual liquid supply pipe 15A.

  Further, individual drainage pipes 15 </ b> C are connected to the coating liquid discharge ports of the respective coating heads 6. The other ends of these individual drainage pipes 15C are connected to a common drainage pipe 15D connected to the bottom of the storage tank 13, respectively. The individual drainage pipe 15C is provided with an on-off valve 17 that opens and closes the flow path of the individual drainage pipe 15C.

  The supply tank 11 is disposed at a position above the coating head 6, and a communication pipe 15 </ b> E communicating with the atmosphere is connected to the upper surface of the supply tank 11. The communication pipe 15E is provided with an on-off valve 18 that opens and closes the flow path of the communication pipe 15E. A suction pipe 15 </ b> F connected to the vacuum pump 19 is connected between the connection part of the communication pipe 15 </ b> E with the supply tank 11 and the on-off valve 18.

  The suction pipe 15F is provided with a pressure control valve 20, an on-off valve 21, a flow rate control valve 22, and a buffer tank 23 in this order from the vacuum pump 19 side. The pressure control valve 20 adjusts the magnitude of the negative pressure sucked by the vacuum pump 19. The on-off valve 21 opens and closes the flow path of the suction pipe 15 </ b> F between the vacuum pump 19 and the buffer tank 23. The flow control valve 22 is a conductance variable valve or the like, and controls the flow rate of the gas flowing through the suction pipe 15F. The buffer tank 23 stores the negative pressure generated by the vacuum pump 19.

  Further, an opening / closing valve 24 for opening and closing the flow path of the communication pipe 15E is provided between the connection portion of the suction pipe 15F with the communication pipe 15E and the buffer tank 23. A liquid level detector 25 for detecting the liquid level of the coating liquid is provided on the side surface of the supply tank 11 in order to keep the liquid level of the coating liquid in the supply tank 11 at a predetermined liquid level.

  The storage tank 13 is provided adjacent to the supply tank 11, and a liquid level pipe 26 that functions as a liquid column pressure gauge (manometer) is provided through the upper surface of the storage tank 13. The liquid level pipe 26 is a straight pipe formed of a material having translucency such as transparent glass or resin. The lower end of the liquid level pipe 26 hangs down from the upper surface of the storage tank 13 to a predetermined height position. The upper end of the liquid level pipe 26 extends upward from the upper surface of the storage tank 13 to a predetermined height position. Furthermore, a communication pipe 15G that communicates with the atmosphere is connected to the upper end of the liquid level pipe 26. The communication pipe 15G is provided with an open / close valve 27 for opening and closing the flow path of the communication pipe 15G. Further, a branch suction pipe 15H communicating with the suction pipe 15F is connected between the connection part of the communication pipe 15G with the liquid level pipe 26 and the on-off valve 27. The branch suction pipe 15H is provided with an opening / closing valve 28 for opening and closing the flow path of the branch suction pipe 15H.

  A communication pipe 15 </ b> I that communicates with the atmosphere is connected to the upper surface of the storage tank 13. The communication pipe 15I is provided with an open / close valve 29 for opening and closing the flow path of the communication pipe 15I. Further, a liquid level detector 30 for detecting the liquid level of the coating liquid in the liquid level pipe 26 is provided on a side surface of a portion of the liquid level pipe 26 extending upward from the upper surface of the storage tank 13.

  Here, the upper end of the liquid level pipe 26 may be communicated with the atmosphere without providing the communication pipe 15G. In this case, an open / close valve 27 is provided in the liquid level detection pipe 26, and a branch suction pipe 15 </ b> H is connected between the storage tank 13 and the open / close valve 27 in the liquid level detection pipe 26.

  In the above-described configuration, the vacuum pump 19, the on-off valve 21, the flow control valve 22, the buffer tank 23, the liquid level pipe 26, and the liquid level detector 30 function as pressure adjusting means.

  Supply tank 11 and supply tank 12 are connected via supply pipe 15J. That is, one end of the supply pipe 15J is connected to the bottom of the supply tank 12, and the other end is connected to the bottom of the supply tank 11. The supply pipe 15J includes, in order from the supply tank 12 side, a filter 31 that captures bubbles and foreign matters in the coating solution, an open / close valve 32 that opens and closes the flow path of the supply pipe 15J, and a flow rate that controls the flow rate in the supply pipe 15J. A control valve 33 is provided.

  The replenishment tank 12 is disposed on the side of the gantry 2, and has a communication pipe 15 </ b> L connected to a communication pipe 15 </ b> K communicating with the atmosphere and a gas supply source 34 for supplying a pressurized gas such as nitrogen gas on the upper surface thereof. Is connected. The communication pipe 15K is provided with an open / close valve 35 that opens and closes the flow path of the communication pipe 15K. On the other hand, the communication pipe 15L is provided with an on-off valve 36 for opening and closing the flow path of the communication pipe 15L. Further, a communication pipe 15M communicating between the connection portion of the communication pipe 15E with the supply tank 11 and the on-off valve 18 is connected between the gas supply source 34 and the on-off valve 36 in the communication pipe 15L. The communication pipe 15M is provided with an open / close valve 37 for opening and closing the flow path of the communication pipe 15M.

