Washing method, washing device, and coating device

Abstract

To provide a technique that is able to satisfactorily discharge a high-viscosity treatment liquid from a deaeration unit.SOLUTION: When a deaeration unit 16 for deaeration of a high-viscosity treatment liquid is washed, a first diluted liquid having a viscosity lower than that of the treatment liquid is passed through the deaeration unit 16 first (a first liquid-passing step). After the first liquid-passing step, a second diluted liquid having a viscosity lower than that of the first diluted liquid is passed through the deaeration unit 16 (a second liquid-passing step). Thus, the treatment liquid can be satisfactorily discharged from the deaeration unit 16.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a cleaning technique for a degassing unit that degasses a highly viscous processing liquid. [Background technology]

[0002] Conventionally, in the manufacturing process of polyimide films used in flexible displays, a highly viscous treatment liquid containing a polyimide precursor (polyamic acid) is applied to a carrier substrate, and a degassing unit is used to remove air bubbles and dissolved gases in the treatment liquid.

[0003] A conventional coating apparatus equipped with a degassing unit is described, for example, in Patent Document 1. In the coating apparatus of Patent Document 1, a hollow fiber degassing module is used as the degassing unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-044465 A Summary of the Invention [Problem to be solved by the invention]

[0005] In this type of coating apparatus, it is necessary to clean the degassing unit when the processing liquid is replaced with another type of processing liquid, during regular maintenance, when the processing liquid remains for a certain period of time, etc. As a method for cleaning the degassing unit, for example, it is possible to supply high-pressure air into the degassing unit to discharge most of the processing liquid from the degassing unit, and then pass a solvent through the degassing unit to wash away the processing liquid remaining in the degassing unit.

[0006] However, since the treatment liquid is highly viscous, it is difficult to sufficiently discharge the treatment liquid from the degassing unit using the above cleaning method. In particular, when a hollow fiber degassing module is used as the degassing unit, the highly viscous treatment liquid is held in a plurality of fine tubular hollow fibers. In this case, it is difficult to uniformly supply high-pressure air to a plurality of hollow fibers. For this reason, air and solvent are concentrated in the hollow fibers from which the treatment liquid was discharged first, and there is a problem that the treatment liquid cannot be discharged from the other hollow fibers.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a technique capable of satisfactorily discharging a highly viscous treatment liquid from a degassing unit. [Means for solving the problem]

[0008] In order to solve the above problems, a first invention of the present application is a method for cleaning a degassing unit that degasses a highly viscous treatment liquid, the method including a first liquid passing step of passing a first diluent having a lower viscosity than the treatment liquid through the degassing unit, and a second liquid passing step of passing a second diluent having a lower viscosity than the first diluent through the degassing unit after the first liquid passing step.

[0009] A second invention of the present application is the cleaning method of the first invention, further comprising a first dilution step of diluting the treatment liquid with a solvent of the treatment liquid to produce the first diluted liquid before the first liquid passing step, and a second dilution step of diluting the first dilution liquid with the solvent after the first liquid passing step and before the second liquid passing step to produce the second diluted liquid.

[0010] A third invention of the present application is the cleaning method of the second invention, wherein in the first dilution process, the first dilution liquid is generated by supplying the solvent to the processing liquid stored in a dilution tank provided in a circulation line including the degassing unit, in the first liquid passing process, the first dilution liquid is supplied from the dilution tank to the degassing unit, in the second dilution process, the second dilution liquid is generated by supplying the solvent to the first dilution liquid returned from the degassing unit to the dilution tank, and in the second liquid passing process, the second dilution liquid is supplied from the dilution tank to the degassing unit.

[0011] A fourth invention of the present application is the cleaning method of the third invention, wherein in the first dilution process, the solvent is supplied to the treatment liquid stored in the dilution tank in an amount of 15 wt % or less of the treatment liquid stored in the dilution tank.

[0012] A fifth aspect of the present invention is a cleaning method according to the fourth aspect, wherein in the first dilution step, the solvent is supplied to the treatment liquid stored in the dilution tank in an amount of 5 wt % or more of the treatment liquid stored in the dilution tank.

[0013] A sixth aspect of the present invention is the cleaning method according to any one of the first to fifth aspects, wherein the degassing unit has a plurality of hollow fibers through which the treatment liquid passes.

[0014] A seventh invention of the present application is a cleaning device for a degassing unit that degasses a high-viscosity processing liquid, comprising: a circulation line connected to the degassing unit; a dilution tank provided in the circulation line; a circulation pump that generates a liquid flow in the circulation line between the dilution tank and the degassing unit; a solvent supply unit that supplies a solvent for the processing liquid to the dilution tank; and a control unit that controls the circulation pump and the solvent supply unit, wherein the control unit executes a first dilution step of producing a first dilution liquid by supplying the solvent from the solvent supply unit to the dilution tank; a first liquid passing step of passing the first dilution liquid through the degassing unit by driving the circulation pump after the first dilution step; a second dilution step of producing a second dilution liquid by supplying the solvent from the solvent supply unit to the dilution tank after the first liquid passing step; and a second liquid passing step of passing the second dilution liquid through the degassing unit by driving the circulation pump after the second dilution step.

[0015] An eighth invention of the present application is a cleaning apparatus according to the seventh invention, wherein in the first dilution process, the solvent is supplied to the processing liquid stored in the dilution tank in an amount of 15 wt% or less of the processing liquid stored in the dilution tank.

