Patent Application
20240399406
Embodiments of the present invention relate to a coating device, a meniscus head, and a coating method.
An organic thin-film solar cell and an organic/inorganic hybrid solar cell using an organic semiconductor are expected as low-cost solar cells because an inexpensive coating method can be applied when forming an active layer. To realize the organic thin-film solar cell and the organic/inorganic hybrid solar cell at low cost, it is required to uniformly coat a coating material for forming an organic active layer and other layers. The thickness of each layer is about several nm to several 100 nm, and it is required to form such an extremely thin layer to a large area with good uniformity. For example, a meniscus coating method is known as one of roll-to-roll (R2R) coating methods capable of coating an extremely thin layer to a large area at low cost. As the meniscus coating method, a method of supplying a liquid to a coating bar from a plurality of nozzles to obtain a coating film with a large area is simple, and a structure of an instrument is also simple. However, it may be difficult to obtain a uniform film thickness by controlling a film thickness of an intermediate portion of the adjacent nozzle to be the same as a film thickness of other portions.
A coating device according to the embodiment is a device which is configured to supply a coating liquid to a surface of a base material and to form a coating film by a meniscus method, the coating device comprising:
A meniscus head according to the embodiment which id disposed apart from a base material and supplying a coating liquid to a surface of the base material to form a coating film, the meniscus head comprising:
A coating method according to the embodiment for forming a coating film on a surface of a base material by supplying a coating liquid to a space between a coating bar and the base material and forming a meniscus, the coating method comprising:
Note that the same reference numerals are assigned to the same configurations throughout the embodiments, and a redundant description thereof will be omitted. In addition, each drawing is a schematic view for promoting the embodiments and the understanding thereof, the shape, size, ratio, and the like are different from those of the actual device, and the shape, size, ratio, and the like can be appropriately changed in design considering the following description and known techniques.
The coating device can further comprise a coating liquid tank 108 and a pipe 109. Such members feed the coating liquid 104 stored in the coating liquid tank 108 to the slot die 106.
The base material conveyed from the coating device is usually conveyed to a drying device (not illustrated) and is dried.
In the coating device according to the embodiment, each of the members is disposed such that the coating liquid discharged from the slot die is not directly applied to the surface of the base material, but the coating liquid supplied from the slot die is supplied to a space between the coating bar and the base material via the surface of the coating bar to form the meniscus.
The number of slot dies may be one, or a plurality of slot dies may be arranged as illustrated in
As one of coating methods of forming a coating film on a base material, meniscus coating is known. The “meniscus” is a phenomenon in which a surface of a liquid forms a concave or convex curved surface. When a coating liquid containing various materials is injected into a space between a coating bar and the base material, the meniscus is formed on the liquid surface. When the base material is moved while the meniscus is formed, the coating film can be formed on the base material.
In meniscus coating using a coating bar, a liquid is generally supplied to the coating bar by a syringe needle. In addition, when continuous coating is required as in a roll-to-roll method (sometimes referred to as R2R), a coating liquid is often supplied from a plurality of needles to a single coating bar. Here, an interval between the adjacent needles varies depending on physical properties of a coating liquid to be used, a coating liquid film, a specific speed, and the like. Since the number of needles that can be arranged for a single coating bar is limited as a supply structure of the coating liquid becomes complicated, it is difficult to use a long coating bar. In addition, it is difficult to stably supply the coating liquid to an intermediate portion of the adjacent needles, and streaks may occur in the coating liquid.
In coating by a slot die (slot coating), a liquid is generally supplied to one slot die. When a wide coating width is required, a discharge port of the slot die also becomes long. A coating liquid is usually injected into the slot die from a central injection port, and the coating liquid is distributed to the entire discharge port. When a viscosity of the coating liquid is small, pressure is less likely to be transmitted to both end sides of the discharge port of the long slot die, and it is difficult to uniformly discharge the liquid from the slot die discharge port.
