Coating apparatus and coating method

Abstract

According to an embodiment of the present invention, a coating apparatus and a coating method that are capable of forming a uniform coating film are provided. This coating apparatus 100 comprises: a coating bar; a substrate conveying member that conveys a substrate; and a coating liquid supply member that supplies coating liquid to the coating bar. The coating apparatus 100 further comprises a leveling bar downstream of the coating bar with respect to a coating process, and the leveling bar is positioned at a position at which the coating liquid forms a meniscus between the leveling bar and the substrate.

Description

Coating device and coating method

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to a coating apparatus and a coating method that can be used in forming devices.

[0002] Organic thin-film solar cells and organic / inorganic hybrid solar cells using organic semiconductors are expected to be low-cost solar cells because inexpensive coating methods can be used to form the active layer. To realize organic thin-film solar cells and organic / inorganic hybrid solar cells at low cost, it is necessary to uniformly apply the coating materials that form the organic active layer and other layers. The thickness of each layer is on the order of a few nanometers to a few hundred nanometers, and it is necessary to form such extremely thin layers uniformly over a large area. For example, meniscus coating and slit coating are known as roll-to-roll (R2R) coating methods that can coat extremely thin layers over large areas at low cost. However, simply adopting these conventional methods can sometimes make it difficult to achieve a uniform film thickness. Therefore, a coating device that can apply a liquid using a more uniform coating bar and form a uniform coating film is desired.

[0003] Japanese Patent Application Laid-Open No. 2003-251256

[0004] An embodiment of the present invention provides a coating apparatus and a coating method that can form a uniform coating film.

[0005] The embodiments provided by the present invention are as follows. [1] A coating device including a coating bar, a substrate transport member that transports a substrate, and a coating liquid supply member that supplies a coating liquid to the coating bar, further including an equalizing bar downstream of the coating bar, the equalizing bar being positioned so that the coating liquid forms a meniscus between the equalizing bar and the substrate. [2] The coating device according to [1], further including an equalizing bar position adjustment member that controls the distance between the equalizing bar and the substrate. [3] The coating device according to [1] or [2], wherein the equalizing bar is positioned so that it does not rotate. [4] The coating device according to any one of [1] to [3], further including a coating bar position adjustment member that controls the position of the coating bar. [5] The coating device according to any one of [1] to [4], wherein the coating liquid is supplied from a plurality of nozzles. [6] The coating device according to [5], wherein the opening faces of the plurality of nozzles are needle-shaped and cut at an angle of 75 degrees or more and 105 degrees or less. [7] The coating device according to [5] or [6], wherein the nozzle is removable. [8] The coating device according to any one of [5] to [7], further comprising a nozzle that supplies the coating liquid to the equalizing bar. [9] The coating device according to any one of [1] to [4], wherein the coating liquid is supplied from a slit die head.

[10] The coating device according to any one of [1] to [9], wherein the equalizing bar is curved.

[11] A coating method for forming a coating film by applying a coating liquid to the surface of a substrate using a coating bar, wherein the equalizing bar is disposed downstream of the coating bar, and a meniscus is formed between the substrate and the equalizing bar by the coating liquid supplied from the primary coating film formed by the coating bar, thereby forming a secondary coating film.

[12] The coating method according to

[11] , wherein the coating liquid is supplied from multiple nozzles to the surface of the coating bar, and the coating liquid is supplied from the surface to between the coating bar and the substrate, thereby forming the primary coating film.

[13] The coating method according to

[12] , wherein the positions of the plurality of nozzles are adjusted to detect the distance between the coating bar and the plurality of nozzles, and then the coating liquid is supplied.

[14] The coating method according to

[13] , wherein the distance is detected by measuring an electrical resistance between the nozzle and the coating bar.

[15] The coating method according to any one of

[12] to

[14] , wherein the plurality of nozzles are mounted on a single cantilever fixed plate that is capable of rotation, horizontal movement, or vertical movement.

