PURPOSE: To prevent the unnecessary discharge along the surface of a spacer glass, and to supplement the function as an acceleration electrode and unify the diffusion of electron beams so as to improve the luminous level, by coating an electroconductive layer of carbon or the like at the upper portion at a face glass side of the spacer glass facing to the bottom plate glass side.

CONSTITUTION: At the upper portion of a spacer glass 3 at a face glass side, an electroconductive layer 4 of carbon or the like is coated facing to a bottom plate glass 2 side. The electroconductive layer 4 is coated up to about the middle portion between the face glass 1 and the bottom plate glass 2. Therefore, a specific resistance is given by the coating of the conductive layer 4 to prevent the unnecessary discharge along the surface of the spacer glass 3 and to maintain a specific potential, so that the function of screening plates 1b as acceleration electrodes is supplemented and the diffusion property of electron beams can be exercised. Therefore, the diffusion of the electron beams is made even and the decrease of the luminous level at the periphery of the face glass 1 can be prevented.