US Patent 7915441 Oligophosphazene compound

The oligophosphazene compound capable of forming a polymer which can be used as an optical material is a cyclic or linear compound including constituent units represented by the general formula (I) below in a range from 3 to 14. In the general formula (I), k is an integer of 1 to 4 and X1 is one selected from the group consisting of an oxygen atom, a sulfur atom, an NH group and an NCH3 group. A polymer made of this oligophosphazene compound exhibits high transparency and a high refractive index and is also less likely to cause optical dispersion, and thus it can be used as an optical lens, a retardation film, a light transmission body and other optical moldings.