Secure card e.g. prepaid telephone card, has surface containing visual information, where card is arranged to display or disappear visual information in response to mechanical deformation

摘要

The card (1) has a surface containing visual information (4, 9), where the card is arranged to display the visual information when the visual information is previously invisible, or to disappear the visual information when the visual information is previously visible in response to mechanical deformation (2, 5, 7, 10) such as twisting, folding, stretching or pressure. The mechanical deformation causes disappearance or appearance of microscopic cracks ready to block passage of a part of an incidental light through the card. An independent claim is also included for a method for using a secured card.