Patent ID: 7317285

Claim:
A method for cleaning fine particles from an electron emission device comprising: an electron emitter including a lower electrode, an upper electrode made of a thin film, and a semiconductor layer formed between the lower electrode and the upper electrode, a surface of the upper electrode being exposed to an external space; a counter electrode disposed opposite the upper electrode across the external space; first voltage control means for selectively applying between the lower and upper electrodes (i) an electron emitting voltage having a polarity for accelerating electrons in the semiconductor layer such that the accelerated electrons are passed through the upper electrode and emitted to the external space, (ii) a predetermined voltage for charging fine particles adhered to the surface of the upper electrode, (ii) a voltage of opposite polarity to the polarity of the electron emitting voltage, or (iv) no voltage; and second voltage control means for selectively applying at least one voltage between the upper electrode and the counter electrode having a predetermined relationship to the voltage applied between the lower and upper electrodes by the first voltage control means; said method comprising the steps of: applying the predetermined voltage for charging fine particles adhered to the surface of the upper electrode between the upper electrode and the lower electrode while at the same time applying a voltage having a predetermined relationship to the voltage applied between the upper electrode and the lower electrode between the upper electrode and the counter electrode for a period sufficient for the fine particles adhered to the surface of the upper electrode to assume a predetermine level of charge; thereafter, applying a voltage for causing the charged fine particles to fly toward the counter electrode from the upper electrode between the upper electrode and the counter electrode without atmospheric discharge while at the same time applying between the upper and lower electrodes either no voltage or a voltage of opposite polarity to the polarity of the voltage then being applied between the upper electrode and the counter electrode; and thereafter, applying between the upper electrode and the lower electrode an electron emitting voltage for accelerating electrons in the semiconductor layer such that the accelerated electrons are passed through the upper electrode and emitted to the external space while at the same time applying a voltage having a predetermined relationship to the voltage then being applied between the upper electrode and the lower electrode so as to convey the emitted electrons toward the counter electrode through the external space.