[0006] Fig. 1 is a schematic side view illustrating a coating apparatus according to a first embodiment. Fig. 2 is a schematic top view illustrating the coating apparatus according to the first embodiment. Fig. 3 is a flowchart illustrating a coating method according to a second embodiment.

[0007] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0008] The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing.

[0009] In the present specification and the drawings, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0010] First Embodiment Fig. 1 is a schematic side view illustrating a coating apparatus according to a first embodiment. Fig. 2 is a schematic top view illustrating the coating apparatus according to the first embodiment.

[0011] As shown in FIG. 1 , a coating apparatus 100 according to an embodiment includes a coating bar 101, a substrate transport member 102 for transporting a substrate, a coating liquid supply member 104 for supplying a coating liquid 103 stored in a liquid reservoir 112 to the coating bar, and an equalizing bar 105. The equalizing bar 105 is positioned so that the coating liquid forms a meniscus between the equalizing bar and the substrate. In this example, the coating bar is used to form a primary coating film by the so-called meniscus method. The components are arranged so that the coating liquid 103 is supplied from a nozzle 106 to the surface of the coating bar 101, the coating liquid flows from the surface of the coating bar between the coating bar 101 and the substrate 107, forming a meniscus 103Ma, and the substrate is transported in the direction of the arrow to form a primary coating film 108a.

[0012] In the embodiment, the cross-sectional shape of the coating bar 101 is arbitrary. The cross-sectional shape may be, for example, a circle, a flattened circle, or a polygon. The cross-sectional shape may have a curved portion corresponding to the meniscus forming portion and a linear portion. For example, the cross-sectional shape of the surface of the coating bar 101 facing the substrate 107 may be curved.

[0013] The applicator bar can be arranged so that it does not rotate. By not having the applicator bar rotate like a roller, the meniscus becomes more stable.

[0014] The coating bar 101 includes, for example, at least one selected from the group consisting of stainless steel, aluminum, titanium, and glass. This allows for easy processing when preparing the coating bar 101. In one example, the surface of the coating bar 101 is a mirror finish. In another example, the surface of the coating bar 101 may include a textured structure.

[0015] As shown in FIGS. 1 and 2, the equalizing bar 105 is disposed downstream of the coating bar 101 .

[0016] The coating bar 101 applies the coating liquid 103 to almost the entire surface of the substrate 107, forming a coating film 108a, but the coating film 108a may not be sufficiently uniform. In this embodiment, the coating film 108a formed comes into contact with the equalizing bar 105 disposed downstream of the coating bar as the substrate is transported. As shown in FIG. 1 , a meniscus 103Mb of the coating liquid 103 can be formed between the substrate 107 and the equalizing bar 105. The surface tension of the coating liquid spreads the coating liquid laterally across the gap between the equalizing bar 105 and the substrate 107, creating a uniform meniscus 103Mb. When the meniscus 103Mb contacts the substrate 107, a highly uniform secondary coating film 108b is formed on the substrate 107 by the coating 103. The coating film 108b can be solidified, for example, by drying, to obtain the desired film (solid film). This can be achieved, for example, by disposing a drying member 109 downstream of the equalizing bar.

[0017] In this way, for example, by moving the substrate 107 along the movement direction (the direction of the arrow in the figure), it is possible to form a coating film 108b with a large area on the substrate 107. The coating device illustrated in Figures 1 and 2 forms a primary coating film by the meniscus method, and can further include a nozzle position adjustment member 110 that adjusts the position of the nozzle 106, a nozzle position detection member 111 that detects the distance between the coating bar 101 and the nozzle 106, etc.

