Self-relaxation characteristics of roll-to-roll imprinted nanogratings on plastic film

A strong need exists for an effective nanopatterning technique to fabricate devices of the next generation at low cost. Nanoimprint lithography (NIL) has recently received considerable attention because of its process simplicity. In particular, there are strong expectations that thermal roll-to-roll NIL (T-R2RNIL) might be permit high-throughput nanopatterning. In fabricating nanoscale patterns by T-R2RNIL, it is important to understand the transfer characteristics of the materials to permit the prediction of properties of the fabricated pattern. We previously reported the transfer characteristics of a cellulose acetate (CA) film in T-R2RNIL, and we showed that the height of the patterns obtained at temperatures near the glass-transition temperature of the polymer (Tg) was lower than that obtained at temperatures below the Tg. Moreover, we found that the replication behavior of nanoscale gratings differed from that of microscale gratings. However, we did not examine the self-relaxation behavior after T-R2RNIL. In this study, we investigated changes deformation characteristics after a prolonged development time for nano- and microspace patterns on CA film. The self-relaxation behavior was shown to depend on the process temperature for T-R2RNIL, as well as on the features of the mold. In addition, a unique pattern whose pattern density was almost double that of the original mold was obtained by T-R2RNIL at a certain temperature.