| 摘要 |
The device (1) has two juxtaposed printed patterns (2, 4) to cover a printed pattern (8), where each pattern is printed with an ink containing fluorescent pigments. Composition of the inks of the patterns (2, 4) is such that the patterns (2, 4) form an opaque filter under an UV ray for radiation emitted towards or re-transmitted by the pattern (8) to make the pattern (8) to remain invisible. The effect of filter is diminished or disappeared when a document is exposed to another UV ray (UV2) such that the pattern (8) appears in a color distinct from colors of the patterns (2, 4). |
