JP4914708B2 - Solution coating apparatus and coating method - Google Patents

Description

  The present invention relates to a solution coating apparatus and a coating method for coating a solution on a substrate.

  For example, in the manufacturing process of a liquid crystal display device, there is a film forming process for forming a circuit pattern on a glass substrate. In this film forming process, a functional thin film such as an alignment film or a resist is formed on the plate surface of the substrate.

  When a functional thin film is formed on a substrate, a so-called ink jet type coating apparatus is sometimes used in which a solution for forming the functional thin film is discharged from a nozzle and applied to the plate surface of the substrate.

  The coating apparatus has a mounting table for transporting a substrate, and a plurality of coating heads on which the nozzles are formed are arranged above the mounting table in a direction substantially orthogonal to the substrate transport direction. Are arranged. Thereby, the solution discharged from the nozzles of the plurality of coating heads is applied to the upper surface of the substrate to be transported at a predetermined interval in a direction intersecting the transport direction.

  Each coating head is provided with a piezoelectric element through a flexible plate so as to face each nozzle. When a voltage is applied to the piezoelectric element, the flexible plate is deformed, and the solution is discharged and supplied from the nozzle.

  Even if the same voltage is applied to the piezoelectric elements of each coating head, the characteristics of each coating head differ depending on the piping resistance from the solution supply source, manufacturing accuracy, assembly accuracy, etc. There will be a difference. As a result, the thickness of the functional thin film formed on the substrate may not be uniform.

  Therefore, conventionally, the solution discharged from the nozzle is imaged with a high-speed camera, and the volume (amount) of the solution is calculated from the projected area of the imaged solution, and the amount of solution discharged from each nozzle is uniform by this volume. The voltage applied to each piezoelectric element was adjusted so that

Patent Document 1 discloses that a solution discharged from a nozzle of a coating head is imaged with a high-speed camera, and a volume, that is, an amount is obtained from the projected area.
JP 2005-40690 A

  By the way, when the solution discharged from the nozzle of the coating head is imaged with a high-speed camera and the liquid area of the imaged solution is obtained, a calculation error occurs for the following reason.

That is, the high-speed camera has a light source disposed opposite to the ejection path of the discharged solution. When the solution discharged from the nozzle receives light emitted from the light source, the image is formed on a solid-state image sensor in which hundreds of light-receiving elements are arranged in a vertical and horizontal matrix on the imaging surface of a high-speed camera. Is done. At this time, each light receiving element outputs a signal corresponding to the amount of received light . That is, the light receiving element positioned off the solution portion (located on the background portion) receives light emitted from the light source, outputs an output signal a having a magnitude corresponding to the light amount, and receives light corresponding to the solution portion. Since the light from the light source is weakened by the solution, the element outputs an output signal b smaller than the output signal a.

  Further, since the light receiving element corresponding to the contour portion of the solution also has light diffraction or the like, the output signal c having a magnitude between the output signal a and the output signal b is output.

Here, when the projected area of the solution is obtained by binarization, the output signal from each light receiving element is compared with a threshold value set to a size between the output signal a and the output signal b, and corresponds to the solution portion. It is divided into a signal and a signal corresponding to the background portion. Specifically, a signal smaller than the threshold is a signal corresponding to the solution portion, and a signal larger than the threshold is a signal corresponding to the background portion.

At this time, the output signal c from the light receiving element corresponding to the contour portion of the solution is set as a solution portion or a background portion depending on the magnitude thereof. Therefore, even if the contour portion of the solution actually corresponds, a signal c that is determined not to correspond to the solution is generated. Since many such determinations occur in the contour portion of the solution, the projected area of the solution calculated from such a determination result includes an error, and the measurement accuracy is lowered. Therefore, the volume calculated from the projected area is also low in accuracy, and the amount of the solution discharged from the nozzle cannot be measured accurately .

  An object of the present invention is to provide a solution coating apparatus and a coating method in which the amount of a solution discharged from a nozzle can be obtained with high accuracy regardless of the area of the solution.

The present invention, in the coating apparatus of the solution applying the solution to the substrate,
An application head having a nozzle for discharging the solution;
A driving means provided in the coating head, for discharging the solution from the nozzle by application of a voltage ;
Detecting means for detecting the length of the solution discharged from the nozzle in the discharge direction;
A solution coating apparatus comprising: a control unit that controls a voltage value applied to the driving unit according to the length of the solution detected by the detection unit .

