Printed Plastic Bags

Printed Plastic Bags

Printed plastic bags are often imprinted with bar codes, ingredients, warnings and other such information. Retail industries, however, often add print to bags not as a requirement, but as an opportunity for cost-effective advertisement. Logos, brands, store names and slogans are common features added to plastic merchandise and shopping bags. Bags with generic phrases such as "Have a Great Day!" or "Thank you for Shopping" are also mass produced and available at a lower price. Other printed bags do not have text or logos, but rather a blank surface on which individual labels and tags may be written more easily than on the plastic substrate. Vinyl, polyethylene and polypropylene bags with minimal stretch ability are best suited to printing processes, though many other types of printed plastic bags are also available.   

The printing process is performed after the sheets of plastic film have been formed, but before they are sealed and cut into the desired bag shape and size. Casting, winding and extrusion are common methods used to produce the film which is loaded into the printing machine. Flexography is the preferred method for plastic bag printing, though traditional methods such as stamping and inkjet are available as well. Flexography employs a rotary press similar to a letter press. A flexible relief plate made of plastic or rubber has a slightly raised pattern that is the inverse of the desired print. These plates are partially submerged in ink allowing only the raised image to be coated before rolling over the plastic film onto which the ink is transferred. The ink is specially formulated to suit the printing process as well as the plastic and its intended application. The ink can be water based, alcohol based, solvent based, electron beam or UV curing and must be continually circulated to retain its viscosity. Soy based inks are also used to print on biodegradable bags and in some instances acrylics are used for their superior adhesion to non-porous surfaces. Although capabilities vary among manufacturers, most can print as many as seven different colors at the same time allowing for greater possibility in the creation of unique or complicated design schemes.