Electron emitting device and image displaying apparatus using the same

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:
• T4=T5, and i)
• T4<T5 and T12<T13, ii)
• where T4 [m] represents a width of the cathode, T5 [m] represents a width of the projected region of the gate, T12 [m] represents a length of a portion where the projected region of the gate protrudes from a region opposed to the cathode, and T13 [m] represents a shortest distance between an end of the cathode and the gate, and
• wherein
• a control electrode is arranged on the surface of the insulating member opposed to the anode via the recessed portion, and
• if it is assumed that voltage applied between the cathode and the gate is Vf [V], the voltage applied between the control electrode and the cathode is Vc [V], the voltage applied between the anode and the cathode is Va [V], a distance between a surface of the insulating member opposed to a side where the gate is disposed and the anode is h [m], a width of the projected region of the gate is T5 [m], and a circular constant is π, then an expression T5<5×(Vc/Va)×(h/π) and an expression Vf≧Vc are satisfied.