Uniform Thermal Nanoimprinting at Low Pressure by Improved Heat Transfer Using Hydrofluoroethers

Abstract

We propose a low-pressure process of thermal nanoimprinting by improved heat transfer. In poly(ethylene terephthalate) (PET; Tg=75 °C), poly(methyl methacrylate) (PMMA; Tg=105 °C), and polycarbonate (PC; Tg=150 °C), in which fine pattern transfer can be performed at 12.9 MPa, if the imprinting pressure is reduced to one-third, poor transfer occurs at the edges of the patterned area, and the uniformity of the entire patterned area degrades. However, it turned out that moldability can be improved significantly by introducing hydrofluoroether (HFE) between the mold and the surface of thermoplastic sheets. A dispensing method using a pipette was chosen to introduce HFE, and three types of HFE liquid, namely, Novec 7100 (bp=61 °C), Novec 7200 (bp=76 °C), and Novec 7300 (bp=98 °C), were tested. It was confirmed that the uniformity was greatly improved by combinations of PET and Novec 7100, PMMA and Novec 7200, and PC and Novec 7300. The heat of the mold spread efficiently onto the surface of thermoplastics via the HFE liquid, and it seems to result in the same effect as a preliminary heating process before the mold comes into contact with the thermoplastic sheet.