  The common liquid supply pipe 15B and the common drain pipe 15D are located in the vicinity of the connection part with the supply tank 11 in the common liquid supply pipe 15B and in the vicinity of the connection part with the storage tank 13 in the common drain pipe 15D. The communication pipe 15N communicates. The communication pipe 15N is provided with an on-off valve 38 for opening and closing the flow path of the communication pipe 15N.

  Further, a waste pipe 15O communicated with the waste tank 14 is connected to a position in the vicinity of the connection portion with the storage tank 13 in the common drain pipe 15D. The waste pipe 15O is provided with an open / close valve 39 for opening and closing the flow path of the waste pipe 15O. The disposal tank 14 is disposed on the side of the gantry 2.

  As shown in FIG. 2, the coating liquid coating apparatus 1 includes a control device 40 and operates under the control of the control device 40. That is, the control device 40 includes a storage unit 41, and based on the control information stored in the storage unit 41, the Y-axis movement table 4, the application head 6 (the piezoelectric element of the application head 6), the vacuum pump 19, On-off valve 16, 17, 18, 21, 24, 27, 28, 29, 32, 35, 36, 37, 38, 39, pressure control valve 20, flow control valves 22, 33, liquid level detectors 25, 30 Control. The control information stored in the storage unit 41 includes, for example, a drawing pattern formed on the surface to be coated of the coating object W, a moving speed and a coating head on the Y-axis moving table 4 for drawing the drawing pattern. Application conditions such as a voltage value applied to each piezoelectric element 6, a voltage application cycle (pulse), a pattern drawing position on the application surface of the application object W, and the like.

  Next, the operation of the coating liquid coating apparatus 1 will be described.

  The operation of the solution coating apparatus 1 mainly includes a preparation process and a coating process.

  The preparation process is a process of filling the application head 6, the supply tank 11, the storage tank 13, and the like with a required amount of the application liquid before executing the application of the application liquid to the application object W.

  The coating process is a process of coating the coating liquid on the substrate W placed on the substrate stage 5.

  First, the preparation process will be described.

  In a state before the preparation process is started, the coating liquid is stored in other tanks, that is, the supply tank 11, the storage tank 13, and the waste tank 14, except that the coating liquid is stored in the replenishing tank 12. It shall not be.

  Therefore, a replenishment operation for supplying a predetermined amount of coating liquid from the replenishment tank 12 to the supply tank 11 is performed from this state. In this embodiment, the coating liquid is supplied until the liquid level detector 25 detects the liquid level of the coating liquid.

  First, the control device 40 opens and closes three of the on-off valves 16, 17, 18, 21, 24, 27, 28, 29, 32, 35, 36, 37, 38, 39 from the closed state. The valves 18, 32 and 36 are opened. At this time, the control device 40 controls the flow rate control valve 33 so as to have a preset throttle amount so that the coating liquid is supplied to the supply tank 11 at a predetermined flow rate.

  As a result, pressurized nitrogen gas is supplied from the gas supply source 34 into the replenishment tank 12, the pressure in the space in the replenishment tank 12 increases, and the coating liquid in the replenishment tank 12 is supplied through the replenishment pipe 15J. It is supplied into the tank 11. When the coating liquid is supplied into the supply tank 11, the volume of the space in the supply tank 11 is reduced by that amount, so that the corresponding amount of gas (air) is discharged to the atmosphere through the communication pipe 15E.

  The control device 40 closes the on-off valves 18, 32, and 36 when the liquid level detector 25 detects the liquid level of the coating liquid.

  Next, a filling operation for filling the common liquid supply pipe 15B, the individual liquid supply pipe 15A, the coating head 6, the individual drainage pipe 15C, and the common liquid supply pipe 15D with the coating liquid is performed.

  First, the control device 40 opens the on-off valves 16, 17 and 18. In addition, the vacuum pump 19 is operated, the on-off valve 21 is opened, and the inside of the buffer tank 23 is reduced to a preset pressure controlled by the pressure control valve 20. At this time, the other on-off valves 24, 27, 28, 29, 32, 35, 36, 37, 38, and 39 are kept closed. Note that the buffer tank 23 may be depressurized in advance, and the vacuum pump 19 may be always driven, or may be driven when the on-off valve 21 is opened. good.

  By opening the on-off valves 16, 17, 18, the coating liquid in the supply tank 11 flows out into the common liquid supply pipe 15 B due to its own weight, and into the coating head 6 through the common liquid supply pipe 15 B and the individual liquid supply pipe 15 A. Inflow.