[0016] A ninth aspect of the present invention is a cleaning apparatus according to the eighth aspect, wherein in the first dilution process, the solvent is supplied to the processing liquid stored in the dilution tank in an amount of 5 wt% or more of the processing liquid stored in the dilution tank.

[0017] A tenth aspect of the present invention is the cleaning apparatus according to any one of the seventh to ninth aspects, wherein the degassing unit has a plurality of hollow fibers through which the treatment liquid passes.

[0018] An eleventh invention of the present application is a coating apparatus for applying a highly viscous processing liquid to a substrate, comprising: a coating section for applying the processing liquid to the substrate; and a liquid supply section for supplying the processing liquid to the coating section, wherein the liquid supply section has the degassing unit and a cleaning apparatus according to any one of the seventh to tenth inventions. Effect of the Invention

[0019] According to the first to eleventh aspects of the present invention, the high-viscosity treatment liquid in the degassing unit is replaced with a first diluent having a lower viscosity than the treatment liquid, and then replaced with a second diluent having a lower viscosity than the first diluent, thereby allowing the treatment liquid to be efficiently discharged from the degassing unit.

[0020] In particular, according to the second aspect of the present invention, the degassing unit can be cleaned without mixing in any substance other than the solute and solvent of the processing liquid.

[0021] In particular, according to the third aspect of the present invention, dilution and liquid passing can be repeated while circulating the liquid in a circulation line including a degassing unit and a dilution tank.

[0022] In particular, according to the fourth or eighth aspect of the present invention, the treatment liquid in the degassing unit can be satisfactorily replaced with the first diluent having a similar viscosity.

[0023] In particular, according to the fifth or ninth aspect of the present invention, the number of times dilution and liquid passing are repeated can be reduced.

[0024] In particular, according to the sixth or tenth aspect of the present invention, the treatment liquid can be effectively removed from the inside of the hollow fibers where the treatment liquid is likely to remain. [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is a diagram showing a configuration of a coating device. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a control block diagram of the coating device. [Figure 4] FIG. 2 is a diagram showing the configuration of a degassing unit. [Diagram 5] FIG. 2 is a diagram showing a configuration of a cleaning device. [Figure 6] 10 is a flowchart showing a procedure for cleaning the degassing unit. [Figure 7] FIG. 13 is a diagram showing the results of cleaning a degassing unit using a cleaning device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] <1. Configuration of the coating device> FIG. 1 is a diagram showing the configuration of a coating apparatus 1 according to one embodiment of the present invention. This coating apparatus 1 is used in a manufacturing process of a polyimide film that serves as a base material for a flexible display. In the manufacturing process of a polyimide film, first, in this coating apparatus 1, a high-viscosity treatment liquid (varnish) is applied to the upper surface of a glass carrier substrate 9 (hereinafter simply referred to as "substrate 9"). Then, in another device, the treatment liquid applied to the substrate 9 is subjected to treatments such as heating, decompression, and baking. In this way, a thin polyimide film is manufactured.

[0028] As shown in FIG. 1, the coating device 1 of the present embodiment includes a liquid supply unit 10, a coating unit 20, and a control unit 30.

[0029] The liquid supply unit 10 is a unit that supplies a high-viscosity processing liquid to the coating unit 20. As shown in FIG 1, the liquid supply unit 10 has a plurality of liquid supply tanks 11, a liquid supply pipe 12, a main pump 13, an assist pump 14, a filter 15, and a degassing unit 16.

[0030] The supply liquid tank 11 is a container for storing the treatment liquid before supply. The treatment liquid stored in the supply liquid tank 11 is, for example, a liquid containing a polyimide precursor (polyamic acid) as a solute and NMP (N-methyl-2-pyrrolidone) as a solvent. The concentration of the solute in the treatment liquid is, for example, 15 to 20 wt %. The viscosity of the treatment liquid is, for example, 1000 to 10000 cP (1 to 10 Pa·s). In the following description, "high viscosity" refers to a viscosity of 1000 cP (1 Pa·s) or more.

[0031] 1, the liquid supply unit 10 has six liquid supply tanks 11. However, the number of liquid supply tanks 11 included in the liquid supply unit 10 may be one to five, or seven or more.

[0032] The liquid supply pipe 12 is a pipe connecting the liquid supply tank 11 and the coating unit 20. An upstream end of the liquid supply pipe 12 is connected to the liquid supply tank 11 via an on-off valve 17. A downstream end of the liquid supply pipe 12 is connected to a nozzle 22 (described later) of the coating unit 20. In addition, a filter 15, an assist pump 14, a degassing unit 16, and a main pump 13 are provided on the path of the liquid supply pipe 12.

[0033] The main pump 13 is a pump for sending the processing liquid from the liquid supply pipe 12 to the nozzle 22. The main pump 13 is provided at a position downstream of the degassing unit 16 of the liquid supply pipe 12. As the main pump 13, for example, a tubephragm pump such as a CT (Coaxial Tubephragm) pump or a constant volume discharge PT (Parallel Tubephragm) pump is used.

[0034] The assist pump 14 is a pump for sending the treatment liquid downstream in the liquid supply pipe 12 together with the main pump 13. The assist pump 14 is provided in the liquid supply pipe 12 at a position downstream of the filter 15 and upstream of the degassing unit 16. As the assist pump 14, for example, a tubephragm pump such as a CT (Coaxial Tubephragm) pump or a constant volume discharge PT (Parallel Tubephragm) pump is used.

