Illumination: LEDs and the evolution of plastics

Photos courtesy Bayer MaterialScience

Photos courtesy Bayer MaterialScience

By Ken Licklider
The evolution of plastics for outdoor signage has followed a complex path. Innovations in the formulation of these materials have been driven by several factors, including a push to use plastic channel letters and sign faces in more diverse physical environments. New forming and fabrication techniques have led to new grades and types of plastics, which in turn have expanded signmakers’ design options.

At the same time, innovations in sign lighting technology have also played a significant role in the development of plastics. Today, light-emitting diodes (LEDs) have become the industry standard for sign illumination, as they offer design versatility and help save energy and costs, but they have posed new challenges for the performance of plastics.

In response, plastic manufacturers have invested in new polymer technologies specifically to optimize the quality of lighting from LEDs. This trend has further supported the long-term growth of plastic sign faces and channel letters for outdoor applications.

Before plastic sheet products reached the sign industry, painted metal was the substrate of choice for neon signs.

Before plastic sheet products reached the sign industry, painted metal was the substrate of choice for neon signs.

The use of plastics was originally driven by wartime applications, leading to spinoff products by the late 1940s for both consumer markets and industrial sectors like signage. Major suppliers of acrylic resins, such as DuPont and Rohm & Haas, entered the sign market with plastic sheet-based products, which quickly replaced painted and/or externally illuminated opaque wooden and metallic sign faces.

Signmakers embraced these plastics for a number of advantages over wood and metal substrates, including lower costs, greater versatility, lower material weight and greater ease of fabrication. The ability to backlight a colourful, translucent sign face with incandescent bulbs installed inside the ‘sign can’ quickly became popular.

Given the fast growth of the sign market at the time, signmakers and sheet manufacturers alike became keenly aware of both the benefits and shortcomings of early plastics. The market acknowledged these advantages and unforeseen limitations as signmakers pushed their suppliers for improvements. Lessons learned from real-world experiences led to successful investments in newer technologies for better performance.

Design and production techniques evolved rapidly. With bright illumination and low material weight, new possibilities emerged for retailers and marketers, including dramatic lighting effects at night. New plastics not only enabled greater design freedom for messaging, but also offered easier installation for overhead signs.

Channel letters improved the identification of retail locations by day and night. And the thermoforming of plastics led to multi-dimensional characters, brands and images beyond lettering.

Another change during this period was in illumination itself. Fluorescent backlighting saw widespread adoption for acrylic signs, offering more uniform light dispersion and longer-lasting bulbs, compared to incandescent illumination.

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