GB1341860A - Fluorescent screens for use in cathode ray tubes - Google Patents

Abstract

1341860 Etching glass HITACHI Ltd 30 Dec 1971 60881/71 Heading C1M [Also in Division H1] The faceplate 6, Fig. 2, of a cathode ray tube is provided with grooves 9 separating the phosphor areas 7, the side walls 10 of the grooves being inclined preferably at 10-40 degrees so that they reflect light from the phosphors in the forward direction, as illustrated by rays 13, and thereby increase the brightness. The grooves may be 5-500 microns deep and may be coated with reflective material such as aluminium or a reflective powder such as magnesium oxide or aluminium oxide; alternatively the grooves may be filled with black particles which absorb stray light passing into the faceplate. The phosphor areas may be dots which are preferably smaller than the electron beam, or may be stripes. In one example of the latter, Fig. 3 (not shown), the surface of the faceplate is corrugated, either by etching or by machining, and the phosphor is deposited only on the peaks of the corrugation. In one example of the manufacture of a multidot colour screen, the faceplate is roughened and coated with acid-proof photo-resist which is exposed to ultra-violet light or to electrons and developed to leave a pattern of dots of about 0À27 mm. diameter. The faceplate is then etched with a mixture of hydrofluoric, phosphoric and hydrochloric acids to remove portions of the glass not covered by the photo-resist dots to a depth of about 100 microns. The photo-resist is then removed and phosphor dots are formed on the raised portions of the faceplate in known manner. A multi-line colour screen may be formed in a similar manner.