Patent ID: 6812630
Filing Date: 2004-11-02
Classification: H01J

Abstract:
A cathode ray tube comprising:a bulb whose inside volume is maintained in vacuum; an electron gun located inside of said bulb for ejecting electron beams; a fluorescent material located on an inside wall of said bulb, for emitting light when electron beams ejected from said electron gun are applied thereto; beam deflection means for deflecting such electron beams to scan the surface of said fluorescent material; an inner magnetic shield located inside said bulb for decreasing the deviation of the trajectory of electron beams deflected by the beam deflection means in an external magnetic field; a shadow mask arranged in front of an inside surface of said fluorescent material; and a polygon-shaped mask frame for fixing said shadow mask, the frame comprising a side member for each side of said frame and a joint portion for joining adjacent side members, wherein the adjacent side members connected by each joint portion satisfy the following condition: &mgr;r,1>&mgr;r,s>1 where &mgr;r,1 represents a relative magnetic permeability of a longer side member and &mgr;r,s represents a relative magnetic permeability of the other member.