Method of producing a segmented lens and a screen for a color display device

Abstract

In the manufacturing process of color display tubes with a dotted screen pattern, to form the screen ( ), a segmented lens ( ) is used for exposing the display window ( ) in order to apply a structure of a black matrix layer and a layer with electroluminescent material to it. Principally, a segmented lens ( ) gives rise to a phenomenon that is called facet marking; this is a result of the fact that the images of consecutive facets ( ) of the lens on the screen ( ) are disjunct or partly overlap, giving dark lines ( ) or bright lines ( ). In present day color display tubes—especially for use as computer monitors—it is getting more and more important to reduce facet marking as far as possible. It is proposed to manufacture the segmented lens ( ) according to a new process in which the mold ( ) for the manufacture of said segmented lens is significantly changed. In the new process, the poles ( ) for the mold ( ) are stacked by placing them with cylindrical projections ( ) into apertures ( ) of the carrier plate ( ). This prevents leaning poles ( ), which result in errors in the inclination of the facets ( ). This method of manufacturing the mold ( ) makes it possible to decrease the facet size and significantly improve the facet marking in color display tubes.