Patent ID: 6268692
Filing Date: 2001-07-31
Classification: H01J

Abstract:
A cathode ray tube comprising:a vacuum envelope made of glass, said vacuum envelope includinga substantially rectangular panel having an inner surface on which a substantially rectangular phosphor screen is formed, the phosphor screen having a horizontal axis and a vertical axis passing through a tube axis said horizontal and vertical axes being perpendicular to each other,a substantially cylindrical neck, anda funnel connected between the neck and the panel and having a first portion positioned on a side of the panel and a substantially truncated quadrangular pyramid-like second portion positioned on a side of the neck, at least one cross-section perpendicular to the tube axis of the second portion having a non-circular shape which maximizes a distance from the tube axis, the panel, the funnel, and the neck being disposed along the tube axis at a portion between the horizontal axis and the vertical axis;an electron gun arranged in the neck, for emitting electron beams to the phosphor screen; anda deflection yoke mounted on an outer surface of the vacuum envelope to extend from the second portion of the funnel to the neck, and having a deflection coil for deflecting the electron beams emitted from the electron gun to scan the phosphor screen;wherein, in a cross-section of the vacuum envelope cut along a plane including the tube axis, the first portion of the funnel has a concave shape which provides a negative value by twice differentiating r(z) by a tube-axis coordinate z and the second portion of the funnel has a convex shape which projects toward the tube-axis and provides a positive value by twice differentiating r(z) by the tube-axis coordinate z, where the tube-axis coordinate z is given in a direction in which the phosphor screen side is positive along the tube-axis and a distance between the tube axis and the outer surface of the funnel is r(z),wherein a boundary between the second and first portions of the funnel is an inflection point which provides a value of zero by twice differentiating r(z) by the tube-axis coordinate z, andwherein, in a cross-section of the vacuum envelope cut along the plane including the tube axis, the boundary between the second and first portions of the funnel is within a range of at most 17 mm from the tube axis coordinate of the end of the deflection coil on the side of the phosphor screen.