One-Step Preparation of Antireflection Film by Spin-Coating of Polymer/Solvent/Nonsolvent Ternary System

An antireflection film was prepared by spin-coating of poly(methyl methacrylate) (PMMA) solution in chloroform in the presence of small amounts of nonsolvent alkanes. When the vapor pressure of a nonsolvent was lower than that of chloroform, a dense skin layer was formed because of the rapid solvent evaporation during spin-coating, whereas increasing the nonsolvent content below this layer resulted in a phase-separated structure. The phase-separated structure below the dense skin layer became a porous layer after the complete evaporation of both chloroform and nonsolvent. Since the film thickness after spin-coating was on the order of hundreds of nanometers, the size of the pores formed at the inner layer was also a few hundred nanometers. The two layers consisting of a dense skin layer and an inner porous layer exhibited excellent antireflection (AR) when coated on glass substrate. By a one-step procedure of spin-coating of PMMA, the film has high transmittance of over 98% at visible wavelengths. Furthermore, due to the dense skin layer in this AR film, an additional spin-coating could be easily performed on this film.