JP5949038B2 - Coating device - Google Patents

Description

  The present invention relates to a coating apparatus that feeds a coating liquid from a sub tank to a die head using a coating pump.

  As a coating apparatus for coating a material on a sheet material in a semiconductor production process or any other coating process, the one shown in FIG. 5 is known. This coating apparatus includes a primary tank 1 that stores a coating liquid manufactured in a separate process, and a sub tank 2 that supplies the coating liquid from the primary container 1. A sub-tank liquid feeding pipe R1 is provided. A die head liquid feeding pipe R2 is provided between the sub tank 2 and the die head 3, and a coating pump P2 is installed in the die head liquid feeding pipe R2. Then, the coating pump P2 is operated to feed the liquid from the sub tank 2 to the die head 3, and the coating liquid is slightly pushed out from the slit provided in the die head 3. On the other hand, the sheet material is wound on a roll (not shown), and is unwound from the roll and travels so as to wind around the back roller 4. The gap between the die head 3 and the back roller 4 is about 120 to 150 μm, and the coating liquid is applied to the sheet material by bringing the traveling sheet material into contact with the coating liquid extruded into the gap. The thickness of the coating film is about 100 to 150 μm, and the required film thickness accuracy is within 1 μm. A large variation in film thickness and coating mass affects the performance and quality of the manufactured secondary battery. In the figure, V1 indicates a return valve. When not applied, the return valve V1 is closed, and the coating liquid is returned to the sub tank 2 through the return pipe R4. Further, at the time of application, both the return valve V1 and the application valve V2 are opened.

  In this apparatus, since the coating liquid in the sub tank 2 decreases with long-time coating, the sub tank 2 is provided with a lower limit sensor LL and an intermediate sensor ML. When the decrease is detected, feeding of the coating liquid from the primary tank 1 is started. Further, when the intermediate sensor ML detects an increase in the coating liquid, the liquid feeding is stopped.

  Patent Document 1 proposes a coating apparatus in which a sub tank can be moved up and down using a motor and a ball screw. This device is provided with a level sensor that detects the liquid level of the coating liquid in the sub-tank. When this level sensor detects a liquid level fluctuation, the sub-tank itself is raised using a motor and a ball screw. Maintain liquid level.

  Patent Document 2 also proposes a coating apparatus in which a sub tank is configured to be movable up and down. The sub tank has an overflow tank structure, and before the start of coating, the entire sub tank is moved in the vertical direction so that the liquid level coincides with the tip height of the coating nozzle. Then, the pressure feeding device installed in the pipe between the sub tank and the coating nozzle is operated to feed the coating liquid to the coating nozzle, and the coating is started.

JP 2008-264782 A JP 2001-321709 A

  However, in the coating apparatus shown in FIG. 5, even if the liquid level of the coating liquid in the sub tank 2 is controlled by the lower limit sensor LL and the intermediate sensor ML, it is difficult to prevent the fluctuation of the liquid level. And since the primary pressure with respect to the coating pump P2 changes with this liquid level fluctuation | variation, even if it rotates the coating pump P2 by fixed rotation speed, the flow volume which flows through the coating pump P2 changes, and it discharges from the die head 3. The amount of coating solution was fluctuating.

  That is, as shown in FIG. 5, in this apparatus, when the liquid level in the sub tank 2 decreases and the lower limit sensor LL detects the liquid level at time T1, supply of the coating liquid from the primary tank is started. At this time, since the liquid level in the sub tank 2 is low and the primary pressure with respect to the coating pump P2 is small, the flow rate through the coating pump P2 is small. With the supply from the primary tank, the liquid level in the sub tank 2 rises, the primary pressure for the application pump P2 increases, and the flow rate flowing through the application pump P2 also increases. When the intermediate sensor ML detects the liquid level in the sub tank 2 at time T2, the supply of the coating liquid from the primary tank is stopped. With this stop, the liquid level in the sub-tank 2 gradually decreases, and with this decrease, the primary pressure for the application pump P2 also decreases, and the flow rate flowing through the application pump P2 also decreases. As the amount of the coating solution varies, the thickness and coating mass of the coating film formed on the sheet material become non-uniform, and stable quality coating cannot be performed.

  On the other hand, there is a method in which the space between the lower limit sensor LL and the intermediate sensor ML is narrowed to frequently control liquid feeding from the primary tank 1, but this method also applies the coating liquid in the sub tank 2. However, the liquid level fluctuation cannot be completely eliminated. Moreover, since it is necessary to frequently control the liquid feed pump P1 of the sub-tank liquid feed pipe R1, the service life thereof is reduced. Although it is possible to reduce the liquid level fluctuation by increasing the capacity of the sub tank 2, in this method, the coating liquid is stored in the sub tank 2 for a long time, and the state of the coating liquid may change. Becomes higher.

