The invention relates to a transparent window panel with a field of view that can be darkened on part of the surface thereof, by electrically controlling at least one functional element which is built into a composite material comprising several layers, the transmission of light being reversibly variable. The aforementioned functional element, which, in particular, takes the form of a solid electrochromic layer system, comprises at least one electrochromic functional layer which is enclosed between two surface electrodes. According to the invention, the surface electrodes (2E, 4) of the functional element (2) and the connectors thereof (12, 14, 16, 18, 19, 20) are adapted to one another and are disposed spatially in relation to one another such that the darkening process begins at one edge of the functional element and, under a remaining voltage applied between the surface electrodes (2E, 4), propagates continuously over the surface thereof until it has been completely and uniformly coloured. The invention also relates to a method of controlling one such functional element, which can preferably be used as an electrically-controlled sun visor for vehicle windscreens and similar. |