Rare earth complex having heat resistance

The present invention can be uniformly dispersed in the plastic material, and is excellent in heat resistance, provides a phosphor having a high fluorescence intensity after high temperature heating in molding process of the plastic product. More particularly, the present invention is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, a benzophenone or benzoyl substituted with an acyl group or an alkoxy group as a basic skeleton, one molecule having a photosensitizing function providing a phosphor comprising a rare earth complex comprising by coordinating the above plurality of rare earth ions.