Abstract: A passive display device comprising a first and a second supporting plate at least one of which is transparent, a number of display elements for controlling the reflection or transmission of light each having at least one fixed electrode and an electrode which is movable with respect to said electrode by electrostatic forces and which is kept separated from the fixed electrode by means of at least one electrically insulating oxidic layer, the insulating oxidic layer comprising a layer of a compound which comprises a polar and a non-polar group and the polar group of which is adsorbed or linked to the surface of the insulating oxidic layer.