[0018] When a nozzle is used to form the primary coating film, multiple nozzles 106 or multiple pumps 104 can be used, as shown in FIG. 2. The multiple nozzles 106 can face the coating bar 101. As shown in FIG. 2, the multiple nozzles 106 can supply the coating liquid 103 toward the coating bar 101. An additional nozzle can also be provided to supply the coating liquid to the equalizing bar 105. By providing such an additional nozzle, a meniscus can be formed between the substrate and the equalizing bar before the start of coating and before the primary coating film is formed.

[0019] As shown in Figure 2, the multiple nozzles 106 are aligned along a first direction. The first direction is, for example, the Y-axis direction. A direction perpendicular to the Y-axis direction is defined as the X-axis direction. The movement direction of the substrate can coincide with the X-axis. A direction perpendicular to the Y-axis direction and the X-axis direction is defined as the Z-axis direction. The coating bar 101 extends along, for example, the Y-axis direction.

[0020] In an embodiment, the number of the plurality of nozzles 106 can be three or more. This allows a large-area primary coating film 108a to be stably formed. In the example of FIG. 2, the number of the plurality of nozzles 106 is four. In an embodiment, the number may be any integer of three or more.

[0021] In an embodiment, the nozzle may be a slot die or may be needle-shaped. Using multiple needle-shaped nozzles 106 allows, for example, the discharge amount of the coating liquid 103 to be controlled with high precision. When the nozzles are needle-shaped, for example, the tips of the multiple nozzles can easily come into contact with the coating bar 101. Needle-shaped nozzles provide high flexibility. High flexibility can prevent the nozzle from being damaged by, for example, vibration of the coating bar 101. In needle-shaped nozzles, the length of the nozzle is, for example, 10 mm or more and 100 mm or less, and the inner diameter of the nozzle is, for example, 0.5 mm or more and 2 mm or less. The angle between the end face of the nozzle tip and the direction in which the nozzle extends is, for example, approximately 90 degrees (for example, 75 degrees or more and 105 degrees or less). This shape can prevent scratches on the coating bar 101, for example.

[0022] However, when there are multiple nozzles, the distance between the coating bar 101 and the tip of each nozzle is likely to vary. If there is variation, the meniscus 103Ma formed from each nozzle is likely to be disturbed, and as a result, the coating film 108a is likely to become non-uniform.

[0023] 1 and 2, by providing a nozzle position adjustment member 110 that adjusts the position of each nozzle and a nozzle position detection member 111 that detects the distance between the coating bar 101 and each nozzle 106, it is possible to reduce variations in the position and distance between the tip of each nozzle and the coating bar, enabling uniform coating.

[0024] In an embodiment, a member for detecting contact between the coating bar and each nozzle may be further provided. Contact can be easily detected, for example, by measuring the electrical resistance between the nozzle and the coating bar, and coating conditions can be adjusted based on this detection result to reduce variation. When contact is present, the coating liquid can be applied directly to the coating bar, making it less likely for the coating liquid to repel.

[0025] In an embodiment, a component for measuring the electrical resistance between each nozzle and the coating bar can be used to detect contact between the coating bar and each nozzle. If each nozzle and coating bar are made of conductive stainless steel or the like and the nozzles are insulated, measuring the electrical resistance between the coating bar and each nozzle will reveal a sharp drop in electrical resistance the moment they make contact. Furthermore, since electrical resistance changes as the contact state changes, it is possible to monitor the contact state. For example, if the nozzle is pressed so strongly against the coating bar that it bends too much, the coating bar will contact not only the tip of the nozzle but also its side, resulting in very low electrical resistance. In this case, the coating liquid is likely to be ejected from the tip of the nozzle to areas other than the coating bar, resulting in uneven coating. The optimal electrical resistance varies depending on the shape and material of the nozzle and coating bar, so it is desirable to measure it in advance.

[0026] It is desirable to install wiring between each nozzle and the coating bar in advance to connect them to an electrical resistance measuring device. An opening and closing section is provided in the wiring, so that each nozzle can be moved before coating to check contact with the coating bar. Furthermore, if electrical resistance is measured during coating, any abnormalities in the contact between the nozzle and coating bar can be detected. The electrical resistance measuring device can also be an external device separate from the coating device.