[0035] When the on-off valve 17 is opened and the main pump 13 and the assist pump 14 are operated, a flow of the treatment liquid from the liquid supply tank 11 to the coating unit 20 is formed in the liquid supply pipe 12. As a result, the treatment liquid is supplied from the liquid supply tank 11 to the coating unit 20. Note that the liquid supply unit 10 may further include a pressurizing mechanism that supplies gas to the liquid supply tank 11 to push out the treatment liquid from the liquid supply tank 11.

[0036] The filter 15 is a unit that filters the processing liquid. The filter 15 is provided at a position upstream of the assist pump 14 in the liquid supply pipe 12. The processing liquid is filtered by the filter 15. As a result, fine dust contained in the processing liquid is collected and removed by the filter 15. In the example of FIG. 1, the liquid supply unit 10 has one filter 15. However, the liquid supply unit 10 may have multiple filters 15. In that case, multiple filters 15 may be connected in parallel on the path of the liquid supply pipe 12. In addition, another filter 15 may be provided at a position downstream of the assist pump 14 in the liquid supply pipe 12.

[0037] The degassing unit 16 is a unit that reduces the amount of gas dissolved in the treatment liquid. The degassing unit 16 is provided in a position on the liquid supply pipe 12 downstream of the assist pump 14 and upstream of the main pump 13. A hollow fiber degassing module is used for the degassing unit 16. The coating apparatus 1 removes air bubbles in the treatment liquid and dissolved gas contained in the treatment liquid by the degassing unit 16. This makes it possible to prevent air bubbles from being generated in the treatment liquid when the treatment liquid applied to the substrate 9 is heated, depressurized, and baked in a later process.

[0038] Coating unit 20 is a unit that coats substrate 9 with the treatment liquid supplied from liquid supply unit 10. FIG. 2 is a perspective view of coating unit 20. As shown in FIGS. 1 and 2, coating unit 20 has a stage 21, nozzle 22, nozzle holder 23, and traveling mechanism 24. In the following, for ease of explanation, the movement direction of nozzle 22 in coating unit 20 is referred to as the "front-rear direction", and the horizontal direction perpendicular to the front-rear direction is referred to as the "left-right direction".

[0039] The stage 21 is a roughly rectangular parallelepiped holding platform on which the substrate 9 is placed and held. The stage 21 is formed, for example, from a single piece of stone material. The upper surface of the stage 21 is a flat substrate holding surface 211. The substrate holding surface 211 is provided with a large number of vacuum suction holes (not shown). When the substrate 9 is placed on the substrate holding surface 211, the lower surface of the substrate 9 is suctioned to the substrate holding surface 211 by the suction force of the vacuum suction holes. This fixes the substrate 9 in a horizontal position on the stage 21. In addition, a plurality of lift pins (not shown) are provided inside the stage 21. When the substrate 9 is to be removed from the stage 21, the plurality of lift pins protrude above the substrate holding surface 211. This causes the substrate 9 to be separated from the substrate holding surface 211.

[0040] The nozzle 22 is disposed above the stage 21. The nozzle 22 has a nozzle body 221 extending in the left-right direction. A slit-shaped discharge port 223 extending in the left-right direction is provided at the lower end of the nozzle body 221. The discharge port 223 faces the upper surface of the substrate 9 placed on the stage 21. The processing liquid supplied from the liquid supply unit 10 is stored inside the nozzle 22. Then, the processing liquid is discharged from the discharge port 223 towards the upper surface of the substrate 9.

[0041] The nozzle holding part 23 is a mechanism for holding the nozzle 22 above the substrate holding surface 211. The nozzle holding part 23 has a bridge part 231 extending in the left-right direction above the stage 21, and a pair of support parts 232 supporting both ends of the bridge part 231. The nozzle 22 is fixed to the lower surface of the bridge part 231. The nozzle holding part 23 also has a lifting mechanism 233 for adjusting the height of both ends of the bridge part 231.

[0042] The traveling mechanism 24 is a mechanism for moving the nozzle 22 in the front-rear direction. The traveling mechanism 24 has a pair of rails 241 and a pair of linear motors 242. The pair of rails 241 extend in the front-rear direction near the left and right side portions of the stage 21. The pair of rails 241 support the pair of support parts 232, respectively, and guide each of the support parts 232 in the front-rear direction. The pair of linear motors 242 move the pair of support parts 232 in the front-rear direction along the rails 241 by magnetic power. As a result, the nozzle 22 moves in the front-rear direction together with the nozzle holding part 23.

[0043] When performing the coating process, the coating unit 20 discharges the processing liquid from the discharge port 223 while moving the nozzle 22 in the front-rear direction above the substrate 9. In this way, the processing liquid is applied to the upper surface of the substrate 9.

[0044] The control unit 30 is a unit for controlling the operation of each part in the coating apparatus 1. FIG. 3 is a control block diagram of the coating apparatus 1. The control unit 30 is realized by, for example, a computer. As conceptually shown in FIG. 3, the control unit 30 has a processor 31 such as a CPU, a memory 32 such as a RAM, and a storage unit 33 such as a hard disk drive. A computer program P for operating the coating apparatus 1 is stored in the storage unit 33. The computer program P is read from a computer-readable storage medium such as a CD or a DVD, and stored in the storage unit 33. However, the computer program P may be downloaded to the control unit 30 via a network.

