By Stephen Montgomery
Market research shows the worldwide consumption value for complete signage and display systems based on light-emitting diodes (LEDs) reached new heights in 2017 at an estimated US$56.5 billion. This overall figure, however, does not convey the many different ways LEDs are used in professional displays today.
Market forecasts are segmented based on specific applications, including on-premise and off-premise outdoor displays (e.g. roadway digital billboards) and indoor screens for airports, bus and train terminals, shopping centres, restaurants, hotels, sports facilities, entertainment venues, office buildings and educational institutions. One of the most notable trends, given the categorization of such segments, is the increasing migration of large-format LED arrays from their traditional outdoor locations to open indoor spaces, as well.
Categorized by purpose
With LED cluster displays, multiple LEDs are mounted on boards to form tile modules for digital signage applications. This category includes not only video walls and digital billboards, but also flexible LED-based displays, where even a curtain or drapery can become a dynamic screen.
While liquid crystal displays (LCDs) backlit by LEDs are also commonly used for digital signage applications, they are quantified separately, as their LEDs serve a different purpose; rather than display content themselves, they illuminate the LCDs, which display the content.
LEDs are also commonly used to illuminate conventional or traditional sign media by day and night, including static billboards, paper- or canvas-based graphics, channel letters and sign boxes. In this context, their role is comparable to that of neon, fluorescent and electroluminescent (EL) illumination before them.
While neon and fluorescent lighting are still fairly commonly used today and can prove effective for many years, LEDs have provided a strong alternative with their energy efficiency, solid-state construction and cooler operation. Indeed, their rise may signal the eventual demise of older sign illumination technologies.
Even the latest high-brightness LEDs (HB-LEDs) are low-voltage and operate with minimal running costs, allowing signs to be both bright and energy-efficient. Further, LEDs are highly durable, offering greater longevity than other traditional forms of sign lighting and reducing the frequency and costs of maintenance.
Sign lighting techniques
LED illumination can be implemented with a variety of techniques, including back, front, edge and halo lighting.
Metal and acrylic letters can be front- or backlit, respectively, as sign faces or halo-illuminated for a subtler, esthetically pleasing effect. Acrylic panels can be edge-lit with LEDs to serve as ‘light sheets’ or collectively as ‘light walls’ or integrated into aluminum frames to serve as ultra-thin lightboxes. More traditional aluminum lightboxes, which have been used for decades and remain very common today, can also be illuminated with LEDs from within.
With these common signage applications in mind, different LED products have been specially developed for optimal lighting of channel letters and lightboxes, to name a few. By packaging ultra-high-intensity LED semiconductor chips, uniform illumination can be achieved across a wide range of angles.
By way of example, most 203-mm (8-in.) stroke channel letters can be illuminated by using just a single row of LEDs, without creating visible ‘hot spots.’ These systems can also illuminate channel letters with depths as little as 64 mm (2.5 in.).
As mentioned, LEDs can be used to create flexible lighting systems. With a bending radius of less than 1.3 mm (0.05 in.) and an anticipated 500,000-plus bending cycle ‘lifetime,’ they can be flexed at almost any angle, follow the tightest contours and be installed in one continuous strip, with only one or two connecters needed per channel letter.