U.S. Philips Corporation

Leo H Krings

Erik Paul Boonekamp

Emmanuel W Oomen

Petrus H Notten

Gerardus V Aben

Johan Van De Ven

A description is given of an electro-optical switching device (1) comprising a transparent substrate (3), a switching layer (5) of yttrium hydride as a first electrode, a palladium layer (7), an electrolyte layer of, e.g. Ta.sub.2 O.sub.5 (9), a layer of WO.sub.3 hydride as the second electrode (11), and a transparent ITO-layer (13). Under the influence of a potential difference or direct current between the electrodes (5) and (11), the yttrium hydride is electrochemically converted from a low-hydrogen-content state to a high-hydrogen-content state, or vice versa. The conversion between both compositions is reversible, and is accompanied by a change in optical transmission. Apart from Y, other trivalent metals may be used, such as Gd and La.

Electro-optical switching device

The electrochromic element comprises an electrochromic layer (22) whose transmission properties change when a voltage difference is applied across the element. Said electrochromic layer (22) comprises a first metal oxide of the group formed by WO.sub.3, MoO.sub.3, Nb.sub.2 O.sub.5, MnO.sub.2 and ZrO.sub.2 (and combinations thereof) and a second metal oxide containing V.sub.2 O.sub.5, TiO.sub.2 and/or ZnO. If the concentration of the second metal in the mixture ranges from 1 to 15 at. %, preferably from 3 to 10 at. %, the electrochromic layer (22) is transparent and colorless if no guest atoms are incorporated in the layer, and it is (color neutral) grey if a substantial concentration of guest atoms is incorporated in the layer. Electrochromic elements are provided, for example, on the outer surface of a display screen of a display device.

Electrochromic element

The display screen 3 of a cathode ray tube 1 is provided with an electroconductive coating 8 of poly-3,4-ethylene dioxythiophene. The layer 8 has a sheet resistance of 1 k.OMEGA./.quadrature. and a high transmission. The layer 8 provides an effective shield against electromagnetic radiation. The coating can be provided with additional layers of, for example, silicon dioxide to improve the mechanical properties.

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Eindhoven, Netherlands

Leo H Krings