JP7555804B2 - Reduced pressure drying apparatus and reduced pressure drying method - Google Patents

Description

The present invention relates to a reduced-pressure drying apparatus and a reduced-pressure drying method for drying a coating layer formed on the upper surface of a substrate by reducing pressure.

Conventionally, in the manufacturing process of an organic EL display, a coating layer that will become a hole injection layer, a hole transport layer, or a light emitting layer is formed on the upper surface of a substrate. The coating layer is partially applied to the upper surface of the substrate by an inkjet device. The substrate on which the coating layer has been formed is then transported into the chamber of a reduced pressure drying device and subjected to a reduced pressure drying process. This causes the solvent contained in the coating layer to evaporate, and the coating layer dries.

The reduced pressure drying apparatus includes a chamber that houses the substrate and a reduced pressure mechanism that sucks gas from the chamber. A conventional reduced pressure drying apparatus is described, for example, in Patent Document 1.

JP 2018-49806 A

In conventional reduced pressure drying devices, an exhaust port for discharging gas from the chamber is provided on the bottom surface of the chamber. This is to create a uniform airflow on the upper surface side of the substrate when the chamber is depressurized. However, in the coated area of the upper surface of the substrate that is covered with a coating layer, the solvent in the coating layer evaporates as the pressure is reduced, whereas in the non-coated area that is not covered with a coating layer, the solvent does not evaporate. For this reason, if the direction of the airflow on the upper surface side of the substrate is constant throughout, the effect of the solvent vapor will cause a difference in the degree of drying progress at the edge of the coated area between the area where the gas flows from the non-coated area to the coated area and the area where the gas flows from the coated area to the non-coated area. As a result, uneven drying may occur in the coated layer.

The present invention has been developed in consideration of these circumstances, and aims to provide a reduced-pressure drying apparatus and a reduced-pressure drying method that can uniformly dry a coating layer formed on the upper surface of a substrate.

In order to solve the above-mentioned problems, a first invention of the present application is a reduced-pressure drying apparatus that dries a coating layer containing a solvent formed on an upper surface of a substrate by reducing pressure, the apparatus comprising: a chamber that accommodates the substrate; a stage that supports the substrate from below inside the chamber; a plurality of exhaust ports provided in the chamber; a reduced-pressure mechanism that sucks in gas from the chamber through the plurality of exhaust ports; and a control unit that controls the reduced-pressure mechanism, the reduced-pressure mechanism having a plurality of individual pipes connected at one end to the plurality of exhaust ports, a main pipe connected to the other end of the plurality of individual pipes, a plurality of individual valves provided in each of the plurality of individual pipes and individually adjusting the amount of exhaust from the plurality of exhaust ports , and a main valve with adjustable opening provided in the main pipe , the control unit changes the open/closed state or opening of some of the plurality of individual valves while maintaining the opening of the main valve , and executes a switching process that sequentially changes the some of the individual valves.

The second invention of the present application is the reduced pressure drying apparatus of the first invention, in which the multiple exhaust ports are located below the substrate supported by the stage.

The third invention of the present application is a reduced pressure drying apparatus according to the first or second invention, in which the individual valves are open/close valves, and the control unit closes some of the individual valves and opens other individual valves, sequentially changing the state of the individual valves.

The fourth invention of the present application is the reduced pressure drying device of the third invention, in which the control unit closes one individual valve and opens the other individual valve, sequentially changing the one individual valve.

The fifth invention of the present application is a reduced pressure drying apparatus according to any one of the first to fourth inventions, in which the individual valves are adjustable opening control valves, and the control unit sequentially changes the opening of some of the individual valves by making the opening of some of the individual valves smaller than the opening of other individual valves.

The sixth aspect of the present invention is the reduced pressure drying device of the fifth aspect, in which the control unit makes the opening of one individual valve smaller than the opening of the other individual valves, and sequentially changes the opening of the one individual valve.

A seventh aspect of the present invention is the reduced pressure drying apparatus according to any one of the first to sixth aspects, wherein the control unit executes the switching process at least when the coating layer boils.

The eighth invention of the present application is a reduced pressure drying apparatus of any one of the first to seventh inventions, wherein the upper surface of the substrate has a portion covered by the coating layer and a portion exposed from the coating layer.

A ninth invention of the present application is a reduced-pressure drying method for drying a coating layer containing a solvent formed on an upper surface of a substrate by reducing pressure, the method comprising the steps of: a) accommodating the substrate in a chamber; and b) sucking gas from the chamber through a plurality of exhaust ports provided in the chamber, the reduced-pressure drying mechanism for performing the step b) comprising a plurality of individual pipes each having one end connected to the plurality of exhaust ports, a main pipe connected to the other end of the plurality of individual pipes, a plurality of individual valves provided in each of the plurality of individual pipes for individually adjusting the amount of exhaust from the plurality of exhaust ports, and a main valve provided in the main pipe and having an adjustable opening, the step b) including a switching process for sequentially changing the open/closed state or opening of some of the plurality of individual valves while maintaining the opening of the main valve.

According to the first to ninth aspects of the present invention, when the pressure inside the chamber is reduced, the exhaust amount from the multiple exhaust ports is switched sequentially. This changes the direction of the airflow formed along the upper surface of the substrate. As a result, it is possible to suppress uneven drying caused by the vapor of the solvent evaporated from the coating layer. Therefore, it is possible to uniformly dry the coating layer on the upper surface of the substrate.

