Effects of Preheat Supply on Embossed Pattern Depth in Roll-to-Roll Process

In this study, we examined the sensitivity of embossed pattern depth to preheat supply and cooling, and also tested how pattern type and density affect the embossed depth. The main factors such as roller temperature, roller speed, and applied force that mostly affect embossed pattern qualities of roll-to-roll hot embossing were determined based on the response surface methodology. Eight conditions were then added to know the time-dependent effects of heat transfer with custom designed preheating and cooling systems (Fig. 1). Extended preheat time for the PMMA substrate contributed to the significant change of the embossed depth, whereas the substrate-cooling showed no straightforward increasing or decreasing trend. Larger embossed depths were achieved in horizontal patterns with lower density compared to vertical patterns, and the lower pattern densities showed the greater embossed depths regardless of pattern types. We expect that this result may help to understand the effects of preand post-treatment of roll-to-roll (R2R) hot embossing by employing time duration factors of heat transfer, depending on mold pattern type and density.