JP7747692B2 - Cleaning method, cleaning device, and coating device - Google Patents

Description

The present invention relates to cleaning technology for degassing units that degas highly viscous processing liquids.

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

A conventional coating device equipped with a degassing unit is described, for example, in Patent Document 1. The coating device in Patent Document 1 uses a hollow fiber degassing module as the degassing unit.

Japanese Patent Application Laid-Open No. 2020-044465

In this type of coating device, the degassing unit needs to be cleaned when the processing liquid is replaced with another type of processing liquid, during regular maintenance, or when the processing liquid has remained for a certain period of time. One possible method for cleaning the degassing unit is to supply high-pressure air into the degassing unit to drain most of the processing liquid from the degassing unit, and then pass a solvent through the degassing unit to wash away any processing liquid remaining in the degassing unit.

However, because the treatment liquid is highly viscous, it is difficult to fully 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 within multiple fine tubular hollow fibers. In this case, it is difficult to evenly supply high-pressure air to multiple hollow fibers. As a result, air and solvent tend to concentrate in the hollow fibers from which the treatment liquid was discharged first, making it impossible to discharge the treatment liquid from the other hollow fibers.

The present invention was developed in consideration of these circumstances, and aims to provide technology that can effectively discharge highly viscous treatment liquid from a degassing unit.

In order to solve the above problems, the first invention of the present application is a cleaning method for a degassing unit that degasses a treatment liquid having a viscosity of 1 Pa·s or more , comprising 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.

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

A third invention of the present application is the cleaning method of the second invention, wherein in the first dilution step, the first diluted liquid is produced 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 step, the first diluted liquid is supplied from the dilution tank to the degassing unit; in the second dilution step, the second diluted liquid is produced by supplying the solvent to the first diluted liquid returned from the degassing unit to the dilution tank; and in the second liquid passing step, the second diluted liquid is supplied from the dilution tank to the degassing unit.

A fourth invention of the present application is the cleaning method of the third invention, wherein 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 and 15 wt % or less of the processing liquid stored in the dilution tank.

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

A sixth aspect of the present invention is a cleaning device for a degassing unit that degasses a processing liquid having a viscosity of 1 Pa s or more , the device 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. The control unit performs the following steps: a first dilution step of producing a first dilution by supplying the solvent from the solvent supply unit to the dilution tank; a first liquid passing step of passing the first dilution through the degassing unit by driving the circulation pump after the first dilution step; a second dilution step of producing a second dilution 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 through the degassing unit by driving the circulation pump after the second dilution step.

A seventh invention of the present application is the cleaning apparatus of the sixth invention, wherein 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 and 15 wt % or less of the processing liquid stored in the dilution tank.

An eighth aspect of the present invention is the cleaning apparatus of the sixth or seventh aspect , wherein the degassing unit has a plurality of hollow fibers through which the treatment liquid passes.

A ninth invention of the present application is a coating apparatus that coats a substrate with a processing liquid having a viscosity of 1 Pa·s or more , and includes a coating section that coats the substrate with the processing liquid, and a liquid supply section that supplies the processing liquid to the coating section, and the liquid supply section has the degassing unit and a cleaning apparatus according to any one of the sixth to eighth inventions.

According to the first to ninth aspects of the present invention, the high-viscosity treatment liquid in the degassing unit is first 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 enabling the treatment liquid to be efficiently discharged from the degassing unit.

In particular, according to the second invention of the present application, the degassing unit can be cleaned without mixing in substances other than the solute and solvent of the processing liquid.

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

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

In particular, according to the fourth or seventh invention of the present application, the number of times dilution and liquid passing are repeated can be reduced.

In particular, according to the fifth or eighth invention of the present application, the treatment liquid can be effectively removed from the inside of the hollow fibers where the treatment liquid is likely to remain.

FIG. 2 is a diagram illustrating a configuration of a coating device. FIG. FIG. 2 is a control block diagram of the coating device. FIG. 2 is a diagram showing the configuration of a degassing unit. FIG. 2 is a diagram showing the configuration of a cleaning device. 10 is a flowchart showing a procedure for cleaning the degassing unit. FIG. 10 is a diagram showing the results of cleaning a degassing unit using a cleaning device.

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

<1. Configuration of the Coating Apparatus>
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 the manufacturing process of polyimide film, which serves as the base material for flexible displays. In the polyimide film manufacturing process, 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 processes such as heating, decompression, and baking. This produces a thin polyimide film.

