| 摘要 |
A seal (12) that provides visual evidence if the seal is forced open or cooled below a breakdown temperature. The seal (12) includes a plastic strip (20), a layer of ink (22) printed on a surface of the plastic strip (20), and a layer of pressure-sensitive adhesive (24). The seal (12) can be incorporated into a bag (10) for sealing the bag (10) closed. When the bag (10) is sealed closed, the ink layer (22) is sandwiched between the plastic strip (20) and the adhesive layer (24), and the adhesive layer (24) is adhered to a back wall (18) of the bag (10). If the seal (12) is forced open, the ink layer (22) visibly delaminates from the plastic strip (20). The adhesive layer (24) and the plastic strip (20) are chosen to have different rates of shrinking when cooled, so that when the seal (12) is cooled below its breakdown temperature, the ink layer (22) delaminates. In an alternative embodiment of the plastic strip (20'), two layers (60, 62) of ink are printed onto the plastic strip (20'). The first layer of ink (60) is clear and is printed onto the untreated plastic strip (20') in a pattern. The second layer of ink (62) is opaque and is printed uniformly over the plastic strip (20') and the clear ink (60) after the plastic strip (20') is treated.
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