  The control device 40 further opens the on-off valve 28 when a preset time elapses after the on-off valves 16, 17, 18 are opened.

  Thereby, the storage tank 13 is communicated with the buffer tank 23, and the inside of the storage tank 13 is decompressed. As a result, the pressure in the storage tank 13 becomes negative with respect to the pressure in the supply tank 11, and the coating liquid in the supply tank 11 is transferred to the common liquid supply pipe 15B, the individual liquid supply pipe 15A, the coating head 6, the individual discharge. It is sucked into the storage tank 13 through the liquid pipe 15C and the common liquid supply pipe 15D. Thereby, the liquid level of the coating liquid in the storage tank 13 rises. By opening the on-off valve 28, a negative pressure also acts on the nozzle 6a communicating with the atmosphere, but the flow path of the nozzle 6a is compared with the flow path resistance in the pipes 15C and 15D and the coating head 6. Since the resistance is extremely large, it does not hinder the suction of the coating liquid to the storage tank 13 side.

  In the above description, the preset time includes, for example, the time required for the coating liquid flowing out to the common liquid supply pipe 15B due to its own weight to reach the liquid chamber of each coating head 6. However, the present invention is not limited to this, and can be set arbitrarily and may be set to zero.

  When the liquid level of the coating liquid rises in the storage tank 13 and the liquid level of the coating liquid reaches the lower end of the liquid level pipe 26, the communication between the liquid level pipe 26 and the space in the storage tank 13 is blocked by the coating liquid. Therefore, the rise of the liquid level of the coating liquid in the storage tank 13 is stopped, and the coating liquid is sucked through the liquid level pipe 26 and rises. The liquid level of the coating liquid rising in the liquid level pipe 26 eventually reaches the height of the liquid level detector 30.

  The control device 40 closes the on-off valves 16, 17, 18, and 28 when the liquid level detector 30 detects the liquid level of the coating liquid. At this time, the on-off valve 21 may be left open or closed, but here, it will be described as being open.

  When the filling operation is completed, in the same manner as the above-described replenishing operation, the supply liquid reduced by the filling operation is replenished into the supply tank 11. That is, the coating liquid is supplied into the supply tank 11 until the liquid level detector 25 detects the liquid level.

  When the replenishment of the coating liquid is completed, a negative pressure application operation is performed in which the inside of the supply tank 11 is set to a preset negative pressure.

  In the negative pressure application operation, the control device 40 opens the on-off valves 16, 24, 28, and 29. As a result, the supply tank 11 and the liquid level pipe 26 have a negative pressure controlled by the pressure control valve 20, and the space in the storage tank 13 is an atmospheric pressure.

  The magnitude of the negative pressure at this time, that is, the above-described preset pressure is a magnitude that allows a predetermined negative pressure to act on the coating liquid in the liquid chamber 6c of the coating head 6, and is non-ejection. Even when the coating liquid does not leak from the nozzle 6a of the coating head 6 and the coating liquid is not drawn into the nozzle 6a, the position of the liquid surface of the coating liquid in the nozzle 6a is a predetermined position of the nozzle 6a. For example, the size is maintained in the vicinity of the opening (nozzle formation surface 6b) of the nozzle 6a. The magnitude of this negative pressure can be obtained in advance by experiments or the like.

  In this state, the inside of the storage tank 13 is atmospheric pressure, and a negative pressure of a preset magnitude is applied in the supply tank 11, so that the inside of the liquid level pipe 26 that communicates with the inside of the supply tank 11. The liquid level of the coating liquid is located at a height corresponding to the differential pressure between the supply tank 11 and the storage tank 13. The liquid level detector 30 is attached according to this height position.

  The liquid level of the coating liquid in the liquid level pipe 26 (difference between the liquid level in the liquid level pipe 26 and the liquid level in the storage tank 13) H is expressed by the following equation: H = (P1-P2) / It can be obtained by ρg. Here, P1 is the pressure (atmospheric pressure) in the storage tank 13, P2 is the pressure in the supply tank 11, ρ is the density of the coating liquid, and g is the acceleration of gravity.

  In the negative pressure application operation described above, the timing for opening the on-off valve 28 may be delayed by a predetermined time with respect to the timing for opening the on-off valve 24. That is, since the inside of the liquid level pipe 26 is at a negative pressure while the inside of the supply tank 11 is at atmospheric pressure, if the on-off valve 24 and the on-off valve 28 are opened simultaneously, the atmospheric pressure in the supply tank 11 is changed to the liquid level pipe. It is conceivable that the liquid level of the coating liquid in the liquid level pipe 26 is greatly lowered as a result of the pressure in the liquid level pipe 26 being increased. Therefore, the on-off valve 24 is opened and the inside of the supply tank 11 is set to the same negative pressure as that in the liquid level pipe 26, and then the on-off valve 28 is opened. In this way, since the pressure in the supply tank 11 and the liquid level pipe 26 can be set to a predetermined negative pressure before the opening / closing valve 28 is released, the application in the liquid level pipe 26 by opening the on / off valve 28 is possible. A drop in the liquid level of the liquid can be suppressed.