In particular, according to the second aspect of the present invention, the gas in the chamber is exhausted from below the substrate. This makes it possible to uniformize the gas flow on the upper surface side of the substrate.

In particular, according to the fourth aspect of the present invention, by closing only one individual valve, the amount of exhaust can be ensured.

In particular, according to the fifth aspect of the present invention, the airflow formed along the upper surface of the substrate can be changed more gradually than when an on-off valve is used.

In particular, according to the sixth aspect of the present invention, the exhaust volume can be ensured by using only one individual valve to narrow the opening.

In particular, according to the eighth aspect of the present invention, it is possible to suppress changes in the exhaust volume of the entire pressure reduction mechanism.

In particular, according to the seventh aspect of the present invention, it is possible to prevent solvent vapor, which is generated in large quantities due to boiling of the coating layer, from flowing in one direction, thereby preventing uneven drying caused by the solvent vapor.

FIG. 2 is a vertical cross-sectional view of the reduced pressure drying apparatus. FIG. 2 is a cross-sectional view of the reduced pressure drying apparatus. FIG. 4 is a block diagram conceptually showing functions realized in a control unit. FIG. 1 is a flowchart showing the flow of reduced pressure drying treatment. 13 is a graph showing changes in air pressure within a chamber. FIG. 13 is a diagram showing the state inside the chamber when the stage is placed in the raised position. 4 is a timing chart showing changes in the open/closed states of four individual valves. FIG. FIG. 13 is a diagram showing the state inside the chamber when the stage is placed in the lowered position. 10 is a timing chart showing changes in the open/closed states of four individual valves according to a modified example. FIG. 11 is a vertical sectional view of a reduced pressure drying apparatus according to a modified example. FIG. 11 is a vertical sectional view of a reduced pressure drying apparatus according to a modified example.

The following describes an embodiment of the present invention with reference to the drawings.

<1. Configuration of the reduced pressure drying device>
Fig. 1 is a longitudinal sectional view of a reduced-pressure drying apparatus 1 according to an embodiment of the present invention. Fig. 2 is a transverse sectional view of the reduced-pressure drying apparatus 1. The reduced-pressure drying apparatus 1 is an apparatus for performing a reduced-pressure drying process on a substrate 9 in a manufacturing process of an organic EL display. A rectangular glass substrate is used as the substrate 9. A coating layer 90 (see Fig. 9) containing an organic material and a solvent is partially formed in advance on the upper surface of the substrate 9. The coating layer 90 becomes a hole injection layer, a hole transport layer, or a light-emitting layer of the organic EL display by being dried in the reduced-pressure drying apparatus 1.

3 is a perspective view of the substrate 9. The substrate 9 has a rectangular shape with different vertical and horizontal lengths when viewed from above. As shown in FIG. 2, a plurality of circuit regions A1 for forming a circuit pattern of an organic EL display are arranged on the upper surface of the substrate 9. In the example of FIG. 2, four rectangular circuit regions A1 are arranged in a matrix of two rows and two columns on the upper surface of the substrate 9. However, the shape, number, and arrangement of the circuit regions A1 are not limited to this example. The coating layer 90 is formed in each circuit region A1 according to the circuit pattern by an inkjet device in a coating process prior to the reduced pressure drying process. Therefore, each circuit region A1 has a portion covered by the coating layer 90 and a portion exposed from the coating layer 90. In addition, the boundary region A2 between adjacent circuit regions A1 is a portion exposed from the coating layer 90.

As shown in Figures 1 and 2, the reduced pressure drying apparatus 1 includes a chamber 10, a stage 20, a reduced pressure mechanism 30, a bottom rectifying plate 40, a side rectifying plate 50, an air supply mechanism 60, a pressure gauge 70, and a control unit 80.

The chamber 10 is a pressure-resistant vessel having an internal space in which the substrate 9 is housed. The chamber 10 is fixed onto an apparatus frame (not shown). The shape of the chamber 10 is a flat rectangular parallelepiped. The chamber 10 has a substantially square bottom plate portion 11, four side wall portions 12, and a substantially square top surface portion 13. The four side wall portions 12 connect the four end edges of the bottom plate portion 11 and the four end edges of the top surface portion 13 in the vertical direction.

One of the four side walls 12 is provided with a loading/unloading port 14 and a shutter 15 for opening and closing the loading/unloading port 14. The shutter 15 is connected to a shutter drive mechanism 16 composed of an air cylinder or the like. When the shutter drive mechanism 16 is operated, the shutter 16 moves between a closed position where the loading/unloading port 14 is closed and an open position where the loading/unloading port 14 is opened. When the shutter 16 is in the closed position, the internal space of the chamber 10 is sealed. When the shutter 16 is in the open position, the substrate 9 can be loaded into and unloaded from the chamber 10 via the loading/unloading port 14.

The stage 20 is a support part that supports the substrate 9 inside the chamber 10. The stage 20 has a plurality of support plates 21. The plurality of support plates 21 are arranged at intervals in the horizontal direction. A plurality of support pins 22 are provided on the upper surface of each plate 21. The substrate 9 is placed on top of the plurality of plates 21. The upper ends of the plurality of support pins 22 come into contact with the lower surface of the substrate 9, thereby supporting the substrate 9 in a horizontal position.

