| 摘要 |
PCT No. PCT/GB97/01600 Sec. 371 Date Dec. 22, 1998 Sec. 102(e) Date Dec. 22, 1998 PCT Filed Jun. 13, 1997 PCT Pub. No. WO97/47478 PCT Pub. Date Dec. 18, 1997A security device comprises a substrate (1) having a viewing region (3) which is provided on one side with first indicia (7) and on the other side with second indicia (9) overlying the first indicia. The substrate carries an obscuring material (10) aligned with the second indicia (9) so as to prevent at least the second indicia from being viewed from the one side of the substrate under reflected radiation. The substrate is sufficiently transparent while the obscuring material permits the passage of sufficient transmitted radiation to allow the second indicia (9) to be viewed from the one side of the substrate under transmission conditions. |