It is preferable to have a timing setting means for setting a timing for applying a driving signal to the driving means and a timing for detecting the length of the solution by the detecting means.

The present invention relates to a solution coating method in which a solution is applied to a substrate using a coating head that discharges a solution from a nozzle by applying a voltage to a driving unit .
Detecting the length in the direction of ejection of the solution discharged from the nozzle, the voltage value that this detected and compared to the length set in advance the length of the solution is applied to the drive means on the basis of the comparison result In the method of applying a solution, the method is characterized in that

The discharge of the solution is performed by a plurality of nozzles provided in the coating head,
The detection of the length of the solution is preferably performed based on a captured image obtained by capturing an image of the solution discharged from two or more nozzles at a time using the imaging camera .

  According to this invention, the length of the solution discharged from the nozzle is detected. Therefore, since the amount of the solution discharged from the nozzle can be obtained by the length, the measurement accuracy can be improved as compared with the case where the amount is obtained from the projected area of the solution.

  An embodiment of the present invention will be described below with reference to the drawings.

  The coating apparatus according to the present invention shown in FIGS. 1 and 2 has a rectangular parallelepiped base 1. Legs 2 are provided at predetermined positions on the lower surface of the base 1, and the base 1 is horizontally supported by the legs 2.

  As shown in FIG. 2, attachment plates 3 having a predetermined width dimension are provided along the longitudinal direction at both ends in the width direction of the upper surface of the base 1. Guide members 4 are respectively provided along the longitudinal direction at one end in the width direction of the upper surfaces of the mounting plates 3. On the upper surfaces of these guide members 4, a rectangular plate-shaped X table 5 is slidably engaged with a pair of first receiving members 6 having substantially U-shaped cross sections provided in parallel on both sides of the lower surface in the width direction. It is supported together. On the upper surface of the X table 5, a mounting table 7 smaller than the X table 5 is provided. That is, the mounting table 7 is movable in the X direction along the guide member 4 via the X table 5.

  The guide member 4 is provided with a stator 4a, the first receiving member 6 is provided with a mover 6a, and the stator 4a and the mover 6a form a linear motor 8 serving as a driving means. Yes.

  For example, a glass substrate W used for an active matrix type liquid crystal display device is supplied to the mounting table 7. The substrate W is sucked and held on the mounting table 7 by means such as vacuum suction or electrostatic suction. Therefore, the substrate W held on the mounting table 7 is driven in the X direction by the X table 5.

  A gate-shaped support 11 is erected in the middle of the base 1 in the longitudinal direction so as to straddle the pair of guide members 4. A mounting member 12 made of a prism is horizontally installed on both sides of the support 11.

  A head table 19 is provided on the attachment member 12 so as to be movable along a Y direction (indicated by an arrow in FIG. 2) perpendicular to the X direction which is the driving direction of the X table 5. A first Y drive source 21 composed of a pulse motor is provided on one side of the support 11 in the width direction. The Y drive source 21 drives the head table 19 along the Y direction. The head table 19 may be driven in the Y direction by a linear motor instead of the pulse motor.

  On one side of the head table 19, a plurality of coating heads 22 that are functional thin films by an inkjet method, for example, eject a solution (polyimide solution) for forming an alignment film in a dot shape are arranged along the Y direction. . In this embodiment, for example, seven coating heads 22 are arranged in two rows in a staggered manner.

  As shown in FIGS. 3 and 4, each coating head 22 includes a head body 28. The head main body 28 is formed in a cylindrical shape, and its lower surface opening is closed by a flexible plate 29. The flexible plate 29 is covered with a nozzle plate 31, and a plurality of liquid chambers 32 are formed between the nozzle plate 31 and the flexible plate 29.

  Each liquid chamber 32 communicates with a main pipe line 31A formed in the nozzle plate 31 via a branch pipe (not shown), and a solution is transferred from the main pipe line 31A via the branch pipe line to each liquid chamber 32. To be supplied. One end of the main pipeline 31A is connected to a liquid supply hole 33 described later, and the other end is connected to a recovery hole 37 described later.

  The liquid supply hole 33 communicating with the liquid chamber 32 is formed at one longitudinal end of the head body 28. The solution for forming a functional thin film is supplied from the liquid supply hole 33 to the liquid chambers 32. Thereby, the inside of the liquid chamber 32 is filled with the solution.