The multiple support plates 21 of the stage 20 are connected to a lifting mechanism 23. To avoid complicating the drawing, the lifting mechanism 23 is shown conceptually in FIG. 1, but in reality, the lifting mechanism 23 is composed of an actuator such as an air cylinder. When the lifting mechanism 23 is operated, the stage 20 moves up and down between a lowered position H1 (position shown by a solid line in FIG. 1) and an upper position H2 (position shown by a two-dot chain line in FIG. 1) that is higher than the lowered position H1. At this time, the multiple plates 21 move up and down as a unit.

The decompression mechanism 30 is a mechanism that sucks gas from the internal space of the chamber 10 to reduce the pressure inside the chamber 10. As shown in Figures 1 and 2, the bottom plate portion 11 of the chamber 10 is provided with four exhaust ports 16a to 16d. The four exhaust ports 16a to 16d are located below the substrate 9 supported by the stage 20 and below the bottom surface straightening plate 40 described below. The decompression mechanism 30 has an exhaust pipe 31 connected to the four exhaust ports 16a to 16d, four individual valves Va to Vd, a main valve Ve, and a vacuum pump 32.

The exhaust pipe 31 has four individual pipes 31a to 31d and one main pipe 31e. One end of each of the four individual pipes 31a to 31d is connected to the four exhaust ports 16a to 16d, respectively. The other ends of the four individual pipes 31a are joined together and connected to one end of the main pipe 31e. The other end of the main pipe 31e is connected to the vacuum pump 32. The four individual valves Va to Vd are provided on the paths of the four individual pipes 31a, respectively. The main valve Ve is provided on the path of the main pipe 31e.

With the loading/unloading port 14 closed by the shutter 15, at least some of the four individual valves Va to Vd and one main valve Ve are opened, and the vacuum pump 32 is operated, the gas in the chamber 10 is exhausted to the outside of the chamber 10 through the exhaust pipe 31. This makes it possible to reduce the pressure in the internal space of the chamber 10.

The four individual valves Va to Vd are valves for individually adjusting the exhaust volume from the four exhaust ports 16a to 16d. In this embodiment, the individual valves Va to Vd are opening/closing valves that switch between an open state and a closed state based on a command from the control unit 80. The main valve Ve is a valve for adjusting the total exhaust volume from the four exhaust ports 16a to 16d. In this embodiment, the main valve Ve is an opening control valve whose opening can be adjusted based on a command from the control unit 80.

In this reduced pressure drying apparatus 1, the four exhaust ports 16a to 16d are located below the substrate 9 supported by the stage 20. This allows for more uniform gas flow on the upper surface side of the substrate 9 compared to when exhaust ports are located above the substrate 9. This makes it possible to suppress uneven drying of the coating layer 90 formed on the upper surface of the substrate 9.

The bottom flow plate 40 is a plate for regulating the flow of gas when the pressure inside the chamber 10 is reduced. The bottom flow plate 40 is located between the substrate 9 supported by the stage 20 and the bottom plate portion 11 of the chamber 10. More specifically, the bottom flow plate 40 is located below the stage 20 at the lowered position H1 and above the upper surface of the bottom plate portion 11. The bottom flow plate 40 also extends horizontally along the upper surface of the bottom plate portion 11. The bottom flow plate 40 is fixed to the bottom plate portion 11 of the chamber 10 via multiple supports (not shown).

As shown in FIG. 2, the shape of the bottom rectifying plate 40 is a square when viewed from above. The length of each side of the bottom rectifying plate 40 when viewed from above is longer than both the long and short sides of the rectangular substrate 9. Therefore, regardless of the orientation of the substrate 9 placed on the stage 20, the bottom rectifying plate 40 is larger than the substrate 9 when viewed from above.

The side rectifying plate 50, together with the bottom rectifying plate 40, is a plate for regulating the flow of gas when the pressure inside the chamber 10 is reduced. The side rectifying plate 50 is located between the substrate 9 supported by the stage 20 at the lowered position H1 and the side wall portion 12 of the chamber 10. More specifically, the side rectifying plate 50 is located outside the end of the substrate 9 supported by the stage 20 at the lowered position H1 and inside the inner surface of the side wall portion 12 at a distance. In this embodiment, four side rectifying plates 50 are arranged around the substrate 9 supported by the stage 20. Each side rectifying plate 50 extends along the inner surface of the side wall portion 12. Therefore, the four side rectifying plates 50 as a whole form a rectangular cylindrical rectifying plate surrounding the substrate 9. In addition, the bottom rectifying plate 40 and the four side rectifying plates 50 as a whole form a box-shaped rectifying plate with a bottomed cylinder.

When the internal space of the chamber 10 is depressurized, the gas within the chamber 10 is exhausted to the outside of the chamber 10 through the space between the side straightening plate 50 and the side wall portion 12, the space between the bottom straightening plate 40 and the bottom plate portion 11, and the exhaust ports 16a-16d. In this way, the gas flows through a space away from the substrate 9, thereby reducing the airflow formed near the substrate 9. In particular, the concentration of the airflow at the peripheral portion of the substrate 9 can be suppressed. As a result, uneven drying of the coating layer 90 formed on the upper surface of the substrate 9 can be suppressed.

