UV laser marking tea packaging bag production date QR code RFH 355nm UV laser for non-contact marking of tea packaging QR code High-speed marking of plastic packaging bags by solid-state nanosecond ultraviolet laser   At present, many tea packages on the market have product QR codes. After buying tea, many people will scan the QR code on the package with their mobile phones to learn about relevant information and trace the source of the product. But everyone knows how the QR code does it. Is it on the bag?