Separating the Really New from the Merely Dazzling

Many of the exhibits at SID 2005 were impressive, although not really new. But a variety of significant developments and the start of an industry-wide revolution in backlight technology highlighted the show.

by Ken Werner

Upon entering the show floor of the exhibit hall on the second level of the Hynes Convention Center in Boston, where the 2005 Society for Information Display Symposium, Seminar & Exhibition was held on May 22–27, attendees found themselves facing two astounding Samsung displays: a plasma display measuring 102 in. on the diagonal and a TFT-LCD measuring 82 in. on the diagonal (Fig. 1). Both displays are the largest of their kind, both are remarkable demonstrations of their maker's expertise, both are prototypes, and neither is particularly new, having been introduced at the Consumer Electronics Show in January.

Justifiably, many gaped, took photographs, or simply watched the huge, apparently defect-free images. But analysts, editors, and other professional seekers of the really new soon walked on. Just around the corner from the gigantic duo, also in Samsung's booth, a 40-in. active-matrix OLED was on display (Fig. 2). This new prototype, introduced at SID 2005, is the largest OLED ever made on a single sheet of glass, i.e., it is not tiled, and the largest to use thin-film transistors (TFTs) made from amorphous silicon (a-Si).

Amorphous-Si is the semiconducting material used to make TFT-LCD panels, so a very large existing infrastructure can be harnessed if a-Si can be applied reliably to OLEDs. It is well known that a-Si and OLEDs are not an ideal match, but the payoff is so large that a great deal of ingenuity is being applied to making this marriage work. A Samsung representative was careful to say that the 40-in. OLED was part of a long-term technology-development program and would not be a product soon.

The President and CEO of Samsung Electronics's LCD business, Sang Wan Lee, revealed a bold manufacturing strategy when he delivered the symposium's first keynote address (Fig. 3). Lee announced that Samsung will build a Gen 9 LCD fab within the next few years. Having a motherglass size of 2400 x 2800 mm, Samsung's Gen 9 fab will be the largest facility ever built by an LCD supplier. Because of the vast investments made in such fabs, Lee said, the LCD-TV market will grow to 100 million units by 2010.

 Jeff Page for SID

Fig. 1: Samsung SDI's 102-in. plasma display and Samsung Electronics's 82-in. TFT-LCD – each the largest of its kind – greeted SID 2005 attendees as they came through the main entrance to the second-level show floor.

Lee also called for LCD manufacturers to standardize large TV displays at 40, 46, 52, and 57 in., which are Samsung's sizes. LG.Philips LCD's large LCD-TV sizes are 37, 42, 47, and 55 in., and they do not seem inclined to change. Indeed, in a press conference, LG.Philips LCD's Bruce Berkoff claimed that since Taiwan's Gen 6 and 7 fabs are the same size as LG.Philips's, and since their panel sizes are the same, there is a de facto standard – for everybody except Samsung.

LG.Philips LCD is openly disdainful of Samsung's bravura performance with very large prototypes. "They're impressive," said Berkoff, "but we like to focus on what consumers will actually buy." Among the products LG.Philips thinks consumers will buy are full-HD LCD-TV sets, and the company showed 47-, 42-, and 37-in. LCD TVs with full-HD (1920 x 1080) pixel formats which will be phased into commercial production over the next few months (Fig. 4). Because 1080-line 37-in. LCD TVs are going into production, is there a future for 720-line 37-in. plasma TVs?

The largest display in LG.Philips's booth was the company's 55-in. LCD-TV module, billed as "the World's largest LCD TV in mass production." After the keynote addresses, this display received the SID/Information Display magazine Display of the Year Gold Award (Fig. 5).

Two Records, One Display

Toshiba's WXGA 32-in. optically compensated bend (OCB) TFT-LCD module, which received its North American debut at SID 2005 and was also the subject of a paper by Kazuhiro Nishiyama, is a dual record holder. It is the largest OCB-mode display module ever shown and it is the largest polysilicon TFT-LCD ever shown. Even more impressive, it is currently in production, with the first customers being Japanese makers of premium TVs.