As shown in FIG. 2, the box-shaped straightening plate formed by the bottom straightening plate 40 and the four side straightening plates 50 is square in top view. The length of each side of the box-shaped straightening plate in top view is longer than both the long and short sides of the rectangular substrate 9. This makes it possible to make the flow of gas in the chamber 10 uniform during decompression, regardless of the orientation of the substrate 9 placed on the stage 20. In other words, it is possible to prevent the flow of gas in the chamber 10 from changing depending on the orientation of the substrate 9.

As shown in FIG. 2, all four exhaust ports 16a-16d are located on diagonals 41 of the square-shaped bottom airflow plate 40 when viewed from above. In this way, each exhaust port 16a-16d can create an airflow that is symmetrical with respect to the center of the bottom airflow plate 40 (the intersection of the two diagonals 41). This allows a more uniform airflow to be created inside the chamber 10.

The three side rectifying plates 50 are fixed to the side wall 12 of the chamber 10. However, the remaining side rectifying plate 50 is movable relative to the side wall 12 and the bottom rectifying plate 40 to ensure a path for loading and unloading the substrate 9. The side rectifying plate 50 is configured to move, for example, together with the shutter 15. In this way, when the shutter 15 moves from the closed position to the open position, the side rectifying plate 50 also moves, ensuring a path for loading and unloading the substrate 9.

However, if the movable side straightening plate 50 comes into contact with another side straightening plate 50 or a bottom straightening plate 50, dust may be generated due to the sliding contact between the straightening plates. For this reason, it is desirable that the movable side straightening plate 50 does not come into contact with the other side straightening plates 50 and the bottom straightening plate 40 even when placed in the correct position (the position that constitutes the box-shaped straightening plate described above). However, if emphasis is placed on further enhancing the effect of regulating the airflow, the movable side straightening plate 50 may come into contact with the other side straightening plates 50 and the bottom straightening plate 40 to close the gaps between these straightening plates.

The air supply mechanism 60 is a mechanism for returning the inside of the chamber 10 to atmospheric pressure at the end of the reduced pressure drying process. As shown in FIG. 1, an air supply port 16f is provided on the bottom plate portion 11 of the chamber 10. The air supply port 16f is located below the bottom surface straightening plate 40. The air supply mechanism 60 has an air supply pipe 61 connected to the air supply port 16e, an air supply valve Vf, and an air supply source 62. One end of the air supply pipe 61 is connected to the air supply port 16f. The other end of the air supply pipe 61 is connected to the air supply source 62. The air supply valve Vf is provided on the path of the air supply pipe 61.

When the air supply valve Vf is opened, gas is supplied from the air supply source 62 through the air supply pipe 61 and the air supply port 16f to the internal space of the chamber 10. This increases the air pressure inside the chamber 10. The gas supplied from the air supply source 62 may be an inert gas such as nitrogen gas, or may be clean dry air.

The pressure gauge 70 is a sensor that measures the air pressure inside the chamber 10. As shown in FIG. 1, the pressure gauge 70 is attached to a part of the chamber 10. The pressure gauge 70 measures the air pressure inside the chamber 10 and outputs the measurement result to the control unit 70.

The control unit 80 is a unit for controlling the operation of each part of the reduced pressure drying apparatus 1. The control unit 80 is composed of a computer having a processor 801 such as a CPU, a memory 802 such as a RAM, and a storage unit 803 such as a hard disk drive. The storage unit 803 stores computer programs and various data for executing the reduced pressure drying process. The control unit 80 reads the computer programs and various data from the storage unit 803 into the memory 802, and the processor 801 performs arithmetic processing in accordance with the computer programs and data, thereby controlling the operation of each part in the reduced pressure drying apparatus 1.

Figure 4 is a block diagram conceptually illustrating the functions realized by the control unit 80. As shown in Figure 4, the control unit 80 is electrically connected to the shutter drive mechanism 16, the lifting mechanism 23, the four individual valves Va to Vd, the main valve Ve, the vacuum pump 32, the air supply valve Vf, and the pressure gauge 70. The control unit 80 controls the operation of each of the above-mentioned parts while referring to the measurement values output from the pressure gauge 70.

As conceptually shown in FIG. 4, the control unit 80 has a shutter control unit 81, a lift control unit 82, a switching control unit 83, an exhaust control unit 84, a pump control unit 85, and an air supply control unit 86. The shutter control unit 81 controls the operation of the shutter drive mechanism 16. The lift control unit 82 controls the operation of the lift mechanism 23. The switching control unit 83 individually controls the open/closed states of the four individual valves Va to Vd. The exhaust control unit 84 controls the open/closed state and the opening degree of the main valve Ve. The pump control unit 85 controls the operation of the vacuum pump 32. The air supply control unit 86 controls the open/closed state of the air supply valve Vf. The functions of each of these units are realized by the operation of the processor 801 based on the above-mentioned computer program and various data.

<2. Regarding reduced pressure drying treatment>
Next, a description will be given of the reduced pressure drying process of the substrate 9 using the above-mentioned reduced pressure drying apparatus 1. Fig. 5 is a flow chart showing the flow of the reduced pressure drying process. Fig. 6 is a graph showing the change in air pressure inside the chamber 10.