[0045] 3, the control unit 30 is electrically connected to the on-off valve 17, the main pump 13, the assist pump 14, and the linear motor 242 described above. The control unit 30 is also electrically connected to the pressure reducing pump 432, the first three-way valve 55, the second three-way valve 56, the vane 521, the circulation pump 53, the on-off valve 543, and the on-off valve 582 described below. The control unit 30 temporarily reads out the computer program P and data stored in the storage unit 33 into the memory 32, and the processor 31 performs arithmetic processing based on the computer program P and data, thereby controlling the operation of each unit in the coating apparatus 1. As a result, the coating process for the substrate 9 progresses.

[0046] <2. About the degassing unit> Next, the above-mentioned degassing unit 16 will be described in more detail. Fig. 4 is a diagram showing the configuration of the degassing unit 16. The degassing unit 16 in Fig. 4 is a hollow fiber degassing module. By using the hollow fiber degassing module, the degassing configuration can be made more space-saving than when a degassing tank is used.

[0047] As shown in FIG. 4, the degassing unit 16 has a casing 41 , a plurality of hollow fibers 42 , and a pressure reducing mechanism 43 .

[0048] The casing 41 is a cylindrical housing. The casing 41 has an inlet 411, an outlet 412, and two exhaust ports 413. The inlet 411 is provided at one end of the casing 41. The inlet 411 is connected to a downstream end of a portion of the liquid supply pipe 12 upstream of the degassing unit 16. The outlet 412 is provided at the other end of the casing 41. The outlet 412 is connected to an upstream end of a portion of the liquid supply pipe 12 downstream of the degassing unit 16. The two exhaust ports 413 are provided on a side surface of the casing 41. The exhaust port 413 is connected to a pressure reducing mechanism 43.

[0049] The hollow fibers 42 are long, tubular membranes. The hollow fibers 42 are formed of a gas-permeable membrane that allows only gas to pass through of liquids and gases. The inner diameter of the hollow fibers 42 is sufficiently smaller than the inner diameter of the liquid supply pipe 12. The inner diameter of the hollow fibers 42 is, for example, 0.5 mm to 3 mm. The plurality of hollow fibers 42 are housed in the casing 41 in a bundle state. The number of hollow fibers 42 housed in the casing 41 is, for example, 100 to 1000. However, the inner diameter of the hollow fibers 42 and the number of the hollow fibers 42 may be appropriately changed depending on the type and viscosity of the treatment liquid.

[0050] One end of each of the hollow fibers 42 is connected to a portion of the liquid supply pipe 12 upstream of the degassing unit 16 via an inlet 411. The other end of each of the hollow fibers 42 is connected to a portion of the liquid supply pipe 12 downstream of the degassing unit 16 via an outlet 412. When a flow of the treatment liquid is formed in the liquid supply pipe 12, the treatment liquid flows from the inlet 411 through the inside of each hollow fiber 42 to the outlet 412.

[0051] The pressure reduction mechanism 43 is a mechanism for reducing the pressure in the internal space of the casing 41. The pressure reduction mechanism 43 has a pressure reduction pipe 431 and a pressure reduction pump 432. One end of the pressure reduction pipe 431 is connected to the two exhaust ports 413 of the casing 41. The other end of the pressure reduction pipe 431 is connected to the pressure reduction pump 432. When the pressure reduction pump 432 is driven, the gas in the casing 41 is discharged to the outside through the pressure reduction pipe 431. As a result, the air pressure in the casing 41 decreases.

[0052] When the air pressure inside the casing 41 decreases, air bubbles contained in the treatment liquid inside the hollow fibers 42 and gas dissolved in the treatment liquid inside the hollow fibers 42 are discharged to the outside of the hollow fibers 42. This allows the treatment liquid passing through the hollow fibers 42 to be degassed.

[0053] <3. Cleaning equipment for degassing unit> In the coating apparatus 1 described above, it becomes necessary to clean the degassing unit 16 when the processing liquid is replaced with another type of processing liquid, when regular maintenance is performed, when the processing liquid remains for a certain period of time, etc. Therefore, the liquid supply section 10 of the coating apparatus 1 of this embodiment is provided with a cleaning device 50 for cleaning the degassing unit 16.

[0054] Fig. 5 is a diagram showing the configuration of the cleaning apparatus 50. As shown in Fig. 5, the cleaning apparatus 50 has a circulation line 51, a dilution tank 52, a circulation pump 53, a solvent supply unit 54, and a drainage unit 58. The above-mentioned control unit 30 also functions as a control unit that controls each unit of the cleaning apparatus 50.

[0055] The circulation line 51 is a ring-shaped pipe. In this embodiment, a first three-way valve 55 is provided on the liquid supply pipe 12 on the upstream side of the degassing unit 16, and a second three-way valve 56 is provided on the liquid supply pipe 12 on the downstream side of the degassing unit 16. One end of a cleaning pipe 57 separate from the liquid supply pipe 12 is connected to the first three-way valve 55, and the other end of the cleaning pipe 57 is connected to the second three-way valve 56.

