紫外线吸收剂的机理
Mechanism of UV absorber
紫外线吸收剂之所以能吸收紫外光是由于该类化合物分子中含有共轭π电子体系的结构与能够进行氢原子移动的结构两部分所致。也有的只有前一部分。紫外线吸收剂其结构分子中至少含有一个邻位羟基苯基取代基，这类化合物中由邻位羟基与氮原子或氧原子形成一螯合环，在吸收紫外线后，氢键断裂发生分子异构，分子内结构发生热振动，氢键破坏，螯合环打开，分子内结构发生变化，这样就将有害的紫外光变为无害的热能放出，从而保护了材料，在这个过程中，分子内所形成的螯合环是其具有吸收紫外线功能的关键，打开此环的能量敏感范围正好为290～400nm波长的紫外线能量范围。另外，作为紫外线吸收剂，还必须能在紫外光或可见光的作用下不进行光化学反应；对化学药品 及水稳定性好，对热的稳定性好；挥发性小；对高分子材料的相容性好及不被溶剂萃取等。
The reason why UV absorbers can absorb UV light is due to the structure of conjugated π electron system and the structure of hydrogen atom moving. There are also only the former part. UV absorbers contain at least one ortho hydroxy phenyl substituent in their structural molecules. In these compounds, the ortho hydroxy and nitrogen or oxygen atoms form a chelating ring. After UV absorption, the hydrogen bond breaks and isomerizes, the intramolecular structure vibrates, the hydrogen bond breaks, the chelating ring opens and the intramolecular structure changes, which will change the harmful UV light In order to release harmless heat energy and protect the material, the chelating ring formed in the molecule is the key to its UV absorption function. The energy sensitive range of opening the ring is exactly the UV energy range of 290-400nm wavelength. In addition, as an ultraviolet absorber, it must not undergo photochemical reaction under the action of ultraviolet or visible light; it has good stability for chemicals and water, good stability for heat, small volatility, good compatibility for polymer materials and not be extracted by solvent, etc.