Slot-Die Coating Research Articles

Influence of interfacial roughness on slot-die coatings for scaling-up high-performance perovskite solar cells

Slot-die coating (SDC) technology is a potential approach to mass produce large-area, high-performance perovskite solar cells (PSCs) at low cost. However, when the interface in contact with the perovskite ink has low wettability, the SDC cannot form a uniform pinhole-free perovskite film, which reduces the performance of the PSC. To address this issue, in this study, the wettability of the hole transport layer (HTL) interface was investigated in depth by analyzing the variation of wettability with process and its correlation with the roughness of the HTL interface. As a result, it was found that SDC could increase the roughness of the HTL interface to improve wettability and form a uniform high-quality perovskite layer without pinholes, and furthermore, SDC-based NiOx/Me-4PACz HTL suppressed energy losses at the HTL/perovskite interface. In addition, a unit cell achieved 19.17% of efficiency with long-term stability and lab cell-sized modules showed up to 17.42%.

Manufacturing supported loose-nanofiltration polymeric membranes with eco-friendly solvents on an R2R System

In this study, loose nanofiltration membranes made of polysulfone dissolved in co-solvents PolarClean and gamma-Valerolactone were prepared via slot die coating (SDC) on a roll-to-roll (R2R) system by directly coating them onto a support layer or free standing. A solution flow rate of 20 mL/min, substrate speed of 17.1 mm/s, and coating gap of 0.1 mm resulted in the formation of membranes without structural defects. Pre-wetting the support layer with dope solution minimized shrinkage of membrane layer thickness and improved interfacial adhesion. Membrane samples produced using SDC exhibited properties and performance consistent with bench-scale doctor blade extruded samples; pre-wetted and uncompressed samples (SDC-3) exhibited the highest rejection of bovine serum albumin (99.20% ± 1.31%) and along with adequate mean permeability during filtration (70.5 ± 8.33 LMH/bar). This study shows that combining sustainable materials development with SDC provides a holistic approach to membrane separations to bridge materials discovery and membrane formation.

Controlling Thin Film Morphology Formation during Gas Quenching of Slot-Die Coated Perovskite Solar Modules.

Transferring record power conversion efficiency (PCE) >25% of spin coated perovskite solar cells (PSCs) from the laboratory scale to large-area photovoltaic modules requires significant advances in scalable fabrication techniques. In this work, we demonstrate the fundamental interrelation between drying dynamics of slot-die coated precursor solution thin films and the quality of resulting slot-die coated gas-quenched polycrystalline perovskite thin films. Well-defined drying conditions are established using a temperature-stabilized, movable table and a flow-controlled, oblique impinging slot nozzle purged with nitrogen. The accurately deposited solution thin film on the substrate is recorded by a tilted CCD camera, allowing for in situ monitoring of the perovskite thin film formation. With the tracking of crystallization dynamics during the drying process, we identify the critical process parameters needed for the design of optimal drying and gas quenching systems. In addition, defining different drying regimes, we derive practical slot jet adjustments preventing gas backflow and demonstrate large-area, homogeneous, and pinhole-free slot-die coated perovskite thin films that result in solar cells with PCEs of up to 18.6%. Our study reveals key interrelations of process parameters, e.g., the gas flow and drying velocity, and the exact crystallization position with the morphology formation of fabricated thin films, resulting in a homogeneous performance of corresponding 50 × 50 mm2 solar minimodules (17.2%) with only minimal upscaling loss. In addition, we validate a previously developed model on the drying dynamics of perovskite thin films on small-area slot-die coated areas of ≥100 cm2. The study provides methodical guidelines for the design of future slot-die coating setups and establishes a step forward to a successful transfer of solution processes towards industrial-scale deposition systems beyond brute force optimization.

High-Performance Perovskite Solar Cells and Modules Fabricated by Slot-Die Coating with Nontoxic Solvents.