As shown in FIG. 1, the application device 1 of this embodiment includes a liquid supply unit 10, an application unit 20, and a control unit 30.

The liquid supply unit 10 is a unit that supplies a highly viscous treatment liquid to the coating unit 20. As shown in FIG. 1, the liquid supply unit 10 has multiple liquid supply tanks 11, liquid supply piping 12, a main pump 13, an assist pump 14, a filter 15, and a degassing unit 16.

The liquid supply tank 11 is a container that stores the treatment liquid before supply. The treatment liquid stored in the liquid supply 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 10,000 cP (1 to 10 Pa·s). In the following description, "high viscosity" refers to a viscosity of 1000 cP (1 Pa·s) or higher.

In the example shown in Figure 1, the liquid supply unit 10 has six liquid supply tanks 11. However, the number of liquid supply tanks 11 that the liquid supply unit 10 has may be one to five, or seven or more.

The liquid supply pipe 12 connects the liquid supply tank 11 and the application unit 20. The upstream end of the liquid supply pipe 12 is connected to the liquid supply tank 11 via an on-off valve 17. The downstream end of the liquid supply pipe 12 is connected to a nozzle 22 (described below) of the application 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.

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 located downstream of the degassing unit 16 on the liquid supply pipe 12. The main pump 13 may be a tubephragm pump, such as a CT (Coaxial Tubephragm) pump or a metered discharge PT (Parallel Tubephragm) pump.

The assist pump 14, together with the main pump 13, is a pump that sends the treatment liquid in the liquid supply pipe 12 downstream. The assist pump 14 is located in the liquid supply pipe 12 downstream of the filter 15 and upstream of the degassing unit 16. The assist pump 14 may be, for example, a tubephragm pump such as a CT (Coaxial Tubephragm) pump or a constant-volume discharge PT (Parallel Tubephragm) pump.

When the on-off valve 17 is opened and the main pump 13 and assist pump 14 are operated, a flow of treatment liquid is formed in the liquid supply pipe 12 from the liquid supply tank 11 to the application unit 20. This causes the treatment liquid to be supplied from the liquid supply tank 11 to the application unit 20. The liquid supply unit 10 may further include a pressurizing mechanism that supplies gas to the liquid supply tank 11 to push the treatment liquid out of the liquid supply tank 11.

The filter 15 is a unit that filters the treatment liquid. The filter 15 is provided in a position upstream of the assist pump 14 on the liquid supply pipe 12. The treatment liquid is filtered by the filter 15. As a result, fine dust particles contained in the treatment liquid are captured and removed by the filter 15. In the example shown in 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. Furthermore, another filter 15 may be provided in a position downstream of the assist pump 14 on the liquid supply pipe 12.

The degassing unit 16 reduces the amount of gas dissolved in the treatment liquid. The degassing unit 16 is located 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 uses the degassing unit 16 to remove air bubbles and dissolved gases contained in the treatment liquid. This prevents air bubbles from being generated in the treatment liquid when the treatment liquid applied to the substrate 9 is heated, depressurized, or baked in subsequent processes.

The coating unit 20 is a unit that coats the substrate 9 with the processing liquid supplied from the liquid supply unit 10. Figure 2 is a perspective view of the coating unit 20. As shown in Figures 1 and 2, the coating unit 20 has a stage 21, a nozzle 22, a nozzle holder 23, and a traveling mechanism 24. For ease of explanation, the movement direction of the nozzle 22 in the coating unit 20 will be referred to as the "front-to-back direction," and the horizontal direction perpendicular to the front-to-back direction will be referred to as the "left-to-right direction."

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. The upper surface of the stage 21 forms a flat substrate holding surface 211. The substrate holding surface 211 is provided with a number of vacuum suction holes (not shown). When the substrate 9 is placed on the substrate holding surface 211, the suction force of the vacuum suction holes causes the underside of the substrate 9 to adhere to the substrate holding surface 211. This fixes the substrate 9 in a horizontal position on the stage 21. In addition, multiple lift pins (not shown) are provided inside the stage 21. When the substrate 9 is removed from the stage 21, the multiple lift pins protrude above the substrate holding surface 211. This separates the substrate 9 from the substrate holding surface 211.

The nozzle 22 is positioned above the stage 21. The nozzle 22 has a nozzle body 221 that extends in the left-right direction. A slit-shaped outlet 223 that also extends in the left-right direction is provided at the lower end of the nozzle body 221. The outlet 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. The processing liquid is then ejected from the outlet 223 toward the upper surface of the substrate 9.

