The role of cations in thermal stability of azo-Fe complexes used as charge-control agents from the standpoint of the crystal structure

摘要

Azo-Fe complexes and their sodium salts are well-known charge-control agents (CCAs) used widely in electrophotography. Aside from the CCA performance, a high thermal stability is also required because pulverized toners are prepared by kneading CCA with various toner components at about 130-180 ℃. Therefore, thermal stability has been investigated in azo-Fe complexes from the standpoint of the crystal structure. X-ray analysis revealed that the ammonium cations bridge neighboring azo-Fe complex anions through intermolecular NH O hydrogen bonds. On the other hand, the Na cations are also found to connect different azo-Fe complex anions through the formation of Na complexes. These facts lead us to conclude that the high thermal stability of azo-Fe complexes is attributed to the intermolecular bonds formed by ammonium or sodium cations.