Cationic photoinitiators are another very important type of photoinitiating reagents, including diazonium salts, diaryliodonium salts, triarylsulfonium salts, alkylsulfonium salts, iron aromatic hydrocarbon salts, sulfonyloxy Ketones and triaryl siloxane ethers.

Its basic function is characterized by light activation to bring the molecule to an excited state, and the molecule undergoes a series of decomposition reactions, and finally produces super strong proton acid (also called Bronsted acid), which acts as an active species for cationic polymerization to trigger epoxy compounds, Polymerization of vinyl ethers, lactones, acetals, cyclic ethers, etc.