Energy shortage has become a global issue in the twenty-firt century, as energy consumption grows at an alarming rate as the fossil fuel supply exhausts. Perovskite solar cells (PSCs) are a promising photovoltaic technology that has grown quickly in recent years. Its power conversion efficiency (PCE) is comparable to that of traditional silicon-based solar cells, and scale-up costs can be substantially reduced due to its utilization of solution-processable fabrication. Nevertheless, most PSCs research uses hazardous solvents, such as dimethylformamide (DMF) and chlorobenzene (CB), which are not suitable for large-scale ambient operations and industrial production. In this study, we have successfully deposited all of the layers of PSCs, except the top metal electrode, under ambient conditions using a slot-die coating process and nontoxic solvents. The fully slot-die coated PSCs exhibited PCEs of 13.86% and 13.54% in a single device (0.09 cm2) and mini-module (0.75 cm2), respectively.

Numerical Simulation on Preparing Uniform and Stable Perovskite Wet Film in Slot-Die Coating Process.

Slot-die coating is regarded as a reliable and potential technology for preparing large-area perovskite solar cells with high efficiency and low cost. Therein, the formation of continuous and uniform wet film is of significance to obtain a high-quality solid perovskite film. In this work, the rheological properties of the perovskite precursor fluid are analyzed. Then, the ANSYS Fluent is introduced to establish an integrated model of internal and external flow fields during the coating process. The model is applicable to all perovskite precursor solutions with near-Newtonian fluids. Based on the theoretical simulation of finite element analysis, the preparation of 0.8 M-FAxCs1-xPbI3, one of the typical large-area perovskite precursor solutions, is explored. Accordingly, this work indicates that the coupling process parameters like the fluid supply velocity (Vin) and coating velocity (V) determine the uniformity that the solution flows out of the slit and is coated onto the substrates, and the coating windows for a uniform and stable perovskite wet film is obtained. For the upper boundary range of the coating windows, the maximum value of V and Vin follows V = 0.003 + 1.46Vin (Vin ≤ 0.1 m/s), while for its lower boundary range, the minimum value of V and Vin is V = 0.002 + 0.67Vin (Vin ≤ 0.1 m/s). When Vin is higher than 0.1 m/s, the film will break due to the excessive V. Finally, the real experiment verifies the accuracy of the numerical simulation. Hopefully, this work is of reference value for the development of the slot-die coating forming process on the perovskite precursor solution approximating Newtonian fluid.

Manipulating Organic Semiconductor Morphology with Visible Light (Adv. Funct. Mater. 10/2023)

Roll-To-Roll Slot-Die Coating In article number 2212835, Jens Wenzel Andreasen and co-workers study the optical excitation during roll-to-roll slot-die coating of a semiconducting polymer that enables morphological manipulation of thin-films for organic photovoltaics and flexible electronics. Combined theoretical and experimental techniques elucidate the morphological changes upon polymer excitation while the thin-film solidifies. The induced changes in nanostructure increase the out-of-plane electron mobility, which may be applied to modify the performance of organic electronic devices.

Reaching Highly Uniform Perovskite Ink Flow from a Slot‐Die Head Toward Printed Solar Cells

Large‐scale manufacturing of perovskite solar cells (PSCs) requires the deposition of homogeneous and defect‐free perovskite films on large‐area substrates. Up to now, the knowledge developed for industrial slot‐die processing has not been fully transferred to the perovskite photovoltaic community. Here, the deposition of uniform perovskite layers by slot‐die coating (SDC). Computer fluid dynamics (CFD) simulations, experimental validation, and calculation of industrial uniformity parameters are demonstrated, which enabled to establish processing conditions for SDC of perovskite ink. This approach allowed for obtaining stable cross‐web flow in the slot‐die head resulting in the formation of a stable coating bead yielding uniform perovskite films. The best processing parameters are used for the fabrication of slot‐die‐coated PSCs, which showed a more homogeneous spatial distribution of photovoltaic parameters compared to their spin‐coated counterparts. Better reproducibility observed in device performance is a step forward toward the commercialization of perovskite photovoltaic technology. For the first time, the industrial approach used for the optimization of slot‐die coating is applied for the processing of perovskite inks that have special conditions such as low viscosity and in situ crystallization on the substrate.

Large-Scale Preparation of Silver Nanowire-Based Flexible Transparent Film Heaters by Slot-Die Coating.

