| 摘要 |
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. |