The module combines an optimized cell design and a blinking backlight to deliver a total effective response time of less than 5 msec gray-to-gray. In a demanding demonstration in the Toshiba booth (a displayed video image consisting of a rapid horizontal pan along a picket fence), this combination reduced motion artifacts to almost OLED-like levels.

Toshiba's innovations were not confined to large displays. The company showed a prototype dual-mode display for cellular telephones that added 25 pixel lines to the traditional 320 lines of a QVGA format. These lines make up a reflective display, so status indicators such as battery charge and signal strength can be visible at all times while consuming minimal power. The remaining QVGA display is transmissive, producing the high-quality color images that consumers expect from today's mobile phones.

 Samsung

Fig. 2: Samsung's 40-in. active-matrix OLED is the largest OLED made on a single sheet of glass and the largest to be made with a-Si TFTs.

Another clever Toshiba prototype was a touch-screen display using the system-on-glass LTPS technology seen last year in Toshiba's portable image-scanning devices. In those devices, a sensor at each pixel location recorded the light reflected from a business card or other document placed on the display to produce an image. In the current application, light reflected from a stylus or finger tip is registered by the sensor to generate the location of the touch. This is a touch screen without any additional layers of glass or plastic to degrade image quality or increase weight. The entire touch-sensing process goes on inside the display.

Royal Philips Electronics's booth continued the theme that innovation is not limited to large displays. The Polymer Vision unit showed several prototypes with rollable displays, combining Polymer Vision active-matrix backplanes using polymer electronics with E Ink Corp. electrophoretic frontplanes (Fig. 6). The demonstrated QVGA displays had a diagonal of 5 in., a pixel density of 85 ppi, and a contrast ratio of 10:1. Although not perfect, the displays looked remarkably good. Panel thickness was a scant 100 μm and panel weight was only 1.6 grams.

The displays were rollable to a radius of 7.5 mm, and a display was constantly being rolled and unrolled by an automatic device. Displays had been tested to 25,000 roll–unroll cycles. A Philips representative said that the durability of the display and the substrate were good; OTFT lifetime is the remaining significant challenge. Polymer Vision expects to implement the needed performance enhancements by the end of 2006, which will also be the time of the first product introductions. E-readers will be the first application.

Philips Mobile Display Systems (MDS) introduced its CloseView^™ technology, which does away with the glass covers that are conventionally used in handset displays. This "windowless" design allows handset makers to reduce the size and thickness of mobile phones, and it brings the display's front surface closer to the surface of the handset. The innovation is made possible by an enhanced front polarizer stack that integrates scratch and chemical resistance and by shock absorption for the entire display module. The new design produces better blacks in reflective mode, an MDS spokesman said.

A further announcement was that LifePix^™ smart color mapping, which improves perceived color rendition without sacrificing transmissivity or power consumption and was introduced at SID 2004, has now been implemented in a commercial product, the Nemesis P8894-I transflective LCD, which is designed for high-end mobile phones.

Philips did not restrict itself to small displays. Philips 3D Solutions prominently showed an effective 42-in. autostereoscopic LCD for the digital-signage market. The panel uses a lenticular lens that is slanted rather than vertical, with the replication layer inside the TN cell, and avoids the distinct view-to-view transitions common in other lenticular displays. The group settled on four 2-D/3-D views for some "look-around" capability with reasonable viewing angle. A complete system, including a powerful rendering engine to map inputs to the different views, will be marketed for POS applications in the second half of this year. Philips believes that 3-D will be able to cut through the visual clutter of 2-D advertising and will therefore offer substantial added value.

 Jeff Page for SID

Fig. 3: Sang Wan Lee, President and CEO of Samsung Electronics's LCD business, announced in his SID 2005 keynote address that Samsung will build a Gen 9 LCD fab within the next few years.

Finally, the 3D Solutions group also introduced the IC3D display signal processor. Although it can perform many functions, one specific goal is that it can handle real-time 3-D rendering and interweaving and the real-time depth calculation of 2-D content, i.e., it does what needs to be done to convert 2-D content to convincing 3-D images. The chip was designed for low power consumption and low cost, so it is a suitable display signal processor for both mobile and large-screen applications, Philips says.

