Non-migrating control indicia for a plastic web or sheet article

摘要

An article in web or sheet form, especially useful in the packaging or container art, having control indicia. The indicia are detectable under special conditions for controlling operations in the manufacture and/or use of the article. In the preferred embodiment the indicia are invisible and of a polar or ionic organic material that will not significantly migrate through a plastic web. The indicia emit electromagnetic wavelength-shifted radiation in response to incident electromagnetic radiation of a selected wavelength.