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

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This invention provides a novel phosphorescent material that has a narrow afterglow spectrum width, can select an afterglow wavelength, has high moisture resistance, has high heat resistance, and is free from optical anisotropy. The novel phosphorescent material comprises a single crystal of scandium oxide and a rare earth element in which scandium in the single crystal has been replaced. Upon exposure to ultraviolet light having energy corresponding to a difference in energy between a 5d orbit of the rare earth ion and a 4f ground orbit of the rare earth ion, or ultraviolet light having energy corresponding to a difference in energy between a 4f excitation orbit of a rare earth ion and a 2p orbit of oxygen of scandium oxide, afterglow having wavelength and spectral width based on 4f-4f transition of the rare earth ion occurs. The afterglow wavelength can be selected by selecting the rare earth element. Since the matrix crystal is scandium oxide, the heat resistance is 1000ºC or above. Further, since the crystal structure of scandium oxide is cubic, there is no birefringence.