Color cathode ray tube

A color cathode ray tube including an evacuated envelope constituted of a panel which forms a phosphor screen on an inner surface thereof, a neck which houses an electron gun and a funnel which connects the panel and the neck, wherein

• the panel has an approximately rectangular screen which has a long axis in the X direction and a short axis in the Y direction and the diagonal effective diameter of the screen is set to approximately 51 cm,
• the electron gun housed in the neck includes an electron beam generating part which is made of a cathode and first electrode and second electrode which are arranged in sequence from the cathode to the screen side, and a focusing electrode and an anode electrode which are arranged in sequence at the screen side of the electron beam generating part,
• assuming the equivalent radius of curvature in the X direction of the inner surface of the panel as Rix and the equivalent radius of curvature in the Y direction of the inner surface of the panel as Riy, the distance Lm between the cathode and a screen-side end portion of the focusing electrode which constitutes the main lens is set to a following value.
• 37≦Lm≦37+23.4−(Rix−{square root}{square root over ( )}((Rix−Riy+{square root}{square root over ( )}(Riy2−1502))2−2002))