GB1314805A - Method of forming the screen of a black matrix type colour cathode ray tube and a cathode ray tube incorporating said screen - Google Patents

Abstract

1314805 Luminescent screens TOKYO SHIBAURA ELECTRIC CO Ltd 23 Dec 1971 [25 Dec 1970] 60193/71 Heading H1D A method of forming a black matrix type colour cathode ray tube comprises forming a photo-sensitive resin film on the faceplate, light exposing through a perforated mask from an annular light source to expose dots smaller than the mask holes, washing (e.g. with water) and removing unexposed portions, forming a graphite film over the entire surface, removing the remaining photosensitive areas with the associated graphite film (e.g. with hydrogen peroxide) to obtain matrix holes, and coating the matrix holes with red, green and blue emitting phosphors. The photosensitive resin may be polyvinyl alcohol, an etchant at the washing and removing is a solution of hydrogen peroxide. The annular light source (e.g. h.v. Hg and lamp) may have the width of an annulus of 0À5 to 1 mm. and a mean diameter of 1À5 to 3À0 mm. The matrix film area may be 40 to 50% of the picture area, the reflection of external light is prevented, phosphor emission ducts secondary electrons is suppressed and contrast is increased, Fig. 1 (not shown), indicates three electron guns (17) and Al film (7) prevents build up of electrostatic charge and reflects phosphor emissions towards the observer. Connecting lens (21), Fig. 2b (not shown), includes connecting lens (21) ensuring central holes are larger than peripheral ones. After coating the matrix holes and matrix material with the phosphor layer, exposure is by a point source (30), Fig. 2 (not shown). In Fig. 3 (not shown), light source to faceplate distance L 0 may be 280 mm., faceplate to mask distance 10 mm., mask holes 0À33 mm. diameter, annulus d 0À7 mm., diameter D 2 mm., the matrix having holes of 0À26 mm. diameter at the central part and 0À23 at the periphery.