Form for concealing variable printed information

摘要

Variable confidential information (12) is printed over scrambling pattern (14) which is formed of thermochromatic ink. Information (12) cannot be read due to the presence of the underlying scrambling pattern. The information becomes readable when heat is applied to the thermochromatic ink and the optical properties of the thermochromatic ink are altered. Preferably, the alteration of the optical properties of the thermochromatic ink is irreversible