Specialty overlaminates are formulated with different applications and needs in mind, such as graffiti resistance for posters and cleanability for window graphics.
Light management
Clear, translucent and perforated films offer a variety of light management properties for signs and graphics.
Many sign faces use a clear or milky white translucent plastic film with a front and back surface, such that the light source is installed behind the back. In other cases, a multi-layered approach is taken, with light passing through a diffuser film, a clear rigid sign face and a translucent colour film. The diffuser film can help mask ‘hot spots’ created by the spacing and layout of the light-emitting diodes (LEDs), to create more uniform illumination of the sign face.
With dual-colour films, a sign can appear different by day and night. A channel letter populated by white LEDs and treated with a light enhancement film can be augmented with a diffuser film, translucent colour film, clear film and perforated dual-colour film. By day, the non-illuminated sign exhibits the perforated film’s colour in reflected light. By night, it is backlit by the LEDs and visually transforms into the colour of the translucent film. By way of example, black letters on a white background, which are highly visible
in daylight, can become bright blue letters on a dark background at night. There is still colour contrast, but it is reversed. And the light management properties of translucent films mean white LEDs can be ‘tuned’ to create other colours as desired.
Graphic protection
As mentioned, the durability of graphics can be enhanced by applying an overlaminate or a clearcoat, to protect against dirt, contaminants, colour fading from ultraviolet (UV) radiation, vandalism and other potential causes of damage. Such an application can add new properties, such as skid and abrasion resistance and cleanability.
Reflective sheeting is useful for nighttime visibility.
It is worth keeping in mind not all graphics require protection. Another reason to laminate or clearcoat graphics, however, is for visual enhancement, as their gloss level, either to reduce glare or to add shine.
Overlamination uses a cold or hot-roll laminator, is compatible with digitally printed graphics and can achieve an ultra-matte, matte, lustre, gloss or high-gloss finish. Specialty overlaminates are often formulated with many different applications in mind, such as car wraps, window graphics, flexible sign faces, awnings, wall murals and box truck graphics.
The process of overlamination adds stiffness for greater ease of installation and supports special optional features like graffiti resistance, slip resistance (usually necessary for floor graphics) and cleanability. The cost ranges from medium to high, depending on the laminator type and model.
Clearcoating requires the use of screenprinting equipment, though it is compatible with both screenprinted and digitally printed graphics. Only three finishes are possible—matte, lustre and gloss—and no stiffness is added to the graphics, but the cost is very low compared to lamination.
Products and performance
Adhesive-backed films have enabled a virtually unlimited breadth of options for surface imaging and customization, both for branding and decor applications. Understanding base films, adhesives, light management films and finishing options—and, in particular, their user-friendly design features—is important for today’s signmakers, so they can consistently choose the best products over time for a variety of projects.
Cordell Hardy is a technical director for 3M’s commercial solutions division. This article is based on a seminar he presented at the 2017 Specialty Graphic Imaging Association (SGIA) Expo in New Orleans, La. For more information, contact him via e-mail at chardy@mmm.com.
