Development of Transparent Super Water-repellent Films by Composing Surface Fine Structure

本课题旨在建立一种在等离子体气相沉积过程中控制防水膜表面形貌和化学键合状态的方法，并开发一种在低温下大面积沉积透明、坚硬和超级防水膜的技术。利用射频等离子体CVD系统与傅里叶变换红外光谱仪（FTIR）相结合，成功地实现了红外反射吸收光谱（IRRAS）在80度入射角下的红外吸收光谱原位测量。特别是，选择p偏振红外光可以实现高灵敏度的测量。我们甚至可以得到单层有机硅分子的红外光谱。通过这种方法，我们建立了一种实时控制薄膜化学键态的沉积技术。一直认为，由于氧的混合物中会形成疏水的Si-OH基团，因此无法合成超级拒水膜。然而，我们明确指出，在相对较高的总压下，在150-200 Pa的范围内，与氧气的混合物，可以实现超级拒水性。从这一结果可以预期，形成具有硬度的拒水膜。薄膜虽然含有Si-OH官能团，但具有超强的防水性。原因尚未阐明，可以是一个有趣的研究对象。用环境扫描电镜观察了其拒水性。即使是μm大小的水滴，接触角也超过150度。

This research project aimed at an establishment of a method to control both the surface morphology and the chemical bonding states of the water-repellent films in plasma CVD processes and at a development of a technique ton deposit transparent, hard and super water-repellent films at low temperature over wide area.We succeeded in in-situ measurement of infrared (IR) absorption spectra by infrared reflection absorption spectroscopy (IRRAS) at an incident angle of 80 degree using an rf plasma CVD system combined with a Fourier-transform infrared spectrometer (FTIR). Especially, selecting p-polarized IR light lead to measurement at a high sensitivity. We could obtain IR spectra even for a monolayer of organsilicon molecules. By means of this method, we established a deposition technique to control the chemical bonding states of the films in real time.It has been supposed that super water-repellent films cannot be synthesized with mixture of an oxygen has gas because of formation of hydrophobic Si-OH groups. We made clear, however, that super water repellency can be realized at relatively higher total pressure, in the range of 150-200 Pa, with the mixture of oxygen. From this result, it can be expected that the formation of water-repellent films with hardness. The films have super water-repellency although they include Si-OH functional groups. The reason has not been elucidated and can be an interesting research object.The water repellency was observed by means of environmental scanning electron microscope. The contact angle was over 150 degree even for the water drops in μm size.