Patent ID: 8072560

Claim:
An electrode for cold cathode tube, comprising: a cylindrical sidewall portion formed by working a tungsten plate into a cylindrical shape, wherein the tungsten plate is made of only tungsten or tungsten containing at least one selected from: potassium in a range from 25 to 200 ppm and an electron emissive material in a range from 25 to 100,000 ppm; a bottom portion provided at one end of the sidewall portion formed by swaging the end of the cylindrical sidewall portion, or by bonding the tungsten plate to the end of the cylindrical sidewall portion; and an opening portion provided at the other end of the sidewall portion, wherein the cylindrical sidewall portion has a fibrous crystalline structure extending substantially perpendicularly to a direction of thickness of the cylindrical sidewall portion, and the fibrous crystalline structure satisfies 0.003â‰¦W/TAâ‰¦0.07, where TA is the thickness of the cylindrical sidewall portion and W is an average width of the fibrous crystalline structures in the direction of the thickness.