Tribology of water and oil repellent sol–gel coatings for optical applications

Oil and water repellent sol–gel silica coatings may be used to extend the use and lifetime of certain computer displays, optoelectronic devices, and optical components such as touch screens. Organic–inorganic coatings consisting of organically modified silica are an optimal class of materials to use for such applications as they are substantially more durable than conventional polymers while having low processing temperatures compatible with organics. This study is concerned with the characterization of wear-resistant coatings derived from polysiloxanes. Organically modified sol–gel silica coatings were deposited on soda-lime glass substrates by dip coating. Mechanical, surface, and tribological properties were investigated using nanoindentation, contact angle goniometry, stylus profilometry, and a reciprocating polishing wear test to determine wear rate by mass loss. The average hardness of films was found to be 1.2 GPa and independent of curing times above 30 min at 150 °C. In polishing wear, failure was caused by gradual abrasive wear through the depth of the coating. Wear rate was found to be independent of curing times above 30 min at 150 °C. The development of these coatings will contribute to the rational design of the next generation of transparent overlays and displays.