Patent Number: 
Section: claims

1. An electron emission method comprising:applying a voltage to a field electron emission element that has a boron nitride material containing crystal, formed on an element substrate to have a conical projection of the boron nitride material and shows a stable electron emitting property in an atmosphere when a voltage is applied thereto to emit electrons,wherein an electron emission threshold of the field electron emission element falls due to formation of a surface electric dipolar layer by bringing it into contact with an operating atmosphere containing polar solvent gas when applying a voltage to the field electron emission element so as to emit electrons. 2. The electron emission method according to claim 1, wherein the boron nitride material containing the crystal that has the conical projection of the boron nitride is made of an sp3 bond type boron nitride, or a mixture of the sp3 bond type boron nitride and an sp2 bond type boron nitride. 3. The electron emission method according to claim 1, wherein the boron nitride material containing the crystal that has the conical projection of the boron nitride is formed in a self-forming manner on the element substrate at intervals and to a density suitable for electron emission. 4. The electron emission method according to claim 3, wherein the boron nitride material containing the crystal that has the conical projection of the boron nitride is made of an sp3 bond type boron nitride, or a mixture of an sp3 bond type boron nitride and an sp2 bond type boron nitride. 5. The electron emission method according to claim 1, wherein the polar solvent gas is water and/or alcohol. 6. The electron emission method according to claim 1, wherein the boron nitride material containing the crystal that has the conical projection of the boron nitride is formed by a reaction from a gas phase when excited by ultraviolet rays. 7. The electron emission method according to claim 6, wherein the polar solvent gas is water and/or alcohol.