In the coating device according to the present embodiment, a coating liquid discharged from a slot die is supplied to a surface of a base material via a coating bar, thereby performing meniscus coating. According to such method, a coating film with improved uniformity can be formed even when the coating liquid is unevenly discharged from the slot die. Furthermore, by using a plurality of slot dies, even in meniscus coating using a long coating bar, it is possible to perform uniform coating liquid supply from a plurality of short slot dies to the coating bar, thereby making it possible to perform uniform coating in a large area as well. In a method in which a plurality of short slot dies are arranged without using the coating bar and discharge liquids from the slot dies are directly coated on the base material, the coating film between the slot dies tends to be non-uniform. On the other hand, in the present embodiment in which the coating liquid is supplied to the surface of the base material via the coating bar, the coating liquid is easily distributed uniformly on the coating bar.
In the coating device according to the present embodiment, the cross-sectional shape of the coating bar in a plane perpendicular to the longitudinal direction can be constant. The cross-sectional shape of the coating bar 101 is arbitrary. The cross-sectional shape of the coating bar 101 is, for example, a circular shape, a flat circular shape, or a polygonal shape. A portion of the cross-sectional shape may be a curved shape, and other portions may be a linear shape. For example, the cross-sectional shape of the surface of the coating bar 101 facing the base material 102 may be a curved shape.
The coating bar 101 preferably comprises, for example, at least one selected from a group consisting of stainless steel, aluminum, titanium, and glass. Accordingly, processing of the coating bar 101 is facilitated. In one example, the surface of the coating bar 101 is a mirror surface. In another example, the surface of the coating bar 101 may have an uneven portion.
In the embodiment, the longitudinal direction of the coating bar and the coating liquid discharge port of the slot die are preferably parallel to each other. Therefore, it is possible to have a position detection member that detects that the longitudinal direction of the coating bar and the coating liquid discharge port of the slot die are parallel to each other before start of coating or during coating. As a detection method, an optical method is preferable, and an image camera is preferable.
In the coating device according to the present embodiment, it is preferable to control a distance between the coating bar and the slot die during coating. Therefore, it is possible to further comprise an interval measuring member that measures an interval between the coating bar and the slot die before start of coating or during coating. Here, in the coating device according to the embodiment, the coating bar and the slot die may be in contact with each other. When the coating bar and the slot die are in contact with each other, the coating liquid can be directly coated on the coating bar, and repelling of the coating liquid tends to hardly occur. Therefore, the interval measuring member can be used as a device that detects contact between the coating bar and the slot die. The contact between the coating bar and the slot die is easily detected, and uniformity of the coating film can be improved by maintaining a contact state therebetween.
In addition, in the coating device according to the present embodiment, a member that measures electric resistance between the coating bar and each slot die (an electric resistance measuring device) can be used as the interval measuring member. When the slot die and the coating bar are made of stainless steel or the like having conductivity and a plurality of slot dies are provided, if the slot dies are insulated from each other, by measuring electric resistance between the coating bar and the slot die, the contact can be detected as the electric resistance is drastically reduced at the moment of contact. In addition, since the electric resistance also changes depending on a contact state, the contact state can be monitored.
It is desirable to install wiring connected to the electric resistance measuring device in advance to the slot die and the coating bar. The wiring can be provided with an opening/closing part, and the slot die can be moved to confirm the contact state with the coating bar before coating. In addition, if the electric resistance is continuously measured during coating as well, it is possible to detect a case in which there is an abnormality in contact between the slot die and the coating bar. The electric resistance measuring device can also be an external device separated from the coating device.
The coating device according to the present embodiment can comprise coating liquid supply members, for example, pumps, the number of which is smaller than the number of slot dies. For example, as illustrated in
When the coating device according to the present embodiment comprises a plurality of slot dies, a member that controls an interval between the slot dies can be provided. An example of the member that controls the interval between the slot dies comprises a spacer provided between the slot dies.
