Integrated Analysis on Transport Phenomena during Thin Film Formation Using Inkjet method

本文从实验和理论两方面探讨了用喷墨方法使薄膜变平的方法。首先分析了溶液液滴在衬底上蒸发时的流体动力学。在目前的体系中，溶剂型和热源型马兰戈尼力影响流体动力学。它们在自由表面上的流动方向相反。热源力随基体温度的升高而增大。然而，随着蒸发时间的推移，溶液导出力最终主导了流体动力学。二元溶剂经常形成扁平薄膜的原因一直被认为是液滴中的流体流动可以通过溶剂的表面张力之间的差异来控制。然而，薄膜结构与溶剂表面张力差异所期望的流体流动无关，因为溶剂衍生的力大于溶剂衍生的力。因此，膜的形状受自钉位置的影响，而自钉位置可以通过粘度、接触角和蒸发速率来控制。马兰戈尼力用于控制微妙的平面度。根据这一结果，提出了一种形成扁平薄膜的新方法。

A way how to flatten a thin film using inkjet method is discussed experimentally and theoretically. Firstly the fluid dynamics in solution droplets evaporating on a substrate are analyzed. On the present system, the solutal-derived and thermal-derived Marangoni forces affect the fluid dynamics. They develop the flow in the opposite direction on the free surface. The thermal-derived forces increase with increasing the temperature of substrate. However, after evaporation is advanced in time, the solutal-derived forces finally dominates the fluid dynamics.The reason why binary solvent often forms a flat thin film has been thought to be that the fluid flow in the droplet can be controlled by the difference between the surface tensions of the solvents. However, the film configuration is not correlated to the fluid flow expected from the difference between the surface tension of the solvents, because the solutal-derived forces are larger than solvent-derived one.Consequently, the film shape is influenced by self-pinning position, which can be controlled by viscosity , contact angle and evaporation rate. The Marangoni forces are used to control delicate flatness. According to this result, a new method is proposed to form flat thin films.