  Thus, the preparation process is completed. When this preparation process is completed, an application process is performed.

  When the preparation process is completed, the substrate stage 5 is moved by a substrate transfer robot (not shown) at the delivery position of the substrate W, which is one end position in the Y-axis direction that is off the lower side of the coating head 6. Suppose that the substrate W is supplied.

  The substrate stage 5 starts to move toward the other end position in the Y-axis direction by driving a drive mechanism (not shown).

  During this movement, the substrate stage 5, that is, the substrate W passes under the coating head 6.

  The control device 40 determines the relative position in the Y-axis direction between the substrate W and the coating head 6 based on a position detection signal from a position detector such as a linear encoder (not shown) provided accompanying the Y-axis movement table 4. The coating liquid is ejected from each nozzle 6a of the coating head 6 in accordance with the drawing pattern stored in the storage unit 41 in accordance with the timing when the substrate W passes under the coating head 6, and the substrate W is discharged onto the substrate W. Apply droplets of coating solution.

  When the substrate stage 5 reaches the other end position in the Y-axis direction, the substrate stage 5, that is, the Y-axis moving table 4 stops, and returns to the one end position (delivery position) in the Y-axis direction described above. Thus, one application operation is completed.

  At this position, the substrate W coated with the droplets of the coating liquid is carried out, and a new substrate W not coated with the coating liquid is supplied.

  If a new substrate W is supplied onto the substrate stage 5, the coating liquid droplet is applied to the new substrate W, that is, a coating operation is performed in the same manner as described above.

  Then, the above-described application operation is repeated until there is no more substrate W to which the application liquid is to be applied.

  During the coating process in which this coating operation is repeated, the on-off valves 16, 17, 21, 24, 28, and 29 are opened.

  Thus, in the coating liquid coating apparatus 1 of the present embodiment, the negative pressure applied by the negative pressure application operation in the supply tank 11 and the liquid level pipe 26 is set to a set magnitude during the above-described coating process. The negative pressure maintaining operation for maintaining is performed as follows.

  This negative pressure maintaining operation is performed using a liquid level pipe 26 provided in the storage tank 13.

  That is, when the coating liquid is consumed by discharging the coating liquid from the nozzle 6a of the coating head 6, the coating liquid in the supply tank 11 decreases. When the coating liquid in the supply tank 11 decreases, the volume of the space in the supply tank 11 increases accordingly, so that the pressure in the space in the supply tank 11 decreases, that is, the negative pressure increases.

  When the magnitude of the negative pressure in the supply tank 11 increases, the magnitude of the negative pressure in the liquid level pipe 26 that communicates with the space in the supply tank 11 via the communication pipes 15E, 15F, 15G, and 15H also increases. As a result, the level of the coating liquid in the liquid level pipe 26 increases. Therefore, the rise in the liquid level is detected by the liquid level detector 30.

  For example, the liquid level detector 30 is configured to be able to detect the liquid level at two positions, an upper limit and a lower limit. Based on the detection value of the liquid level detector 30, the control device 40 keeps the liquid level height of the coating liquid in the liquid level pipe 26 between the upper limit and the lower limit as follows. Take control.

  Here, the upper limit and the lower limit are set in order to keep the magnitude of the negative pressure in the supply tank 11 within the allowable range. For example, the upper limit is the upper limit ( The position of the liquid level when the pressure is at the lower limit) is set, and the lower limit is set at the position of the liquid level when the magnitude of the negative pressure is at the lower limit of the allowable range (the pressure is the upper limit).

  Further, the allowable range of the magnitude of the negative pressure is a fluctuation within this range, the coating liquid does not leak out from the nozzle of the coating head 6, and the coating liquid is not drawn into the nozzle, The range of the magnitude of the negative pressure that can be maintained in the nozzle.

  FIG. 3A shows the state of the liquid level in the liquid level pipe 26 when the pressure in the space in the supply tank 11 is maintained at a negative pressure set in advance. When the coating liquid in the supply tank 11 is consumed from this state, the space in the supply tank 11 gradually increases accordingly, so that the negative pressure in the supply tank 11 gradually increases. As a result, the liquid level of the coating liquid in the liquid level pipe 26 gradually rises and eventually reaches the upper limit position.

  When the liquid level of the coating liquid reaches the upper limit, this is detected by the liquid level detector 30, and a signal indicating that the liquid level has reached the upper limit is transmitted to the control device 40.

  The control device 40 receives this signal, executes a replenishment operation, and adjusts the magnitude of the negative pressure in the supply tank 11.

