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Optoelectronics/Displays??

Flexible screens crawl to market

Posted: 03 Nov 2008 ?? ?Print Version ?Bookmark and Share

Keywords:display market? LCD? flexible screen?

For some time now we've been told about the benefits that flexible displays will bring. But actual display devices have been slow in coming. Recent indications, however, are that flexible displays are beginning to appear in earnest. Opinions differ widely over where their greatest perceived value will liein their inherent ruggedness, thinness, light weight, design freedom or in some other factor altogether.

At the 2008 Society for Information Display International Symposium, Seminar and Exhibition (SID 2008), two companies highlighted the e-skin concept in which the display covers all or most of the electronic product's front surface.

Kent Displays Inc. displayed a cellphone with a face that incorporates one big, irregularly shaped pixel. This cholesteric LCD pixel provides a medium for the user to change the color of the cellphone to any of nine distinct colors. E Ink Corp., meanwhile, showed a mobile phone from Hitachi Ltd featuring a dot-matrix electrophoretic display (EPD) e-skin. The face of the phone displays a set of 95 stored graphics and patterns.

The first flexible active-matrix electrophoretic displays use circuitry fabbed on glass and transferred to plastic.

Highlights
Elsewhere, flexible displays are having their ups and downs. On the up side, Esquire magazine's October 2008 issue featured an electronic cover based on a flexible E Ink EPD.

On the downside, Polymer Vision recently said its much-heralded Readius e-reader has been delayed again. Moreover, the first Readius incarnation, originally crafted with a 5-inch rollout E Ink display, will have a foldout display. The reason, according to the company, is user discomfort with rollout reliability, although the displays readily withstand 15,000 withdraw/insertion cycles. The displays are active-matrix (AM) devices using organic thin-film transistors.

Prime View International Co. Ltd was the first to market flexible AM EPDs, first shown in 2007. These are based on a circuitry transfer technology licensed from Philips that allows an AM to be fabricated on rigid glass and then transferred to a flexible substrate. First products include 1.9-inch, 6-inch and 9.7-inch devices based on E Ink technology.

Safety features
Bridgestone Corp., best known as a tire manufacturer, has shown flexible e-paper displays at SID 2008 based on its homegrown electronic liquid powder material and quick response liquid powder displays (QR-LPDs). The demos of this EPD-variant included a curved 10-inch QR-LPD on a flexible glass substrate. When it comes to near-term plans, however, Bridgestone will be using polyester-film when it starts production of the flexible QR-LPDs at the end of 2008. The primary appeal of flexibility is safety (greater resistance to damage and breakage than rigid displays), according to Bridgestone manager Takahiro Matsuse.

EPDs appear to be in the lead position in flexible displays. E Ink's manufacturing partners have been fielding so-called front-plane laminates for some time, which combine a plastic substrate, conductive coating, EPD layer and adhesive layer for attachment to a second substrate that may be either flexible or rigid.

E Ink showed a slew of customer applications at SID, most of them flexible. These included a Phosphor watch from Art Technology Inc. with a hole in mid-display from which the hands protrude, a smartcard from SmartDisplayer, electronic shelf labels from UPM, the previously mentioned Hitachi phone and an automotive key fob from Delphi Corp. with bidirectional communications.

Elsewhere in the e-paper realm, Kent Displays showed flexible Ch LCDs, fabricated on a roll-to-roll manufacturing line. Other flexible demonstrations included a very thin 120pixel x 160pixel display for smartcards, as well as a writing tablet based on a flexible, pressure-sensitive display.

The hands for this Phosphor watch from Art Technology protrude through the middle of a flexible EPD.

Variety of apps
LG Display Co. Ltd showed its flexible activities on two fronts at SID 2008: e-paper and OLEDs. The flexible 12-inch and 14.3-inch EPDs at its booth are being co-developed with E Ink.

The smaller display is a monochrome device for e-books; the larger is a multicolor EPD with a 1,280pixel x 900pixel WXGA format. Both use a stainless steel foil substrate. A company spokesman said that LG has also developed a myriad of monochrome and color flexible displays. The smallest of them is a 4-inch AMOLED developed jointly with Universal Display Corp.

SiPix Imaging Inc. showed flexible rolls of its Microcup EPD material, and Wintek Corp. displayed a flexible 2-inch, 46-segment EPD.

An Epson spokesman said the company is "exploring" flexible applications for its EPD technology in products that are "thinner and lighter than e-books."

Nemoptic discussed a flexible R&D project for display over 6 inches in diagonal, at which point "breakage becomes an issue." The largest displays the company is currently fielding are 4-inch devices.

David Lieberman
EE Times





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