When performing the reduced pressure drying process, first, the substrate 9 is loaded into the chamber 10 (step S1). An undried coating layer 90 is formed on the upper surface of the substrate 9. In step S1, the shutter control unit 81 first operates the shutter drive mechanism 16. This moves the shutter 15 from the closed position to the open position, opening the loading/unloading port 14. Then, a transport robot (not shown) places the substrate 9 on its fork-shaped hand and loads the substrate 9 into the chamber 10 through the loading/unloading port 14 of the chamber 10.

At this point, the stage 20 is located at the lowered position H1. The transport robot places the substrate 9 on the upper surface of the stage 20 while inserting its fork-shaped hands between the multiple plates 21 of the stage 20. Once the substrate 9 is placed on the stage 20, the transport robot retreats to the outside of the chamber 10. The shutter control unit 81 then operates the shutter drive mechanism 16 again to move the shutter 15 from the open position to the closed position, thereby closing the load/unload port 14. This causes the substrate 9 to be accommodated in the internal space of the chamber 10.

Next, the reduced pressure drying apparatus 1 raises the stage 20 (step S2). Specifically, the lifting control unit 82 operates the lifting mechanism 23 to move the stage 20 from the lowered position H1 to the raised position H2. FIG. 7 is a diagram showing the state inside the chamber 10 when the stage 20 is placed at the raised position H2. As shown in FIG. 7, the upper end of the side straightening plate 50 is lower than the height of the substrate 9 supported by the stage 20 at the raised position H2. Therefore, in step S2, the substrate 9 supported by the stage 20 rises to a position above the upper end of the side straightening plate 50. The upper surface of the substrate 9 faces the top surface 13 of the chamber 10 with a small gap therebetween.

Then, the pressure in the chamber 10 starts to be reduced. That is, the pump control unit 85 starts the operation of the vacuum pump 32. The switching control unit 83 also opens some of the individual valves Va to Vd, and the exhaust control unit 84 opens the main valve Ve. This starts the exhaust of gas from the chamber 10 to the exhaust pipe 16. The reduced pressure drying apparatus 1 first performs a first process (step S3) to gently reduce the pressure in the internal space of the chamber 10. In this first process, the exhaust control unit 84 adjusts the opening of the main valve Ve to a smaller opening than in the second to fourth processes described below. This causes the air pressure in the chamber 10 to gradually decrease from atmospheric pressure P0, as shown in time t1 to t2 in FIG. 6.

In step S3, as described above, the stage 20 is placed in the raised position H2. Therefore, as shown by the dashed arrows in FIG. 7, the gas in the chamber 10 flows from the space below the substrate 9 through the space between the side air straightening plate 50 and the side wall portion 12, the space between the bottom air straightening plate 40 and the bottom plate portion 11, and through the exhaust ports 16a to 16d to the exhaust pipe 61. Therefore, the airflow formed in the chamber 10 is unlikely to affect the upper surface of the substrate 9.

However, even in this step S3, a slight airflow occurs in the space between the upper surface of the substrate 9 and the top surface 13. In addition, the solvent begins to evaporate from the coating layer 90 due to the reduced pressure. Therefore, the switching control unit 83 sequentially switches the open/closed state of the four individual valves Va to Vd to prevent the coating layer 90 from drying unevenly due to the airflow between the upper surface of the substrate 9 and the top surface 13.

Figure 8 is a timing chart showing the change in the open/closed state of the four individual valves Va to Vd. As shown in Figure 8, the switching control unit 83 closes one of the four individual valves Va to Vd and opens the other individual valves. The switching control unit 83 then sequentially changes the individual valve to be closed. Specifically, the switching control unit 83 sequentially switches between a first state (time ta) in which one individual valve Va is closed and the other three individual valves Vb, Vc, and Vd are opened, a second state (time tb) in which one individual valve Vb is closed and the other three individual valves Va, Vc, and Vd are opened, a third state (time tc) in which one individual valve Vc is closed and the other three individual valves Va, Vb, and Vd are opened, and a fourth state (time td) in which one individual valve Vd is closed and the other three individual valves Va, Vb, and Vc are opened.

In this way, during the first process, the direction of the airflow formed in the space between the upper surface of the substrate 9 and the top surface portion 13 changes according to the switching of the individual valves Va to Vd. Therefore, the coating layer 90 on the upper surface of the substrate 9 can be dried uniformly.

In particular, in this embodiment, as shown in FIG. 9, the upper surface of the substrate 9 has a coating area A3 covered with the coating layer 90 and a non-coating area A4 exposed from the coating layer 90. The solvent evaporates from the coating area A3, whereas the solvent does not evaporate from the non-coating area A4. For this reason, if the direction of the airflow is constant, the degree of progress of drying at the edge of the coating area A3 will differ due to the influence of the solvent vapor between the part where the gas flows from the coating area A3 to the non-coating area A4 and the part where the gas flows from the non-coating area A4 to the coating area A3. However, as described above, if the opening and closing states of the four individual valves Va to Vd are sequentially switched to change the direction of the airflow, such a difference in the degree of progress of drying can be reduced. Therefore, it is possible to suppress uneven drying of the coating layer 90 caused by the solvent vapor.

