GB1458909A - Colour television display tubes - Google Patents

Abstract

1458909 Colour television tubes; electron multipliers MULLARD Ltd 4 April 1975 [7 May 1974] 20019/74 Heading H1D A colour TV display tube comprises channel plate I, a gun producing a scanning beam, a colour luminescent screen with phosphor regions P 1 , P 2 , P 3 and a colour-selection electrode system located on, and insulated from the output face of the channel plate, and which comprises two commoned sets of interdigitated selector strip electrodes ES1, ES2. The tube uses lower energy electrons, lower switching voltages and eliminates colour impurities due to non- normal electron emergence (e.g. in 110 degree tubes). The electrode system may be on but insulated from the output electrode of a continuous dynode type plate, or a focusing electrode Mf as in Specification 1,458,910 (Fig. 4, not shown). Cyclical potential differences switch beam bo between strip P 2 and stripes P 1 and P 3 . Electrode Ea may be on the side of the phosphors remote from the support W. Layer Dn may be etched back from the channel exit to reduce charge deposition, may be replaced by dielectric stripes, or may be a pattern of dots or islands on which the strip electrodes are supported, while strips ES1, ES2 may extend partly into the gaps between channels. The phosphors may be dots and electrodes ES1, ES2 need not have straight edges (Figs. 3, not shown). In Fig. 4 (not shown), the dynodes and selector electrode strips are of re-entrant aperture form. Dimension (d7) of electrodes (ES1, (ES2) may be greater than (d5) to reduce unwanted secondary emission. A second focusing grid of the same form and dimensions as a dynode may be included at the position of electrodes ES1, ES2, the latter being replaced by thinner strips insulated from the output face. The spherical form of channels is not essential. Potentials and dimensions are given. Fabrication may be as in Specification 1,434,503, and a continuous type plate may be reduced lead oxide glass. In a flat tube (Fig. 7, not shown), electrodes d(b) provide the horizontal scan of the beam from the offset gun and horizontal strips d(a) provide the vertical scan. Line sequential operation may be used, the system as in Specification 1,331,938 preventing line crawl or colour creep. Alignment problems are avoided by line scanning at right angles to the stripes, line sequential operation avoiding synchronism problems of Indexing type tubes. Colour tube deflection angles may be 130 degrees or more. References are included to several other Specifications 1,458,910 claims a channel plate with focusing electrode provided on but insulated from the input face, the apertures of the focusing electrode having input cross-sectional areas less than the cross-sectional areas of the channel output ends.