Transparent multilayer polymer films for hidden marking of reflective containers

Counterfeit production remains a major socio-economic challenge, and one effective countermeasure is the hidden marking of polymer packaging. When polarized light reflects from mirror-like containers wrapped in anisotropic, transparent shrink films, it generates vivid multicolor effects used for both open and covert labeling. These optical features have been observed across various anisotropic films, revealing a surprising dependence of color and transparency on film scale. Additionally, hidden barcodes can be embedded within internal film layers and later read using polarized light, offering a robust method for product authentication.