Next, the reduced pressure drying apparatus 1 lowers the stage 20 (step S4). Specifically, the lift control unit 82 operates the lift mechanism 23 to move the stage 20 from the raised position H2 to the lowered position H1. FIG. 10 is a diagram showing the state inside the chamber 10 when the stage 20 is placed in the lowered position H1. As shown in FIG. 10, the upper end of the side straightening plate 50 is higher than the height of the substrate 9 supported by the stage 20 at the lowered position H1. Therefore, in step S4, the substrate 9 supported by the stage 20 is lowered to a position lower than the upper end of the side straightening plate 50.

The reduced pressure drying apparatus 1 then performs a second process to rapidly reduce the pressure in the internal space of the chamber 10 (step S5). In this second process, the exhaust control unit 84 changes the opening of the main valve Ve to a larger opening than in the first process. This causes the air pressure in the chamber 10 to drop rapidly, as shown in FIG. 6 from time t2 to t3.

In the second process, as described above, the stage 20 is positioned at the lowered position H1. Therefore, the gas present in the space on the upper side of the substrate 9 flows to the exhaust pipe 61 through the space between the side straightening plate 50 and the side wall portion 12, the space between the bottom straightening plate 40 and the bottom plate portion 11, and the exhaust ports 16a to 16d, as indicated by the dashed arrows in FIG. 8. This makes it possible to prevent the generation of strong air currents near the substrate 9. In particular, it makes it possible to prevent the concentration of air currents at the peripheral portion of the substrate 9. Therefore, it is possible to prevent uneven drying of the coating layer 90 caused by the air current.

In addition, in this second process, the solvent is actively vaporized from the coating layer 90. Therefore, in order to suppress uneven drying of the coating layer 90, the switching control unit 83 sequentially switches the open/closed state of the four individual valves Va to Vd, as in the first process described above. That is, as shown in FIG. 8, the switching control unit 83 closes one of the four individual valves Va to Vd and opens the other individual valves. Then, the switching control unit 83 sequentially changes the individual valve to be closed. In this way, the direction of the airflow formed along the upper surface of the substrate 9 during the second process changes according to the switching of the individual valves Va to Vd. Therefore, the coating layer 90 on the upper surface of the substrate 9 can be dried uniformly.

When the air pressure in the internal space of the chamber 10 drops to a predetermined pressure P1, the coating layer 90 boils. Then, when boiling begins, the air pressure in the chamber 10 becomes almost constant, as shown at times t3 to t4 in FIG. 6. In this way, the reduced pressure drying apparatus 1 performs the third process (step S6), in which the coating layer 90 boils while exhausting air from the chamber 10 continues.

In this third process, the evaporation of the solvent from the coating layer 90 is more active than in the second process. Therefore, in order to suppress uneven drying of the coating layer 90, the switching control unit 83 sequentially switches the open/closed state of the four individual valves Va to Vd, as in the first and second processes described above. That is, as shown in FIG. 8, the switching control unit 83 closes one of the four individual valves Va to Vd and opens the other individual valves. Then, the switching control unit 83 sequentially changes the individual valve to be closed. In this way, the direction of the airflow formed along the upper surface of the substrate 9 during the third process changes according to the switching of the individual valves Va to Vd. Therefore, the coating layer 90 on the upper surface of the substrate 9 can be dried uniformly.

Eventually, when the solvent components of the coating layer 90 have sufficiently evaporated, the boiling of the coating layer 90 ends. Then, as shown in FIG. 6 from time t4 to t5, the air pressure inside the chamber 10 drops rapidly again. In this way, the reduced pressure drying apparatus 1 performs a fourth process (step S7) to further reduce the pressure in the internal space of the chamber 10 after the coating layer 90 has boiled.

In this fourth process, the small amount of solvent remaining in the coating layer 90 evaporates, but compared to the first to third processes described above, the evaporation of the solvent is not vigorous. For this reason, the switching control unit 83 opens all four individual valves Va to Vd. This promotes exhaust from the chamber 10, and the internal space of the chamber 10 is rapidly depressurized to the target pressure P2.

When the air pressure inside the chamber 10 reaches the target pressure P2, the exhaust control unit 84 closes the main valve Ve. This ends the suction of gas from the chamber 10, and the drying of the coating layer 90 is completed.

Then, the air supply control unit 86 opens the air supply valve Vf. Then, gas is supplied from the air supply source 62 through the air supply pipe 61 and the air supply port 16f to the inside of the chamber 10 (step S8). As a result, the air pressure inside the chamber 10 rises again to atmospheric pressure P0. At this time, a relatively strong air current is generated inside the chamber 10, but since the coating layer 90 has already been sufficiently dried, uneven drying due to the air current is unlikely to occur. In addition, the gas supplied from the air supply port 16f flows into the inside of the chamber 10 through the gap between the bottom surface straightening plate 40 and the bottom plate portion 11, and between the side surface straightening plate 50 and the side wall portion 12. This makes it possible to suppress the generation of a strong air current near the substrate 9.

When the air pressure inside the chamber 10 reaches atmospheric pressure, the air supply control unit 86 closes the air supply valve Vf. Then, the shutter control unit 81 operates the shutter drive mechanism 16. This moves the shutter 15 from the closed position to the open position, opening the load/unload port 14. Then, a transport robot (not shown) transports the dried substrate 9 supported on the stage 20 out of the chamber 10 (step S9). This completes the reduced pressure drying process for one substrate 9.