[0056] The first three-way valve 55 has an upstream port 551 connected to the upstream liquid supply piping 12, a downstream port 552 connected to the downstream liquid supply piping 12, and a cleaning port 553 connected to the cleaning piping 57. The first three-way valve 55 is switchable between a "first state" in which the upstream port 551 and the downstream port 552 are open and the cleaning port 553 is closed, and a "second state" in which the upstream port 551 is closed and the downstream port 552 and the cleaning port 553 are open.

[0057] The second three-way valve 56 has an upstream port 561 connected to the upstream liquid supply piping 12, a downstream port 562 connected to the downstream liquid supply piping 12, and a cleaning port 563 connected to the cleaning piping 57. The second three-way valve 56 is switchable between a "third state" in which the upstream port 561 and the downstream port 562 are open and the cleaning port 563 is closed, and a "fourth state" in which the downstream port 562 is closed and the upstream port 561 and the cleaning port 553 are open.

[0058] During normal use when the treatment liquid is supplied to the coating section 20, the first three-way valve 55 is set to the "first state" and the second three-way valve 56 is set to the "third state". However, when cleaning the degassing unit 16, the first three-way valve 55 is set to the "second state" and the second three-way valve 56 is set to the "fourth state". As a result, a circular circulation line 51 including the degassing unit 16 and the cleaning piping 57 is formed.

[0059] The dilution tank 52 is a container that stores a diluting liquid for cleaning the degassing unit 16. The dilution tank 52 is provided in the cleaning pipe 57 of the circulation line 51. The dilution tank 52 has an agitating blade 521 therein. When the blade 521 is rotated, the liquid stored in the dilution tank 52 is agitated.

[0060] The circulation pump 53 is a pump that generates a liquid flow in the circulation line 51. The circulation pump 53 is provided in the cleaning pipe 57 of the circulation line 51. When the circulation pump 53 is operated in a state in which the first three-way valve 55 is switched to the above-mentioned "second state" and the second three-way valve 56 is switched to the above-mentioned "fourth state", a liquid flow from the dilution tank 52 through the first three-way valve 55 to the degassing unit 16 and a liquid flow from the degassing unit 16 through the second three-way valve 56 returning to the dilution tank 52 are formed in the circulation line 51.

[0061] The solvent supply unit 54 has a solvent supply source 541 and a solvent supply pipe 542. The solvent supply source 541 stores a solvent for the processing liquid. The solvent is, for example, NMP (N-methyl-2-pyrrolidone). An upstream end of the solvent supply pipe 542 is connected to the solvent supply source 541. A downstream end of the solvent supply pipe 542 is connected to the dilution tank 52. In addition, an opening / closing valve 543 is provided on the solvent supply pipe 542. When the opening / closing valve 543 is opened, the solvent is supplied from the solvent supply source 541 through the solvent supply pipe 542 to the dilution tank 52.

[0062] The drainage unit 58 has a drainage pipe 581. The drainage pipe 581 is connected to a position downstream of the circulation pump 53 of the cleaning pipe 57. An on-off valve 582 is provided in the drainage pipe 581. When the on-off valve 582 is opened, the diluent is discharged from the circulation line 51 through the drainage pipe 581 to the outside.

[0063] <4. Cleaning of the degassing unit> Next, a cleaning process of the degassing unit 16 using the above-mentioned cleaning device 50 will be described. Fig. 6 is a flow chart showing the procedure of the cleaning process. The process of Fig. 6 is executed by the above-mentioned control unit 30 controlling the operations of the first three-way valve 55, the second three-way valve 56, the vanes 521, the circulation pump 53, the on-off valve 543, and the on-off valve 582 in accordance with the computer program P.

[0064] When cleaning the degassing unit 16, first, the treatment liquid is stored in the dilution tank 52 (step S1). Specifically, the first three-way valve 55 is set to the above-mentioned "first state", and the second three-way valve 56 is set to the above-mentioned "fourth state". Then, the main pump 13 and the assist pump 14 are operated. As a result, the treatment liquid is supplied to the degassing unit 16, and the treatment liquid discharged from the degassing unit 16 flows into the cleaning pipe 57. As a result, the treatment liquid is stored in the dilution tank 52.

[0065] Once the treatment liquid is stored in the dilution tank 52, the first three-way valve 55 is then switched from the "first state" to the "second state". That is, the first three-way valve 55 is set to the "second state" and the second three-way valve 56 is set to the "fourth state". This forms a circular circulation line 51 including the degassing unit 16 and the dilution tank 52 (step S2).

[0066] Next, the processing liquid stored in the dilution tank 52 is diluted with the solvent (step S3: first dilution step). Specifically, by opening the on-off valve 543 of the solvent supply unit 54, the solvent is supplied from the solvent supply source 541 through the solvent supply pipe 542 to the dilution tank 52. When a predetermined amount of solvent has been supplied, the on-off valve 543 is closed to stop the supply of the solvent. Then, the blade 521 in the dilution tank 52 is rotated to agitate the processing liquid and the solvent. As a result, a first dilution liquid having a lower viscosity than the processing liquid is generated in the dilution tank 52.

[0067] If the amount of solvent supplied to the treatment liquid is too large, the viscosity of the first dilution liquid will be excessively reduced. In this case, in the next step S4, it will be difficult to satisfactorily replace the treatment liquid in the hollow fibers 42. For this reason, in step S3, it is desirable to supply the solvent from the solvent supply unit 54 to the dilution tank 52 in an amount of 15 wt % or less of the treatment liquid stored in the dilution tank 52. However, if the amount of solvent supplied to the treatment liquid is too small, it will be necessary to repeat dilution excessively. For this reason, in step S3, it is desirable to supply the solvent from the solvent supply unit 54 to the dilution tank 52 in an amount of 5 wt % or more of the treatment liquid stored in the dilution tank 52.

