The rapid rise of LED technology as a key backlighting source for LCD TVs is creating a new buzz in the market, but is also creating confusion and misunderstanding. While several manufacturers are choosing to call LCD TV’s with LED backlight modules “LED TV”, both sales staff and public are finding it almost impossible to understand hat it means. Is it really an LED TV? No… we just call it that way. It’s still really an LCD TV. In the following pages we aim not only to demystify the LED phenomenon, but also to put some figures on it and give you some solid projections.

According to Dolby organisation, which is heavily involved in LED backlight development, the advantages of LED include:
-    Friendlier to the environment: LEDs contain no mercury and have a long lifespan;
-    Faster response time than CCFLs;
-    Increased colour gamut with RGB LEDs;
-    Projected exponential increases in efficiencies, in terms of lumens per watt;
-    Declining costs, in terms of dollar per lumen per watt.

LED technical improvements and cost reductions are likely to continue, because demand from other industries—for instance, advanced automotive headlight and taillight systems—is expected to drive increased production capacity and efficiencies. Many laptop LCD screens and one television product line already use LED backlights.

The Expert’s Point of View…

To find out more, we spoke with one of the world’s “gurus” in the field of LCD technology, Bruce Berkoff, Chairman of the LCD TV association and former EVP of LG.Philips LCD (still on the board of LG Display), to tell us more…

The most important part of an LCD display really is the light source and how you can control that light source. LED’s are the first DIGITAL light source for digital LCD displays. So this gives you a unique ability to use a more efficient light producer which leads to more energy efficient displays, as well as controlling digitally the light, which also leads to better black levels and contrast. It’s better for motion images as well. You can, for example, turn on and off the LEDs very quickly, with a strobe effect, to create image enhancements. This controls the average light level very quickly and improves motion blur, as well as allowing for regional or local area dimming. This gives better image quality, better perceived motion performance and lower power consumption.

There are different kinds of LED backlights – coloured, white, edge lit and direct lit… what are the trends?

The differences have been overstated and there should be less and less difference over time. By far the majority are white LEDs now. You don’t generally need red, green and blue LEDs unless you’re looking for particularly high colour space. This is however generally not justified by the cost of these units, although this may improve over time. White LEDs are sufficient for the benefits in terms of local area dimming, and even the colour space and energy efficiency and black levels. However I think it’s overblown to  talk about the difference between edge lit and direct lit, because one also should consider the number of parts. Edge lit models use far fewer parts, just like in notebooks. For direct backlit models, you need hundreds more LEDs. I believe the trend will be towards thinner, lighter edge lit systems, or even tiled systems, where you can cover the whole back plate with tiled edge-lit pieces – having the cost benefit of being edge lit, but also the benefits of regional dimming throughout the whole display space. The bad news at the moment is it costs more, so the pressure is on to find ways to integrate solutions so you can save system level costs.

Are LCD displays more eco-friendly using LED backlighting?

Absolutely. The only minute dangerous chemical at all involved in any LCD display, which is the safest display… is the mercury used in the CCFL backlight, so LED’s make LCD even safer, cleaner and greener. People like Corning have already done an incredible job of getting the heavy metals out of the glass, and Merck have made a great job making the liquid themselves crystals safe, so now the final stage is cleaning up the backlights.  

How long will it take until the real cross-over happens to LED backlighting?

It will take a while. It’s the “S-curve” effect, but it could take three to five years until most LCD TVs have LED backlighting.