Effects of the process temperature and rolling speed on the thermal roll-to-roll imprint lithography of flexible polycarbonate film

Thermal roll-to-roll imprint lithography (R2RIL) is a simple and low-cost process for the mass production of micro nanopatterns. However, in that it relies on highly viscous thermoplastic resists, it is limited in its ability to imprint precise patterns at a high speed. Moreover, the concentrated imprint force applied in R2RIL can damage the resist material which is structurally vulnerable at high process temperatures. Therefore, it is important to understand the temperature- and time-dependent characteristics of the resist material as well as the imprinting mechanism when using thermal R2RIL. In this work, the effects of the process temperature and rolling speed on thermal R2RIL of polycarbonate (PC) films were investigated to improve the process efficiency. Micro-scale line patterns were successfully transferred onto PC films from nickel (Ni) mold stamps. Consequently, line patterns with widths in the range of 5-80 µm were achieved at a traveling speed of 28.6 mm s-1 and process temperature of 150 °C, which is just above the glass transition temperature (Tg). In addition, the patterning performance was investigated for different temperatures, rolling speeds and pattern sizes. The imprinted pattern profiles were measured by an alpha-step surface profiler to investigate the patterning performance. The results show that a much better imprint performance was achieved at 150 °C, compared to the result at temperatures below Tg. The physical mechanisms of thermal R2RIL on a PC film were studied by a finite-element analysis and the patterning process was successfully demonstrated by a visco-plastic deformation model.