  Further, in the coating apparatus described in Patent Document 1, since the motor is controlled after detecting the liquid level fluctuation, a control delay during this time cannot be avoided. And there exists a problem that the quantity of the coating liquid sent by this control delay fluctuates.

  Further, in the coating apparatus described in Patent Document 2, the liquid level of the sub tank can be made to coincide with a predetermined height before the start of coating, but there is a problem that the liquid level fluctuation during the coating process cannot be prevented.

  Therefore, the present invention is a coating apparatus that uses a coating pump to feed a coating solution to a die head, and maintains the primary pressure to the coating pump at a constant level to stabilize the solution feeding to the die head, thereby operating for a long time. Even so, an object of the present invention is to provide a coating apparatus capable of forming a uniform coating film.

In order to achieve the above object, a coating apparatus according to the present invention includes a sub tank that stores a coating liquid, and a die head that applies a coating liquid fed from the sub tank to an object to be coated, and is provided between the sub tank and the die head. In a coating apparatus for feeding the coating liquid in the sub tank to the die head by a coating pump installed in the die head liquid feeding pipe, the sub tank overflows from the sub tank main body to which the die head liquid feeding pipe is connected and the sub tank main body. A switching valve that includes an overflow receiving portion that receives the coating liquid and a circulation pipe that circulates and supplies the coating liquid in the overflow receiving section to the sub-tank body, and changes the liquid feeding direction of the coating liquid according to opening and closing of the die head liquid feeding pipe. Is connected, and this switching valve is connected to the overflow receiving part. Turn for piping and said Rukoto provided.

  According to the present invention, the sub tank is constituted by the sub tank main body and the overflow receiving portion, and after the coating liquid overflowing from the sub tank main body is received by the overflow receiving portion, the coating liquid in the overflow receiving portion is circulated to the sub tank main body.

  Therefore, by performing this circulation over the entire process from the start to the end of the coating process, the sub tank body can be maintained in an overflow state, and the liquid level can be kept constant. And since the pipe for die head feeding is connected to the sub tank body, the primary pressure for the coating pump installed in the pipe for feeding the die head can be kept constant, and the feeding to the die head can be stabilized. Even when operated for a long time, a uniform coating film can be stably formed.

Explanatory drawing of the 1st Embodiment of this invention Explanatory drawing of the 2nd Embodiment of this invention Explanatory drawing of the 3rd Embodiment of this invention Explanatory drawing of the 4th Embodiment of this invention Explanatory drawing of conventional coating equipment Explanatory drawing which shows the relationship between the sub tank liquid level and the coating pump flow volume in the conventional coating device.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 of the drawings is an explanatory diagram of a first embodiment of the present invention.
The coating apparatus 10 according to the first embodiment includes a sub-tank 2 that contains a coating liquid and a die head 3 that applies a coating liquid fed from the sub-tank 2 as essential components. In addition, it is desirable to provide a primary tank 1 for storing a coating solution manufactured in a separate process. The coating apparatus according to this embodiment includes a primary tank 1. The coating liquid in the primary tank 1 is sent to the sub tank 2, and the coating liquid necessary for coating is supplied from the sub tank 2 to the die head 3. Yes. For this reason, between the primary tank 1 and the sub-tank 2, a sub-tank liquid feeding pipe R <b> 1 that feeds the coating liquid stored in the primary tank 1 to the sub-tank 2 is provided. Further, between the sub tank 2 and the die head 3, there is provided a die head liquid supply pipe R2 for supplying the coating liquid contained in the sub tank 2 to the die head 3, and in the middle of the die head liquid supply pipe R2. Is provided with a coating pump P2.

