Patent ID: 7176641

Claim:
A cathode ray tube including an evacuated envelope which is constituted of a panel portion having a phosphor screen on an inner surface thereof, a neck portion which accommodates an electron gun, and a funnel portion which connects the panel portion and the neck portion, wherein the electron gun includes an electron beam generating portion which is constituted of an indirectly heated cathode structure, a control electrode and an accelerating electrode and a main lens portion which is constituted of a focusing electrode and an anode electrode, the indirectly heated cathode structure includes an electron irradiation material layer, a substrate metal which holds the electron irradiation material layer and a cathode support sleeve which supports the substrate metal, wherein the cathode support sleeve includes a heater which is formed by winding a core-wire as a coil therein, the heater includes a heat generating portion having the double helical structure which is formed by further twisting and winding the core-wire which is wound as a coil, a leg portion which is contiguously formed with heat generating portion and is wound in a plurality of layers as a coil, and a welding portion which is contiguously formed with the leg portion and is welded to a heater support, the heater has a portion thereof except for the welding portion thereof covered with an insulation film, and the heat generating portion has regions which differ in the number of coil winding layers.