Patent ID: 8154188

Claim:
An electron emitting device comprising: an insulating member having a notch on its surface; a gate positioned on the surface of the insulating member; at least one cathode having a protruding portion protruding from an edge of the notch toward the gate, and positioned on the surface of the insulating member so that the protruding portion is opposed to the gate; and an anode arranged to be opposed to the protruding portion via the gate, wherein the gate is formed on the surface of the insulating member so that at least a part of a region opposed to the cathode is projected outward and recessed portions are provided in which ends of the gate are recessed and interpose the projected region, wherein either of following two conditional expressions is satisfied: T 4 =T 5, and i) T 4 <T 5 and T 12 <T 13, ii) where T 4 [m] represents a width of the cathode, T 5 [m] represents a width of the projected region of the gate, T 12 [m] represents a length of a portion where the projected region of the gate protrudes from a region opposed to the cathode, and T 13 [m] represents a shortest distance between an end of the cathode and the gate, and wherein, if it is assumed that a height of the notch in a laminating direction of the gate and the insulating member is T 2 [m], a recess distance of the recessed portion is T 8 [m], a work function of the cathode is Wf [eV], and energy when one electron is accelerated by voltage Vf [V] applied between the cathode and the gate is EVf [eV], then an expression T 8 ≧6×T 2 ×{1−(Wf/EVf)} is satisfied.