As with every industry, there is a terrific focus currently in the display industry on manufacturing more environmentally friendly products. The components showcased at Display Week 2008 showed how far the industry has come in addressing this vital issue.
by David Eccles
ONE of the major themes at SID's Display Week 2008 in May was energy savings for LCDs, and components and systems shown on the exhibit floor are leading the charge for increased brightness and power savings. Recent improvements in transmission efficiency for LCD panels and backlight systems with brightness-on-demand have reduced operating power in some cases by as much as 50%. Now it seems that LCD component suppliers have teamed up to deliver higher brightness with less power for less cost – to quote the 1980s TV series "A-Team," "I love it when a plan comes together!" So does that mean we are going to save money on the ever-increasing cost of energy, or will we simply spend it on new and better displays?
Dramatic improvements in backlight units (BLUs) and optical filters have resulted in increased light transmission from the backlight through the LCD panel and to the viewer's eye. Product designers now have the option of either increasing the brightness or saving power compared to existing products. Typically, only about 5% of the backlight luminance makes it out to the viewer, so any improvement in diffusers, films, and coatings can result in brighter displays that use less power. In the case of portable displays, it can mean longer battery life.
The revolution in light-emitting-diode (LED) backlight units has lead to more than just deeper color compared to old cold-cathode fluorescent (CCFL) backlights; it has lead to brightness-on-demand which basically results in power-on-demand. LED BLUs allow designers to segment individual backlights into zones and to dynamically adjust their brightness levels as the particular video scene demands. By turning down the LCD backlight in dark scenes and locations when and where it is not needed to be fully on, power savings of as much as to 50% can be realized.
Fig. 1: In its booth, GLT showed a 46-in. LCD TV demonstrating its MicroLens™ edge lighting consisting of eight edge-lit light guides called "blades" that utilize a total of only eight PhlatLight LED modules, with excellent uniformity and color mixing.
Luminus Devices and Global Lighting Technologies (GLT) teamed up to win the 2008 SID Display Component of the Year Gold Award. The PhlatLight BLU integrates Luminus's PhlatLight LEDs with Microlens™ light guides from Global Lighting Technologies, thus requiring only eight RGB chipsets to illuminate a large-screen LCD. Other LED backlight units require hundreds, or even thousands, of conventional LEDs to achieve adequate brightness and uniformity. By requiring fewer LEDs, the PhlatLight BLU dramatically reduces the cost and complexity of LED backlighting for large-screen TVs, enabling enhanced brightness and color uniformity over the life of the TV. Moreover, because it is edge-illuminated, the PhlatLight BLU also enables thinner LCD-TV designs.
GLT demonstrated its new MicroLens™ light-extraction technology, which allows fewer LEDs to be used in ultra-thin edge-lit backlights for products ranging in size from smart phones to 50-in. TVs (Fig. 1). In its booth, GLT showed a 46-in. LCD TV demonstrating MicroLens™ edge lighting. Working with Luminus Devices, supplier of PhlatLight™ LED modules, and Jabil Circuit, GLT has developed a 46-in. LCD-TV backlight consisting of eight edge-lit light guides called "blades" that utilize a total of only eight PhlatLight LED modules, with excellent uniformity and color mixing. GLT also demonstrated some impressive products that have been enabled by the improvement in backlight efficiency, including the use of only one LED to light the Ford Mustang gear shifter and only one LED to light Honeywell thermostats (enabling longer battery life).
FujiFilm won the 2008 SID Display Component of the Year Silver Award for its WV-EA film, which improves the viewing angle for twisted-nematic-mode LCDs (TN-LCDs) (Fig. 2). TN-LCDs are notorious for having a narrow viewing angle, but adding the WV-EA film improves the angle and also reduces the gray-scale inversion. The improved viewing angle at a contrast ratio of 10:1 is 160° in boththe horizontal and vertical directions. The film, which can be added without any change in the panel manufacturing process, also improves the light transmission to 7% vs. 4% typical for vertical-alignment (VA) LC panels. The impact to the industry is that lower-cost TN-LCD panels can match the performance of some higher-cost VA panels. And most customers are indeed concerned about cost.
Have you ever dropped your cell phone and broken the display? Corning learned that the leading cause of failure was a sharp object hit on the screen, leading the company to develop Gorilla Glass. The new thin-sheet glass with chem-strengthening provides a highly durable scratch-resistant LCD cover. It is an environmentally friendly alumino-silicate glass produced with Corning's proprietary fusion-draw process without any heavy metals. Fusion-draw technology enables the production of uniform thin sheets with a pristine surface. By making a deep compression layer in the ion-exchange process, they develop stronger glass for cell-phone, automotive, and TV applications. Corning claimed one other added bonus – Gorilla Glass is "Wii proof" (who hasn't let a Wii game controller slip out of your hand as you threw it at the TV?).
