Glass etching with gaseous hydrogen fluoride: Rapid management of surface nano-roughness

Surface roughness of glass is desired to be arbitrary controlled because it affects a variety of properties such as tactile impression, optical properties, and contact chargeability. While the surface modification is currently achieved by wet etching of the glasses with hydrofluoric acid, there is still room for improvement because the wet etching cannot be simultaneously applied during flat glass production. We recently developed novel etching scheme, which uses gaseous hydrogen fluoride (HF) under high temperature. Because the flat glasses are kept hot during the production, our procedure can be introduced to the flat glass production process. Here, we demonstrate that surface nano-roughness (1-20 nm of arithmetic mean roughness) of silicate glasses can be rapidly and reproducibly controlled by our method with changing the reaction temperature. It was found that the reaction with gaseous HF heterogeneously left metal fluorides on the glasses and that the fluorides partially masked the further reaction. High reaction temperature led the fluoride particles larger, resulting in rougher surface after removing the fluoride layer. It took only a few seconds for this reaction.