  As shown in FIG. 4, a plurality of nozzles 34 are formed in the nozzle plate 31 in a zigzag pattern along the Y direction, which is a direction orthogonal to the transport direction of the substrate W. On the upper surface of the flexible plate 29, as shown in FIG. 3, a plurality of piezoelectric elements 35 are provided as driving means so as to face the nozzles 34.

  Each piezoelectric element 35 is supplied with a driving voltage by a driving unit 36 provided in the head main body 28. As a result, the piezoelectric element 35 expands and contracts and partially deforms the flexible plate 29, so that the solution is ejected in the form of dots from the nozzle 34 facing the piezoelectric element 35 and supplied to the upper surface of the substrate W to be transported. Applied. Therefore, a coating pattern in which dot-like solutions are arranged in a matrix is formed on the upper surface of the substrate W. And this application | coating pattern adheres and it becomes one film | membrane because each dot-like solution flows and spreads wet.

  The recovery hole 37 communicating with the liquid chamber 32 is formed at the other longitudinal end of the head body 28. The solution supplied from the liquid supply hole 33 to the liquid chamber 32 can be recovered from the recovery hole 37. That is, each head 22 can not only discharge the solution supplied to the liquid chamber 32 from the nozzle 34 but also recover the solution from the recovery hole 37 through the liquid chamber 32.

  As shown in FIG. 1, a measuring device 41 for measuring the amount of the solution discharged from the nozzle 34 of the coating head 22 is provided at one end of the guide member 4. The measuring device 41 has a first movable member 42. The first movable member 42 is provided with a pair of second receiving members 43 (only one is shown) at both ends of the lower surface in the width direction. The receiving members 43 are slidably engaged with the guide member 4. Is provided. When the amount of the solution discharged from the nozzle 34 is not measured, as shown in FIG. 1, the guide member 4 waits at a standby position at one end in the longitudinal direction, that is, a position that does not interfere with the reciprocation of the mounting table 7. is doing.

  The first movable member 42 can be driven in the X direction along the guide member 4 by the linear motor 8, and the mounting table 7 provided on the guide member 4 and the first movable member 42 are moved. It can be selectively driven.

  On the upper surface of the first movable member 42, a second movable member 45 movable along the longitudinal direction of the first movable member 42 has a longitudinal direction orthogonal to the first movable member 42. Is provided.

  As shown in FIGS. 5 and 6, a second Y drive source 46 formed of a pulse motor is provided at one end in the longitudinal direction of the first movable member 42, and the second Y drive source 46 provides the second Y drive source 46. The movable member 45 can be driven along the Y direction intersecting with the X direction, that is, along the direction in which the coating heads 22 are juxtaposed.

A high-speed camera 48 is provided at one end in the longitudinal direction of the second movable member 45 along the X direction, and a light source 49 that emits illumination light toward the high-speed camera 48 is provided at the other end. . The high-speed camera 48 and the light source 49 constitute detection means.
A receiving tray 51 for receiving the solution discharged from the nozzle 34 of each coating head 22 is provided on the upper surface of the central portion in the longitudinal direction of the second movable member 45 as will be described later.

  FIG. 7 shows a control circuit for measuring the amount of solution discharged from the nozzle 34 of the coating head 22 by the measuring device 41. In the figure, reference numeral 52 denotes a control device. A timing setting device 53 is connected to the control device 52.

  When the drive signal D1 is input from the control device 52, the timing setting device 53 applies a discharge signal S1 that applies a voltage to each piezoelectric element 35 via the drive unit 36 provided in the coating head 22, and A light emission signal S2 for emitting illumination light from the light source 49 via the light source controller 54 and an imaging signal S3 for operating the high-speed camera 48 are output in synchronization at a predetermined timing. The drive unit 36 that has received the ejection signal S1 supplies the piezoelectric element 35 with a voltage V corresponding to the voltage command signal S11 sent from the control device 52.

  As a result, the solution is discharged from the nozzle 34 of the predetermined coating head 22 and illumination light is emitted from the light source 49, and the solution before being discharged from the nozzle 34 by the high-speed camera 48 and reaching the substrate W is imaged. It has come to be. Note that the light emission signal S2 and the imaging signal S3 may be the same signal or different signals.

  The high-speed camera 48 that images the solution outputs the imaging signal S4 to the image processing device 55. The image processing device 55 processes the imaging signal S4 from the high-speed camera 48, and calculates the length L (length in the ejection direction) of the solution ejected from the nozzle 34 by the imaging signal S4.

