PURPOSE: To lessen unevenness of screen color and illuminance unevenness and at the same time to keep screen illuminance high by carrying out frosting process to make the frosted part of the outer surface of a light emitting bulb covering the bottom part side to the protective coating side gradually change from thinly frosted near the clear face to thickly frosted.

CONSTITUTION: Sealing parts 2, 2 are formed at both ends of a light emitting bulb and a metal cap 3 is fixed at one end. A reflective and protective coating 5 is formed on the outer surface of the light emitting bulb and a frosted part 7 including from the edge part of the protective coating 5 to the chip-off part 6 of the light emitting bulb is formed. The protective coating 5 of the outer surface of the light emitting bulb is formed in the open part side of a relective mirror 10 and the frosted part 7 is formed from the edge part of the protective coating to the bottom part of the reflective mirror 10 and the frosting density is gradually changed to make the center part of the outer surface of the light emitting bulb be thickly frosted part, the neighboring part be rather thinly frosted part, and the end part be thinly frosted part.