PURPOSE: To emit white light in high brightness by setting mole ratio of Ce concentration relating to Eu concentration in a luminous layer to 6 or more and 35 or less.

CONSTITUTION: An ITO electrode of prescribed thickness, Ta2O5, SiO2 and ZnS as a buffer layer are successively formed on a glass substrate. Next, relating to SrS, powder of mixing CeF3, EuF3, KCl and SrSO4 is used for a target, and spatter evaporation is performed at about 300°C substrate temperature, to form a mixture layer of about 800nm thickness. A heating process is performed in the atomosphere of argon gas containing hydrogen sulfide, to prepare a luminous layer. Here is determined mixing ratio of the target so that mole ratio of Ce concentration relating to Eu concentration in the luminous layer is obtained 6 or more and 35 or less. Prescribed thick ZnS, SiO2, TiO2, Ta2O5, Al electrode are laminated by the order thereof on the luminous layer, to prepare an element. Then the element displays white light in high brightness.