  When the length L of the solution is imaged by the high-speed camera 48, the timing setting device 53 may set the imaging timing so that the solution discharged from the nozzle 34 is imaged when it exits from the nozzle 34. The entire length of the solution length L can be imaged.

  As shown in FIG. 12, the high-speed camera 48 has a visual field range A in which the solution discharged from the plurality of nozzles 34 can be imaged at a time. In this embodiment, the high-speed camera 48 can capture images of the five nozzles 34 and the solution Y discharged from the five nozzles 34 in the visual field range A. Therefore, the image processing device 55 can calculate the length L of the solution Y ejected from the five nozzles 34 from the image of the visual field range A captured by the high speed camera 48 at a time.

  The calculation signal S5 calculated by the image processing device 55 is output to the control device 52. Upon receiving the calculation signal S5, the control device 52 controls the voltage V applied to the piezoelectric element 35 that discharges the solution from the nozzle 34.

  FIG. 8 is a graph in which the relationship between the voltage V applied to the piezoelectric element 35 and the amount of the solution discharged from the nozzle 34 is measured in advance. As the applied voltage V is increased, the amount of discharged solution increases linearly. It can be seen that there is a relationship.

  FIG. 9 is a graph obtained by measuring the relationship between the voltage V applied to the piezoelectric element 35 and the length L of the solution discharged from the nozzle 34. When the applied voltage is increased, the length L of the discharged solution is increased. It can be seen that there is a linearly increasing relationship. FIG. 10 is a graph in which the relationship between the amount of the solution discharged from the nozzle 34 and the length L is measured, and it can be seen that the length L of the solution increases linearly as the discharge amount increases. .

  From the above, since the length L of the solution discharged from the nozzle 34 can be changed by the voltage V applied to the piezoelectric element 35, the amount of the solution discharged from the nozzle 34 can be changed by changing the length L. Can be controlled.

  The control device 52 processes the calculation signal S5 from the image processing device 55 to control the voltage V applied to the piezoelectric element 35, and at the same time, to the drive controller 56 that controls the driving of the measuring device 41 in the Y direction. S6 is output.

  Upon receiving the movement signal S6, the drive controller 56 outputs a drive signal D2 to the second Y drive source 46. Accordingly, the second movable member 45 provided with the high-speed camera 48 and the light source 49 is driven a predetermined distance in the Y direction, and the next five nozzles 34 positioned in the Y direction of the coating head 22 are moved to the high-speed camera. The second movable member 45 is positioned with respect to the Y direction so that an image can be captured by 48.

  FIG. 11 is a flowchart for explaining the operation for setting the length of the solution discharged from the nozzle 34. First, a state in which the measuring device 41 is positioned with respect to the coating head 22 to be measured, that is, a state in which the solution discharged from the measurement target nozzle 34 of the coating head 22 passes between the high-speed camera 48 and the light source 49. Thus, when the operation is started in the first step indicated by P1, the solution is discharged from all the nozzles 34 of the coating head 22 in the second step indicated by P2. The solution is discharged from each nozzle 34 not only once but repeatedly until the measurement is completed. The solution discharged from the nozzle 34 is received by the tray 51.

  The solution is discharged based on a drive signal D1 output from the control device 52 to the timing setting device 53 as shown in FIG. When the solution is discharged from the nozzle 34, the illumination light is emitted from the light source 49 at the predetermined timing set by the timing setting device 53 in the third step indicated by P3, and at the same time, the high-speed camera 48 The solution discharged from the five nozzles 34 that can be accommodated in the visual field range A is imaged.

  In the fourth step indicated by P4, the length L of the solution discharged from the nozzle 34 is calculated by the image processing device 55 based on the image signal S4 from the high-speed camera 48. In the fifth step indicated by P5, each nozzle is calculated. The length L of the solution discharged from 34 is compared with an upper limit value set in a comparison unit (not shown) provided in the control device 52.

The length L of the solution is calculated for each measurement area R set corresponding to each nozzle 34 in the visual field range A, as indicated by a one-dot chain line in FIG.
In addition, the image processing apparatus performs a known edge extraction process in the measurement area R and calculates the length L of the solution.

  As a result of comparison, when the length of the solution is longer than the upper limit value, the voltage value applied to the piezoelectric element 35 corresponding to the nozzle 34 that ejected the solution in the sixth step indicated by P6 is the measurement shown in FIG. Lowered based on the graph.

