PHOSPHORESCENT MATERIAL, PROCESS FOR PRODUCING THE SAME, AND PHOSPHORESCENT DISPLAY ELEMENT

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A novel phosphorescent material is provided which has a narrow afterglow spectrum width, a choosable afterglow wavelength, a high moisture resistance, a high thermal resistance, and no optical anisotropy. It comprises a single crystal made of scandium oxide and a rare earth element substituting scandium of said single crystal, and generates the afterglow having a wavelength and spectrum width based on 4f-4f transition of the rare earth ion by irradiating ultraviolet light of the energy corresponding to the energy gap between 5d orbital of the rare earth ion and 2p orbital of oxygen of scandium oxide, or the energy gap between 4f excited orbital of the rare earth ion and 2p orbital of oxygen of scandium oxide. By choosing a rare earth element, the afterglow wavelength can be chosen. Since the host crystal is scandium oxide, it has the thermal resistance of 1000°C or higher. Since the crystal structure of scandium oxide is cubic, there is no double refraction.