Highly flexible silver nanowire-based transparent conductive films (AgNWs TCFs) were large-scale fabricated by slot-die coating AgNWs inks on a flexible polyethylene terephthalate (PET) substrate, and further fabricated into a transparent film heater. Appropriate flow rate, coating speed, and AgNWs concentration allow the construction of the 15 cm × 15 cm AgNW TCFs with a sheet resistance (Rs) of less than 20 Ω/sq, a transmittance (T) at 550 nm higher than 95%, and a haze less than 3.5%. The resultant AgNW TCFs heater possesses high uniformity and superior mechanical stability and can reach a Joule heating temperature of 104 °C with a voltage of 12 V. The slot-die coating method has great potential for large-scale production of AgNW based film heaters promisingly used in window defrost and deicer systems.

Enabling Roll-Processed and Flexible Organic Solar Cells Based On PffBT4T Through Temperature-Controlled Slot-Die Coating

Although the mark of 18% power conversion efficiency (PCE) was surpassed recently, organic solar cells (OSCs) still have several challenges to overcome in order to fully compete with silicon-based solar cells in the energy market. One of the main challenges is the upscaling of the technology. Despite the recent advances in PCEs, a big scalability gap still exists between the best lab-scale device and large-scale modules fabricated via roll-to-roll processing. The polymer donor PffBT4T-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sub> has already shown efficiencies of almost 12% together with PCBM. Combined with the nonfullerene acceptor O-IDTBR, a reduced voltage loss of 0.5 V between the optical band gap and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> is obtained, with an open-circuit voltage up to 1.12 V, which is one of the highest values reported for OSCs. In this work, we demonstrate a route to upscaling OSCs based on PffBT4T-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sub> :O-IDTBR through temperature-controlled slot-die coating, solving the challenges of the temperature dependent aggregation behavior, which strongly affects the efficiency of the device. Efficiencies above 4% were achieved in our flexible and roll-processed devices with an area of ∼1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the different origins of the scalability lag were studied. As an additional necessary step for scalability, we incorporate the use of a hydrocarbon-based solvent to remove the environmentally dangerous halogenated solvents. To the best of our knowledge, this is the first work reporting PffBT4T:O-IDTBR solar cells fabricated in open air using slot-die coating in a roll-platform with flexible substrates, that mimics large-scale roll-to-roll processing.

Scale-up fabrication and characteristic study of oligomer-like small-molecule solar cells by ambient halogen-free sheet-to-sheet and roll-to-roll slot-die coating

The upscale fabrication of the inverted small-molecule organic solar cell (SMOSC) from spin coating to large-area slot-die coating using halogen-free solvent under the ambient air environment is developed. This work successfully adopts thermal annealing treatment to tune the bulk heterojunction (BHJ) structure for two advantages of compatibility to mass production and good photo-stability. By tuning the respective optimum film structure, the power conversion efficiency (PCE) values under AM 1.5G light and indoor light (T5 lamp with 500 lx) illuminations for the ambient spin-coated device achieve 8.5% and 13.26%, respectively. The photo-bleaching and light-soaking tests under the AM 1.5G illumination show that the photo-stability of the thermally-annealed DRCN5T:PC71BM device is much better than PTB7-Th:PC71BM device. The tunable BHJ film morphologies of large-area ITO/glass-based sheet-to-sheet (S2S) and flexible roll-to-roll (R2R) slot-die coatings of DRCN5T:PC71BM SMOSCs are based on different dry-film formation and crystallization mechanisms. The structural control during the drying-film process for S2S and R2R coatings is a critical key to determine the optimum performance. The PCEs of the ITO/glass-based and flexible ITO/PET-based SMOSCs achieve 7.6% and 7.3%, respectively. The PCE of the ambient flexible R2R slot-die-coated SMOSC using halogen-free solvent is much higher than that of the currently flexible R2R coated SMOSCs. The PCEs of S2S slot-die-coated cell device of 1 × 5 cm2 and module achieve 5.1%. We conduct a characteristic, structural and systematic study of how to scale-up SMOSC via slot-die coatings, demonstrating the relationship among processing control, performance and structure for different coatings.

