11.1" TFT LED Backlit Display: A Viable Way Out For The Energy Crisis? Continued
Another issue is that CCFLs can't deliver pure white light. This explains why colors and saturation levels are never as brilliant and bright on a TFT display as they are on a CRT monitor. But by using LEDs as a backlight source, colors on the display appear more saturated, and the color range of a display with LED backlight is also noticeably higher.
The color spectrum on an LED-backlit display is markedly higher than those using conventional CCFL technology (Source: Sony).
These observations were confirmed in our own measurements of the first desktop TFT display with LED backlight. In addition, LEDs also have the advantage of requiring much less real estate for circuitry, along with control electronics, in a system or on a motherboard. Even better, the light guide (which ensures consistent brightness from lamp light) is much thinner for LED-backlit devices. This means that it's possible to build thinner TFT displays that use LED backlighting, and that the non-display portion of the device around the edge of the TFT can be narrower as well.
The overall result is that for devices with the same outside dimensions, the visible portion of a display can be larger for an LED-backlit TFT. As an additional benefit, the lifetime for LED backlit devices is practically infinite - or at least, so long as to be effectively not an issue - and display brightness levels stay constant over a long time frame. A CCFL backlight, on the other hand, dims over the years and from time to time one or more of its elements will give up the ghost.
The use of LED backlighting permits the display to be only 4 mm thick.
According to Sony, the energy savings that a backlit LED display can deliver compared to CCFL backlighting are particularly noticeable at higher output levels, or with higher overall brightness settings. That explains why TX series laptops operating at a brightness setting of 60% or lower can save up to 90% of the energy that the previous, CCFL-using T series laptops consume for the display.
Here's what a typical LED backlit display looks like.
In Sony TX series laptops, a total of 32 LEDs provide background lighting, evenly dispersed beneath the edges of the TFT display.