Synthesis of acrylic rosin derivatives and application as negative photoresist

Functional monomers containing a rosin moiety, maleopimaric acid anhydride (MPA) and fumaropimaric acid (FPA) were synthesized from gum rosin. Monofunctional acrylic rosin derivatives were synthesized from esterification of MPA and various acrylates, (2-hydroxyethyl acrylate) (HEA), 3-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate. Monofunctional monomers were copolymerized with (methyl methacrylate) (MMA) by radical polymerization. Trifunctional acrylate was synthesized from FPA and HEA. All the monomers and polymers showed good solubility and low absorbance in the UV region (200–400 nm). Negative patterns from rosin derivatives were obtained by two methods, one is a photocuring method using trifunctional acrylate and copolymers, and the other is photocrosslinking of copolymers using a photocrosslinker under UV (I-line) radiation. Negative photoresists containing rosin moiety showed high contrast and minimum linewidth of 2.2 μm.