Adhesive Wet-Out and Release Liner Smoothness
Adhesive and liner choice will impact clarity based on the wet-out characteristics of the adhesive and the smoothness of the liner. Polyester liners provide a glass-smooth adhesive result, resulting in exceptional clarity when adhered to the underlying graphic. Wet-out with a clay-coated paper liner will be somewhat less smooth, and wet-out with a plain paper liner will be the least smooth.
Not all graphics require super-smooth adhesive wet out, however. Images that will be viewed from a distance such as a billboard or building graphic, for example, may look fine with the use of a paper liner, while a brand identification label which will be viewed up close may require smoother wet out to achieve the desired graphic quality. If the inks tend to be raised as with UV inkjet and screen printing, an adhesive with good wet-out will conform to the peaks and valleys of the printed graphic to avoid haloing around the ink edges.
The content of the graphics is another factor to be considered. While most overlaminates can be coupled with clear or white print media, good adhesive wet-out is critical for dark colored or metallic base substrates and inks. While the imperfections created by an overlaminate on a paper or clay-coated liner may not be noticeable on a light-colored film or graphic, those same imperfections will be highlighted over a dark surface. An overlaminate backed with a polyester liner can help minimize these concerns.