Electron-emitting element and image display device using the same

An electron emitting-element comprising:

• an electron conveying member;
• a cathode electrode comprising an electron-emitting member fixed to the electron conveying member;
• an anode electrode disposed such that it is spaced from the cathode electrode;
• and
• a grid electrode disposed between the cathode electrode and the anode electrode, earthed by means of an electric circuit through which electrons do not flow from the earthed side, and having an electron passage opening;
• wherein the spatial positioning of the three members, the cathode electrode, the anode electrode and the grid electrode, and their respective shapes are constructed such that an electric field existing between the grid electrode and the anode electrode emanates from the electron passage opening to the cathode electrode side, and the emanated electric field and an electric field existing between the cathode electrode and the grid electrode interact with each other to form a combined electric field;
• and
• electron-emission controlling means is provided for varying the intensity of the combined electric field by varying the potential of at least one of the cathode electrode, the anode electrode, and the grid electrode to control the number of electrons emitted from the cathode electrode.

An electron-emitting element comprising:

• an electron conveying member;
• a cathode electrode comprising an electron-emitting member fixed to the electron conveying member;
• an anode electrode disposed such that it is spaced from the cathode electrode;
• and
• a grid electrode disposed between the cathode electrode and the anode electrode and having an electron passage opening;
• wherein the spatial positioning of the three members, the cathode electrode, the anode electrode and the grid electrode, and then respective shapes are constructed such that an electric field existing between the grid electrode and the anode electrode emanates from the electron passage opening to the cathode electrode side, and the emanated electric field and an electric field existing between the cathode electrode and the grid electrode interact with each other to form a combined electric field, and
• the electron emission controlling means is such that the potential of the anode electrode with respect to the cathode electrode is a potential at which the field emission of electrons from the cathode electrode in the direction of the anode electrode cannot be brought about by only the potential thereof, the potential of the grid electrode has the same polarity as that of the anode electrode, and by varying the potential of the grid electrode, the strength of the combined electric field is varied and the number of electrons emitted from the cathode electrode is controlled.