Preliminary study on the tribology of an organic-molecule-coated touch panel display surface

Abstract The use of touch panel displays has been increasing due to the popularity of tablet PCs and smart phones. In order to protect the touch panel surface from scratches, contaminants from fingerprints and skin oils and so on, anti-contamination coating is necessary. One of the ways to protect the surface is to cover it with a thin and dense organic molecular layer. At the present time, the primary requirement for the coating is fingerprint-resistance or easy removal of contaminants. An adsorbed molecular layer of PFPE-derivatives is currently used for this purpose, in order to reduce the surface energy of the surface. Since the current major concern of panel makers is anti-fingerprint performance, degradation of the molecular layer by both tribological and environmental conditions is a major issue for the development of the coatings. Given the current priorities, however, tribological research into such subjects as the touch feeling of the panel and the friction characteristic has not been conducted. The touch feeling and its relation to the operation are very important but very difficult to study because it is very hard to express the touch feeling numerically. As a preliminary study, several different coated surfaces were prepared and their friction coefficients were measured by rubbing with a finger or a steel or glass ball to clarify the tribological characteristics of the surface. An Si wafer and a glass plate were used in this study as models of the solid substrate of a display. They were coated with an adsorbed organic molecular layer of two PFPE-derivatives with different molecular structures named Type-F and Type-D or several reference molecular layers, such as OTS-SAM and FDTE-SAM. In addition to the tribological data, degradation by UV irradiation was also examined to compare the performance. The results are discussed from the tribological and chemical points of view.