Synthesis of UV-curable polycarbonate diols (PCDL)-based polyurethane acrylate for negative photoresist

Two kinds of UV-curable polyurethane acrylates (PCDL-H-PUA and PCDL-P-PUA) were synthesized starting with polycarbonate diols (PCDL), isophorone diisocyanate and dimethylolpropionic acid and terminated with hydroxyethyl methacrylate or pentaerythritol triacrylate to impart mono-methacrylate or tri-acrylate end-group functionality, respectively. The structures and properties of the products were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, gel permeation chromatography and thermogravimetric analysis. The average molecular weights were between 7500 and 9300 g/mol, and the thermal properties of the products were excellent. The influence of the functionality of the end-capping functional group on the UV-curing behavior was investigated using real-time spectroscopy. Results showed that curing rate and conversion of PCDL-P-PUA were higher than those of PCDL-H-PUA, and the final double bond conversion of the polymers reached 95 %. PCDL-H-PUA and PCDL-P-PUA were applied to negative photoresists as the main film resin. The resolution of the optimal photoresist reached 40 µm.