Synthetic paper itself is a film, so why should it be covered with film? Is it to protect the printed information? Wouldn't it be difficult to print, and the printed content would also be impossible to protect?

Synthetic paper and the covered film have different tensile strengths and tensions. Whether it is warping or wrinkling, it is normal.

Why does paper label lamination not have this phenomenon? Because general coated paper and cardboard have very low stretchability, unlike films such as synthetic paper. If you must solve this problem, it is recommended to use bidirectional non-stretchable PET.