Electrode for cold cathode tube and cold cathode tube employing it

An electrode for cold cathode tube, comprising:

• a cylindrical sidewall portion;
• a bottom portion provided at one end of the cylindrical sidewall portion;
• and an opening portion provided at the other end of the cylindrical sidewall portion, wherein the electrode is formed of a sintered body of a simple substance of a metal selected from tungsten, niobium, tantalum, molybdenum and rhenium, or an alloy containing the metal;
• and wherein the electrode satisfies L≧6 (mm), t1>t2, R≧20 (mm), where L is an overall length of the electrode with respect to an axial direction of the cylindrical sidewall portion, t1 is a wall thickness at a portion of ½ of the overall length L (L/2), d2 is an inside diameter of the bottom portion, t2 is a wall thickness of the cylindrical sidewall portion at the portion of the inside diameter d2, and R is a radius of curvature of an arc of an inner surface of the cylindrical sidewall portion connecting an inside diameter portion of the cylindrical sidewall portion at the portion of L/2 and an inside diameter portion of the bottom portion.