  That is, the liquid level of the coating liquid in the supply tank 11 is at a detection position by the liquid level detector 25 before the coating liquid is consumed. Therefore, the control device 40 replenishes the application liquid from the replenishment tank 12 into the supply tank 11 until the liquid level detector 25 detects the liquid level of the application liquid, that is, replenishes the consumed application liquid.

  By replenishing the coating liquid, the volume of the space in the supply tank 11 returns to the original volume, that is, the volume before the coating liquid is consumed, so that the negative pressure in the supply tank 11 is the original magnitude. Even if the liquid level of the coating liquid in the liquid level pipe 26 is lowered, it returns to the original position.

  For example, when a large amount of the coating liquid is discharged from all the nozzles 6a in a short time, and the coating liquid in the supply tank 11 is rapidly consumed, the magnitude of the negative pressure in the supply tank 11 May suddenly increase and the negative pressure in the supply tank 11 may not be recovered in time when the coating liquid is replenished. In such a case, the magnitude of the negative pressure is recovered by the following operation.

  When the magnitude of the negative pressure in the supply tank 11 increases, the liquid level of the coating liquid in the liquid level pipe 26 rises, and the coating liquid stored in the storage tank 13 is drawn into the liquid level pipe 26, so that The liquid level of the coating liquid in the tank 13 is lowered.

  When the liquid level of the coating liquid in the storage tank 13 decreases and the liquid level becomes lower than the lower end position of the liquid level pipe 26 as shown in FIG. Atmospheric pressure gas, for example, air Gs is sucked into the liquid level pipe 26. As a result, the pressure in the supply tank 11 increases, that is, the negative pressure is reduced, and the negative pressure is restored.

  That is, in this embodiment, even when the magnitude of the negative pressure in the supply tank 11 suddenly increases, before the coating liquid in the nozzle 6a of the coating head 6 is pulled back into the liquid chamber 6c by the negative pressure. Further, the immersion amount of the liquid level pipe 26 with respect to the coating liquid in the storage tank 13 is set so that the liquid level of the coating liquid in the storage tank 13 is lower than the lower end position of the liquid level pipe 26. In other words, before the level of the negative pressure in the supply tank 11 reaches the level that draws the coating liquid in the nozzle 6a into the liquid chamber 6c, the liquid level of the coating liquid in the storage tank 13 becomes the liquid level. The immersion amount of the liquid level pipe 26 with respect to the coating liquid in the storage tank 13 is set so as to be lower than the lower end position of the pipe 26.

  For example, as shown in FIG. 4A, the liquid level Fs of the coating liquid in the nozzle 6a of the coating head 6 in a state where the magnitude of the negative pressure in the supply tank 11 is maintained at a preset level. Is in the vicinity of the opening of the nozzle 6a. From this state, when the magnitude of the negative pressure in the supply tank 11 increases, as shown in FIG. 4B, the liquid level Fs of the coating liquid in the nozzle 6a passes through the nozzle 6a toward the liquid chamber 6c. As shown in FIG. 4 (c), the liquid chamber 6c is eventually reached. When the liquid level of the coating liquid is drawn into the liquid chamber 6c, air enters the liquid chamber 6c. The air that has entered the liquid chamber 6c may remain in the liquid chamber 6c even if the liquid level is returned to the vicinity of the opening of the nozzle 6a. The air Gs remaining in the liquid chamber 6c becomes a factor that significantly deteriorates the discharge performance of the droplets from the nozzle 6a.

  Therefore, it is not preferable that the negative pressure in the supply tank 11 becomes so large that the liquid level of the coating liquid in the nozzle 6a is drawn beyond the upper end of the nozzle 6a (end on the liquid chamber 6c side).

  Therefore, before the liquid level of the coating liquid in the liquid level pipe 26 rises to the liquid level when a negative pressure large enough to draw the liquid level of the coating liquid in the nozzle 6a to the upper end of the nozzle 6a is applied, the liquid is stored. The immersion amount of the liquid level pipe 26 is set so that the liquid level of the coating liquid in the tank 13 is lower than the lower end of the liquid level pipe 26. Here, the liquid level (reference liquid level) when a negative pressure of a preset size is applied in the supply tank 11 and the size of drawing the liquid level of the coating liquid in the nozzle 6a to the upper end of the nozzle 6a. The difference h1 (see FIG. 3A) from the liquid level when the negative pressure is applied is an allowable liquid level displacement amount (hereinafter referred to as “allowable displacement amount h1”).

  The immersion amount can be approximately obtained based on the allowable displacement amount h1 and the ratio between the inner diameter of the liquid level pipe 26 (surface area of the liquid surface) and the inner diameter of the storage tank 13 (surface area of the liquid surface). .