[0068] Moreover, the amount of the first diluent produced in step S3 is preferably equal to or greater than the amount of the treatment liquid in the degassing unit 16.

[0069] When the production of the first diluent is completed, the circulation pump 53 is then driven. This supplies the first diluent from the dilution tank 52 to the degassing unit 16. Then, the first diluent is passed through the hollow fibers 42 of the degassing unit 16 (step S4: first liquid passing step). This replaces the treatment liquid in the hollow fibers 42 with the first diluent. The first diluent is not as low in viscosity as a 100% solvent, but has a viscosity slightly lower than that of the treatment liquid. Therefore, the first diluent can effectively push out and replace the treatment liquid in the hollow fibers 42.

[0070] After circulating the first diluent in the circulation line 51 for a predetermined time, the circulation pump 53 is stopped. Then, the first diluent (strictly speaking, a mixture of the first diluent and the processing liquid) stored in the dilution tank 52 is diluted with the solvent (step S5: second dilution step). Specifically, the on-off valve 543 of the solvent supply unit 54 is opened to supply the solvent from the solvent supply source 541 through the solvent supply pipe 542 to the dilution tank 52. When a predetermined amount of the solvent is supplied, the on-off valve 543 is closed to stop the supply of the solvent. Then, the blade 521 in the dilution tank 52 is rotated to agitate the first diluent and the solvent. As a result, a second diluent having a lower viscosity than the first diluent is generated in the dilution tank 52.

[0071] In step S5, the same amount of solvent as in step S3 is supplied from the solvent supply unit 54 to the dilution tank 52. However, the amount of solvent supplied in step S5 may be different from the amount of solvent supplied in step S3.

[0072] When the production of the second diluent is completed, the circulation pump 53 is then driven. This supplies the second diluent from the dilution tank 52 to the degassing unit 16. Then, the second diluent is passed through the hollow fibers 42 of the degassing unit 16 (step S6: second liquid passing step). This replaces the first diluent in the hollow fibers 42 with the second diluent. The second diluent is not as low in viscosity as a 100% solvent, but has a viscosity slightly lower than that of the first diluent. Therefore, the second diluent can effectively push out and replace the first diluent in the hollow fibers 42.

[0073] After circulating the second diluent in the circulation line 51 for a predetermined time, the circulation pump 53 is stopped. Then, the second diluent (strictly speaking, a mixture of the first diluent and the second diluent) stored in the dilution tank 52 is diluted with the solvent (step S7: third dilution step). Specifically, the on-off valve 543 of the solvent supply unit 54 is opened to supply the solvent from the solvent supply source 541 through the solvent supply pipe 542 to the dilution tank 52. When a predetermined amount of the solvent is supplied, the on-off valve 543 is closed to stop the supply of the solvent. Then, the blade 521 in the dilution tank 52 is rotated to agitate the second diluent and the solvent. As a result, a third diluent having a lower viscosity than the second diluent is generated in the dilution tank 52.

[0074] In step S7, the same amount of solvent as in step S3 or step S5 is supplied from the solvent supply unit 54 to the dilution tank 52. However, the amount of solvent supplied in step S7 may be different from the amount of solvent supplied in step S3 or step S5.

[0075] When the production of the third diluent is completed, the circulation pump 53 is then driven. This causes the third diluent to be supplied from the dilution tank 52 to the degassing unit 16. Then, the third diluent is passed through the hollow fibers 42 of the degassing unit 16 (step S8: third liquid passing step). This causes the second diluent in the hollow fibers 42 to be replaced with the third diluent. The third diluent does not have a low viscosity like a 100% solvent, but has a viscosity slightly lower than that of the second diluent. Therefore, the third diluent can effectively push out and replace the second diluent in the hollow fibers 42.

[0076] After circulating the third diluent in the circulation line 51 for a predetermined time, the first three-way valve 55 is switched from the "second state" to the "first state", and the on-off valve 582 of the drainage unit 58 is opened. This causes the third diluent to be discharged from the circulation line 51 to the outside via the drainage piping 581 (step S9). When the discharge of the third diluent is completed, the circulation pump 53 is stopped, and the on-off valve 582 of the drainage unit 58 is closed again.

[0077] Thereafter, 100% of the solvent is stored in the dilution tank 52 (step S10). Specifically, by opening the on-off valve 543 of the solvent supply unit 54, the solvent is supplied from the solvent supply source 541 through the solvent supply pipe 542 to the dilution tank 52. As a result, an amount of the solvent equal to or greater than the capacity of the degassing unit 16 is stored in the dilution tank 52.

[0078] When the solvent is stored in the dilution tank 52, the first three-way valve 55 is switched from the "first state" to the "second state" again, and the circulation pump 53 is driven. This causes the solvent to be supplied from the dilution tank 52 to the degassing unit 16. Then, the solvent is passed through the hollow fibers 42 of the degassing unit 16 (step S11: solvent passing step). This causes the third diluent in the hollow fibers 42 to be replaced with the solvent. At this point, the hollow fibers 42 are filled with the third diluent, which has a lower viscosity than the treatment liquid, rather than the treatment liquid. Therefore, the inside of the hollow fibers 42 can be successfully replaced with the solvent.

