Patent ID: 6323591
Filing Date: 2001-11-27
Classification: H01J

Abstract:
A picture display device comprising a display tube having an evacuated envelope (1), which envelope comprises, around a longitudinal axis (20), a display window (2) with a display screen (3) on its inner side, a conical portion (4) and a neck portion (5), the conical portion (4) being connected to an upstanding wall (15) of the display window (2),characterized in thatthe conical portion (4) has a wall thickness, wherein the wall thickness d.sub.sa along a short axis (22) of the conical portion (4) as a function of a distance z in a first area (41) of the conical portion (4) adjacent to the upstanding wall (15) of the display window (2) is defined by the relation:.delta.d.sub.sa /.delta.z=C.sub.1,and, in a second area (42) adjacent to the first area (41), is defined by the relation:.delta.d.sub.sa /.delta.z=C.sub.2,in which .vertline.C.sub.1.vertline.>.vertline.C.sub.2.vertline.,and in which the first area (41) comprises a part of the conical portion (4) for which 0.ltoreq.z.ltoreq.a, and the second area (42) comprises a part of the conical portion (4) for which a.ltoreq.z.ltoreq.80%,in which z represents a relative distance measured with respect to the projection on the longitudinal axis (20) between the connection with the upstanding wall (15) of the display window (2) and the transition to at least substantially axial symmetry in the conical portion (4),and in which a is in the range of 10%.ltoreq.a.ltoreq.60%.