  Next, the sub-tank 2 includes a sub-tank main body 21 to which the die head liquid feeding pipe R2 is connected to a side surface, and an overflow receiving portion 22 that receives the coating liquid overflowing from the sub-tank main body 21. In this embodiment, the sub-tank main body 21 is arranged in the center of the overflow receiving part 22, and the application liquid overflowing from the periphery of the upper opening of the sub-tank main body 21 is received by the overflow receiving part 22. In addition to the sub tank main body 21 and the overflow receiving part 22, the sub tank 2 includes a circulation pipe R 3 that circulates and supplies the coating liquid in the overflow receiving part 22 to the sub tank main body. In this way, the sub tank main body 21, the overflow receiving part 22 and the circulation pipe R3 constitute a circulation path for circulating the coating liquid. For this reason, the subtank main body 21 is maintained in the overflow state throughout the entire process from the start to the end of the coating process, the overflowed coating liquid is received by the overflow receiving part 22, and the coating liquid in the overflow receiving part 22 is received. 21 can be circulated. During this period, that is, throughout the entire process from the start to the end of the coating process, the sub tank main body 21 is maintained in the overflow state, so that the liquid level can be kept constant. Since the sub-tank main body 21 is connected to the die head liquid feeding pipe R2, the primary pressure applied to the coating pump P2 installed in the die head liquid feeding pipe R2 is kept constant, and the sub head main body 21 is fed to the die head 3. The liquid can be stabilized.

Next, the sub tank main body 21 will be described.
As described above, the sub tank main body 21 is connected to the die head liquid feeding pipe R2 connected to the die head 3, and the liquid level is kept constant throughout the entire process from the start to the end of the coating process. It plays the role of keeping the primary pressure for the coating pump P2 constant. Since the role of the sub-tank main body 21 is such, its volume may be small. By using the sub tank main body 21 having a small volume, there is an advantage that recoagulation of the coating liquid in the sub tank main body 21 can be prevented.

  The die head liquid feeding pipe R <b> 2 is connected to the side surface of the sub tank main body 21. Since the bubbles contained in the coating liquid in the sub tank main body 21 rise in the coating liquid, they are removed together with the overflowing coating liquid. For this reason, it is possible to prevent bubbles from being mixed into the die head liquid feeding pipe R2 connected to the side surface of the sub tank main body 21. Further, since the foreign matter contained in the coating liquid is deposited on the bottom of the sub tank main body 21, it is possible to prevent the foreign matter from being supplied to the die head 3 through the die head liquid feeding pipe R 2 connected to the side surface of the sub tank main body 21. You can also.

  Next, a liquid level sensor L1 is installed in the vicinity of the opening of the sub tank main body 21, and the liquid level of the sub tank main body 21 is constantly monitored. If the liquid level of the sub tank main body 21 is lowered, the overflow state of the sub tank main body 21 cannot be maintained, and it can be determined that the sub tank main body 21 is in an abnormal state and the application can be stopped. As such an abnormal state, for example, a failure of a circulation pump P3 installed in a circulation pipe R3, which will be described later, a clogged filter F3, or the like can be assumed.

  In addition, in order to remove the settled foreign material, the drain D1 is installed in the lowest position on the bottom surface of the sub tank main body 21. In this embodiment, the bottom surface of the sub tank main body 21 has a conical inclined surface, and the drain D1 is installed at the lowest central portion. Then, by opening the drain D1 in a timely manner, foreign matters that have been precipitated by long-term operation can be removed.

Next, the overflow receiving part 22 will be described.
The overflow receiving part 22 has a role of receiving the coating liquid overflowed from the sub tank main body 21 and circulatingly supplying the coating liquid to the sub tank main body 21 through the circulation pipe R3. The circulation pipe R3 is connected to the bottom surface of the overflow receiving part 22, and a circulation pump P3 is provided. By operating the circulation pump P3, the coating liquid in the overflow receiving part 22 is supplied to the sub tank main body 21. Can be circulated and fed. Note that a filter F3 is disposed in the circulation pipe R3, and foreign matters generated in the overflow receiving portion 22 can be filtered by passing through the filter F3.

  The overflow receiver 22 monitors the amount of the coating liquid present in the sub-tank 2, and reduces the amount of coating liquid supplied from the primary tank 1 to the sub-tank body 21 when the coating liquid is large. Has the role of increasing the amount of the coating liquid supplied from the primary tank 1 to the sub tank main body 21. In order to fulfill this role, the liquid level sensors L2 and L3 are installed in the overflow receiving part 22, and the liquid level of the coating liquid in the overflow receiving part 22 is constantly monitored.

