Data medium with user panel containing push-button circuit, e.g. pocket calculator in chip card form with display field and separate foil key board

摘要

The data medium has a user panel containing a push-button arrangement and several layers, of which at least two are electrode layers (11,12) and part of the push-button arrangement. One layer is an optically switchable layer (10) whose visual appearance changes under the influence of an electrical voltage. One of the electrode layers of the push-button arrangement is also used to drive the optically switchable layer.