| 摘要 |
1281743 Cathode-ray display tubes SIGMATRON Inc 28 July 1969 [26 July 1968] 37833/69 Heading H1D [Also in Division C4] A luminescent device having high contrast ratio and minimal halation effects, such as a c.r.t. E.L. device or fluorescent screen comprises a transparent light emitting phosphor layer 16 having a viewing side and an opposite, the latter coated by a light absorbing layer 26 having a refractive index substantially equal to that of the phosphor layer and being in intimate and continuous contact with same so as to minimize reflection at the interface, the light absorbing layer admitting and absorbing light which impinges on the interface from the viewing side. Layer may be polycrystalline or amorphous and a dielectric substantially transparent at the interface and with a gradually increasing concentration of light absorbing material is included as a function of distance from the interface, e.g. a silicon oxide base with Al additions. To reduce light scattering, the phosphor and light absorbing layer is preferably vacuum deposited to ensure intimate and continuous surface contact. Electrodes 20 and 22 may be included, the latter being opaque with transparent dielectric layer 24. The c.r.t. phosphor layer of Fig. 4 (not shown) may include a rear cathodoluminescent portion emitting short wavelength radiation to excite a forward phosphor layer and light absorbing layer (26<SP>1</SP>) and conductive layer (22) may be a single compound layer. Also in a c.r.t., the layer 26 is thin and of a small atomic number and may be mildly conductive on its rear surface to allow charge dissipation. The light absorbing layer may be arsenic sulphide, selenide, sulphoselenide or mixtures thereof evaporated to 1000 Š to 3 Á thickness, having diffuse reflectance of about 5%. |