  If the amount of coating liquid supplied from the primary tank 1 to the sub tank 2 is larger than the amount of coating liquid discharged from the sub tank 2 through the die head liquid feeding pipe R2, the sub tank The amount of coating solution present in 2 increases. Since the sub-tank main body 21 maintains the overflow state, the amount of the coating liquid stored in the sub-tank main body 21 does not change. Therefore, the increased amount of the coating liquid in the sub-tank 2 is applied in the overflow receiving portion 22. Equal to the increase in liquid. That is, when the amount of the coating liquid supplied to the sub tank 2 is larger than the amount of the coating liquid discharged from the sub tank 2, the amount of the coating liquid stored in the overflow receiving portion 22 increases. Therefore, when the liquid level is detected by the sensor L2 disposed at a higher position of the two liquid level sensors, the amount of the coating liquid discharged from the sub tank 2 is supplied to the sub tank 2 from the primary tank 1. It is determined that the amount of coating liquid to be applied is large, and the supply amount from the primary tank 1 is reduced or the supply is stopped. Even when the supply from the primary tank 1 is stopped, since the coating liquid in the overflow receiving portion 22 is supplied to the sub tank main body 21, the overflow state of the sub tank main body 21 can be maintained.

  On the other hand, when the amount of the coating liquid supplied from the primary tank 1 to the sub tank 2 is smaller than the amount of the coating liquid discharged from the sub tank 2 through the die head liquid feeding pipe R2, the coating is continued for a long time. Then, the overflow of the sub tank main body 21 cannot be maintained. In this case, since the liquid level of the coating liquid in the overflow receiving portion 22 is lowered, when the liquid level is detected by the sensor L3 arranged at the lower position of the two liquid level sensors, the liquid is discharged from the sub tank 2. It is determined that the amount of the coating liquid supplied from the primary tank 1 to the sub tank 2 is smaller than the amount of the coating liquid, and the supply amount from the primary tank 1 is increased or the supply is resumed.

  In addition, in order to remove the settled foreign matter, the drain D2 is installed at the lowest position on the bottom surface of the overflow receiving portion 22. That is, the overflow receiving portion 22 has a bottom surface that is simply inclined in one direction, and the drain D2 is installed at the lowest end. And the settled foreign material can be removed by opening the drain D2 in a timely manner.

  Next, the sub tank liquid supply pipe R1 will be described. Since the coating liquid circulates in the circulation path between the sub tank main body 21 and the overflow receiving part 22, the coating liquid in the primary tank 1 may be supplied to any position in this circulation path. In the first embodiment, the discharge port of the sub-tank liquid feeding pipe R <b> 1 is arranged in the sub-tank main body 21, and the coating liquid in the primary tank 1 is supplied to the sub-tank main body 21. For this reason, the coating liquid supplied from the primary tank 1 through the sub tank feeding pipe R1 and the coating supplied to the sub tank main body 21 through the circulation pipe R3 accommodated in the overflow receiving portion 22 are supplied. Both liquids will be supplied. The subtank liquid supply pipe R1 is provided with a liquid supply pump P1 and a filter F1, and the liquid supply pump P1 is operated to supply the coating liquid in the primary tank 1 to the subtank main body 21. Further, by passing through the filter F1, dust and foreign matters in the coating liquid are removed to obtain a clean coating liquid.

Next, the die head liquid feeding pipe R2 and the return pipe R4 branched from the die head liquid feeding pipe R2 will be described.
The die head liquid feeding pipe R2 feeds the coating liquid in the sub tank main body 21 to the die head 3. For this reason, a coating pump P2 is installed in the middle of the die head liquid feeding pipe R2. The coating liquid in the sub tank body 21 can be supplied to the die head 3 by operating the coating pump P2. At this time, since the primary pressure applied to the coating pump P2 is maintained constant, the flow rate of the coating liquid to be fed can be maintained constant, and the amount of the coating liquid discharged from the die head 3 is also stabilized. A filter F2 is installed between the coating pump P2 and the die head 3, and liquid is fed to the die head 3 through the filter F2. For this reason, the foreign material produced | generated in the middle of the pipe | tube R2 for die head liquid feeding can be removed, Therefore, a clean coating liquid can be supplied to the die head 3. FIG.

A return valve V1 and a coating valve V2 are sequentially provided in the die head liquid supply pipe R2.
The return valve V1 changes the liquid feeding direction of the coating liquid according to the opening and closing thereof. When not applied, the return valve V1 is closed to stop the liquid supply to the die head 3, and the application liquid is supplied to the return pipe R4 branched from the die head liquid supply pipe R2. Further, the liquid supply to the return pipe R4 is stopped by opening the return valve V1, and then the coating liquid can be fed to the die head 3 by opening the coating valve V2. The return valve V1 also has a function of improving the rising characteristics of the coating liquid when the coating valve V2 is opened by applying a back pressure to the die head liquid feeding pipe R2.

