Moth-eye structured mold using sputtered glassy carbon layer for large-scale applications

Surface reflection is a problem in applications such as solar panels, smartphones, and tablet computers. To prevent such reflection, we previously developed a moth-eye structure that can be fabricated with a single film. This antireflection structure (ARS) suppresses reflection over a wide range of light wavelengths and incident angles. The production of large-area ARS films, which can be achieved using ultraviolet nanoimprint lithography (UV-NIL), is required for solar panels and displays. In our previous study, a moth-eye structure was fabricated by irradiating a glassy carbon (GC) substrate with an oxygen ion beam. However, it is difficult to fabricate a large GC substrate because GC is made using powder metallurgy. To overcome this problem, we used a sputtered GC layer as the ARS master mold material. In this study, we demonstrate that a moth-eye structure can be formed by irradiating sputtered GC with an oxygen ion beam using an inductively coupled plasma (ICP) system. We formed a moth-eye structure on sputtered GC using two-step ICP etching. The fabricated moth-eye structured mold had a reflectance of approximately 0.1% in the visible-light region. In addition, a moth-eye film transferred using UV-NIL with the fabricated moth-eye structured mold had a low reflectance of approximately 0.4% in the visible-light region.