Sulfonium, arsonium, ammonium and sphosphonium salts, useful as photoinitiators, comprise:
a chromophore which absorbs visible radiation, the chromophore (1) having a removable positive hydrogen ion and (2) exhibiting a higher energy occupied molecular orbital than at least one other substituent attached to the S, As, N or P atom of the salt;
an insulating group which links the chromophore to the S, As, N or P atom of the salt, the insulating group preventing π resonance between the chromophore and the other substituents in the salt;
at least one substituent comprising an electron withdrawing group and exhibiting a lower unoccupied molecular orbital than the chromophore; and,
an anion;
the salts being capable, upon exposure to visible radiation, of forming a Bronsted acid.
可用作光
引发剂的锍盐、胂盐、
铵盐和
鏻盐包括
一种可吸收可见辐射的发色团,该发色团 (1) 具有一个可移动的正氢离子,(2) 与盐的 S、As、N 或 P 原子上连接的至少一个其他取代基相比,显示出更高的能量占据分子轨道;
将发色团与盐的 S、As、N 或 P 原子相连的绝缘基团,该绝缘基团可防止发色团与盐中其他取代基之间的 π 共振;
至少一个取代基,该取代基包含一个取电子基团,并显示出比发色团更低的未占用分子轨道;以及
阴离子;
这些盐在暴露于可见辐射时能够形成勃朗斯特酸。