Television picture tube having a composite frontal pane

DETAILED DESCRIPTION In view of the above, it is an object of the invention to provide a television picture tube having a composite frontal pane which provides improved image and viewing quality but which is easier to manufacture and is extremely satisfactory in its overall aesthetic impression.
This object is accomplished by a television picture tube which includes a composite frontal pane comprising a viewing screen which is spherically or aspherically convexly curved relative to the viewer.
A convexly curved supplementary pane, preferably made of clear glass, gray glass or machine glass is spaced from the viewing screen by a transparent cast resin layer inserted between the viewing screen and the supplementary pane.
The resin layer glues the screen and the pane to one another and has a refraction index which corresponds approximately to that of the supplementary pane and the viewing screen.
The supplementary pane is cylindrically curved only about the pane's vertical axis and its radius of curvature is significantly larger than the radius of curvature of the viewing screen.
Accordingly, the supplementary pane is curved cylindrically merely in a single direction--namely about the vertical axis.
Its radius of curvature is substantially larger than the radius of curvature of the viewing screen.
The combination of these features with those of the viewing screen and resin layer results in the following advantages: Firstly, the frontal face of the invention'supplementary pane is a greatly improved approximation of the planar rectangular shape considered to be optimal for good viewing quality even from acute angles.
Due to the lens and distortion effects which result from the great differences in layer thicknesses between the center and the edge regions, this type of good viewing quality has generally not been realized in large-area television picture tubes.
Because of the present invention's considerably increased radius of curvature about its vertical axis and the complete absence of curvature in the vertical direction, the television picture tube according to the invention gives the impression to the viewer of a completely planar frontal face