Display Week 2009 Review: LCDs

LCD innovation continues to set the standard.

by Alfred Poor

DISPLAY WEEK 2009 may have been held in the hill country of Texas, but the terrain of the display world is decidedly flat these days. From the exhibit hall to the meeting rooms, from displays for pockets to walls, it was clear in San Antonio that LCD technology is the standard against which all challengers must continue to be measured. While novel and exotic technologies garnered a large share of the attention at the exhibition, the LCD industry is the engine that is truly driving the market. If you were lucky enough to be on the show floor in June, you saw a number of developments that made the forceful point that LCD technology is not about to surrender its dominant position any time soon. On the contrary, the technology is pressing ahead with significant improvements on a variety of fronts.

Backlighting

One of the most significant demonstrations of this ability to advance the state of the art of LCD panels was the broad application of solid-state LED backlights, which are known for their environmentally friendly materials, lower-energy consumption, and better temperature and shock tolerance compared with conventional fluorescent backlight tubes. Although they are often used in an edge-lighting array, when the LEDs are instead placed in a matrix behind the panel, they can support local dimming, which boosts contrast performance while also providing energy savings. Local dimming is not new, but the art of it is being refined, as evidenced by manufacturers such as Samsung, which featured side-by-side demonstrations of displays using local dimming versus those not using it. In these demonstrations, the reduced power consumption was clearly evident, though very dependent on the type of content being displayed.

Although there were some new wrinkles on the LED-backlight theme at the show, one of the most dramatic examples was to be found in the Samsung exhibit, where demonstrations of "needle thin" edge-lit LED technology resulted in a 24-in.-diagonal LCD panel that was a mere 3.5 mm thick. A 12.1-in. panel using a similar design and destined for notebook applications was just 1.64 mm thick. And LG Electronics showed its UltraThin HDTV panels that use LED blacklights, with a 47-in. unit that was 5.9 mm thick.

Fig. 1: LG's multiview digital signage presented three different images, depending on viewer perspective.

LED backlights are also becoming part of the standard toolkit for display designers. NEC Displays, Hitachi, Toshiba, and Optrex all showed a variety of LCD panels designed for industrial applications in which extra-long lifetimes are required. For example, Toshiba showed an LCD panel with a white-LED backlight rated with a mean-time-between-failure (MTBF) rate of 70,000 hours. Up until recently, white LEDs have not lasted nearly this long, and the extended life opens up a range of new display applications for this technology. Planar showed a low-power 29-in. LCD digital-signage panel that produced 500 cd/m² using just 30 W of power, thanks to an LED backlight.

Another fascinating demonstration from Samsung was a portrait-mode LCD panel – such as you might employ for digital signage – that used white LEDs for the backlight. A mobile device with a simple photosensor was placed in front of it, and data was transferred from the panel to the mobile device. How did it work? The backlight was modulated at a frequency much higher than what would be visible to viewers to transmit the digital data. According to a Samsung representative, the white LEDs support 1–2-MHz modulation, but an RGB LED backlight could support up to 40 MHz per channel. This could make it possible to transfer a great deal of data in a very short time, opening up all sorts of enticing application possibilities.

A final note about backlights: It's a sign of the times (both economic and LCD-centric) that Endicott Research Group, among other companies, has been putting together retrofit LED units for customers with a need to replace CCFLs with LEDs. "These retrofits are not going to be around forever," notes Bill Abbott, Corporate Distribution Manager and Global Market Strategist for ERG, meaning that the business opportunity will eventually taper off, but for the time being, they do represent a decent bit of business aimed at helping customers upgrade their equipment during lean times.

Other LCD Innovations

Energy-saving designs were prominently showcased. In addition to the local-dimming efforts mentioned above, Sharp displayed new "Memory LCD" reflective panels that have memory circuitry for each pixel, which makes it possible to refresh the image just once per second. This saves a great deal of power compared with standard designs. The color version of this panel appeared to be fairly low contrast, but the monochrome example was very legible.

A clever approach to making reflective LCD panels readable in low-light conditions was presented in Poster Paper P-75, "Improved Optical Characteristics of a Front-Light System Using Fine-Pitch Patterned OLEDs," from Seiko Epson. The title more or less says it all; by placing tiny OLED devices inside a top glass layer with a barrier, light is prevented from going out the top of the display. Instead, the light is directed down at the surface of the display, providing light for reflection. The result is more efficient operation with a broader viewing angle than edge-lit front-light designs.

For digital signage, LG demonstrated a portrait LCD panel that produced three different images depending on the viewing angle (Fig. 1). Similar designs have been shown before with smaller panels intended for applications such as automotive-dashboard displays, but this was much larger. And in one of the SID keynote addresses, InJae Chung, Executive Vice President and CTO of LG Display, described another innovative use of controlling the viewing angle on LCD panels. LG's "Viewing Image Control" technology allows a selectively switchable viewing angle of a display – or even just a portion of the display – that can be used as a privacy feature.

Sharp demonstrated a 60-in. LCD panel that used five-primary-color filters, adding cyan and yellow to the standard red, green, and blue (Fig. 2). The result is a panel capable of showing over 130% of the typical color gamuts used today, including improved performance for metallic images. The resulting rich imagery made this panel a stand-out in the "stop you in your tracks" category at Display Week.

And, of course, Samsung showed its Display of the Year Gold Award-winning 240-Hz LCD panel, which fights motion blur by interpolating three additional frames between each frame in a 60-Hz signal.

Fig. 2: The addition of cyan and yellow to RGB on a large scale made viewers take notice of Sharp's 60-in panel on display at the show.

Adding a Dimension

3-D displays based on LCD technology were also generating excitement at Display Week this year. There were LCD panels that produced 3-D images using active shutter glasses and others that used passive glasses. And there were autostereoscopic demonstrations at many exhibits, including NEC Displays, Toshiba, and LG.

One of the most intriguing autostereoscopic devices was on display at the 3M booth. The company makes a lenticular film that presents one image to the left eye and another to the right eye. Unlike most similar designs, however, the 3M film does not have to be aligned with the display's subpixels, which makes the fabrication of the panel much simpler. Instead of displaying left and right images at the same time, however, it displays just a left image, then just a right image. It achieves this by using LED edge lights on both sides. A light guide causes light from one side to project only to one eye and light from the other side to the other eye. The 3-D image is created by changing the image on the panel in sync with alternating the backlight from one set of LEDs to the other.

The result is a time-sequenced presentation of the two images that make the 3-D image. A side benefit is that if a viewer gets too far off-axis from the stereoscopic "sweet spot," the viewer still sees the uninterrupted image intended for just one eye. This 2-D image is a bit fainter – it is only receiving half the light of the 3-D image – but is completely legible. This simple design is very effective, and a wide-QVGA panel using this technology is expected to appear in a commercial product before the end of this year.

Wait Until Next Year!

This summary just scratches the surface of the LCD news at Display Week this year. From new printable display technologies to integrating touch technology, from advances in substrates to liquid-crystal materials, from lower energy consumption to fabrication processes that are friendlier to the environment, a wide range of advances were presented in the meet-ing rooms and on the show floor. If you missed the LCD developments exhibited at Display Week 2009, you missed a lot of developments in the display industry as a whole. •