  By the way, by repeatedly opening and closing the return valve V1, a lump of coating liquid may be caught on the valve seal surface. The coating liquid supplied to the return pipe R4 may contain a lump of the coating liquid thus generated.

  When such a lump of coating solution is supplied to the die head 3, the coating film formed on the object to be coated becomes non-uniform, which causes a problem that stable quality coating cannot be performed. For example, when the die head 3 extrudes a coating liquid slightly from a minute slit-shaped gap and the coating object is brought into contact with the slight coating liquid, the coating is performed between the tip of the die head and the coating object. The gap is only 120 to 150 μm. When the above-mentioned foreign matter is caught in such a minute gap, streaky coating unevenness occurs. Further, such foreign matters and lumps of the coating liquid may pass through the die head liquid feeding pipe R2, and the filter F2 may be clogged, and the life of the filter F2 and the coating pump P2 may be shortened.

  Therefore, in the first embodiment, the return pipe R4 is connected to the overflow receiving part 22, and the coating liquid in the return pipe R4 is fed to the overflow receiving part 22. In the overflow receiving part 22, the foreign substance in the coating liquid is precipitated, and the foreign substance in the coating liquid thus precipitated is removed by the drain D2, and the foreign substance in the coating liquid that is not removed by the drain D2 is also removed by passing through the filter F3. Yes. Therefore, the foreign substances of these coating liquids are not supplied to the die head liquid feeding pipe R2 and the die head 3 through the sub tank main body 21. For this reason, it is possible to prevent uneven coating due to the foreign matter of the coating liquid generated in the return valve V1. Further, it is possible to reduce the clogging of the filter F2, reduce the change in the output of the coating pump P2, and send the coating liquid at a stable flow rate to the die head 3. Moreover, since the output change of the coating pump P2 can be reduced, the life of the coating pump P2 can be extended.

  Next, as the die head 3 applied to this coating apparatus, for example, the die head 3 having a minute slit-like gap at the tip of the die head 3 can be used. In such a die head 3, the coating liquid can be pushed out from the slit so that the coating liquid slightly protrudes from the tip of the die head 3, and the coating object can be applied in contact with the coating liquid thus slightly projected. As the object to be coated, a wound sheet material can be employed. For example, a wound foil. Then, the back roller 4 is arranged through a gap of 120 to 150 μm from the tip of the die head 3, and the coating liquid can be applied to the sheet material while running the wound sheet material on the back roller 4. .

Next, the usage method of this coating device is demonstrated.
This coating apparatus uses the sub-tank main body 21 in an overflow state throughout the entire process from the start to the end of the coating process. At this time, the coating liquid supplied to the sub-tank main body 21 is fed from the primary tank 1 through the sub-tank liquid feeding pipe R1 and from the overflow receiving part 22 through the circulation pipe R3. Both of the coating liquids to be applied. On the other hand, the coating liquid discharged from the sub tank main body 21 is both the coating liquid fed through the die head liquid feeding pipe R <b> 2 and the coating liquid overflowing from the sub tank main body 21.

The coating liquid sent from the overflow receiving part 22 includes the coating liquid sent to the overflow receiving part 22 through the return pipe R4 in addition to the coating liquid overflowed from the sub tank main body 21. Yes.
Therefore, when the sensor L2 detects that the amount of the coating liquid supplied from the primary tank 1 to the sub tank 2 is large, the supply amount from the primary tank 1 is reduced or the supply is stopped. When the sensor L3 detects that the amount of the coating liquid supplied from the primary tank 1 to the sub tank 2 is small, the supply amount from the primary tank 1 is increased or the supply is resumed. Further, when the sensor L1 detects a decrease in the liquid level of the sub tank main body 21, the coating device is stopped.

  Further, when not applied, the return valve V1 is closed, and the application liquid is sent to the overflow receiving part 22 through the return pipe R4. In addition, the drains D1 and D2 are opened in a timely manner to remove the precipitated foreign matter.

Next, a second embodiment of the present invention will be described with reference to FIG.
The coating device 20 of the second embodiment is different from the coating device 10 of the first embodiment in the configuration of the sub tank 2. That is, in the first embodiment, the sub tank 2 is configured by disposing the sub tank main body 21 in the center of the overflow receiving portion 22, but in the second embodiment, the sub tank 2 is composed of two tanks having steps. Is configured. That is, of the two tanks, the tank having a high top opening is the sub tank main body 21, the other tank is the overflow receiving part 22, and the coating liquid overflowing from the sub tank main body 21 is received by the overflow receiving part 22. .
The bottom surface of the sub tank main body 21 is an inclined surface that is simply inclined in one direction, and the drain D1 is installed at the lowest end.