More Display Electronics

Improvements in display system performance and packaging are often due as much to innovations in display electronics as they are to improvements in panel design. In addition to the Philips LifePix^™ and IC3D processors mentioned above, here are just two more examples of innovations in display electronics introduced at SID 2005.

National Semiconductor Corp. introduced the AVC5000 Dual 3D Video Format Converter, which brings the de-interlacing pioneered by the Faroudja FLI2200 for standard-definition signals into today's high-definition era. "It is the world's most highly integrated TV IC," said National Semiconductor's Hugo Steemers.

The AVC5000's first major functional block is a universal front end that accepts standard- and high-definition video formats, PC graphics formats, and DVI signals, and decodes the signals into component video or RGB. Any two outputs from the universal front end can be selected for the converter's second main functional block: a dual-channel display processor containing two 3-D decoders (with time being the third dimension), two 3-D noise reducers, two 3-D interlacers, two high-order scalers, luma and chroma enhancement, frame-rate conversion, adaptive contrast enhancement, intelligent color remapping, overlay of a bit-mapped on-screen display, and multi-picture functions, including the side-by-side display of two full-quality images on a wide screen.

"Side-by-side viewing of two images on a display is one of the compelling features enabled by high-resolution wide-screen televisions," said Nikhil Balram, CTO for National Semiconductor's Displays Group. "The AVC5000 is the industry's first dual 3-D solution that enables two high-quality images on one screen."

Although the types of impressive demos National Semiconductor mounted in behalf of the AVC5000 do not apply to power semiconductors, Analog Devices' introduction of a chip that integrates a high-frequency step-up dc-dc converter, logic voltage regulator, dedicated VCOM amplifier, and gate-pulse-modulation circuit into a single module is significant in that it reduces board complexity and cost for display designers. But use of this ADD8754 power module will not be invisible to users, said Analog Devices' George Hill. Their design for the VCOM amplifier in the ADD8754, which drives the frontplane of an LCD panel and is therefore shared by all the pixels, reduces cross talk and its resulting image artifacts, Hill said.

Doing Away with Silicon

Ever since an early flirtation with cadmium selenide, backplanes for active-matrix displays have relied on some version of thin-film silicon to provide pixel switches, which have usually been transistors – Philips made a serious effort with diode switches some years ago and Epson commercialized several generations of small displays using MIMs. Now, as we have already seen, Philips is working hard to replace amorphous-silicon TFTs with organic ones, but the basic idea is still to use a transistor as a pixel switch.

 Ken Werner

Fig. 4: LG.Philips LCD announced that it will soon have 47-, 42-, and 37-in. LCD TVs with full-HD (1920 x 1080) pixel formats in commercial production.

Rolltronics has an even more revolutionary approach that utilizes an electromechanical switch matrix to perform the pixel switching. The company's FASwitch is a membrane switch that is driven electrostatically and can be made to be bistable. A FASwitch is made with standard flex-circuit materials and techniques, said CEO Glenn Sanders.

The current Gen 1 implementation of the technology will support pixels measuring 1–2 mm, but Rolltronics's Nicholas Pasch is confident that 200–300-μm pixels can be supported in forthcoming versions.

Future versions will also overcome another limitation in the present one – the metal electrodes cover the entire pixel area, so the technology is only suitable for reflective displays. By using thinner materials, electrode coverage of 15–25% should be possible, Pasch said, to make the FASwitch applicable to transmissive displays.

Although the Rolltronics booth was buried at the rear of the lower level of the Hynes Convention Center's two-level exhibit hall, the buzz was out and a cluster of attendees surrounded the booth.

The Mysterious SED

For the first time, the SID technical symposium continued on Friday morning of Display Week. The question was whether attendees would show up?

On Friday morning, in room 312 of the Hynes Convention Center, Session 71 was overflowing with attendees anxious to hear about the Canon/Toshiba/SED, Inc., surface-conduction electron-emitter display (SED).

