Organic synthetic photoinitiator: Benzophenone

Benzophenone is a typical type II (or Norrish II) photoinitiator, widely used in UV curing. It cannot directly cleave to generate free radicals and requires the cooperation of a "hydrogen donor" (usually an amine compound) under illumination to initiate polymerization through a hydrogen abstraction reaction.

In recent years, to overcome some limitations of traditional benzophenones, such as short absorption wavelength, easy migration, and the need for external amines, research on their synthesis has mainly focused on chemical modifications of the parent structure. The table below summarizes the main modification directions and their corresponding synthesis strategies.

 Application and development trend

Through chemical modification, the application fields of benzophenone photoinitiators have been greatly expanded:

Traditional UV curing: Commercial products such as SpeedCure PBZ (4-phenylbenzophenone) are widely used in inks and coatings, and when combined with amine synergists, they provide excellent surface curing effects.

Emerging LED curing: Modified LED photoinitiators, such as bisbenzylamino benzophenone derivatives, can efficiently initiate radical polymerization, cationic polymerization, and hybrid UV curing, and have potential applications in cutting-edge fields such as 3D printing and interpenetrating polymer networks.

High-performance and environmentally friendly materials: Macromolecular and polymerizable photoinitiators are key to addressing issues related to small molecule migration and odor, and have garnered significant attention in fields where safety is of utmost importance, such as food packaging and biomedical materials.