In the coating device according to the embodiment, the slot die can be individually attached and detached.
In the coating device according to the embodiment, a pipe for supplying the coating liquid to the slot die may comprise a joint that can be attached to and detached from the slot die. With such a structure, the individual slot die can be easily attached and detached.
The coating device according to the embodiment can comprise each pipe connected from one coating liquid tank to each slot die. As a result, the arrangement of the pipes can be simplified, and it is easy to uniformly control the supply amount of the coating liquid to each pipe by uniformly applying pressure from the tank.
In the coating device according to the embodiment, the moving direction of the base material is not particularly limited, but it is preferable to coat the base material while conveying the base material from the bottom to the top in the vertical direction. By moving the base material from the bottom to the top in the vertical direction, gravity is applied to a meniscus portion, such that a uniform film can be easily formed, and coating can be performed at a higher speed. However, the moving direction can be adjusted depending on the configuration of the device, the physical properties of the coating liquid, and the like, and is generally in the range of +30° from the vertical direction.
A base material conveyance member preferably conveys the base material from the bottom to the top, and here, the slot die is preferably disposed to supply the coating liquid from an upper portion of the coating bar. Liquid dripping can be suppressed by supplying the coating liquid from the upper portion of the coating bar.
The coating device according to the embodiment may further comprise a member that measures and controls a distance between the coating bar and the base material. Since the meniscus is formed between the coating bar and the base material, the uniformity of the thickness of the coating film can be further increased by controlling the distance between the coating bar and the base material.
The coating device according to the embodiment may further comprise a member that cleans the coating bar. As a result, the coating bar can be periodically washed to remove impurities mixed from the atmosphere and solid matters precipitated from the coating liquid. Specific examples thereof comprise a member that sprays or emits a solvent such as water, a member that applies ultrasonic waves, and the like.
The coating device according to the embodiment can further comprise a member that collects an excessive coating liquid. By providing such a member, it is easy not only to prevent a reverse flow of the coating liquid and loss of the expensive coating liquid after completion of coating, but also to prevent release of the solvent or the like to the environment.
A second embodiment relates to a meniscus head. The meniscus head according to the embodiment is used, for example, as a part of the coating device 10 (and a modification thereof) described in relation to the first embodiment.
In the meniscus head according to the embodiment,
The coating liquid discharged from the slot die is supplied to a gap between the coating bar and the base material disposed apart from the coating bar via the surface of the coating bar to form a meniscus, and the base material is conveyed to form a coating film.
The fixing member can adopt various structures, and a structure that is easy to remove and easy to clean is preferable. It is preferable that a shaft of the coating bar and a shaft connecting the respective slot dies to each other are connected and fixed to each other, and an interval between the coating bar and a discharge port of the slot die is adjusted by an adjustment member 204.
Each of the slot dies preferably comprises a member (not illustrated) for removing air mixed into the slot die after the coating liquid is introduced into the slot die from a coating liquid introduction port 202a.
In the meniscus head 200 of the embodiment, a length of the coating bar in the longitudinal direction may be equal to or greater than 30 cm, and a length of a coating liquid discharge port (not illustrated) of the slot die 202 may be equal to or less than 10 cm.
The third embodiment relates to a coating method. In the coating method according to the embodiment, for example, coating is performed using the coating device 100 (and a modification thereof) described in relation to the first embodiment.
In the coating method according to the present embodiment, a length of the coating bar in the longitudinal direction can be equal to or greater than 30 cm, and a length of the discharge port of the slot die can be equal to or less than 10 cm.
In the coating method according to the present embodiment, a viscosity of the coating liquid at a temperature during coating can be equal to or less than 2×10−3 kg·m/s (2 cp).
In the step (S32) of the coating method according to the present embodiment, a method of confirming the interval between the slot die and the coating bar may be to measure electric resistance therebetween.
