Coating technology plays a critical role in determining product functionality, durability, and appearance. As a result, optimizing the drying process, which strongly influences final coating quality, remains a major challenge in many manufacturing environments.
Particularly, achieving a uniform, high-quality coating layer within a limited processing time requires drying techniques that minimize uneven drying and ensure stable film formation. To meet these demands, air-knife-based drying technology has gained attention across a wide range of coating applications due to its precise control of airflow.
Effects of Air Knife Drying in Coating Processes
Uniform Drying Without Unevenness
Air knife drying delivers a high-speed, uniform sheet of airflow through a narrow slit, enabling consistent drying while suppressing uneven evaporation in runoff-prone or recessed areas. In applications such as inkjet printing and film coating, uniform drying of ink and coating liquids also helps achieve a clean finish without bleeding or streaking.
Reduction of Drying Time
The high-density airflow supplied by air knife drying efficiently delivers heat and dry air to the coating surface, accelerating the evaporation of solvents and moisture. By applying uniform airflow over a wide area, heat transfer efficiency is improved, allowing drying time to be significantly reduced.
At the same time, rapid drying can be achieved with a relatively low thermal load on the substrate. This makes air knife drying suitable for heat sensitive materials and delicate coating layers, enabling efficient drying without compromising quality.
Improvement of Coating Surface Quality
One of the major challenges in the drying process is the formation of surface defects. When solvent evaporation is uneven or changes in surface tension occur too abruptly, fine defects are more likely to develop.
Uniform and well controlled air knife drying effectively suppresses these defects. By guiding changes in surface tension in a gradual manner, the coating layer stabilizes as a whole, resulting in a smooth, defect free, and high-quality surface. This directly contributes to improved optical transparency and enhanced performance in functional coatings.
Improving Dip Coating Efficiency Using Air Knives
Overview of Dip Coating
Dip coating is a method in which a substrate is immersed in a coating solution and then withdrawn at a controlled speed to form a uniform thin film. Because it produces minimal coating irregularities and can be applied to large-area substrates, it is widely used across many industries.
However, if drying is uneven, defects such as film thickness variation or whitening may occur, potentially degrading product performance and appearance quality.
Air Knives for Uniform Drying
Immediately after dip coating, the liquid film on the substrate surface is influenced by a complex interaction of gravity, surface tension, viscosity, and solvent evaporation rate. As a result, the film thickness tends to become uneven.
Air knives address this issue by ejecting a uniform, high-speed sheet of air through a narrow slit. This controlled airflow stabilizes the liquid film while promoting uniform drying at the same time. Even in areas prone to coating runs, such as lower edges or uneven surfaces, precise airflow control helps equalize film thickness. This makes it possible to achieve both high optical transparency and strong adhesion.
Summary
Drying processes that incorporate air knives into dip coating operations contribute greatly to uniform finishes without drying irregularities, shorter drying times that improve productivity, and high-quality coating surfaces with reduced defects.
Coating efficiency improves when challenges in the existing coating process are clearly identified and an air knife system with suitable performance specifications is selected. In this context, air knife integration offers a practical and effective approach to drying optimization.