| abstract |
Sulfonium, selenonium, arsonium, ammonium and phosphonium 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, Se, As, N or P atom of the salt; a group which links the chromophore to the S, Se, As, N or P atom of the salt, the group partially 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. |