In the coating method according to the present embodiment, a coating liquid discharge port of the slot die is preferably parallel to the coating bar, and the coating method may further comprise a step of confirming that the coating liquid discharge port and the coating bar are arranged to be parallel to each other.
In the coating method according to the present embodiment, it is preferable that the supply of the coating liquid is started before the base material is conveyed to form the meniscus between the coating bar and the base material. A uniform film can be formed by starting conveyance of the base material after the meniscus is formed.
In Example 1, a transparent electrode film is produced as follows using the coating device 100 illustrated in
A Teflon tube is connected to each of the slot dies by an attachable and detachable joint, and a coating liquid is supplied to each of the slot dies by three small pumps. As the coating liquid, a silver nanowire aqueous dispersion liquid having a viscosity of 1.7×10−3 kg·m/s at a temperature during coating is prepared. The coating liquid is supplied to the slot die and air is removed. An interval between the coating bar and each slot die is adjusted, and it is confirmed that an outlet of the slot die is parallel to the coating bar. A PET base material is used as a base material, and the coating bar is disposed using an actuator such that a minimum gap distance between the coating bar and the PET base material is 200 μm. A meniscus column is formed by supplying 0.2 mL of the coating liquid from each of the slot dies before conveying the base material. While controlling the gap distance between the coating bar and the PET base material, the PET base material is conveyed and the coating liquid is continuously supplied to obtain a coating film. The moving speed of the PET base material is constant at 83 mm/s. After coating, the PET base material is continuously dried in a hot air drying furnace corresponding to R2R. The prepared coating film has high uniformity.
Instead of the coating device illustrated in
Instead of the coating device illustrated in
Instead of the coating device illustrated in
An ITO/Ag alloy/ITO transparent electrode having sheet resistance of 10Ω/□ is prepared on a rolled PET film having a width of 300 mm by an R2R-compatible sputtering device. Next, the transparent electrode is patterned by laser scribing into a strip shape having a separation region with a cell pitch of 12 mm and a width of 50 μm.
Coating is performed on the coating device illustrated in
A PEDOT/PSS aqueous dispersion liquid is prepared as a coating liquid for producing a hole transport layer, and the coating bar is disposed using an actuator such that a minimum gap distance between the coating bar and a PET base material having a transparent electrode formed thereon is 150 μm.
After removing air in the slot die, it is confirmed by measuring electric resistance that the coating bar and the slot die are in contact with each other, and a meniscus column is formed by supplying the coating liquid from the slot die to the coating bar before conveying the base material. The PET base material is conveyed, and the coating liquid is continuously supplied to obtain a coating film. The moving speed of the PET base material is constant at 83 mm/s. The coating film is continuously dried in a hot air drying furnace corresponding to R2R.
Next, 8 mg of 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}]/p-type semiconductor) and 12 mg of PC70BM ([6,6]phenyl C71 butyric acid methylester/n-type semiconductor) are dispersed in 1 ml of monochlorobenzene, thereby preparing a coating liquid as a material for forming an organic active layer of a solar cell. The coating bar is disposed on the PET base material having a hole transport layer formed thereon using an actuator such that a minimum gap distance between the coating bar and the PET base material is 300 μm. The meniscus column is formed by supplying the coating liquid from each of the slot dies to the coating bar before conveying the base material. While controlling a distance of the PET base material of the slot die, the PET base material is conveyed and the coating liquid is continuously supplied to obtain a coating film. The moving speed of the PET base material is constant at 83 mm/s. The PET base material is continuously dried in a hot air drying furnace corresponding to R2R. Both the prepared coating films are uniform.
Although some embodiments of the present invention have been described, the embodiments have been presented as examples, and are not intended to limit the scope of the invention. The novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. The embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the scope equivalent thereto.
This application is based upon and claims the benefit of priority from the prior International Patent Application PCT/JP2022/042173, filed on Nov. 14, 2022, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/042173 | Nov 2022 | WO |
| Child | 18804283 | US |