Slot-Die Coating of an On-the-Shelf Polymer with Increased Dielectric Permittivity for Stack Actuators

Slot-Die Coating of an On-the-Shelf Polymer with Increased Dielectric Permittivity for Stack Actuators

Transmittance Control of a Water-Repellent-Coated Layer on a Tensioned Web in a Roll-to-Roll Slot-Die Coating System.

Solar cells are important alternatives to fossil fuels for energy generation in today’s world, where the demand for alternative, renewable sources of energy is increasing. However, solar cells, which are installed outdoors, are susceptible to pollution by environmental factors. A solution to overcome this limitation involves coating solar cell surfaces with functional coatings. In this study, we propose a transmittance control method for a tensioned web in a roll-to-roll, transparent, water-repellent film coating. First, we analyzed the effects of process conditions on the transmittance and contact angle of the transparent water-repellent film during roll-to-roll slot-die coating. It was confirmed that the tension was the most dominant factor, followed by the coating gap. Through the tension control, the transmittance was changed by 3.27%, and the contact angle of the DI water was changed by 17.7°. In addition, it was confirmed that the transmittance was changed by 0.8% and the contact angle of DI water by 3.9° via the coating gap control. Based on these results, a transmittance prediction model was developed according to the tension and coating gap, and was then verified experimentally. Finally, a water-repellent film with a high transmittance of 89.77% was obtained using this model.

Numerical Modeling of Ink Widening and Coating Gap in Roll-to-Roll Slot-Die Coating of Solid Oxide Fuel Cell Electrolytic Layer.

Slot-die coatings are advantageous when used for coating large-area flexible devices; in particular, the coating width can be controlled and simultaneous multi-layer coatings can be processed. To date, the effects of ink widening and the coating gap on the coating thickness have only been considered in a few studies. To this end, we developed two mathematical models to accurately estimate the coating width and thickness that consider these two effects. We used root mean square deviation (RMSD) to experimentally verify the developed method. When the coating gap was increased, the coating width increased and the coating thickness decreased. Experimental results showed that the estimated performances of the coating width and thickness models were as high as 98.46% and 95.8%, respectively. We think that the developed models can be useful for determining the coating conditions according to the ink properties to coat a functional layer with user-defined widths and thicknesses in both lab- and industrial-scale roll-to-roll slot-die coating processes.

Suppression of Capillary Flow in Slot-Die Coating for the Fabrication of Fine OLED Stripe

Due to lateral and vertical capillary flows appearing in a slot-die head with $\mu $ -tip for fine line coating, line breakup occurs at a relatively low coating speed, making it difficult to narrow the stripe. Through computational fluid dynamics (CFD) simulations, we demonstrate that capillary flow can be substantially suppressed by increasing the contact angle of the head lip and forming the microscale groove patterns in the dual plate (shim and meniscus guide). It is shown that the corresponding contact angle of the groove patterns increases up to 120°. Based on the simulation results, we have coated the head lip with a hydrophobic material and embedded the dual plate with micropatterns fabricated by a laser cutter into the slot-die head. Using such a hydrophobic slot-die head, we can suppress the lateral capillary flow of an aqueous poly(3,4-ethylenedioxythiophene):poly (4-styrenesulfonate) (PEDOT:PSS) to a great extent and, hence, increase the coating speed, rendering the stripe narrow ( $\approx 76~\mu \text{m}$ ). To demonstrate its applicability to organic light-emitting diodes (OLEDs), we have also fabricated fine red, green, and blue OLED stripes and successfully achieved light emission from them with the emission area of $80\,\,\mu \text{m}\,\,\times {5}$ cm.

Influence of Coating Method on Performance of Roll-to-Roll Coated PEM Fuel Cell Catalyst Layers

