Study of cationic UV curing and UV laser ablation behavior of coatings sensitized by novel sensitizers

To improve the laser ablation performance of cycloaliphatic epoxide cationic UV curable coatings, two novel reactive sensitizers were synthesized and characterized and their effect on coating properties examined. The sensitizers were synthesized based on the reaction between naphthalene or anthracene derivatives and monomers or oligomers used in the coating system. HPLC and GC-MS confirmed the formation of the desired products. Three coating systems based on cycloaliphatic epoxide with either oxetane or polycaprolactone polyol were formulated with the reactive sensitizers. The sensitized coatings had higher conversion during UV curing in the oxetane containing formulation and did not deter the curing in the polyol containing formulation. Better UV laser ablation performance was observed in all sensitized coatings compared to the controls. Coatings with the anthracene based sensitizer even had better laser ablation performance than a commercial polyimide. The sensitized coatings had higher hardness, Tg and crosslink density while the adhesion and solvent resistance were not affected. An optimal amount of sensitizer was found for each coating formulation in terms of UV curing behavior. The relationship between coating Tg and laser ablation behavior was investigated and it was found that the higher the Tg and crosslink density, the poorer the laser ablation performance.