Record carrier with safety features capable of being checked mechanically and method of checking said safety

摘要

The record carrier has a card base, on which there are deposited an electrically highly conductive layer and an electrically highly insulating layer with the interposition therebetween of a chemically homogeneous intermediate layer into which safety features or information can be introduced by varying the conductivity of selected areas of the intermediate layer to provide areas of different respective electrical conductivities. In the method, the safety features or information are mechanically checked or read by applying a short voltage pulse between the conductive layer and an auxiliary electrode in contact with the insulating layer, with the charge image produced on the insulating layer being then scanned and evaluated in a measuring instrument, after which evaluation the charge image is deleted. For mechanically checking the record carrier for intactness, as a safeguard against erasure, a longer voltage pulse is applied between the auxiliary electrode and the conductive layer, the longer voltage pulse having a length such that a uniform distribution of charge is obtained on the insulating layer, after which the charge image of the insulating layer is scanned by a measuring instrument, evaluated, and deleted after the evaluation. Either procedure may be used alone or both may be used successively.