  That is, since the volume of the coating liquid increased by the displacement amount h1 in the liquid level pipe 26 is equal to the volume of the coating liquid decreased in the storage tank 13, the displacement amount h1 and the change amount h2 of the liquid level in the storage tank 13 are the same. This relationship can be expressed approximately by h2 = (S1 × h1) / S2. Here, S1 is the surface area of the liquid level in the liquid level pipe 26, and S2 is the surface area of the liquid level in the storage tank 13.

  For example, the surface area S2 of the liquid level in the storage tank 13 is 10 times the surface area S1 of the liquid level in the liquid level pipe 26, and the allowable displacement h1 of the liquid level in the liquid level pipe 26 is 10 mm. In this case, h2 = (S1 × 10) / 10S1 = 1, and the immersion amount can be determined to be 1 mm.

  In this way, even when a problem such as a sudden increase in the negative pressure in the supply tank 11 occurs by setting the amount of immersion of the liquid level pipe 26 with respect to the coating liquid in the storage tank 13, the negative pressure is generated. By increasing the pressure, it is possible to prevent the liquid level of the coating liquid in the nozzle 6a of the coating head 6 from being drawn into the liquid chamber 6c.

  On the other hand, if the magnitude of the negative pressure in the supply tank 11 is smaller than a preset magnitude, that is, if the pressure is higher than a preset value, the vacuum pump 19, the pressure regulating valve 20, the on-off valve 21. Since the negative pressure generated by the negative pressure generating means constituted by the flow control valve 22 is constantly acting, it is usually difficult to generate.

  However, when the magnitude of the negative pressure in the supply tank 11 becomes smaller than a preset magnitude, control such as adjusting the pressure regulating valve 20 so as to temporarily increase the magnitude of the negative pressure to be applied. May be executed by the control device 40.

  Accordingly, the liquid level detector 30 can set the position of the liquid level of the coating liquid in the liquid level pipe 26 when the magnitude of the negative pressure in the supply tank 11 is a preset size as the lower limit. it can.

  The above-described adjustment of the immersion amount h2 of the liquid level pipe 26 with respect to the coating liquid in the storage tank 13 can be performed as follows.

  As explained in the above filling operation, the liquid level of the coating liquid in the storage tank 13 stops rising when it reaches the lower end of the liquid level pipe 26. Therefore, when the filling operation of the coating liquid to the coating head 6 or the like is completed, the coating head 6 is substantially in contact with the lower end of the liquid level pipe 26.

  Therefore, the on-off valves 37 and 38 are opened after the filling operation is completed. As a result, pressurized nitrogen gas is supplied from the gas supply source 34 to the space in the supply tank 11, the pressure in the space in the supply tank 11 rises, and the coating liquid in the supply tank 11 passes through the communication pipe 15N. And supplied to the storage tank 13.

  Thereafter, when the immersion amount of the liquid level pipe 26 with respect to the coating liquid reaches a predetermined immersion amount h2 that has been obtained in advance, the on-off valves 37 and 38 are closed, and the supply of the coating liquid to the storage tank 13 is stopped. .

  Here, it is possible to determine whether or not the immersion amount of the liquid level pipe 26 with respect to the coating liquid has reached the predetermined immersion amount h2 by detecting the position of the liquid level in the storage tank 13. For example, as shown in FIG. 3, a liquid level detector 50 is disposed at a position of height h2 from the lower end of the liquid level pipe 26, and the time when the liquid level detector 50 detects the liquid level is determined as a predetermined immersion. It can be determined that the amount h2 has been reached.

  When the amount of the coating liquid in the storage tank 13 is large, the on-off valve 24 is opened to supply negative pressure into the supply tank 11 and the on-off valve 38 is opened to open the inside of the storage tank 13. The coating liquid may be returned to the supply tank 11 side through the communication pipe 15N, or the on-off valves 29 and 39 are opened so that the coating liquid in the storage tank 13 is discharged to the exhaust tank 14 by its own weight. May be.

  The adjustment of the immersion amount h2 is preferably performed after the above-described filling operation and before the negative pressure applying operation.

  Thus, according to the coating liquid coating apparatus 1 of this embodiment, it has the following effect | action.

  Since the change in the negative pressure in the supply tank 11 is detected by the displacement of the liquid level of the coating liquid in the liquid level pipe 26, expensive equipment such as a high-precision pressure sensor is not used, and the cost increases. The pressure applied to the liquid chamber 6c in the coating head 6 can be maintained at an appropriate negative pressure while suppressing the above.