The nozzle holding unit 23 is a mechanism for holding the nozzle 22 above the substrate holding surface 211. The nozzle holding unit 23 has a bridge portion 231 that extends in the left-right direction above the stage 21, and a pair of supports 232 that support both ends of the bridge portion 231. The nozzle 22 is fixed to the underside of the bridge portion 231. The nozzle holding unit 23 also has an elevation mechanism 233 that adjusts the height of both ends of the bridge portion 231.

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 sides of the stage 21. The pair of rails 241 support the pair of support parts 232, respectively, and guide each support part 232 in the front-rear direction. The pair of linear motors 242 use magnetic power to move the pair of support parts 232 in the front-rear direction along the rails 241. As a result, the nozzle 22 moves in the front-rear direction together with the nozzle holding part 23.

When performing the coating process, the coating unit 20 ejects the processing liquid from the ejection port 223 while moving the nozzle 22 back and forth above the substrate 9. This causes the processing liquid to be applied to the upper surface of the substrate 9.

The control unit 30 is a unit for controlling the operation of each part within the coating device 1. Figure 3 is a control block diagram of the coating device 1. The control unit 30 is realized, for example, by a computer. As conceptually shown in Figure 3, the control unit 30 has a processor 31 such as a CPU, a memory 32 such as RAM, and a storage unit 33 such as a hard disk drive. A computer program P for operating the coating device 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 DVD and stored in the storage unit 33. However, the computer program P may also be downloaded to the control unit 30 via a network.

As shown in FIG. 3, the control unit 30 is electrically connected to the on-off valve 17, main pump 13, assist pump 14, and linear motor 242 described above. The control unit 30 is also electrically connected to the pressure reducing pump 432, first three-way valve 55, second three-way valve 56, blades 521, circulation pump 53, on-off valve 543, and on-off valve 582 described below. The control unit 30 temporarily reads 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 component within the coating apparatus 1. This allows the coating process on the substrate 9 to proceed.

<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.

As shown in Figure 4, the degassing unit 16 has a casing 41, multiple hollow fibers 42, and a pressure reduction mechanism 43.

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 flow path at the downstream end of the portion of the liquid supply piping 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 a flow path at the upstream end of the portion of the liquid supply piping 12 downstream of the degassing unit 16. The two exhaust ports 413 are provided on the side of the casing 41. The exhaust ports 413 are connected to the pressure reduction mechanism 43.

The hollow fibers 42 are long, tubular membranes. They are formed from a gas-permeable membrane that allows only gas to pass through, out 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. Multiple hollow fibers 42 are housed inside the casing 41 in a bundled state. The number of hollow fibers 42 housed in the casing 41 is, for example, 100 to 1,000. However, the inner diameter of the hollow fibers 42 and the number of hollow fibers 42 may be changed as appropriate depending on the type and viscosity of the treatment liquid.

One end of each hollow fiber 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 hollow fiber 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 treatment liquid is formed in the liquid supply pipe 12, the treatment liquid flows from the inlet 411 through the interior of each hollow fiber 42 to the outlet 412.

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, gas inside the casing 41 is discharged to the outside through the pressure reduction pipe 431. This reduces the air pressure inside the casing 41.

When the air pressure inside the casing 41 drops, 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 expelled to the outside of the hollow fibers 42. This allows the treatment liquid passing through the hollow fibers 42 to be degassed.

<3. Cleaning device 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, during regular maintenance, when the processing liquid has remained 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.

Figure 5 shows the configuration of the cleaning apparatus 50. As shown in Figure 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 control unit 30 described above also functions as a control unit that controls each unit of the cleaning apparatus 50.

The circulation line 51 is a circular pipe. In this embodiment, a first three-way valve 55 is provided on the liquid supply pipe 12 upstream of the degassing unit 16, and a second three-way valve 56 is provided on the liquid supply pipe 12 downstream 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.

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

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

During normal use when supplying treatment liquid to the application 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." This forms a circular circulation line 51 that includes the degassing unit 16 and the cleaning piping 57.

The dilution tank 52 is a container that stores the dilution liquid used to clean 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 agitation blade 521 inside. When the blade 521 is rotated, the liquid stored in the dilution tank 52 is agitated.

