Optical Characteristics of Moth-Eye Structures on Poly(methyl methacrylate) and Polycarbonate Sheets Fabricated by Thermal Nanoimprinting Processes

In this study, moth-eye structures on poly(methyl methacrylate) (PMMA) and polycarbonate (PC) sheets are fabricated by nanoimprinting processes and their antireflective characteristics are discussed. Different substrate temperatures and pressures are used to imprint these structures on PMMA and PC sheets. In both cases, transmittance generally increases with imprinting pressure but does not depend obviously on substrate temperature. The antireflectance of the structures improves with increasing substrate temperature and applied pressure. The reflectance of moth-eye structures on PMMA decreases optimally from 8.36 to 4.54% at a wavelength of 550 nm for a pressure of 27 kg/cm2, and the transmittance increases from 92.50 to 95.03%. However, for the optimal result of moth-eye structures on PC, their reflectance decreases from 11.48 to 8.56% and their transmittance increases markedly from 89.54 to 93.56%. Moth-eye structures show a greater transmittance improvement on PC sheets than on PMMA sheets owing to the synergy effect of the protrusion shape and the height of the imprinted structures. High and/or sharp structures increase transmittance and decrease reflectance.