  In addition, the level of the coating liquid in the liquid level pipe 26 and the liquid level of the coating liquid in the nozzle 6a when a negative pressure of a preset magnitude is applied in the supply tank 11 to the upper end of the nozzle 6a. A difference h1 from the liquid level of the coating liquid in the liquid level pipe 26 when a negative pressure of the drawing size is applied is set as an allowable liquid level displacement amount, and the liquid level of the coating liquid in the liquid level pipe 26 is set. Of the liquid level pipe 26 with respect to the coating liquid in the storage tank 13 so that the liquid level of the coating liquid in the storage tank 13 is lower than the lower end position of the liquid level pipe 26. An immersion amount h2 was set. As a result, even when a problem such as a sudden increase in the negative pressure in the supply tank 11 occurs, the liquid level of the coating liquid in the nozzle 6a of the coating head 6 changes to the liquid chamber 6c due to the increase in the negative pressure. It can be reliably prevented from being pulled in. Thereby, since the pressure applied in the coating head can be maintained at an appropriate negative pressure, it is possible to prevent a problem that air enters the liquid chamber 6c of the coating head 6 and to prevent the coating apparatus 1 from Since the operation rate can be improved, productivity can be improved as a result.

  Further, as described above, the position of the liquid surface of the coating liquid in the nozzle 6a of the coating head 6 can be stably maintained at a predetermined position in the nozzle 6a, for example, in the vicinity of the opening, so that the liquid is discharged from the nozzle 6a. It is possible to stably obtain the amount of the coating liquid without causing variations in each discharge.

  As described above, according to this embodiment, the pressure applied in the coating head can be maintained at an appropriate negative pressure, so that the coating liquid can be applied onto the substrate W with a stable discharge amount. Thus, productivity can be improved.

  In the above-described embodiment, the liquid level pipe 26 functioning as a liquid column pressure gauge is a straight pipe arranged vertically, but is not limited to this, and may be arranged inclined. good. In short, any configuration capable of detecting a change in the liquid level in the liquid level pipe 26 may be used.

  Further, the shape of the liquid level pipe 26 is not limited to a straight pipe. For example, even if it has a shape having a bent portion in the middle, one end side is immersed in the coating liquid in the storage tank 13, and the other end side is at a level higher than the liquid level of the coating liquid in the middle tank 13. It suffices to have a shape having a linear portion capable of detecting the above.

  The liquid level pipe 26 may be configured such that its inner diameter changes midway. For example, the inner diameter of the portion located below the inner diameter of the portion corresponding to the position where the liquid level detector 30 for detecting the liquid level in the liquid level pipe 26 is provided is configured to be smaller. Also good. In such a configuration, the amount of the coating liquid accumulated in the liquid level pipe 26 can be reduced as compared with the case where the inner diameter of the part for detecting the liquid level and the part located below the same are the same. The amount of coating liquid used for pressure detection can be reduced. It should be noted that the liquid level pipe 26 preferably has a linear portion for detecting the liquid level regardless of its shape.

  Moreover, the cross-sectional shape of the liquid level pipe 26 is not limited to a circular shape, and may be a pipe having another shape, for example, a polygonal shape such as an ellipse or a quadrangle.

  Further, the inner diameter of the liquid level pipe 26 is not particularly limited. However, the liquid level of the liquid in the liquid level pipe 26 is curved due to wettability with the inner wall of the liquid level pipe 26, so even if such a curve occurs, the liquid level It is preferable to have such a size that a horizontal plane is formed in the central portion of the.

  Moreover, although the example which connected common drainage pipe | tube 15D to the storage tank 13 demonstrated, it is not restricted to this, You may make it provide the storage tank 13 independently from piping which supplies or discharges coating liquid. good. In this case, in FIG. 1, it can comprise by removing the part between the connection part with the piping 15N and 15O in the common drainage pipe 15D, and the storage tank 13. FIG. When the storage tank 13 is provided independently as described above, the liquid stored in the storage tank 13 may be a liquid different from the coating liquid. As the liquid used at this time, it is preferable to use a liquid that does not easily evaporate, and it is preferable to use a degassed liquid. In addition, using a liquid with a lower specific gravity than a liquid with a higher specific gravity has a larger amount of displacement with respect to a change in pressure, so it is possible to detect a smaller pressure change. The liquid to be used should be selected accordingly.

  Further, the storage tank 13 is provided adjacent to the supply tank 11, but the storage tank 13 is not limited to this, and the storage tank 13 may be disposed at a remote position with respect to the supply tank 11. You may arrange | position in the same height position as the tank 11, or may arrange | position in a different height position.

  Further, in the above-described embodiment, the negative pressure in the supply tank 11 is adjusted based on the detection signal of the liquid level detector 30 by supplying the application liquid in the supply tank 11. Instead, it may be performed by supplying gas into the supply tank 11.