Canon and Toshiba have been careful about releasing information on the novel SED, so the two papers had unusual appeal – and a forest of cameras rose on extended arms to photograph each slide. The first paper, "A 36-in. Surface-Conduction Electron-Emitter Display (SED)" by T. Oguchi and colleagues, summarized the architecture of the 36-in. SED prototype that has been shown selectively since late last year, an architecture that is generally similar to that of a field-emission display (FED).

 Jeff Page for SID

Fig. 5: During the SID Keynote Session, the SID/Information Display magazine Display of the Year Gold Award was presented to LG.Philips LCD for its 55-in. LCD-HDTV module, the largest currently in mass production. From left to right: Chang-Ho Oh, Sr. Manager, Panel Design; Eddie Yeo, Executive V.P., Product Development; Budiman Sastra, Executive V.P. and CTO; Bruce Berkoff, Executive V.P., Marketing; and Ernst Lueder, Chair, Display of the Year Awards Committee.

 Ken Werner

Fig. 6: Philips Polymer Vision showed this rollable 5-in. QVGA display, combining a Polymer Vision organic TFT active-matrix backplane with an E Ink Corp. electrophoreticfrontplane. The panel thickness is a scant 100 μm and the panel weight is only 1.6 grams.

The display has a pixel format of 1280 x 768 (RGB stripe), a peak luminance of 400 cd/m², a contrast ratio of 10,000:1, and a response time of less than 1 msec. The power consumption was reported as being low but varied with material, as would be expected for an emissive display. Typical power consumption for news programming is 120 W; for cinema, 100 W. In the Q&A period, Larry Weber asked about the luminous efficiency. The response was 5 lm/W now, 10 lm/W in the future.

The second paper, "Fabrication and Characterization of Surface-Conduction Electron Emitters" by K. Yamamoto and a team from SED, Inc., and Canon, described the fabrication of the emitters in the panel. A 10-nm PdO thin film is applied by ink-jet printing ona glass substrate and baked, and a gap is formed in the PdO. Then, in a process whose description seemed unclear to many members of the audience, a carbon film is applied from a source gas and a nano-gap created in what the team calls a "forming and activation process."

The authors seemed pleased with their results, and reported that emission decreased only 10% over a 60,000-hour accelerated life test. During the test, the current density was kept at more than 33 mA/cm², which is the level required for sufficient luminance in SED panels.

In the Q&A period, reflecting the general uncertainty concerning the description of the two-step gap-forming process, Daan den Engelsen asked, "If the gap is formed and then activated with graphite, what is the mechanism of activation?" The answer was "a strong electric field."

Reinventing the Backlight

The revolution mentioned in the beginning of this article is a widely shared compulsion to explore new approaches to making backlights, especially for LCD TVs. A quick look around the show floor at SID 2005 might tempt one to call this movement "The LED Invasion," as OSRAM did. Certainly, LED backlights are the most obvious manifestation, but the movement is broader than that.

The attraction of LED backlights is that they permit a broader range, or gamut, of colors to be displayed. The downside for the moment is higher cost and higher power consumption. Bob Dunhouse of NEC Electronics commented that LED-backlight units (BLUs) have problems with color shift as the temperature changes, but it is becoming a real trend in medical and color-proofing applications, and for applications in which the European Reduction of Hazardous Substances (RoHS) requirement are an immediate issue.

But it is not only LEDs. Backlights based on hot-cathode fluorescent lamps (HCFLs) instead of the standard cold-cathode fluorescent lamps (CCFL) are also part of the new mix, as are blinking and dynamically addressed backlights that work with LCD panels to improve motion blur and/or improve contrast and dark detail.

At the present time, only a very few premium LCD TVs and professional monitors have anything other than the standard CCFL backlight, which produces a color gamut of about 72% of the 1953 NTSC standard for TV applications. But there were technology demonstrators, prototypes, and pre-production units all over the show floor at SID 2005. Let's take a look at a few of them.

