Patent attributes
In a spacer having concave/convex portions to prevent short-time charging in a flat type image forming apparatus in which an electron source substrate and an anode substrate are arranged so as to face each other through the spacer, the charging upon long-time driving due to the concave/convex portions is suppressed. In the spacer in which the surface of an insulating substrate having a rough surface is coated with a high resistance film, the high resistance film has double layers of a low resistance region locating on the substrate side and a high resistance region locating on the front surface side, and a thickness (t) of high resistance film on the slant surface of each of the concave/convex portions and a thickness (s) of high resistance region are set to (t≧dp+λ≧s) for the primary electron penetration length (dp) and the ionization electron diffusion length (λ).