[0027] In the coating device according to the embodiment, it is preferable that the nozzles are removable. Nozzles are prone to clogging due to their small openings. In the coating device according to the embodiment, when such clogging occurs, the discharge rate of each nozzle can be adjusted using a coating liquid supply member or a coating liquid supply rate adjustment member. However, if the clogging becomes significant or if discharge becomes completely impossible, the nozzles must be cleaned or replaced. In such cases, it is preferable that the nozzles are removable, as this facilitates maintenance.

[0028] The above description has been given of the case where the coating liquid is supplied from multiple nozzles as shown in Figures 1 and 2 to form the primary coating film 108a by the meniscus method, but the primary coating film may also be formed by other methods. For example, instead of multiple nozzles, a coating bar can be used for slit coating, and a slit die head can be used which has an internal manifold and supplies the coating liquid to the substrate surface from the manifold via a slit. Furthermore, instead of the nozzles in Figures 1 and 2, a slit die head can be used to supply the coating liquid to the coating bar.

[0029] The coating device 100 may further include a drying member 109. The drying member 109 is capable of drying the coating film 108b applied to the substrate 107. The drying member 109 may include, for example, an air nozzle or a far-infrared lamp.

[0030] The distance between the coating bar 101 and the equalizing bar 105 can be freely changed. It is also preferable to provide a member for controlling the gap between the equalizing bar 105 and the substrate 107. For this purpose, a gap ring, a micrometer, or the like can be used.

[0031] The equalizing bar may be straight or curved. A straight bar makes it easier to achieve uniform thickness of the coating film. A curved bar makes it easier to vary the thickness, for example, making it thicker in the center, but it also makes it easier to achieve uniformity in the coating direction.

[0032] In the embodiment, the cross-sectional shape of the equalizing bar 105 is arbitrary. The cross-sectional shape may be, for example, a circle, a flattened circle, or a polygon. A portion of the cross-sectional shape may be curved and another portion may be linear. For example, the cross-sectional shape of the surface of the equalizing bar 105 facing the substrate 107 may be curved.

[0033] The equalization bar can be positioned so that it does not rotate. By not rotating the equalization bar like a roller, the meniscus becomes more stable.

[0034] The equalizing bar 105 includes, for example, at least one selected from the group consisting of stainless steel, aluminum, titanium, and glass. This allows for easy processing when preparing the equalizing bar 105. In one example, the surface of the equalizing bar 105 is a mirror finish. In another example, the surface of the equalizing bar 105 may include a textured structure.

[0035] Second Embodiment The second embodiment relates to a coating method. In the coating method according to the embodiment, coating is performed using, for example, the coating apparatus 10 (and its modifications) described in relation to the first embodiment.

[0036] FIG. 3 is a flow chart illustrating a coating method (S30) according to a second embodiment. This coating method involves forming a meniscus of coating liquid and applying the liquid. It includes a step of detecting and adjusting the distance between the coating bar and meniscus equalizing bar and the substrate (S31), a step of detecting and adjusting the distance between the coating bar and each nozzle (S32), a step of creating a meniscus between the substrate and the equalizing bar (S33), and a step of supplying the coating liquid and applying the liquid to the substrate (S34). By performing step S33 before step S34, the meniscus M22 is stably generated during the coating process. In this way, it is preferable to provide an additional nozzle that supplies the coating liquid to the equalizing bar in order to form a meniscus between the substrate and the equalizing bar before the start of coating.

[0037] In an embodiment, the distance between the coating bar and each nozzle can be detected by measuring the electrical resistance between the coating bar and the nozzle. Each nozzle can be mounted on a single cantilevered plate that can rotate, move horizontally, or move vertically. This arrangement allows the positions of all nozzles to be adjusted simultaneously.

