High aspect ratio surface relief structures by photoembossing

Photoembossing is a convenient and economical process to form complex surface relief structures in polymer thin films. We have improved the aspect ratio of photoembossed microstructures by adding t-butyl hydroquinone (TBHQ) to the polymerization mixture. The mechanism that is proposed is based on the radical transfer principle, where TBHQ converts acrylate radicals into stable phenol radicals that at elevated temperatures act as latent initiators, thereby controlling the kinetics without changing the number of polymerization active sites. As a result, the aspect ratio can be improved with a factor of 5–7 in comparison with previously proposed similar processes.