As described above, in the reduced pressure drying apparatus 1, a switching process is performed in which the open/closed state of the four individual valves Va to Vd is switched sequentially during the first to third processes. Therefore, the exhaust amount from the four exhaust ports 16a to 16d is switched sequentially during each of the first to third processes. This changes the direction of the airflow formed along the upper surface of the substrate 9. Therefore, the coating layer 90 on the upper surface of the substrate 9 can be dried uniformly.

3. Modifications
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Various modified examples will be described below, focusing on differences from the above embodiment.

<3-1. First modified example>
In the above embodiment, a switching process is performed in which the four individual valves Va to Vd are sequentially switched between the first process and the third process. However, the switching process may be performed only during some of the first process to the third process. For example, during the third process in which the coating layer 90 boils, the evaporation of the solvent component is most active. For this reason, the switching process may be performed only during the third process.

<3-2. Second modified example>
In the above embodiment, in the switching process, one of the four individual valves Va to Vd is closed, the other three individual valves are opened, and the individual valve to be closed is changed sequentially. However, two of the four individual valves Va to Vd may be closed, the other two individual valves may be opened, and the two individual valves to be closed may be changed sequentially. Alternatively, three of the four individual valves Va to Vd may be closed, the other one individual valve may be opened, and the three individual valves to be closed may be changed sequentially. That is, the switching control unit 83 may change the open/closed state of some of the multiple individual valves, and change the part of the individual valves sequentially. However, closing the individual valves Va to Vd one by one as in the above embodiment makes it easier to ensure the exhaust volume of the exhaust pipe 61 as a whole.

<3-3. Third modified example>
In the above embodiment, one of the four individual valves Va to Vd is always closed during the switching process. However, the switching process may include a period during which all four individual valves Va to Vd are open. In that case, the exhaust control unit 84 may control the opening degree of the main valve Ve according to the number of open individual valves. For example, when all four individual valves Va to Vd are open, the opening degree of the main valve Ve may be smaller than when one individual valve is closed. In this way, changes in the exhaust volume of the entire exhaust pipe 61 can be suppressed.

<3-4. Fourth Modified Example>
In the above embodiment, the four individual valves Va to Vd are sequentially closed for the same time. That is, the times ta, tb, tc, and td in FIG. 8 are all the same time. However, the drying of the coating layer 90 progresses even during this switching process. Therefore, the amount of solvent vaporized from the coating layer 90 may gradually decrease during the switching process. In consideration of this point, the times ta, tb, tc, and td may be changed. Specifically, as shown in FIG. 11, the times ta, tb, tc, and td may be gradually lengthened (ta<tb<tc<td). In this way, the amount of solvent vaporized at each time can be made uniform.

<3-5. Fifth Modified Example>
In the above embodiment, the four individual valves Va to Vd are on-off valves that only switch between an open state and a closed state. However, the four individual valves Va to Vd may be aperture control valves that can adjust the aperture. In addition, in the switching process, some of the individual valves may not be completely closed, but may be opened less than the other individual valves. That is, the switching process may be a process in which the aperture of some (for example, one) of the multiple individual valves is changed, and the aperture of the some individual valves is changed sequentially. In this way, the airflow in the chamber 10 can be changed more gently than when on-off valves are used.

<3-6. Sixth Modified Example>
The reduced pressure drying apparatus 1 of the above embodiment includes a bottom surface straightening plate 40 and four side surface straightening plates 50 in the chamber 10. However, as shown in FIG. 12, the reduced pressure drying apparatus 1 does not need to include the side surface straightening plate 50. Even in this case, the length of each side of the bottom surface straightening plate 40 in a top view is longer than both the long side and the short side of the rectangular substrate 9. Therefore, regardless of the orientation of the substrate 9 placed on the stage 20, when the pressure in the chamber 10 is reduced, the gas on the upper side of the substrate 9 can flow below the bottom surface straightening plate 40 through the side of the side surface straightening plate 40 as shown by the dashed arrow in FIG. 12. This makes it possible to suppress the concentration of the air flow on the peripheral portion of the substrate 9. Therefore, it is possible to suppress uneven drying of the coating layer 90 formed on the upper surface of the substrate 9.

<3-7. Seventh Modified Example>
The reduced pressure drying apparatus 1 of the above embodiment includes the bottom surface flow plate 40 and four side surface flow plates 50 in the chamber 10. However, the reduced pressure drying apparatus 1 may include a top surface flow plate 51 as shown in FIG. 13 in addition to the bottom surface flow plate 40 and the four side surface flow plates 50. The top surface flow plate 51 is located between the upper surface of the substrate 9 supported by the stage 20 and the lower surface of the top plate portion 13 of the chamber 10. The top surface flow plate 51 extends horizontally along the lower surface of the top plate portion 13 of the chamber 10. The top surface flow plate 51 is fixed to the top plate portion 13 of the chamber 10 via a plurality of supports (not shown).

The top surface straightening plate 51 has a plurality of openings 52 through which gas can pass. In this way, when the pressure inside the chamber 10 is reduced, the gas on the upper side of the substrate 9 flows through the plurality of openings 52 and into the upper side of the top surface straightening plate 51. Then, as shown by the dashed arrows in FIG. 13, an airflow is formed toward the exhaust ports 16a to 16d through the space between the top surface straightening plate 51 and the top plate portion 13, the space between the side surface straightening plate 50 and the side wall portion 12, and the space between the bottom surface straightening plate 40 and the bottom plate portion 11. Even with this configuration, the gas flows through a space away from the substrate 9, thereby reducing the airflow formed near the substrate 9. In addition, the concentration of the airflow at the peripheral portion of the substrate 9 can be suppressed. Therefore, the coating layer 90 formed on the upper surface of the substrate 9 can be prevented from drying unevenly.