  As a result of the comparison in the fifth step P5, when the length of the solution is smaller than the upper limit value, the length is compared with the lower limit value set in the comparison unit in the seventh step indicated by P7. . As a result of comparison, when the length of the solution is smaller than the lower limit value, the voltage value applied to the piezoelectric element 35 corresponding to the nozzle 34 that ejected the solution in the eighth step indicated by P is the measurement shown in FIG. Raised based on the graph.

  If the voltage value to be applied to the piezoelectric element 35 is controlled in the sixth step indicated by P6 or the eighth step indicated by P8, the step of discharging the solution from each nozzle 34 and picking up an image takes 5 steps within the visual field range A. This is performed sequentially for the two nozzles 34. Thereby, the length L, that is, the amount of the solution discharged from the five nozzles 34 imaged by the high-speed camera 48 is set within a predetermined range.

  As a result of comparison in the seventh step P7, when the length of the solution is larger than the lower limit value, from the five nozzles 34 in the visual field range A captured by the high speed camera 48 in the ninth step indicated by P9. It is confirmed whether or not the measurement of the length L of the discharged solution is completed. If not completed, the measurement area R is switched in the tenth step indicated by P10, and the length L of the solution discharged from the nozzles 34 that have not been measured among the five nozzles 34 is determined. Measured.

  When it is confirmed in P9 that the measurement of the length L of the solution discharged from the five nozzles 34 in the visual field range A is completed, in the eleventh step shown in P11, all the nozzles of one coating head 22 are used. It is confirmed whether or not the measurement of the length L of the solution discharged from 34 is completed. If not completed, the measuring device 41 is driven in the Y direction by a predetermined distance by the second Y drive source 46 in the twelfth step indicated by P12. Thereby, the visual field range A of the high-speed camera 48 is a position where the plurality of unmeasured nozzles 34 are imaged, and the length of the solution discharged from the nozzles 34 is measured.

  When the measurement of the solution discharged from all the nozzles 34 of the coating head 22 and the setting of the length L of the solution based on the measurement are completed, the measurement for one coating head 22 is completed in the thirteenth step indicated by P13. It becomes. A similar operation is sequentially performed on the plurality of coating heads 22.

  Thus, in this embodiment, the length L of the solution discharged from the nozzle 34 of the coating head 22 is measured, and the discharge amount is calculated from the length. As shown in FIG. 10, since the length of the solution discharged from the nozzle 34 has a relationship that increases linearly as the discharge amount increases, the discharge amount can be accurately known from the length L of the solution from this relationship. it can.

  When the length L of the solution is obtained from the image signal S4 of the high-speed camera 48, the pixels of the light-receiving element (the light-receiving element of the solid-state image sensor included in the high-speed camera 48) corresponding to the contour portion of the solution image that causes an error There is only one each at the top and bottom of the solution. Therefore, for example, if the length L of the solution discharged from the nozzle 34 is the length of 100 light receiving elements, the error factor is two of 100 light receiving elements.

  On the other hand, in the conventional case where the amount of the solution is obtained by the projected area, if the solution ejected from the nozzle 34 corresponds to 100 pieces in the length direction and n pieces in the width direction, Since there are (200 + 2n) light receiving elements corresponding to the contour portion, this is an error factor in calculating the projected area of the solution.

  Therefore, according to this embodiment in which the discharge amount is obtained from the length L of the solution, the number of pixels that cause an error is extremely small as compared with the conventional case that is obtained from the projected area of the solution. Can be measured with high accuracy.

  When the solution is ejected from the nozzle 34, it is in the form of an elongated line, but it is deformed into a spherical shape as time elapses after being ejected by the surface tension of the solution itself. Therefore, in order to improve the measurement accuracy, it is preferable to measure the length L of the solution immediately after being discharged from the nozzle 34 or at a timing close thereto.

  Moreover, if the discharge length L of the solution discharged from the nozzle 34 can be measured with high accuracy, the discharge amount of the solution from the nozzle 34 can be set with high accuracy based on the discharge length L. That is, since the amount of solution discharged from the plurality of nozzles 34 of the coating head 22 can be set with high accuracy, the functional thin film can be formed on the substrate W with a uniform thickness. It becomes.

