IMAGING AND DISPLAYS: Display technology grows along with industry

This year’s SID 2006 annual conference (June 4-9, San Francisco, CA) provided evidence of “explosive” technological growth in several areas, according to Steve Atwood, board member of the Society for Information Display (SID) and organizer of the conference.

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This year’s SID 2006 annual conference (June 4-9, San Francisco, CA) provided evidence of “explosive” technological growth in several areas, according to Steve Atwood, board member of the Society for Information Display (SID) and organizer of the conference. Organic light-emitting diodes (OLEDs), which encompassed 13 of the 70 technical sessions, represented the largest single technological concentration at the symposium. Sessions on OLEDs focused on device structures, active-matrix OLEDs, OLED manufacturing, materials, and blue-emitting OLEDs. Light-emitting-diode backlighting, heavily represented within four sessions on backlighting, was another hot area, while new color-gamut technology in liquid-crystal displays (LCDs) enlivened two LCD sessions. Atwood also noted a lot of “cool physics in flexible displays and electronic paper, and manufacturing technology.”

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A combination of existing high-brightness LEDs (Luminus; Woburn, MA) and microlens light guides (Global Lighting Technologies; Brecksville, OH) has resulted in development of large-sized edge-lit panels for LCD TVs.
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The most significant change, however, may have been that in 2006, for the first time in the history of the SID conference, no cathode-ray-tube (CRT) papers were presented. Three sessions focused on field-emission displays, however, and six sessions covered plasma displays. “Years ago, the only real choice was CRT-with any major product, you had to put a CRT or buttons in it. But over the last 20 years, there has been an explosion of multiple options for displays and how to implement them,” Atwood said. “So the core technology keeps getting better, the enhancements to what you can do with the technology keep getting better and the prices keep coming down.”

Among new technology announcements at SID 2006 in the OLED area, Royal Philips Electronics (Eindhoven, The Netherlands) and Novaled (Dresden, Germany) announced that a collaborative effort between Philips Lighting, Philips Research and Novaled, had yielded a new record for the power efficiency of a white OLED. The researchers obtained 32 lm/W and a CRI (color-rendition index) of 88 at a brightness of 1000 cd/m2. The device is also expected to achieve a lifetime on the order of at least 20,000 hours, based on previous results achieved with a similar structure. “This result combines, for the first time, ultrahigh power efficiency and high operational stability and can pave the way to a bright future of OLED lighting,” said Jan Blochwitz-Nimoth, chief technology officer of Novaled. “We expect to be able to increase this efficiency to values above 50 lm/W in the near future.”

Using LEDs to edge-light LCDs

In an interesting twist on the concept of LED backlighting of LCD TVs, Global Lighting Technologies (GLT; Brecksville, OH) and Luminus Devices (Woburn, MA) partnered to produce modular LED-based edge-lighting assemblies for large-screen LCD TVs. Luminus’ PhlatLight technology, combined with GLT’s MicroLens light guides, enabled large-size LCD panels to be edge-lit, as opposed to directly backlit. The result was dramatically reduced LED count, and simplified color and thermal management compared to conventional LED-based backlighting solutions (see figure).

The combination may result in LCD TV screens with brightness in excess of 8500 cd/m2 at the backlight surface, thickness less than 15 mm in production units, passive thermal management, and significantly lower production costs. For instance, a 32 in. LCD TV that formerly required hundreds or even thousands of LEDs to backlight might be edge-lit with less than 12 chipsets-each containing a single red, green, and blue die, and future developments are expected to reduce the number of chipsets even further, according to David DeAgazio, director of worldwide sales at GLT. Global Lighting demonstrated a 24 in. working prototype on the exhibit floor, and announced a long-term strategy focused on edge-lit LCD TVs of 40 in. diagonal and larger.

A record 8000 attendees were expected for this year’s meeting, and more than 300 companies were represented in the exhibits.

Hassaun A. Jones-Bey and Kathy Kincade

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