[0038] Specific examples of the coating apparatus and coating method according to the embodiment will be described below.

[0039] For example, a solar cell can be formed by coating using the coating device 100. In one example, the number of pumps is four. A pipe connected to one pump is connected to four nozzles. The total number of nozzles is 16. The nozzles are attached to a single cantilever bar. Each nozzle is equipped with an actuator for movement and wiring for measuring electrical resistance. The wiring is connected to an electrical resistance meter. A nozzle position detection member, such as a camera, is installed to observe the positional relationship between the nozzle and the coating bar.

[0040] For example, the substrate 107 is a roll of PET film. The width of the PET film is, for example, 330 mm. A light-transmitting electrode having a width of 300 mm is formed on the PET film using a roll-to-roll sputtering device. The sheet resistance of the electrode is, for example, 10 Ω / □. The electrode has, for example, a laminated structure of ITO film / Ag alloy / ITO film. For example, multiple electrodes are provided. The length of each of the multiple electrodes is, for example, approximately 10 mm. The spacing between the multiple electrodes is, for example, 50 μm.

[0041] The coating bar 101 and the equalizing bar 105 have a circular cross section. The radius of the circle is 10 mm. The length of the coating bar 101 and the equalizing bar 105 is 300 mm. The coating bar 101 and the equalizing bar 105 include, for example, stainless steel (e.g., SUS303).

[0042] The nozzle includes a stainless steel locking member. The nozzle is 50 mm long. The piping for the coating liquid is a polytetrafluoroethylene tube. The nozzle and the tube are connected by a detachable joint. The tube is connected to a pump.

[0043] In one example, a hole transport layer is formed by the coating liquid 103. In this case, the coating liquid 103 is an aqueous solution containing PEDOT and PSS.

[0044] For example, the relative positional relationship between the coating bar 101 and the equalizing bar 105 and the substrate 107 is controlled by a gap ring or an actuator.

[0045] For example, the nozzle is placed in a horizontal position, and in this state, the coating liquid 103 is supplied and the air in the nozzle is discharged.

[0046] After this, lower the tip of the needle nozzle and tilt it 20° from the horizontal. Bring the cantilever bar close to the coating bar. Next, bring each nozzle close to the coating bar one by one until they come into contact and the electrical resistance becomes 10 to 50 Ω.

[0047] A coating liquid is supplied to the equalizing bar 105 by a syringe to form a meniscus 103Mb between the equalizing bar and the substrate 107.

[0048] While the substrate 107 is being transported, the coating liquid 103 is continuously supplied by a pump. The moving speed of the substrate 107 is, for example, 5 m / min. The drying member 109 blows heated dry air onto the applied coating liquid 103. A solidified coating film is obtained from the coating liquid 103.

[0049] In an embodiment, after the above coating, another coating liquid may be further coated. The other coating liquid may include, for example, a semiconductor material. The other coating liquid may include, for example, PTB7 ([poly{4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-1t-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl}]) and PC70BM ([6,6]phenyl C71 butyric acid methyl ester). PTB7 is, for example, a p-type semiconductor. PC70BM is, for example, an n-type semiconductor. The other coating liquid may further include, for example, monochlorobenzene. The amount of PTB7 per 1 mL of monochlorobenzene is 8 mg. The amount of PC70BM per 1 mL of monochlorobenzene is 12 mg. Another coating liquid is a dispersion containing an organic semiconductor.

[0050] The other coating liquid becomes, for example, a semiconductor film for a solar cell. In coating the other coating liquid, the minimum gap distance between the coating bar 101 and the substrate 107 is 300 μm. The moving speed of the substrate 107 is, for example, 5 m / min. After coating, drying is performed by a drying member 109.