Fig. 2: FujiFilm's WV-EA film improves the viewing angle and reduces gray-scale inversion for twisted-nematic-mode LCDs (TN-LCDs). At a contrast ratio of 10:1, the improved viewing angle is 160° in both the horizontal and vertical directions. The film also improves light transmission to 7% vs. 4% typical for vertical alignment (VA) LC panels.
3M Optical Systems Division is into recycling – recycling light. Its dual brightness-enhancement film (DBEF) is the world's first reflective polarizer. As a multilayer film, it increases the efficiency of LCDs by recycling light for higher brightness. At Display Week, 3M introduced the highest-gain prism film on the market, the Vikuiti Brightness Enhancement Film (BEF)-G2, which increases brightness up to 10% over their current prism film. 3M showed a 32-in. LCD TV optimized with its various films that ran on 60 W – a 50% savings compared to similar-sized TVs. The company claimed that by recycling light, it can provide 30% energy savings for monitors and up to 50% for TVs.
Digital View demonstrated new products designed to aid in compliance monitoring of digital-signage applications. Digital View provides both networked and remote internet access to serial devices including an advanced LCD controller and a variety of add-on enhancement products providing monitoring and control of temperature, power, ambient light, cooling, and general-equipment status. Their products allow digital-signage displays to be monitored remotely and adjusted for varying conditions, including saving power by turning down the brightness at night (Fig. 3). Digital View also provides LCD controllers up to high-resolution (1920 x 1080 pixels) for harsh environments.
Microsemi has not been content with its market lead in CCFL BLU controllers, so the company introduced the DAZL (digital advanced zone lighting) LED BLU family of controller chips. The DAZL chips monitor and control voltage and current for LED strings and can provide the advanced features of scanning backlights and zone dimming. Microsemi's LED controller chips were featured in the Chi Mei Optoelectronics (CMO) booth, where a standard 42-in. LCD TV with a CCFL backlight was compared to the new version with an LED backlight with 80 zones. The power meters showed that the CCFL LCD consumed 187 W while the LED version with zone control consumed from 60 to 90 W, depending upon scene material – once again, power savings of about 50% were achieved by using intelligent LED backlight controls.
Solomon Systech, a leader in display controllers for portable devices, launched a series of new single-chip TFT-LCD drivers with dynamic backlight control that can reduce backlight power consumption by as much as 50% for portable devices. Since the backlight consumes the most power in portable applications, this savings translates into longer battery life. Solomon Systech also introduced the SSD1961, a new multifunction display-controller IC. It is a low-cost low-power display controller for mobile and handheld applications and has an embedded frame buffer for seamless integration between the host processor and LCD panel, as well as incorporating Solomon's backlight power-saving technology. The company also provides bistable display drivers for e-paper products, which offer the ultimate in power savings.
Fig. 3: Digital View controllers allow digital-signage displays to be monitored remotely and adjusted for varying conditions, including saving power by turning down the brightness at night.
Fig. 4: ERG's new SFDE (Economical) and SFDM (Mini) Series of LED driver boards provide full-function power supplies with optimum power for high brightness as well as lower power consumption and lower cost in exceptionally compact sizes. Both are less than 5 mm in height, can power up to six LED strings, and provide brightness stability over a wide input voltage.
Endicott Research Group (ERG) introduced new product lines of dramatically smaller driver boards for LED and CCFL LCD backlights. The new drivers are less than 5 mm in height, can power up to six LED strings, and provide brightness stability over a wide input voltage.
"The demise of CCFL backlights has been exaggerated," said ERG Sales & Marketing Director Bill Abbott. "They will be around for a while for a number of applications that do not require the higher performance and higher price of LED backlights."
The CCFL inverters also come in single- and dual-lamp versions with dimming and feature a low profile (< 6 mm high) and a ruggedized transformer for wide temperature ranges. ERG demonstrated 8.4- and 10.4-in. LED-backlit TFT-LCDs with a luminance of 1000 nits driven by new Smart Force™ driver boards, as well as a 6.5-in. OEM LED-backlit LCD with 800 nits of luminance powered by the new miniature SFDM driver board (Fig. 4).
Earth LCD provides a display subsystem that makes it easy for designers and OEMs to develop a display product with a graphical user interface (GUI ) using an embedded processor. Its ezLCD development kits help system designers to go to market with customized products for medical or small-kiosk applications without having to re-do the design from scratch.
Conclusion
With gas prices climbing higher and higher and energy costs at a premium, it is excellent timing for the display component and systems industries to provide dramatic improvements. More-efficient LCD films give the option of brighter displays or getting the same brightness with less power. The revolution in LED backlights not only provides deeper colors, but up to 50% reduction in power as well as darker blacks for contrast-ratio improvement. Now if only the auto industry would follow suit. •