Printed Plastic Bags
Printed plastic bags are mass manufactured and custom made bags with logos, pictures, text or graphics on the front. Used in the retail, medical and packaging industries, plastic bags with printing on them are generally made of polyethylene or polypropylene that has minimal stretch ability, making them easier to print on. Text like contents, warnings, ingredients, UPC codes or any message like "Have a great day" or "Thanks for shopping" can be printed on transparent bags or plastic of virtually any color. Multiple colors can be used at one time. This is often seen on shopping bags in retail settings of any kind, since plastic bags have become much more popular than paper bags within the last couple decades. Some plastic bag manufacturers offer pre-printed bags with a common phrase or product name (like "fine jewelry") as a less expensive alternative to custom printing.
The printing process happens after the sheets have been formed, but before the sheets are sealed and cut into the bag shape. The ink can be water based, alcohol based, solvent based, electron beam or UV curing inks, and must be continually circulated to retain its viscosity. The pattern or text impressions are applied by inking rollers on long sheets of plastic soon after they have been cooled. Flexographic printing is another method option. During this process, a flexible plate made of rubber or polymer material with a raised image or text is partially submerged in an ink tank and then stamped onto the plastic sheet.