[0051] For example, there are organic thin-film solar cells using organic semiconductors, or organic / inorganic hybrid solar cells. High-performance solar cells can be produced by fabricating these solar cells using a coating method. In an embodiment, the coating liquid 103 may be applied to the substrate 107 at a position where the substrate 107 is transported in the vertical direction. This applies, for example, the effect of gravity to the meniscus, making it easier to obtain a uniform film even at high speeds.

[0052] According to the embodiment, a coating device and a coating method capable of forming a uniform coating film are provided.

[0053] The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, the specific configurations of the elements included in the coating device, such as the pipe, pump, nozzle, and holder, are within the scope of the present invention as long as a person skilled in the art can implement the present invention in a similar manner and obtain similar effects by appropriately selecting them from known ranges.

[0054] Furthermore, any combination of two or more elements of each specific example within the scope of technical feasibility is also included within the scope of the present invention as long as it includes the gist of the present invention.

[0055] In addition, all coating devices and coating methods that can be implemented by a person skilled in the art by appropriately modifying the design based on the coating head, coating device, and coating method described above as embodiments of the present invention also fall within the scope of the present invention, as long as they include the gist of the present invention.

[0056] In addition, within the scope of the concept of the present invention, a person skilled in the art may come up with various modifications and alterations, and it will be understood that these modifications and alterations also fall within the scope of the present invention.

[0057] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0058] DESCRIPTION OF SYMBOLS 100 Coating device 101 Coating bar 102 Substrate transport member 103 Coating liquid 104 Coating liquid supply member 105 Uniformity bar 106 Nozzle 107 Substrate 108a Primary coating film 108b Secondary coating film 109 Drying member 110 Nozzle position adjustment member 111 Nozzle position detection member 112 Liquid reservoir

Claims

1. A coating device comprising a coating bar, a substrate transport member that transports a substrate, and a coating liquid supply member that supplies a coating liquid to the coating bar, further comprising an equalizing bar downstream of the coating of the coating bar, the equalizing bar being positioned at a position where the coating liquid forms a meniscus between the equalizing bar and the substrate, and further comprising an equalizing bar position adjustment member that controls the distance between the equalizing bar and the substrate.

2. (delete)

3. The coating apparatus of claim 1 , wherein the leveling bar is arranged not to rotate.

4. The coating device according to claim 1 or 3, further comprising a coating bar position adjustment member that controls a position of the coating bar.

5. The coating device according to claim 1 or 3, wherein the coating liquid is supplied from a plurality of nozzles.

6. The coating device according to claim 5 , wherein opening faces of the plurality of nozzles are in the shape of needles cut at an angle of 75 degrees or more and 105 degrees or less.

7. The coating device of claim 5 , wherein the nozzle is removable.

8. The coating apparatus of claim 5 , further comprising a nozzle supplying the coating fluid to the leveling bar.

9. The coating device according to claim 1 or 3, wherein the coating liquid is supplied from a slit die head.

10. The coating apparatus of claim 1 or 3, wherein the leveling bar is curved.

11. A coating method for forming a coating film by applying a coating liquid to the surface of a substrate using a coating bar, comprising: disposing an equalizing bar downstream of the coating bar; forming a meniscus between the substrate and the equalizing bar using the coating liquid supplied from a primary coating film formed by the coating bar; and forming a secondary coating film while controlling the distance between the equalizing bar and the substrate.

12. The coating method according to claim 11, further comprising supplying a coating liquid from a plurality of nozzles onto a surface of the coating bar, and supplying the coating liquid from the surface to between the coating bar and the substrate, thereby forming the primary coating film.

13. The coating method according to claim 12, further comprising the step of adjusting positions of the plurality of nozzles, detecting a distance between the coating bar and the plurality of nozzles, and then supplying the coating liquid.

14. The coating method according to claim 13 , wherein the distance is detected by measuring an electrical resistance between the nozzle and the coating bar.

15. The coating method according to claim 12, wherein the plurality of nozzles are mounted on a single cantilever fixed plate that is capable of rotation, horizontal movement, or vertical movement.