  In the above embodiment, an inkjet type coating apparatus that applies a voltage to a piezoelectric element as a driving unit and discharges the solution has been described as an example. However, as the coating apparatus, the solution is heated to remove bubbles in the solution. A system may be used in which the solution is discharged at the pressure by expansion, and in that case, a heater whose heating value varies depending on the voltage value is used as the driving means instead of the piezoelectric element.

  In addition, the high-speed camera and the light source of the measuring device are provided on the guide member of the base, but may be provided on a support standing on the base.

  Further, since the head table provided with the coating head can be driven in the Y direction, the measuring device is provided so as to be driven only in the X direction, and the Y direction is driven along the Y direction of the coating head by driving the coating head. Alternatively, the length of the solution discharged from a plurality of nozzles provided may be sequentially measured.

  Furthermore, although the example using a high-speed camera and a light source as the measuring device has been described, the measuring device may be any means that can measure the length of the solution discharged from the nozzle, for example, intersects with the solution discharge direction. A laser device and a light receiver for receiving the laser light oscillated from the laser device are arranged at predetermined intervals along the direction, and the time for the solution discharged from the nozzle to block the laser light oscillated from the laser device is set. The structure which measures and calculates | requires the length of the solution from the time may be sufficient.

  Moreover, although the solution was measured for 5 nozzles at a time, the number of nozzles to be measured may be more or less than 5, and the number is not limited.

  Further, the number of solutions imaged in the visual field range A of the high speed camera may be set based on the relationship between the length of the solution and the lens magnification of the high speed camera. That is, the total number of pixels in the visual field range A of the high-speed camera is determined. For this reason, when the solution is imaged as large as possible in the visual field range A, more pixels can be used for calculating the solution length L, thereby improving the resolution and increasing the measurement accuracy.

  Since the solution is long and long in the ejection direction, the lens magnification of the high-speed camera is set so that the solution is imaged almost full of the length of the visual field range A in the vertical direction. Thereby, the resolution is improved, so that the measurement accuracy can be increased. In this case, the number of solutions that can be accommodated in the horizontal direction of the field of view range A of the magnification of the set high-speed camera may be imaged at a time.

The front view which shows schematic structure of the coating device of one Embodiment of this invention. The side view of the coating device shown in FIG. The longitudinal cross-sectional view of an application | coating head. The figure which shows the lower surface in which the nozzle of the coating head was formed. The side view of a measuring device. Plan view of the measuring device The block diagram which shows a control system. The graph which shows the relationship between the voltage applied to a piezoelectric element, and the quantity of the solution discharged from a nozzle. The graph which shows the relationship between the voltage applied to a piezoelectric element, and the length of the solution discharged from a nozzle. The graph which shows the relationship between the quantity of the solution discharged from a nozzle, and the length of the solution discharged from a nozzle. The flowchart explaining the procedure which sets the quantity of the solution discharged from each nozzle of a coating head. Explanatory drawing which shows the solution discharged from five nozzles imaged with the high speed camera.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 22 ... Coating head, 35 ... Piezoelectric element (drive means), 41 ... Measuring apparatus (detection means), 48 ... High-speed camera (detection means), 49 ... Light source (detection means), 52 ... Control apparatus, 53 ... Timing setting apparatus.

Claims (4)

In the coating apparatus of the solution applying the solution to the substrate,
An application head having a nozzle for discharging the solution;
A driving means provided in the coating head, for discharging the solution from the nozzle by application of a voltage ;
Detecting means for detecting the length of the solution discharged from the nozzle in the discharge direction;
And a control means for controlling a voltage value applied to the driving means according to the length of the solution detected by the detecting means .   2. The solution coating apparatus according to claim 1, further comprising timing setting means for setting a timing for applying a driving signal to the driving means and a timing for detecting the length of the solution by the detecting means. In a method of applying a solution, a solution is applied to a substrate using an application head that discharges the solution from a nozzle by applying a voltage to a driving unit .
Detecting the length in the direction of ejection of the solution discharged from the nozzle, the voltage value that this detected and compared to the length set in advance the length of the solution is applied to the drive means on the basis of the comparison result A method for applying a solution, characterized in that control is performed . The discharge of the solution is performed by a plurality of nozzles provided in the coating head,
Detection of the length of the solution, using the imaging camera, the image of the discharged solution from two or more of the nozzle and performing based on the captured image obtained by imaging at a time by the image pickup camera according Item 4. A method for applying the solution according to Item 3 .

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