[0079] After circulating the solvent in the circulation line 51 for a predetermined time, the first three-way valve 55 is switched from the "second state" back to the "first state", and the on-off valve 582 of the drainage part 58 is opened. This causes the solvent to be discharged from the circulation line 51 to the outside via the drainage pipe 581 (step S12).

[0080] As described above, in the cleaning device 50, the highly viscous treatment liquid in the degassing unit 16 is replaced with a first diluent having a lower viscosity than the treatment liquid, and then replaced with a second diluent having a lower viscosity than the first diluent. In this manner, the liquid in the degassing unit 16 is repeatedly replaced with diluents having gradually lower viscosities. This allows the liquid in the degassing unit 16 to be effectively replaced. Therefore, the treatment liquid can be effectively discharged from the degassing unit 16. In particular, the highly viscous treatment liquid can be effectively removed from the inside of the hollow fibers 42 where the treatment liquid is likely to remain.

[0081] In addition, in this cleaning apparatus 50, a circulation line 51 including the degassing unit 16 and a dilution tank 52 is provided, and a solvent for the processing liquid is supplied to the dilution tank 52 to generate a diluted liquid for cleaning. In this way, dilution and liquid passage can be repeated while circulating the liquid in the circulation line 51. In addition, the degassing unit 16 can be cleaned without mixing with substances other than the solute and solvent of the processing liquid.

[0082] By satisfactorily removing the processing liquid from the degassing unit 16, it is possible to prevent the processing liquid before and after replacement from becoming cloudy when the processing liquid is replaced with another type of processing liquid. It is also possible to prevent the processing liquid from solidifying and adhering in the degassing unit 16. It is also possible to prevent the generation of particles due to the solidification of the processing liquid.

[0083] <5. Experimental Results> FIG. 7 shows the results of cleaning the degassing unit 16 using a cleaning device 50 equivalent to the above. In the experiment of FIG. 7, the degassing unit 16, which is a hollow fiber degassing module, was filled with a treatment liquid, and then the degassing unit 16 was cleaned using a procedure equivalent to the above. As the treatment liquid, a high-viscosity liquid containing a polyimide precursor (polyamic acid) as a solute and NMP (N-methyl-2-pyrrolidone) as a solvent was used. The amount of treatment liquid initially stored in the dilution tank 52 was 1200 g.

[0084] The amount of solvent supplied to the dilution tank 52 in one dilution step was 1200 g (100 wt%) in Example 1 of FIG. 7, 240 g (20 wt%) in Example 2, and 120 g (10 wt%) in Example 3. Then, as in steps S3 to S8 above, the dilution step and the liquid passing step were repeated three times, and the cleaning results of the degassing unit 16 were evaluated. In the comparative example of FIG. 7, the degassing unit 16 was cleaned only with the solvent, without using the dilution liquid as described above.

[0085] 7, the amount of treatment liquid remaining in the plurality of hollow fibers 42 of the degassing unit 16 was reduced in Examples 1 to 3 compared to the comparative example. This shows that the treatment liquid can be satisfactorily discharged from the degassing unit 16 by repeatedly replacing the liquid in the degassing unit 16 with a diluent having a gradually lower viscosity.

[0086] In particular, in the case of Example 3, compared to Examples 1 and 2, the treatment liquid could be almost completely discharged from the hollow fibers 42 of the degassing unit 16. This shows that the cleaning performance is particularly improved when the amount of solvent supplied in one dilution step is 10 wt % relative to the treatment liquid. From this result, it is considered desirable to set the amount of solvent supplied in one dilution step to, for example, 5 wt % or more and 15 wt % or less relative to the amount of the treatment liquid.

[0087] <6. Variations> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

[0088] In the above embodiment, the dilution process in the dilution tank 52 is repeated three times. However, the dilution process in the dilution tank 52 may be repeated two times, or four or more times.

[0089] In the above embodiment, the cleaning device 50 has the solvent supply unit 54 that automatically supplies the solvent to the dilution tank 52. However, the solvent may be supplied to the dilution tank 52 manually by an operator.

[0090] In the above embodiment, the direction in which the diluent flows through the degassing unit 16 is the same as the direction in which the treatment liquid flows through the degassing unit 16 under normal conditions. However, the direction in which the diluent flows through the degassing unit 16 may be opposite to the direction in which the treatment liquid flows through the degassing unit 16 under normal conditions. In other words, the direction of circulation in the circulation line 51 may be opposite to that in the above embodiment.

[0091] In the above embodiment, the diluent or solvent after cleaning is discharged to the drain pipe 581 connected to the circulation line 51. However, the diluent or solvent after cleaning may be discharged to the outside via the liquid supply pipe 12 and the nozzle 22.

[0092] In the above embodiment, the liquid supply section 10 has one degassing unit 16. However, the liquid supply section 10 may have a plurality of degassing units 16. In this case, one cleaning device 50 may be provided for the plurality of degassing units 16. Furthermore, a cleaning device 50 may be provided for each of the degassing units 16.

[0093] In the above embodiment, the cleaning device 50 is incorporated in the liquid supply section 10 of the coating apparatus 1. However, the cleaning device 50 may be a device separate from the liquid supply section 10 of the coating apparatus 1. In that case, the degassing unit 16 may be removed from the liquid supply section 10 and set in the cleaning device 50 to perform the cleaning process.