Industrial production of polymer electrolyte membrane fuel cell (PEMFC) electrodes will rely on continuous roll-to-roll (R2R) coating methods to meet the rates needed for mass production.1–5 R2R production commonly uses solution coating methods to coat liquids onto a moving substrate at linear speeds over 100 m/min.6 There are many coating methods, which have different coating physics and require different ink formulations. For PEMFC catalyst layers these differences may result in different morphologies and performance. As production of fuel cell vehicles and power systems increases there is a need to understand the process science of fuel cell manufacturing. Here we present the results of a study comparing fuel cell catalyst layers coated using two R2R coating methods: slot-die and gravure, shown in Figure 1. These two methods were selected because the physics of applying the liquid to the substrate is very different between the two cases. Also, they have different viscosity and wet-film thickness ranges, which may make one method better suited to certain materials or catalyst loadings. In slot die coating, the pre-metered liquid is fed through the cavity of a metal die and extruded onto the substrate, as shown in Figure 1a. In gravure coating, an engraved metal roller is used to transfer the liquid from a pan to the substrate (Figure 1b). In both of these methods the coated liquid film then consolidates into the final dry film. These methods are quite different than common lab-scale coating methods like ultrasonic spraying or hand painting where ink is repeatedly applied to the same area to build up the thickness of the catalyst layers. Pt/C catalysts layers were coated directly onto carbon-fiber gas diffusion media to create gas diffusion electrodes (GDEs), without the use of a decal transfer process. These GDEs were assembled into membrane electrode assemblies (MEAs) by hot pressing to Nafion membranes. In situ performance and other electrochemical diagnostics were used to determine the influence of coating method on catalyst layer electrochemical properties. Electron microscopy was utilized to understand the influence of coating method on electrode morphology and its influence on electrochemical properties. We also explored the influence of solvent ratio to understand the potential coupling between ink formulation and coating methodology. Through this work we demonstrate R2R-coated GDEs with performance equal to ultrasonic spray-coated GDEs and a 200x increase in production rate. This demonstrates that R2R coating methods are suitable for mass-production of high-performance fuel cells. It also lays a foundation for further process science studies. (1) Mauger, S. A.; Neyerlin, K. C.; Yang-Neyerlin, A. C.; More, K. L.; Ulsh, M. Gravure Coating for Roll-to-Roll Manufacturing of Proton-Exchange-Membrane Fuel Cell Catalyst Layer. J Electrochem Soc 2018, 165 (11), F1012–F1018. https://doi.org/10.1149/2.0091813jes. (2) Bodner, M.; García, H. R.; Steenberg, T.; Terkelsen, C.; Alfaro, S. M.; Avcioglu, G. S.; Vassiliev, A.; Primdahl, S.; Hjuler, H. A. Enabling Industrial Production of Electrodes by Use of Slot-Die Coating for HT-PEM Fuel Cells. Int. J. Hydrog. Energy 2019. https://doi.org/10.1016/j.ijhydene.2018.11.091. (3) Steenberg, T.; Hjuler, H. A.; Terkelsen, C.; Sánchez, M. T. R.; Cleemann, L. N.; Krebs, F. C. Roll-to-Roll Coated PBI Membranes for High Temperature PEM Fuel Cells. Energy Environ. Sci. 2012, 5 (3), 6076–6080. https://doi.org/10.1039/c2ee02936g. (4) Ding, X.; Didari, S.; Fuller, T. F.; Harris, T. A. A New Fabrication Technique to Manufacture an MEA Using Direct Coating of Nafion® onto Catalyzed GDL. In 218th ECS Meeting; ECS, 2010; pp 255–265. https://doi.org/10.1149/1.3484523. (5) Ding, X.; Didari, S.; Fuller, T. F.; Harris, T. A. L. Membrane Electrode Assembly Fabrication Process for Directly Coating Catalyzed Gas Diffusion Layers. J. Electrochem. Soc. 2012, 159 (6), B746. https://doi.org/10.1149/2.103206jes. (6) Ding, X.; Liu, J.; Harris, T. A. L. A Review of the Operating Limits in Slot Die Coating Processes. AIChE J. 2016, 62 (7), 2508–2524. https://doi.org/10.1002/aic.15268. Figure 1

