Abstract: In order to form safety markings at a planar card made of a plastics material, which card may be used, for instance, as credit card, this card is built up from at least two parts. The inner border area between these two parts comprises a relief-like structure which is the carrier of the safety marking. In order to generate a watermark-like effect the upper part is made of a opaque plastic material and the other part is made of a transparent plastics material. When viewing through this card the areas of the opaque layer having the largest thickness appear as darker areas, whereby when viewing the same way the areas having a smaller thickness show a certain brightness. After being embossed the two parts of the thermoplastic material are joined to each other such that they cannot be separated such that no access from the outside is possible to this safety marking.

Abstract: A card is disclosed which is made of a thermoplastic material and having visually recognizable, internal safety markings. The card comprises a first sheet of a transparent thermoplastic material and a second sheet of an opaque thermoplastic material. The second sheet has an inner surface provided with a relief structure such that the varying thickness of the opaque material will influence the local absorption of transmitted light. The first sheet has an inner surface provided with a corresponding negative relief structure. The first and second sheets are laminated together with their inner faces in contact to form an interface. Thus, when viewing the card in transmitted light, the relief structure is visually recognizable as a varying brightness due to varying absorption of the light transmitted through the opaque sheet.