COLOUR DISPLAY TUBE, METHOD OF MANUFACTURING SUCH A DISPLAY TUBE HAVING A SHADOW MASK, AND REPRODUCTION MASK FOR USE IN SUCH A METHOD

摘要

By making the bridges in n few rows of apertures situated at the edge of the shadow mask of a colour display tube at least 20 % wider, the mask is not so readily destroyed during drape drawing. In addition, by keeping the width of the bridges in a row constant and increasing it regularly, preferably substantially linearly per row from a row through the centre of the shadow mask to a row at the edge of the shadow mask, a continuously varying brightness distribution is also obtained. The reproduction mask for the manufacture of such a mask can be obtained in a simple manner by rotating the pattern of bridges between two exposures necessary for printing on photo-sensetive material and combination of the resulting copy with a pattern of stripes.