LED-backlit LCD

LED TV (Light-emitting diode television) is a term used by Samsung to describe its line of LCD (liquid crystal display) TVs that use LED backlighting. The term LED TV is disputed and currently a war of words and advertisements is going on between Samsung and its competitors. The competitors' complaint is that the display is not composed of 100% LEDs and so should not be called LED TV.

LEDs in their current form are much too large to be individual pixels on a conventional television. The use of a true LED display is therefore reserved for much larger screens in sports grounds and other commercial locations. It is most likely that Samsung has chosen to brand their LED-lit range of LCD TVs in this way in order to capture some of the hype around O-LED TVs, which are still not commercially available except for the Sony XEL-1.

LED-backlit LCD TVs do differ from conventional LCD TVs in some important areas:

• They can produce a very bright image and deep blacks (doesn't work for Edge-LED).
• With Edge-LED lighting they can be extremely slim.
• They can offer lower power consumption.
• They can offer a wider colour gamut, especially when RGB-LED backlighting is used.

Technology

TV manufacturers can use an LED backlight instead of the standard Cold Cathode Fluorescent Lamps (LCD-CCFL) used in most LCD televisions. It is important to distinguish this method of backlighting a conventional LCD panel, from a true LED display, or an OLED display. Televisions described as 'LED TVs' are vastly different from the self-illuminating OLED, OEL or AMOLED display technologies

There are several methods of backlighting an LCD panel using LEDs including the use of either White or RGB (Red, Green and Blue) LED arrays positioned behind the panel; and Edge-LED lighting, which uses white LEDs arranged around the inside frame of the TV along with a special light diffusion panel designed to spread the light evenly behind the LCD panel.

An LED backlight offers several general benefits over regular CCFL backlight TVs, typically including lower power consumption and higher brightness. Compared to regular CCFL backlighting, there may also be benefits to colour gamut. However advancements in CCFL technology mean wide colour gamuts and low power consumption are also possible. The principal barrier to wide use of LED backlighting on LCD televisions is cost.

The variations of LED backlighting do offer different benefits. The first commercial LED backlit LCD TV was the Sony Qualia 005 (introduced in 2004). This featured RGB LED arrays to offer a colour gamut around twice that of a conventional CCFL LCD television (the combined light output from red, green and blue LEDs produces a more pure white light than is possible with a single white light). RGB LED technology continues to be used on selected Sony BRAVIA LCD models, with the addition of 'local dimming' which enables excellent on-screen contrast through selectively turning off the LEDs behind dark parts of a picture frame.

Edge LED lighting was also first introduced by Sony (September 2008) on the 40inch ZX1 BRAVIA. The principal benefit of Edge-LED lighting for LCD televisions is the ability to build thinner housings (the ZX1 BRAVIA is as thin as 9.9mm). Samsung have also introduced a range of Edge-LED lit LCD televisions (described incorrectly as "LED TVs") with thin housings. Edge-lighting however is at risk of a loss of screen uniformity compared to back-lighting.

LED-backlit LCD TVs are considered a more sustainable choice, with a longer life and better energy efficiency than plasmas and conventional LCD TVs,. Unlike CCFL backlights, LEDs also use no mercury in their manufacture, however other elements such as gallium and arsenic are used in the manufacture of the LED emitters themselves, meaning there is some debate over whether they are a significantly better long term solution to the problem of TV disposal.

Because LEDs are able to be switched on an off more quickly than CCFL displays and can offer a higher light output, it is theoretically possible to offer very high contrast ratios. They can produce deep blacks (LEDs off) and a high brightness (LEDs on), however care should be taken with measurements made from pure black and pure white outputs, as technologies like Edge-LED lighting do not allow these outputs to be reproduced simultaneously on-screen.

History

Sony was the first manufacturer to produce a commercial LED-backlit LCD television with the Qualia KDX-46Q005 in 2005. However, Samsung was the first to coin the term "LED TV" on their 2009 range of Luxia LED edge-lit televisions. Previously, Samsung had also integrated LED backlights into the 40, 48, 52, and 57-inch versions of their LN-T81F series in 2007 and their A950-series in 2008. Sony, in addition to RGB LED backlighting (still used on 46 and 55-inch versions of the BRAVIA KDL-XBR8 series), also introduced the first flat-panel monitor to use edge-LED lighting in 2008. In 2008, Sharp introduced the AQUOS LC-XS1US series, 52 and 65-inch HDTVs to use LED back-lighting, and plans to release LED edge-lit HDTVs in the second half of 2009. While LED TVs are still expensive to manufacture, Vizio will release the VF551XVT, the cheapest HDTV to use LED backlighting. It will retail for $1999.99. LG has also released their own LED-backlit HDTVs. LED backlighting is also becoming common in computer monitors. Examples of monitors that use LEDs are Apple's 24" and 30" cinema displays, the Sony BRAVIA KLV-40ZX1M, and Dell's G2210 and 2410 monitors.