  For example, when the magnitude of the negative pressure in the supply tank 11 becomes large, control to temporarily open the on-off valve 18 is performed to supply atmospheric pressure air into the supply tank 11. Even in this case, the negative pressure in the supply tank 11 can be maintained at a predetermined level. Further, the on-off valve 37 may be temporarily opened instead of the on-off valve 18 to supply pressurized gas. However, when the gas is supplied in this way, the application liquid in the supply tank 11 continues to decrease due to the consumption of the application liquid by the application head 6. Therefore, it is preferable to replenish the coating liquid into the supply tank 11 at a predetermined timing. As a timing for replenishing the coating liquid, a period during which the ejection of the coating liquid from the nozzle 6 a of the coating head 6 is stopped, for example, the coating process for the current substrate W is completed, and the next substrate W is supplied to the substrate stage 5. It is good to do it before it is done. Further, when the gas is supplied into the supply tank 11 by opening the on-off valve 18 or the on-off valve 37, a leak valve or the like is added to the communication pipe 15E or the communication pipe 15M so that the pressure in the supply tank 11 gradually increases. A flow rate control valve may be provided to adjust the flow rate of the gas supplied into the supply tank 11.

  In the above-described embodiment, the liquid level detector 30 is provided in the liquid level pipe 26 so that the liquid level in the liquid level pipe 26 can be maintained within a predetermined range, that is, the space in the supply tank 11. In the above description, the liquid level detector 30 is not necessarily provided, but is controlled so that the negative pressure is maintained within a predetermined range.

  Further, the allowable displacement amount h1 is set so that the liquid level when a negative pressure of a preset magnitude is applied in the supply tank 11 in the liquid level pipe 26 and the liquid level of the coating liquid in the nozzle are set in the nozzle 6a. Although the value of the difference from the liquid level when a negative pressure of a magnitude that draws to the upper end is applied is not limited to this, it may be a value smaller than this value. In short, it is only necessary that the negative pressure of the magnitude that draws the liquid level of the coating liquid in the nozzle 6a to the upper end of the nozzle 6a does not act in the supply tank 11.

  Further, although the buffer tank 23 for storing the negative pressure generated by the vacuum pump 19 is provided, the buffer tank 23 is not necessarily provided. However, the negative pressure generated by the vacuum pump 19 may vary regularly or irregularly due to the structure or capacity of the vacuum pump 19. Therefore, it is preferable to provide the buffer tank 23 because the buffer tank 23 functions as a buffer for the fluctuation.

  In the common drainage pipe 15D, an open / close valve may be provided between the storage tank 13 and the connection part between the common drainage pipe 15D and the communication pipe 15N. In this case, when the coating liquid is discharged from the coating head 6, the on-off valve 38 is opened with the on-off valve closed, so that the coating liquid in the supply tank 11 can be supplied from the common liquid supply pipe 15B side. In addition, it can be supplied from the common drainage pipe 15D side. By doing in this way, a coating liquid is supplied with respect to the coating head 6 from both the inlet and outlet of a coating liquid. Therefore, even in the case of a coating head having a structure in which an introduction port is arranged on one end side of the nozzle row and a discharge port is arranged on the other end side, the discharge port side is not used for a nozzle located far from the introduction port. Since the coating liquid is supplied and compensated for, the variation in the amount of the coating liquid supplied to each nozzle can be suppressed.

DESCRIPTION OF SYMBOLS 1 Coating liquid coating apparatus 6 Coating head 10 Coating liquid supply system 11 Supply tank 13 Collection tank (storage tank)
15 Piping 19 Vacuum pump 20 Pressure control valve 21 On-off valve 22 Flow control valve 23 Buffer tank 26 Liquid level detection pipe 30 Liquid level detector 40 Control device 41 Storage unit W Substrate (application object)

Claims (6)

An application head having a nozzle for discharging the application liquid as droplets; a supply tank for storing the application liquid supplied to the application head; and a pressure adjusting means for adjusting the pressure in the space in the supply tank to a negative pressure. A coating liquid coating apparatus for spraying the droplets from the nozzle of the coating head and coating the coated object on a coating object;
The pressure adjusting means is
A storage tank for storing liquid;
A liquid level pipe having one end immersed in the liquid stored in the storage tank and the other end communicating with the supply tank;
Have
The level of the liquid stored in the storage tank is lower than the lower end of the level pipe when the negative pressure in the space in the supply tank reaches a predetermined level. A coating liquid coating apparatus, wherein the amount of immersion in the liquid is set so as to be low.   2. The coating liquid coating apparatus according to claim 1, wherein the liquid level detection pipe is constituted by a straight pipe member and is erected vertically. The application head is an ink jet type application head,
The coating liquid coating apparatus according to claim 1, wherein the supply tank is disposed at a position higher than the coating head.   4. The coating liquid coating apparatus according to claim 3, wherein the storage tank is connected to a discharge port of the coating liquid in the coating head and stores the coating liquid discharged from the discharge port. . A detector for detecting a liquid level of the liquid in the liquid level pipe;
A control device for controlling the magnitude of the negative pressure in the supply tank based on the detection value of the detector;
The coating liquid coating apparatus according to claim 1, further comprising: A replenishment tank for replenishing the coating liquid to the supply tank;
6. The application according to claim 5, wherein the controller reduces the magnitude of the negative pressure in the space in the supply tank by replenishing the supply liquid in the supply tank to the supply tank. Liquid coating device.

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