Method for manufacturing a data medium and data medium thus obtained

Method for manufacturing a multilayer data medium (1) in which:

• a multilayer data medium is selected comprising at least one security layer (16) and at least one layer, named marking layer (17), which is sensitive to electromagnetic marking radiation (5), said marking layer being arranged at least in part facing said security layer (16),
• said security layer (16) comprises at least one printed image comprising at least one thermochromic pigment adapted to change colour upon a predetermined temperature variation,
• in a marking step, at least one mark (30) is formed in said marking layer (17) using said electromagnetic marking radiation through said printed image, wherein:
• said printed image is a semi-transparent printed image which causes at least one semi-transparent visible pattern to appear in a first state, named non-activated state, at at least a first temperature, allowing, after said marking step, said mark (30) to be seen through this image, said pattern not being visible in a second state, named activated state, at at least a second temperature which is different from the first temperature,
• said printed image is prepared from at least one printing composition comprising at least one transparent binder and a predetermined proportion of thermochromic pigments adapted to form a semi-transparent printed image allowing said mark to be seen through this image in the non-activated state of the thermochromic pigments.