Achieving Scalable Production of Hybrid Electrolytes through Slot-Die Coating

Lithium metal based all-solid-state batteries (ASSBs) can achieve high energy densities due to high theoretical capacity of lithium and low redox potential (3860 mAh/g, 3.04 V)1-2. Solid electrolyte materials are being sought to replace liquid electrolytes to enable the lithium metal chemistry. Solid electrolytes are mainly classified into two material categories (1) organic and (2) inorganic3. Organic materials are mechanically robust and easier to process but they possess poor ion transport properties. Inorganic materials possess high ionic conductivity but have poor manufacturability. Gravimetric calculations suggest that electrolytes with ≤ 60 μm thickness need to be manufactured to achieve competitive energy densities4. Additionally, the processing platform should ideally merge with existing battery manufacturing infrastructure to enable the transition to ASSBs. Hybrid electrolytes combine an inorganic conductor with a polymer electrolyte which improves the mechanical properties and inhibits dendrite growth in metal batteries (i.e. short circuiting). This work demonstrates the use of slot-die coaters to manufacture hybrid electrolytes with functional gradation. A custom-made bench-top slot-die coater is used to investigate the impact of ink composition. Initial results have shown that the system is sensitive to processing variability, with nano-scale interactions in the ink phase impacting the macroscopic ink properties and the coating structure5-6. This work focuses on demonstrating manufacturing capabilities for hybrid electrolytes with local control using slot-die coaters. Slot-die coaters are extensively used in industrial scale roll-to-roll manufacturing7 making the process technically viable.

Improvement of Lithium‐Ion Battery Performance by Two‐Layered Slot–Die Coating Operation

AbstractThe cathode and anode electrodes in lithium‐ion batteries typically contain a significant proportion of particles and binders. During the electrode drying process, high temperature will lead to the binder migration phenomenon. Uneven particle/binder distribution can cause poor adhesion between coating and substrate, disruption of conductive paths, and decrease in electrode performance. In this study, a two‐layered cathode was designed by using separate compositions of slurry ingredients in each layer, as produced by means of a simultaneous multilayer coating method. The two‐layered cathode with the top layer containing less binder than the bottom layer yielded a better particle/binder distribution in the final structure under high‐temperature drying. A battery made with the two‐layered cathode appeared to give a better overall performance.

Practical Design Guidelines for the Development of High-Precision Roll-to-Roll Slot-Die Coating Equipment and the Process

This paper proposes practical design guidelines for roll-to-roll (R2R) slot-die coating equipment with a precision mechanism enabling high-accuracy coating performance. The equipment is developed for specially fabricating organic photovoltaic devices. An R2R transportation module (capable of unwinding, in-feeding, out-feeding, and rewinding), a slot-die coating module, a far-infrared drying module, and a cleanliness control module are incorporated into the equipment. When used to apply an organic solution, the developed equipment can provide an operating tension of 2.3%–11.3%, a coating velocity of 2–7 m/min, a coating thickness of 28–95 nm, a uniformity of 8%–23%, and a roughness of 2.86–7.71 nm. A review of this equipment on the basis of theoretical and experimental approaches is included in the detailed equipment specifications and design guidelines for R2R slot-die coating machines.

Performance of SCO Buffers Prepared by Dip Coating and Slot-Die Coating Methods

Bi-axially textured, smooth, uniform, and crack-free Sm0.2Ce0.8 O 1.9−x (SCO) single buffer tapes have been prepared on textured Ni-5 %W alloy substrate by dip coating and slot-die coating methods, respectively, for REBCO(RE=Y, La and other lanthanides)-coated conductors. The influence factors in the preparation of SCO buffers by two methods have been discussed. Each technique has its advantages and disadvantages. This work is going to find a feasible and cost-effective road to fabricate a long coated conductor via all chemical solution deposition (CSD) route.

슬롯다이 코팅의 최적화 조건에 관한 연구

본 연구에서는 코팅 공정에 사용되는 슬롯다이(slot-die)에 대해 조건에 따른 코팅 성능을 연구하였다. 슬롯다이 코팅은 코팅 되는 필름의 속도, 코팅액의 점도 그리고 슬롯다이로 주입 되는 압력에 따라 코팅 품질이 많이 달라진다. 따라서 본 논문에서는 CFD 코드를 이용하여 안정적인 코팅을 위한 최적의 조건을 찾았다. 다양한 코팅액의 점도와 슬롯다이 입구의 압력 그리고 코팅 필름의 속도에 대해서 해석을 수행하였다. 그 결과로 5kgf/cm2 의 압력과 100cps 의 점도 그리고 20m/min 의 속도조합에서 가장 안정적으로 코팅액이 잘 도포되었다.