To enhance luminous efficient of a luminescent ionic liquid at high temperatures.

An ionic liquid having cations containing a cyclic phosphazene structure is blended into a resin and formed into a film. The ionic liquid is preferably represented by the general formula (I): (NPR¹₂)_n, wherein R¹s each independently represent a halogen element or a monovalent substituent, at least one R¹ is an ionic substituent represented by the general formula (II): -N⁺R²₃X^- (wherein R²s each independently represent a monovalent substituent or hydrogen, provided that at least one R² is not hydrogen, and R²s may bond to each other to form a ring; and X^- represents a monovalent anion); and n represents 3-6. The resin is preferably polymethyl methacrylate and polycarbonate.