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 with the first three-way valve 55 switched to the above-mentioned "second state" and the second three-way valve 56 switched to the above-mentioned "fourth state," a liquid flow is formed in the circulation line 51 from the dilution tank 52 through the first three-way valve 55 to the degassing unit 16, and a liquid flow is formed from the degassing unit 16 through the second three-way valve 56 and back to the dilution tank 52.

The solvent supply unit 54 has a solvent supply source 541 and a solvent supply pipe 542. The solvent supply source 541 stores the solvent for the treatment liquid. The solvent is, for example, NMP (N-methyl-2-pyrrolidone). The upstream end of the solvent supply pipe 542 is connected to the solvent supply source 541. The downstream end of the solvent supply pipe 542 is connected to the dilution tank 52. The solvent supply pipe 542 is also provided with an on-off valve 543. When the on-off 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.

The drainage section 58 has a drainage pipe 581. The drainage pipe 581 is connected to the cleaning pipe 57 at a position downstream of the circulation pump 53. An on-off valve 582 is provided on the drainage pipe 581. When the on-off valve 582 is opened, the dilution liquid is discharged from the circulation line 51 through the drainage pipe 581 to the outside.

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

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 "first state" described above, and the second three-way valve 56 is set to the "fourth state" described above. Then, the main pump 13 and the assist pump 14 are operated. This causes the treatment liquid to be supplied to the degassing unit 16, and the treatment liquid discharged from the degassing unit 16 flows into the cleaning pipe 57. This causes the treatment liquid to be stored in the dilution tank 52.

Once the treatment liquid has been 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 that includes the degassing unit 16 and the dilution tank 52 (step S2).

Next, the processing liquid stored in the dilution tank 52 is diluted with a solvent (step S3: first dilution process). 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. Once a predetermined amount of solvent has been supplied, the on-off valve 543 is closed to stop the supply of solvent. Then, the blades 521 in the dilution tank 52 are rotated to agitate the processing liquid and solvent. This produces a first dilution liquid in the dilution tank 52 that has a lower viscosity than the processing liquid.

If too much solvent is supplied to the treatment liquid, the viscosity of the first dilution liquid will decrease excessively. In this case, it will be difficult to effectively replace the treatment liquid in the hollow fibers 42 in the next step S4. For this reason, in step S3, it is desirable to supply solvent from the solvent supply unit 54 to the dilution tank 52 in an amount that is 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, excessive dilution will be required. For this reason, in step S3, it is desirable to supply solvent from the solvent supply unit 54 to the dilution tank 52 in an amount that is 5 wt% or more of the treatment liquid stored in the dilution tank 52.

Furthermore, it is desirable that the amount of the first dilution liquid produced in step S3 be equal to or greater than the amount of treatment liquid in the degassing unit 16.

Once the production of the first diluent is complete, the circulation pump 53 is then driven. This supplies the first diluent from the dilution tank 52 to the degassing unit 16. The first diluent is then passed through the multiple hollow fibers 42 in the degassing unit 16 (step S4: first liquid passing process). This replaces the treatment liquid in the hollow fibers 42 with the first diluent. The first diluent does not have as low a viscosity as 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.

After circulating the first diluent in the circulation line 51 for a predetermined time, the circulation pump 53 is stopped. The first diluent (more precisely, a mixture of the first diluent and the processing liquid) stored in the dilution tank 52 is then diluted with a solvent (step S5: second dilution process). Specifically, the on-off valve 543 of the solvent supply unit 54 is opened to supply solvent from the solvent supply source 541 to the dilution tank 52 through the solvent supply pipe 542. Once a predetermined amount of solvent has been supplied, the on-off valve 543 is closed to stop the supply of solvent. The blades 521 in the dilution tank 52 are then rotated to agitate the first diluent and the solvent. This produces a second diluent in the dilution tank 52, which has an even lower viscosity than the first diluent.

In step S5, the solvent supply unit 54 supplies the dilution tank 52 with, for example, the same amount of solvent as in step S3. However, the amount of solvent supplied in step S5 may be different from the amount of solvent supplied in step S3.

Once the production of the second diluent is complete, the circulation pump 53 is then driven, supplying the second diluent from the dilution tank 52 to the degassing unit 16. The second diluent is then passed through the multiple hollow fibers 42 in the degassing unit 16 (step S6: second liquid passing process). This replaces the first diluent in the hollow fibers 42 with the second diluent. The second diluent is not as low in viscosity as 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.