Next, a third embodiment of the present invention will be described with reference to FIG.
The coating device 30 according to the third embodiment is different from the first embodiment in that a sub-tank liquid-feeding pipe R <b> 1 that feeds the coating liquid stored in the primary tank 1 to the sub-tank 2 is connected to the overflow receiver 22. This is different from the coating apparatus 10. Accordingly, the coating liquid sent from the primary tank 1 to the overflow receiving part 22 through the sub tank liquid feeding pipe R1 is sent to the overflow receiving part 22 from the sub tank main body 21 or from the return pipe R4. After mixing with the applied coating solution, the solution is sent to the sub tank main body 21 through the circulation pipe R3, and is sent from the sub tank main body 21 to the die head 3.

  By the way, the coating liquid stored in the primary tank 1 is generally low in viscosity, whereas the coating liquid sent from the return pipe R4 is generally high in viscosity. The viscosity change of the coating solution fed to the die head 3 can be reduced.

  Further, since the coating liquid stored in the primary tank 1 is not directly sent to the sub tank main body 21, the amount of the coating liquid supplied to the sub tank main body 21 is reduced. For this reason, the capacity | capacitance of the subtank main body 21 can be made small. As a result, the coating liquid supplied to the sub-tank main body 21 is quickly sent to the die head 3 and the time for staying in the sub-tank main body 21 is shortened. Can be reduced. In addition, since the coating liquid with little change in the state of the coating liquid and generation of foreign matter is further fed to the die head 3 through the filter F2, there is an advantage that a clean coating liquid can be fed.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
The coating apparatus 40 of the fourth embodiment is different from the coating apparatus 10 of the first embodiment in that the return valve V1 and the return pipe R4 are not provided. Such an apparatus is suitable for continuous application such as stripe application, and can apply the application liquid by opening / closing the application valve V2 and controlling the rotation of the application pump P2.

  The coating apparatus according to the present invention can be used in a semiconductor production process or any other coating process. In particular, the coating film thickness and the coating mass can be accurately controlled even after long-time coating, which is suitable for a coating process with strict required accuracy.

DESCRIPTION OF SYMBOLS 1 Primary tank 2 Sub tank 10 Application | coating apparatus 20 Application | coating apparatus 21 Sub tank main body 22 Overflow receiving part 3 Die head 30 Application | coating apparatus 4 Back roller 40 Application | coating apparatus R1 Sub tank feed piping R2 Die head feed piping R3 Circulation piping R4 Return piping P1 Liquid feed pump P2 Application pump P3 Circulation pump LL Lower limit sensor ML Intermediate sensor L1, L2, L3 Liquid level sensor F1, F2, F3 Filter D1, D2 Drain V1 Return valve V2 Application valve

Claims (6)

A sub-tank that contains the coating liquid and a die head that applies the coating liquid sent from the sub-tank to the object to be coated are provided in the sub-tank by a coating pump installed in a die-head feeding pipe between the sub-tank and the die head. In a coating device for feeding a coating solution to a die head,
The sub tank includes a sub tank main body to which the die head liquid feeding pipe is connected, an overflow receiving part for receiving the coating liquid overflowed from the sub tank main body, and a circulation pipe for circulating the coating liquid in the overflow receiving part to the sub tank main body. Prepared ,
The die head switching valve for changing the feeding direction of the coating liquid according to the opening and closing the liquid feed pipe is installed, and characterized Rukoto return pipe is provided connecting the overflow receiving section and the switching valve A coating device.   The coating apparatus according to claim 1, wherein the die head liquid feeding pipe is connected to a side surface of the sub tank main body. The circulation pipe is connected to the bottom of the overflow receiving section, and coating apparatus according to claim 1 or 2, characterized in that filter for filtering foreign matter in the circulation pipe is installed. Said sub-tank main body and at least one of the overflow receiving section, any one of claims 1 to 3, the drain to remove foreign substances precipitated coating solution, characterized in that it is provided connected to the bottom The coating apparatus as described in. A primary tank that stores a coating liquid to be supplied to the sub-tank, and a sensor that detects the amount of the coating liquid in the overflow receiving portion and controls the amount of the coating liquid fed from the primary tank to the sub-tank; an application unit according to claim 1, any one of 4, characterized in that it comprises a. The coating apparatus according to claim 5 , wherein a filter for filtering foreign matter is installed in a sub-tank liquid feeding pipe that connects the primary tank and the sub-tank.

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