PURPOSE: To improve the heat radiation and prevent the temperature rise of phosphor particles so as to improve the luminous brightness, by making the phosphor in the condition partially buried on the surface of a glass panel.

CONSTITUTION: The process (a) shows the condition where a phosphor powder 2 is spread over the surface of a glass panel 1, and the phosphor powder layer 2 consists practically of three to five particle layers. Then, the glass panel 1 formed with a phosphor powder layer 2 in the process (a) is placed on a flat and smooth board 4 opposing to the board with the phosphor spread side, shown as the figure (b), and heated below the melting point of the glass panel. As the board 4, a material not to be attached to the glass panel by melting while heating, such as a graphite panel or boron nitride panel. When the glass panel is heated in a vacuum on the board, a zinc silicate layer 3 is produced to bury securely the phosphor particles on the glass panel. The process (c) shows the condition where the phosphor powder of the second layer and the above which did not contact the glass panel directly has been removed.