[0094] Although the above-mentioned coating apparatus 1 is used in a process for manufacturing the base material of a flexible device, the coating apparatus of the present invention may be used in a process for forming a protective film on the surface of the base material after the device is formed. The coating apparatus of the present invention may be used in a process for applying an adhesive when bonding substrates together. The coating apparatus of the present invention may be used in a manufacturing process for liquid crystal display devices and semiconductor substrates other than flexible devices. The coating apparatus of the present invention may be used in a manufacturing process for batteries such as lithium ion secondary batteries and fuel cells.

[0095] In the above embodiment, a hollow fiber degassing module is used as the degassing unit 16. However, the degassing unit to be cleaned in the present invention is not limited to a hollow fiber degassing module. For example, a cleaning process similar to that described above may be performed on a degassing unit that stores a treatment liquid in a degassing tank and performs degassing by reducing the pressure inside the tank.

[0096] In addition, the details of the cleaning device and the coating device may differ from those shown in the drawings of the present application. Furthermore, the elements appearing in the above-mentioned embodiment and modified examples may be appropriately combined to the extent that no contradiction occurs. [Explanation of symbols]

[0097] 1 Coating equipment 9 Substrate 10 Liquid supply section 11 Liquid supply tank 12 Liquid supply piping 13 Main pump 14 Assist pump 15 Filters 16 Degassing unit 20 Application section 30 Control section 41 Casing 42 Hollow Fiber 43 Pressure reducing mechanism 50 Cleaning Equipment 51 Circulation Line 52 Dilution Tank 53 Circulation Pump 54 Solvent Supply Section 55 First three-way valve 56 2nd three-way valve 57 Cleaning piping 58 Drain

Claims

1. A method for cleaning a degassing unit that degasses a high-viscosity processing liquid, comprising the steps of: a first liquid passing step of passing a first diluent having a lower viscosity than the treatment liquid through the degassing unit; a second liquid passing step of passing a second diluent having a lower viscosity than the first diluent through the degassing unit after the first liquid passing step; The cleaning method according to claim 1,

2. 2. The cleaning method according to claim 1, a first dilution step of diluting the treatment liquid with a solvent for the treatment liquid to generate the first diluted liquid, prior to the first liquid passing step; a second dilution step of diluting the first dilution with the solvent after the first liquid passing step and before the second liquid passing step to generate the second dilution; The cleaning method further comprises:

3. 3. The cleaning method according to claim 2, In the first dilution step, the solvent is supplied to the treatment liquid stored in a dilution tank provided in a circulation line including the degassing unit to generate the first dilution liquid; In the first liquid passing step, the first dilution liquid is supplied from the dilution tank to the degassing unit, In the second dilution step, the solvent is supplied to the first dilution liquid returned from the degassing unit to the dilution tank to generate the second dilution liquid; In the second liquid passing step, the second diluting liquid is supplied from the dilution tank to the degassing unit.

4. 4. The cleaning method according to claim 3, The cleaning method, wherein in the first dilution step, the solvent is supplied to the processing liquid stored in the dilution tank in an amount of 15 wt % or less of the processing liquid stored in the dilution tank.

5. 5. The cleaning method according to claim 4, A cleaning method comprising: supplying, to the processing liquid stored in the dilution tank, the solvent in an amount of 5 wt % or more of the processing liquid stored in the dilution tank, in the first dilution step.

6. A cleaning method according to any one of claims 1 to 5, comprising: The degassing unit has a plurality of hollow fibers through which the treatment liquid passes.

7. A cleaning device for a degassing unit that degasses a high-viscosity processing liquid, comprising: A circulation line connected to the degassing unit; A dilution tank provided in the circulation line; a circulation pump that generates a liquid flow in the circulation line between the dilution tank and the degassing unit; a solvent supply unit for supplying a solvent for the treatment liquid to the dilution tank; A control unit that controls the circulation pump and the solvent supply unit; Equipped with The control unit is a first dilution step of producing a first dilution solution by supplying the solvent from the solvent supply unit to the dilution tank; a first liquid passing step of passing the first dilution liquid through the degassing unit by driving the circulation pump after the first dilution step; a second dilution step of producing a second diluted solution by supplying the solvent from the solvent supply unit to the dilution tank after the first liquid passing step; a second liquid passing step of passing the second dilution liquid through the degassing unit by driving the circulation pump after the second dilution step; Perform the cleaning equipment.

8. 8. The cleaning device according to claim 7, In the first dilution step, the solvent is supplied to the processing liquid stored in the dilution tank in an amount of 15 wt % or less of the processing liquid stored in the dilution tank.

9. 9. The cleaning device according to claim 8, In the first dilution step, the solvent is supplied to the processing liquid stored in the dilution tank in an amount of 5 wt % or more of the processing liquid stored in the dilution tank.

10. A cleaning device according to any one of claims 7 to 9, The degassing unit has a plurality of hollow fibers through which the treatment liquid passes.

11. A coating apparatus that coats a high-viscosity processing liquid on a substrate, comprising: a coating unit that coats the treatment liquid on a substrate; a liquid supply unit that supplies the treatment liquid to the coating unit; Equipped with The liquid supply unit includes: The degassing unit; A cleaning device according to any one of claims 7 to 9, The coating device has

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