| 摘要 |
A flexible sheet or web (1) comprises a light polarising security element (4) contained within the thickness of the sheet or web, a region of the security element being exposed at a window (6) at both faces of the sheet or web and optionally at a further window (5) at one face of the sheet or web. Folding the sheet to align the windows produces cross polarisation between the exposed security element regions. <IMAGE> |
