LED, signs, LED signs

Edge Lighting LEDs

Any time there’s a discussion of the versatile light-emitting diode (LED), there’s sure to be a lot of acronyms thrown into the mix. And acronyms—unless you have a military background (Lima! Echo! Delta! Sierra!)—can sometimes confuse and befuddle. So, for the sake of this treatise on edge-lit acrylic signs, we’ll keep the acronyms to a minimum, perhaps only to the most important acronym of all: LED.

Regular readers of Sign & Digital Graphics know that LEDs have improved immensely in both quality (higher) and price (lower). Moreover, technological advances have made them far more versatile and flexible as LED manufacturers strive for the ultimate goal of their endeavors, which is to provide economical and practical overhead lighting. In the meantime, the sign and graphics market has surely benefited from this pursuit.

“LEDs are becoming less expensive, brighter and even smaller,” says Bill Evans, general manager at Centsible Lighting in Las Vegas, Nevada. “The beam angle allows us to position them to maximize illumination in ways we haven’t been able to in the past. Plus, it’s easier to hide the LEDs in a slimmer light source as opposed to a bulky fixture.”

Centsible Lighting is a shop that is focused on lighting and electronics for in-store marketing/point-of-purchase. Edge-lit acrylic signage is a part of Centsible’s product mix and it is produced with either printed or with dimension using laser cutting, etching or sandblasting techniques.

One of the interesting properties of edge-lit acrylic is that “when you edge light acrylic, it passes through the entire density of the sheet, so any interruption in the flow of light, such as an etched letter, highlights where it’s been carved out,” says Ken Davis, an independent manufacturers’ sales representative for Plaskolite and SloanLED.

So, if your purpose is to create an illuminated letter or logo effect that glows, sandblasting, laser cutting or etching will do the trick, yielding an eye-catching sign. However, if you’re trying to illuminate the entire surface of the acrylic, such as you would with a full-color digital print on acrylic, any imperfections in the acrylic will stop the light in its tracks, creating inconsistent illumination.

Davis adds that Plaskolite provides a product called OPTIX DA—Digital Acrylic—which is manufactured specifically for flatbed UV-cure printers. The surface is designed to ensure proper adhesion of UV-cure inks to the surface in lieu of adhesion promoters, which can be messy, expensive and create imperfections that lead to inconsistent lighting, Davis says.

Mix and Match

There are basically two ways to create LED edge-lit acrylic signs. One is to mix and match acrylic sheet with LED packages to build a custom sign; and the other is to buy a pre-packaged, self-contained unit where you simply slip a backlit media into a slot or affix to the acrylic and hang it.

The choice is based on how much control the sign maker or graphics provider prefers to have over the final product. Centsible Lighting, for instance, builds its own signs, sourcing the acrylic and LED modules separately. In this case there are a lot of options, and manufacturers of both the acrylic and the LEDs can usually help figure out the best way to achieve the desired effect through design and construction. Improvements in LEDs—beyond brightness and price to variable beam angles and an increased viable color spectrum—allow for more versatility in the lighting outcome.

“Now, you can change the lighting effect not only with the number of LEDs used, but by using dimmers as well as special modules designed to throw light across the surface of the acrylic sheet, illuminating the graphics, as is the case with SloanLED’s PosterBOX module,” says Davis. 

At one time in the not-so-distant past, particularly in the sign market, the red LED was the only one that made practical lighting sense. However, the availability of various colored LEDs has changed for the better.

“Three or four years ago we added a pink and a purple, though they’re generally less stable and fade to white over time. There are a lot of Asian companies making diodes and you need to know the sources of supply and what the useful life is,” explains Centsible Lighting’s Evans. “We’ve also been able to use different color temperatures within white for many years—warm, cool or daylight. However, LEDs do not come in any type of Pantone color, and that’s one of the problems with them. You’re locked into specific colors. So if you’re trying to achieve a certain color it sometimes has to be done through a translucent film or vinyl. The minute you apply light to a color it changes the tone of the color so you sometimes have to adjust for that as well.”

The other alternative is a pre-manufactured unit, such as those provided by LED light panel manufacturer LEDCONN, based in Brea, California. Though LEDCONN’s units are “pre-manufactured,” the company can also produce LED edge-lit panels in various shapes and sizes up to 4' x 8'. For larger signs, LEDCONN provides instructions for multi-panel displays that can be placed together to create one larger image.

The panel is essentially a sandwich—PMMA acrylic plus a reflective layer—with LEDs on the sides of the panel and a heat dissipation plate. The graphic is placed on top of the light panel. The reflective layer—and the one which ensure even, bright lighting—has a dot pattern processed on the bottom of the acrylic (see photo).

“Edge lighting reduces the thickness of the display, and uses fewer LEDs, bringing down the cost and making it more efficient,” says Hanna Huang of LEDCONN. “Typically, backlit signs require that the graphics are three to four inches away from the light source. Edge-lit graphics, on the other hand, can be almost directly on top of the lighted surface, allowing for a thinner profile. And, the brightness of the finished light box can actually be similar for both backlit and edge-lit techniques.”

LED manufacturers are actively attacking the larger outdoor backlit cabinet market with an LED backlit alternative. Edge-lit acrylic panels with LEDs are used primarily for indoor applications.

“An outdoor edge-lit sign can be done, and is for certain applications like menu boards, but it requires a lot of encasing and changing it to outdoor-grade materials so that it’s suitable for outdoor weather. Generally speaking, edge-lit signage is best for indoor signage,” adds Centsible Lighting’s Evans.