The unofficial widest-color-gamut award goes to a prototype WXGA monitor developed by Mitsubishi Electric Corp. that has a six-primary-color backlight that uses Lumileds Luxeon^™ LEDs. It was shown in the Lumileds Lighting booth. The gamut is 175% of the sRGB standard (which is very similar to the modern NTSC standard and about 30% smaller than the 1953 NTSC standard mentioned above) and closely matches the gamut of a good ink-jet printer. A possible application is desktop publishing, since this monitor would extend WYSIWIG to color as well as form.

Personnel at the OSRAM Opto Semiconductors booth were wearing sunglasses, and they needed them. OSRAM was showing the world's largest LED backlight – 82 in. on the diagonal and producing a luminance of 10,000 nits. OSRAM Opto Semiconductors does not ordinarily make BLUs; the one in the booth was there to promote the company's new GoldenDRAGON LEDs with lenses and the LED drivers that go with them. The demonstration BLU contained 280 red, 560 green, and 280 blue GoldenDRAGONs.

Among the offerings from Samsung Electronics was a 46-in. TFT-LCD TV with an LED backlight that produced a color gamut of 105% NTSC. The backlight uses Samsung's "Xmitter" optical technology, which improves light utilization efficiency "by more than 40% relative to today's widely used side-scan method" and is also thin, the company said.

LG.Philips LCD showed a 47-in. TFT-LCD with an LED backlight that delivered a color gamut of 110% NTSC (Fig. 7). It produced the strikingly saturated colors that are typical of this generation of LED-backlit LCDs.

Since higher power consumption is a problem with LED BLUs, a lot of work is being devoted to improving power efficiency. LG.Philips did an end run around the long-term development of more-efficient LEDs by combining LEDs with CCFLs in an hybrid backlight that is competitive with conventional backlights in cost and power consumption and still delivers a color gamut of 105% NTSC, LG.Philips said.

The U.S. LED company CREE took the device-oriented approach when it announced during SID 2005 that it would be delivering complete BLUs by the end of the year. CREE's Mike Dunn said that highly efficient LED chips mounted to a heat-conducting circuit board have resulted in the first LED BLU that consumes less power than an equivalent CCFL BLU. No cooling fans or special structures are required, Dunn said, so the BLU can fit into a standard cabinet as a drop-in replacement. The BLU produces a color gamut of 107% NTSC when dropped into a typical TFT-LCD TV with the original matrix color filter (MCF). By using a customized MCF, the gamut could go as high as 140% NTSC, Dunn said.

The CREE architecture is scalable in that the backlight is constructed as tiles that can be combined to make a backlight of nearly any size. Global Lighting Technologies (GLT) also adopted a tiling approach, but emphasized the use of the company's proprietary color-mixing waveguides and MicroLens^™ technology to provide high uniformity while reducing thickness and overall LED count. GLT used the new Lumileds Lighting 1-W LED lamps.

"As LEDs get brighter, backlights will require fewer LEDs spread over a larger area, so color-mixing waveguides will become increasingly important to LCD-TV backlighting designs," said GLT's David DeAgazio. "Eventually, designs will migrate to edge-lit technology requiring even fewer LEDs."

Philips Lighting is taking a different approach with its Aptura^™ backlight technology. The Aptura BLU uses hot-cathode fluorescent lamps that increase light output of the BLU by more than 300%. The BLU is operated in scanning mode to reduce motion blur. Tantalizingly, Philips said that contrast is also improved by adding additional light and intelligence to the backlight module.Information Display will have a feature article describing the details of Aptura technology shortly. For now, we can say that a side-by-side demo at SID 2005 effectively showed the backlight's ability to reduce motion blur.

Conclusion

In past years, we have devoted an entire oversized issue of ID to SID's Display Week. This year, we are attempting to cover this remarkably rich event in only 4500 words. Inevitably, a lot of very interesting technology and business news has been omitted. What we have tried to do is provide the reader with some of what struck us as being particularly interesting, innovative, or significant. This story will be continued at SID 2006, to be held June 4–9, 2006 at the Moscone Center in San Francisco, California. •

 Ken Werner

Fig. 7: LG.Philips LCD showed a 47-in. TFT-LCD with an LED backlight that delivered a color gamut of 110% NTSC. It produced the strikingly saturated colors that are typical of the current generation of LED-backlit LCDs.