After circulating the second diluent in the circulation line 51 for a predetermined time, the circulation pump 53 is stopped. The second diluent (more precisely, a mixture of the first and second diluents) stored in the dilution tank 52 is then diluted with a solvent (step S7: third dilution process). Specifically, the on-off valve 543 of the solvent supply unit 54 is opened to supply solvent from the solvent supply source 541 to the dilution tank 52 through the solvent supply pipe 542. Once a predetermined amount of solvent has been supplied, the on-off valve 543 is closed to stop the supply of solvent. The blades 521 in the dilution tank 52 are then rotated to agitate the second diluent and the solvent. This produces a third diluent in the dilution tank 52, which has an even lower viscosity than the second diluent.

In step S7, the solvent supply unit 54 supplies the same amount of solvent as in step S3 or step S5 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.

Once the production of the third diluent is complete, the circulation pump 53 is then driven. This supplies the third diluent from the dilution tank 52 to the degassing unit 16. The third diluent is then passed through the multiple hollow fibers 42 in the degassing unit 16 (step S8: third liquid passing process). This replaces the second diluent in the hollow fibers 42 with the third diluent. The third diluent is not as low in viscosity as 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.

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). Once the discharge of the third diluent is complete, the circulation pump 53 is stopped, and the on-off valve 582 of the drainage unit 58 is closed again.

Then, 100% solvent is stored in the dilution tank 52 (step S10). Specifically, by opening the on-off valve 543 of the solvent supply unit 54, solvent is supplied from the solvent supply source 541 to the dilution tank 52 through the solvent supply pipe 542. This causes an amount of solvent greater than the capacity of the degassing unit 16 to be stored in the dilution tank 52.

Once the solvent has accumulated in the dilution tank 52, the first three-way valve 55 is switched back from the "first state" to the "second state" and the circulation pump 53 is driven. This supplies the solvent from the dilution tank 52 to the degassing unit 16. The solvent is then passed through the multiple hollow fibers 42 in the degassing unit 16 (Step S11: Solvent Passing Process). This replaces the third diluent inside the hollow fibers 42 with the solvent. At this point, the hollow fibers 42 are filled not with the treatment liquid, but with the third diluent, which has a lower viscosity than the treatment liquid. This allows the interior of the hollow fibers 42 to be effectively replaced with the solvent.

After circulating the solvent in the circulation line 51 for a predetermined time, the first three-way valve 55 is switched back to the "first state" from the "second state," and the on-off valve 582 of the drainage section 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).

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

In addition, this cleaning device 50 is provided with a circulation line 51 that includes a degassing unit 16 and a dilution tank 52, and the diluted cleaning solution is produced by supplying the solvent of the treatment liquid to the dilution tank 52. In this way, dilution and liquid passage can be repeated while circulating the liquid in the circulation line 51. Furthermore, the degassing unit 16 can be cleaned without mixing in substances other than the solute and solvent of the treatment liquid.

By effectively 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. This also prevents the processing liquid from solidifying and adhering within the degassing unit 16. It also prevents the generation of particles due to the solidification of the processing liquid.

5. Experimental Results
FIG. 7 shows the results of cleaning the degassing unit 16 using a cleaning device 50 equivalent to that described above. In the experiment shown in 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 that described above. The treatment liquid used was a highly viscous liquid containing a polyimide precursor (polyamic acid) as a solute and NMP (N-methyl-2-pyrrolidone) as a solvent. The amount of treatment liquid initially stored in the dilution tank 52 was 1,200 g.

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

The results in Figure 7 show that, compared to the comparative example, the amount of treatment liquid remaining in the multiple hollow fibers 42 of the degassing unit 16 was reduced in Examples 1 to 3. This demonstrates that by repeatedly replacing the liquid in the degassing unit 16 with a dilute liquid with gradually lower viscosity, the treatment liquid can be efficiently discharged from the degassing unit 16.

In particular, compared to Examples 1 and 2, in Example 3, the treatment liquid was able to be almost completely discharged from the multiple hollow fibers 42 of the degassing unit 16. This showed that cleaning performance was particularly improved when the amount of solvent supplied in one dilution step was 10 wt% of the treatment liquid. From these results, it is considered desirable to supply the amount of solvent supplied in one dilution step, for example, at least 5 wt% and no more than 15 wt% of the treatment liquid.

