| 摘要 |
A conventional cigarette packet in a transparent film of bi-axially oriented polypropylene (BOPP) with a tear tape for removing the film adhered to the inside of the film. The tear tape bears an indicium which is either hidden or which changes according to the viewing angle when the image is viewed through the film. The image on the tear tape may be scrambled or coded. The overwrap film includes a descrambling or decoding region which reveals the hidden image or renders the image visible when viewed through the overwrap portion, or creates the visual effect of changing the image according to the viewing angle. The descrambling or decoding region typically comprises a diffraction structure, such as a grating, the characteristics of which, such as its pitch, are complementary with the scrambled or coded image and/or with the pitch of any grid or matrix from which the image is composed.
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