[FPDI] Searching for 'Green Displays' (Korea, Taiwan: Part 1)

Oct 31, 2008
Takuya Otani, Nikkei Electronics

I saw the word "green" everywhere while I was walking around the exhibition site of FPD International 2008 (FPDI). I could see that manufacturers were becoming more and more serious about energy-saving technologies and other green technologies.

First, I visited the exhibition booths of Korean and Taiwanese panel manufacturers, looking for their green technologies. Standing out the most at every booth were low power LCD TV panels.

Backlight area control (local dimming) technology was employed by those manufacturers as a measure to lower the power consumption of LCD TV panels. The technology lowers power consumption and boosts contrast ratios by controlling backlight illumination by area in accordance with the displayed content.

More than a few LCD panels have already adopted the area control technology, but the exhibitors were emphasizing "advanced versions" of the technology at FPDI.

Power consumption halved

Samsung Electronics Co Ltd presented an LCD panel based on its area control technology dubbed "3-Way Dimming." This area control technology uses red, green and blue (RGB) LEDs. Many of existing area control technologies use white LEDs. But, by replacing them with RGB LEDs, it is possible to boost light use efficiency when reproducing colors, further reducing the power consumption.

The RGB LED-based technology can cut power consumption by about 50% compared with the white LED-based area control technology, Samsung said. For example, power consumption is about 80W when displaying a movie on a 46-inch full HD panel, much less than about 188W required by a white LED-based backlit panel.

LG Display Co Ltd also exhibited its advanced area control technology called "Advanced Local Dimming." The company cut the power consumption by 50% on average through optimized operation and other efforts. For example, to render an image on the 47-inch panel exhibited at the booth, the power consumption with the new technology is about 50W, reduced from the 169W previously required.

Ultra slimness, low power achieved at same time

Compared with edge light panels, it is more difficult to make area control panels slimmer because, theoretically, local dimming technology can only be used with a direct type backlight structure. However, Chi Mei Optoelectronics Corp (CMO) of Taiwan overcame this challenge. The company showcased a 55-inch LCD panel that uses area control technology and has a thickness of 9.9mm, which is about half the thickness of the company's previous model.

The light source and the panel move closer to each other when the backlight unit is made slimmer; therefore, there is a need to increase the number of LEDs to obscure each LED. According to CMO, in contrast to 5,500 LEDs used in a 20mm-thick panel, 21,950 LEDs must be used in the 9.9mm-thick panel like the one it exhibited this time.

It is difficult to array such many LEDs in a panel. Hence, CMO optimized the number of LEDs and employed a special sheet to reduce the thickness, the company said.

The power consumption of the prototype ranged from 62 to 90W depending on the content being displayed. CMO realized both ultra slimness and a power consumption of less than half the 200W required by a panel of the same size that doesn't use area control technology.