<3-8. Other Modifications>
In the above embodiment, the chamber 10 has four exhaust ports 16a to 16d. However, the number of exhaust ports included in the chamber 10 may be two, three, five or more.

The reduced pressure drying apparatus 1 in the above embodiment dries the coating layer 90 on the substrate 9 by reducing pressure only. However, the reduced pressure drying apparatus 1 may also dry the coating layer 90 on the substrate 9 by reducing pressure and heating.

In the above embodiment, the side wall portion 12 of the chamber 10 is provided with an entrance/exit 14 for the substrate 9. However, the four side wall portions 12 and the top plate portion 13 of the chamber 10 may form an integrated lid portion, and the lid portion may be separated from the bottom plate portion 11 and retracted upward. In this case, the four side flow straightening plates 50 may be fixed to the lid portion and be movable upward together with the lid portion.

The reduced pressure drying apparatus 1 in the above embodiment processes substrates for organic electroluminescence displays. However, the reduced pressure drying apparatus of the present invention may also process substrates for other precision electronic components such as liquid crystal displays and semiconductor wafers.

Furthermore, the elements appearing in the above embodiments and variations may be combined as appropriate to the extent that no contradictions arise.

REFERENCE SIGNS LIST 1 reduced pressure drying apparatus 9 substrate 10 chamber 11 bottom plate portion 12 side wall portion 13 top plate portion 16a exhaust port 16b exhaust port 16c exhaust port 16d exhaust port 16f air supply port 20 stage 21 support plate 22 support pin 23 lifting mechanism 30 reduced pressure mechanism 31 exhaust piping 32 vacuum pump 40 bottom surface current plate 50 side surface current plate 51 top surface current plate 60 air supply mechanism 61 air supply piping 70 atmospheric pressure sensor 80 control unit 90 coating layer Va individual valve Vb individual valve Vc individual valve Vd individual valve Ve main valve Vf air supply valve

Claims (9)

A reduced pressure drying apparatus for drying a coating layer containing a solvent formed on an upper surface of a substrate by reducing pressure, comprising:
a chamber for housing a substrate;
a stage that supports a substrate from below within the chamber;
A plurality of exhaust ports provided in the chamber;
a pressure reducing mechanism that sucks gas from within the chamber through the plurality of exhaust ports;
A control unit that controls the pressure reduction mechanism;
Equipped with
The pressure reducing mechanism includes:
A plurality of individual pipes each having one end connected to the plurality of exhaust ports;
One main pipe connected to the other end of the plurality of individual pipes;
a plurality of individual valves provided in the plurality of individual pipes, each valve individually adjusting the amount of exhaust from the plurality of exhaust ports;
A main valve whose opening degree is adjustable and is provided in the main pipe;
having
The control unit performs a switching process to change the open/closed state or opening degree of some of the plurality of individual valves while maintaining the opening degree of the main valve, and to sequentially change the opening/closing state or opening degree of some of the individual valves. The reduced pressure drying apparatus according to claim 1,
The reduced pressure drying apparatus, wherein the plurality of exhaust ports are positioned below a substrate supported by the stage. The reduced pressure drying apparatus according to claim 1 or 2,
The plurality of individual valves are on-off valves,
The control unit closes some of the individual valves and opens other individual valves, thereby sequentially changing the some of the individual valves. The reduced pressure drying apparatus according to claim 3,
The control unit closes one individual valve and opens another individual valve, thereby sequentially changing the one individual valve. The reduced pressure drying apparatus according to any one of claims 1 to 4,
The plurality of individual valves are valves capable of adjusting the degree of opening,
The control unit sequentially changes the opening degrees of some of the individual valves by making the opening degrees of some of the individual valves smaller than the opening degrees of other individual valves. The reduced pressure drying apparatus according to claim 5,
The control unit sequentially changes the opening degree of one individual valve to be smaller than the opening degrees of other individual valves. The reduced pressure drying apparatus according to any one of claims 1 to 6,
The control unit executes the switching process at least when the coating layer boils. The reduced pressure drying apparatus according to any one of claims 1 to 7,
The top surface of the substrate is
A portion covered with the coating layer;
a portion exposed from the coating layer; and
A reduced pressure drying apparatus having A reduced pressure drying method for drying a coating layer containing a solvent formed on an upper surface of a substrate by reducing pressure, comprising the steps of:
a) housing a substrate in a chamber;
b) sucking gas out of the chamber through a plurality of exhaust ports provided in the chamber;
having
The pressure reducing mechanism for performing the step b) is
A plurality of individual pipes each having one end connected to the plurality of exhaust ports;
One main pipe connected to the other end of the plurality of individual pipes;
a plurality of individual valves provided in the plurality of individual pipes, each valve individually adjusting the amount of exhaust from the plurality of exhaust ports;
A main valve with adjustable opening provided in the main pipe;
having
The step b) includes a switching process of sequentially changing an open/closed state or an opening degree of some of the individual valves among the plurality of individual valves while maintaining an opening degree of the main valve.

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