6. Modified Examples
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

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

In addition, in the above embodiment, the cleaning device 50 has a solvent supply unit 54 that automatically supplies solvent to the dilution tank 52. However, the supply of solvent to the dilution tank 52 may also be performed manually by an operator.

In addition, in the above embodiment, the direction in which the diluted liquid is passed through the degassing unit 16 is the same as the direction in which the treatment liquid is passed through the degassing unit 16 under normal conditions. However, the direction in which the diluted liquid is passed through the degassing unit 16 may be opposite to the direction in which the treatment liquid is passed 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.

Furthermore, in the above embodiment, the diluent or solvent after cleaning was discharged into the drain pipe 581 connected to the circulation line 51. However, the diluent or solvent after cleaning may also be discharged to the outside via the liquid supply pipe 12 and the nozzle 22.

Furthermore, in the above embodiment, the liquid supply section 10 has one degassing unit 16. However, the liquid supply section 10 may have multiple degassing units 16. In that case, one cleaning device 50 may be provided for the multiple degassing units 16. Furthermore, a cleaning device 50 may be provided for each degassing unit 16.

In addition, in the above embodiment, the cleaning device 50 was incorporated into the liquid supply section 10 of the coating device 1. However, the cleaning device 50 may be a separate device from the liquid supply section 10 of the coating device 1. In that case, the degassing unit 16 can be removed from the liquid supply section 10 and set in the cleaning device 50 to perform the cleaning process.

While the coating apparatus 1 described above was used in the process of manufacturing the substrate itself of a flexible device, the coating apparatus of the present invention may also be used in the process of forming a protective film on the surface of the substrate after the device has been formed. The coating apparatus of the present invention may also be used in the process of applying an adhesive when bonding substrates together. The coating apparatus of the present invention may also be used in the manufacturing process of liquid crystal display devices and semiconductor substrates other than flexible devices. The coating apparatus of the present invention may also be used in the manufacturing process of batteries such as lithium-ion secondary batteries and fuel cells.

In addition, in the above embodiment, a hollow fiber degassing module was 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 similar cleaning process to that described above may be performed on a degassing unit that stores treatment liquid in a degassing tank and degassssssing the tank by reducing the pressure inside the tank.

Furthermore, the details of the cleaning device and application device may differ from the configurations shown in the drawings of this application. Furthermore, the elements appearing in the above embodiments and variations may be combined as appropriate, provided no contradictions arise.

REFERENCE SIGNS LIST 1 Coating device 9 Substrate 10 Liquid supply section 11 Liquid supply tank 12 Liquid supply piping 13 Main pump 14 Assist pump 15 Filter 16 Degassing unit 20 Coating section 30 Control section 41 Casing 42 Hollow fiber 43 Pressure reduction mechanism 50 Cleaning device 51 Circulation line 52 Dilution tank 53 Circulation pump 54 Solvent supply section 55 First three-way valve 56 Second three-way valve 57 Cleaning piping 58 Draining section

Claims (9)

1. A method for cleaning a degassing unit that degasses a treatment liquid having a viscosity of 1 Pa·s or more , comprising:
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;
A cleaning method comprising: 2. The cleaning method according to claim 1,
a first dilution step of diluting the treatment liquid with a solvent of 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 solution with the solvent after the first liquid passing step and before the second liquid passing step to produce the second dilution solution;
The cleaning method further comprises: 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, thereby generating the first diluted solution;
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. The cleaning method according to claim 3,
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 and 15 wt % or less of the processing liquid stored in the dilution tank. 5. The cleaning method according to claim 1 , further comprising:
The degassing unit has a plurality of hollow fibers through which the treatment liquid passes. A cleaning device having a degassing unit for degassing a treatment liquid having a viscosity of 1 Pa·s or more ,
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 treatment liquid to the dilution tank;
a control unit that controls the circulation pump and the solvent supply unit;
Equipped with
The control unit
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;
To perform the cleaning equipment. 7. The cleaning device according to claim 6 ,
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 and 15 wt % or less of the processing liquid stored in the dilution tank. The cleaning device according to claim 6 or 7 ,
The degassing unit has a plurality of hollow fibers through which the treatment liquid passes. A coating apparatus that coats a substrate with a treatment liquid having a viscosity of 1 Pa·s or more ,
an application unit that applies the treatment liquid to a substrate;
a liquid supply unit that supplies the treatment liquid to the application unit;
Equipped with
The liquid supply unit includes:
the degassing unit;
The cleaning device according to claim 6 or 7 ,
The coating device has: