DISPLAY MANUFACTURING ISSUE

Official Monthly Publication of the Society for Information Display • www.informationdisplay.orgDecember 2009Vol. 25, No. 12

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2 EditorialLessons from the Year That Was . . .

Stephen P. Atwood

3 Industry NewsGreen Manufacturing: End-of-Life Issues Are Complex

Jenny Donelan

4 Guest EditorialDisplay Manufacturing on Flexible Substrates

Greg Gibson

6 President’s CornerThe Importance of Light

Paul Drzaic

8 Frontline Technology: Flexible e-Book Displays Produced in Standard TFT and Module FactoriesThin, light, and robust flexible e-book displays are being prepared for mass production with most of the same equipment and processes used for glass displays.

Ian French

12 Frontline Technology: High-Volume Manufacturing of Photonic Components on Flexible SubstratesThe penetration of photonic technologies into the low-cost consumer-electronics marketplace has so far been limited. This article details several flexible-substrate-based manufacturing processes that have been developed for the high-volume low-cost production of optical waveguides – key components of a specific optical touch-screen system.

Robbie Charters

18 Display Marketplace: TFT-LCD Manufacturing Advances Reduce Cost and Energy ConsumptionMuch attention has focused on advances in TFT-LCD panel technology such as LED backlights, 120/240-Hz frame rates, wide viewing angle, and other technologies lead-ing to performance improvements. But behind the scenes, TFT-LCD manufacturingcontinues to evolve, leading to increased manufacturing productivity, lower costs, andimproved power efficiency. Recent developments include color filters, liquid-crystalalignment, and TFT design.

Charles Annis and Paul Semenza

22 Enabling Technology: Overview: Low-Temperature Polysilicon Low-temperature-polysilicon (LTPS) technology is an important part of the active- matrix-LCD manufacturing environment. Will its role expand or has it found its niche?

Jenny Donelan

26 Journal of the SID January Contents

27 SID News

28 Sustaining Members

28 Index to Advertisers

For Industry News, New Products, Current and Forthcoming Articles,see www.informationdisplay.org

DECEMBER 2009VOL. 25, NO. 12

COVER: Samsung LCD's Tanjeong complex inSouth Korea includes three Gen 8 lines that over the past few years have added 200,000 substrates(measuring 2200 × 2500 mm) to Samsung LCD'soverall monthly production capacity. The Gen 8 LCD lines primarily produce LCD panels for 52-in.-diagonal or larger TVs. The sprawling SamsungLCD complex (2 million square meters) also includestwo Gen 7 lines. One, a joint venture with SonyCorp., mainly produces 40- and 46-in. TV panels,and the other, a line exclusive to Samsung, producespanels from 32 to 82 in.

Next Month inInformation Display

Solid-State-Lighting Issue• Next-Generation Solid-State Lighting• Driving Solid-State Lighting• Myriad LED Uses• Solid-State-Lighting Design• Patent Licensing in the Display

Industry: A Primer• Journal of the SID February Contents

INFORMATION DISPLAY (ISSN 0362-0972) is published eleventimes a year for the Society for Information Display by PalisadesConvention Management, 411 Lafayette Street, 2nd Floor, New York, NY 10003; Leonard H. Klein, President and CEO.EDITORIAL AND BUSINESS OFFICES: Jay Morreale, Editor-in-Chief, Palisades Convention Management, 411 Lafayette Street, 2ndFloor, New York, NY 10003; telephone 212/460-9700. Sendmanuscripts to the attention of the Editor, ID. Director of Sales:Michele Klein, Palisades Convention Management, 411 LafayetteStreet, 2nd Floor, New York, NY 10003; 212/460-9700. SIDHEADQUARTERS, for correspondence on subscriptions andmembership: Society for Information Display, 1475 S. Bascom Ave.,Ste. 114, Campbell, CA 95008; telephone 408/879-3901, fax -3833.SUBSCRIPTIONS: Information Display is distributed withoutcharge to those qualified and to SID members as a benefit ofmembership (annual dues $100.00). Subscriptions to others: U.S. &Canada: $75.00 one year, $7.50 single copy; elsewhere: $100.00 oneyear, $7.50 single copy. PRINTED by Sheridan Printing Company,Alpha, NJ 08865. Third-class postage paid at Easton, PA.PERMISSIONS: Abstracting is permitted with credit to the source.Libraries are permitted to photocopy beyond the limits of the U.S.copyright law for private use of patrons, providing a fee of $2.00 perarticle is paid to the Copyright Clearance Center, 21 Congress Street,Salem, MA 01970 (reference serial code 0362-0972/09/$1.00 +$0.00). Instructors are permitted to photocopy isolated articles fornoncommercial classroom use without fee. This permission does notapply to any special reports or lists published in this magazine. Forother copying, reprint or republication permission, write to Societyfor Information Display, 1475 S. Bascom Ave., Ste. 114, Campbell,CA 95008. Copyright © 2009 Society for Information Display. Allrights reserved.

Information Display 12/09 1

CREDIT: Samsung Tanjeong LCD Production ComplexCover design by Acapella Studios, Inc.

InformationDISPLAY

Executive Editor: Stephen P. Atwood617/306-9729, satwood@azonix.comEditor-in-Chief: Jay Morreale212/460-9700, jmorreale@pcm411.comManaging Editor: Jenny Donelan603/924-9628, jdonelan@pcm411.comAdministrative Assistant: Ralph NadellSales Manager: Danielle RoccoSales Director: Michele Klein

Editorial Advisory Board

Stephen P. Atwood, ChairCrane/Azonix Corp., U.S.A.

Bruce GnadeUniversity of Texas at Dallas, U.S.A.

Allan KmetzConsultant, U.S.A.

Larry WeberConsultant, U.S.A.

Guest Editors

Display MetrologyTom Fiske, Rockwell Collins, U.S.A.

LEDsDavid DeAgazio, Global Lighting

Technologies, U.S.A.

Ultra-Low-Power DisplaysRob Zehner, E Ink, U.S.A.

3-D TechnologyBrian T. Schowengerdt, University of

Washington, U.S.A.

OLED TechnologyJulie J. Brown, Universal Display Corp.,

U.S.A.

LCD TechnologyShin-Tson Wu, University of Central

Florida, U.S.A.

Display ManufacturingGreg Gibson, NexTECH FAS, U.S.A.

Lessons from the Year That Was . . .

by Stephen P. Atwood

Every time I sit down to write the December editorial, I get a chance to consider the events of the previous year aswell as look ahead to the coming year. For many of us, thispast year brought challenges both economic and profes-sional that we would rather not dwell on too long. Forsome, the sentiment may even be along the lines of “GoodRiddance.” However, before we say goodbye to 2009 we

should at least be willing to acknowledge that sometimes adversity and hardship servea positive role.

One example can be seen in the triumphs of many display businesses that have con-tinued to innovate and grow their technology portfolios despite the downturn. Whilefacing economic hardship, some companies made smart staffing and expense deci-sions, accepting the challenge to streamline their operations while not stifling theirtechnology developments. These companies have now emerged with an even betterbusiness than they had before. You can spot them as the ones that continue to exhibitnew products, influence the industry trends, lower the costs for adaptation of displaytechnology, and set up world-class manufacturing facilities like the one pictured on thecover of this month’s issue. Not all the winners are large; some are just small engi-neering or consulting firms, but they do typically have some key things in common,such as strong cash positions, good technology portfolios, a lean and aggressivelymotivated workforce, and senior leadership that is not afraid of failure but ratherembraces challenge.

There is a contrasting trend I have seen illustrated by many companies when in themidst of an economic downturn. It starts by hunkering down as though they wereunder siege. They cut expenses, including staff, put technology developments onhold, and struggle to break even while minimizing loss of market share. Sometimesthey have no choice because they lack enough cash or face crippling debt. These com-panies rarely survive a recession anyway. In few cases do those companies emergefrom the crisis better positioned to succeed. However, there is another group that doesessentially the opposite. They re-structure to minimize the cost of the less productiveparts of their business while turning their remaining resources squarely to the goals oftechnology development and product innovation. They use the downturn as a chanceto re-focus their energy and get ahead of the curve while their competitors are standingstill. When the crisis is over, it is obvious they will emerge with better market shareand less competition at the same time. It is these companies and their leaders that Iadmire most.

Consider the acquisition of E Ink by Prime View International. This deal was puttogether in May, just as the hardest period of the recession was looming. Although theeBook field was a hot topic around the water cooler, real sales were not record setting,and many product competitors were entering the space at the same time. A lot of dealswere being scuttled and there was much handwringing about the lack of capital andoptimism in the M&A world. However, both parties could see that a shakeout wouldonly last a short time and the strongest product developers would emerge. Most of thenew products being launched were based on some element of the E Ink system, andPrime View wanted to be positioned to be the supplier of choice for those and manymore developers in the future.

editorial

2 Information Display 12/09

The opinions expressed in editorials,columns, and feature articles do not neces-sarily reflect the opinions of the ExecutiveEditor or Publisher of Information DisplayMagazine, nor do they necessarily reflectthe position of the Society for InformationDisplay.

Information

DISPLAY

(continued on page 25)

Green Manufacturing: End-of-Life Issues Are Complex

by Jenny Donelan

From California’s Electronic Waste RecyclingAct to the European Union’s Waste Electricaland Electronic Equipment Act (WEEE), thegovernment mandates continue to mount: elec-tronics manufacturers must take steps to ensuretheir products, at end of life, are collected andrecycled. California’s legislation calls for awaste-recycling fee at point of sale (end userspay this), and for distribution of payments towaste recycling and collection agencies.WEEE sets targets for collecting and recyclingequipment, with the responsibility for makingthis happen lying mostly with the manufacturer.

“Responsibility” is a big part of the recy-cling equation. Who is responsible for whichactions and can they be made accountable?Due to the complexity of today’s supplychains, answers to these questions can be hardto find. When it comes to recycling electron-ics, getting from mandate to “mission accom-plished” is a difficult path for nearly all theparties involved. But one thing is certain: thesuccess or failure of any given recycling ini-tiative resides mostly with consumers. Theirbuy-in is vital in order for a plan to thrive.

Where Used Electronics End UpThere’s no doubt that measures are necessary.According to a recent report from the U.S.Environmental Protection Agency (http://www.epa.gov/waste/conserve/materials/ecycling/manage.htm), approximately 235million unused electronic devices had accu-mulated in storage in U.S. homes and officesas of 2007. Not all of these contain displays,but most do: this figure includes 43 millioncomputer monitors, 2 million notebooks, and99 million televisions.

Of those items that do make it out of thecloset or the desk drawer and into the wastestream, very few are recycled. According tothe same EPA report, between 2006 and 2007,out of 2.25 million tons of TVs, cell phones,and computer products at end of life, 18% werecollected for recycling and 82% were disposedof primarily in landfills, where they are liableto leach hazardous chemicals into the groundand water supply. Although display manufac-turers and others have been working hard oflate to remove toxic materials from their prod-ucts, the great majority of outdated or brokencell phones and other electronics residing in

storage predate these efforts and so represent aconsiderable environmental hazard. And aselectronic products continue to evolve in termsof features, stimulating consumers’ desire toreplace old models with new ones, the backlogof outdated products will only increase.According to the Consumer Electronics Asso-ciation, U.S. consumers bought 2.9 million HDTVs for Super Bowl 2009 alone.

Recycling Along the Supply ChainPassing legislation to handle the situation,however, and making sure that legislation isexecuted are two different matters. First, theconsumer needs to be coerced. Electronicsare not yet as easy to recycle as paper. Otherthan a guilty conscience, there is little to pre-vent an end user from simply dropping an oldcell phone into the household trash. Sometransfer stations do sort trash, but many donot; and the likelihood of any one consumerbeing tracked down for inappropriate disposalof goods is slim. Some corporate entitieshave been fined for improper disposal of lightbulbs and other items, however. And trashhaulers are sometimes fined for not properlyseparating recyclables from other waste.

Farther back in the supply chain, the manu-facturers, for their part, are encouraged orrequired by current legislation to providerecycling programs, but they cannot generallyforce consumers to carry through. For thetime being at least, much of this legislationlacks teeth. “It’s a tangled area,” says Kim-berly Allen, principal of Pañña Consulting,adding that to further complicate matters, theEU has its own rules, whereas in the U.S.,recycling legislation varies by state.

Companies such as Dell, HP, and Applenow have programs in which consumers canexchange, drop off, or ship off old units. Eachof these manufacturers has a Web site dedi-cated to the ins and outs of recycling proce-dures, depending on where you live and whatproduct you wish to recycle. Because thelogistics of getting units from point A to pointB might be beyond the scope of a given man-ufacturer, a number of third-party coalitionsand businesses have sprung up that exist toprovide these services. But here, as in muchof the current recycling ecosystem, the watersare murky. Some, though not all, electronics end up in landfills in developing nations, where they may be taken apart by indigent laborunder less than ideal conditions. The BaselAction Network (www.basel.org), a groupdedicated to globally responsible recycling,now offers third-party audited certification of

recyclers, including a directory where inter-ested parties can find an authorized recycler.

Product PostmortemsThat developing nations are more eager forused electronics than their economically bet-ter-off counterparts says something about thecurrent value statement, or lack thereof, ofelectronics recycling. Says Allen: “The busi-ness case isn’t super clear. There are chal-lenges with how to collect products and dis-assemble them.” Each component of a displayor other electronic device needs to be sepa-rated and handled differently in order to berecycled. Consider a CRT TV, for example(and there are many such TVs still awaitingdisposal). Some of these, according to a 2008Popular Mechanics article (http://www.popularmechanics.com/technology/how_to/4277703.html), find new life as refurbishedCRT TVs in markets where CRTs are stilldesirable. Otherwise, the glass picture tubes,which contain lead, can be melted down to bereconstructed into new CRTs or sent to leadsmelters. Circuit boards in TVs are non-biodegradable, but can be recycled. Compa-nies specializing in this work are able toremove about 99% of the precious metals fromthe circuitry on the boards by shredding themand extracting the metals. It is also possible todesolder specific components from the boardsfor further use. Plain circuit boards can bereused as building materials. And plastics andmetals in the television casing can also bestripped out and used to create new products.

In the case of LCD TVs, the CCFLs used forbacklighting contain mercury but can brokendown (again by specialty companies) and theglass and metal reused for various purposes.The LCD glass cannot be used to make moreLCD glass (it is not pure enough) but can berepurposed into a variety of building materials.Some experts have even suggested that thepolyvinyl-alcohol (PVA) coating on the LCDglass can be used for various health productsbecause PVAs are helpful in tissue-regrowthapplications. Applications for recycling LEDs,which are increasingly used to backlight LCDTVs, are not numerous yet, but the general con-sensus is that because they contain no mercury,they will be easier to handle and repurpose.

So, there are plenty of useful components tobe gleaned from old displays, but separatingthem from each other is yet another part of thepuzzle. When components are soldered, gluedtogether, etc., it can be difficult and time-con

Information Display 12/09 3

iinndduussttrryy nneewwss

(continued on page 27)

guest editorial

4 Information Display 12/09

Display Manufacturing on Flexible Substrates

by Greg Gibson

The vast majority of commercially available displays andrelated touch-screen technologies are currently manufac-tured on rigid glass substrates. For mature display tech-nologies such as AMLCD, the consumer expects continuedincreases in display size and performance, with a simultaneousreduction in product price. These requirements are typi-cally met both by advancements in the display technology

and by continued improvements in display manufacturing. For emerging display tech-nologies such as OLED, the focus is on commercialization, supported by manufactur-ing processes that can ultimately be driven down in cost to a point that supports theintroduction of competitive mainstream products. The vast majority of these commer-cially available and emerging displays, and related touch-screen technologies, are cur-rently manufactured on rigid glass substrates, which offer many advantages for boththe final display product and the process steps used to manufacture that product.

However, display manufacturing on flexible substrates is a technology segment thatis receiving increasing amounts of development and investment. The move towardflexible substrates is typically driven by the requirements of the final product, forinstance, a flexible plastic display, or the efficiencies that can be realized when themanufacturing process can be executed on flex. Certainly, the recent market successof e-books has been a significant boost to the electrophoretic-display segment, but it isbelieved that additional market penetration can be achieved if this technology can becommercialized on flexible displays. Such a display, and the resulting end product,could be thinner and lighter than the glass-based product, while offering significantlyincreased resistance to breakage. Manufacturing on flex can also enable products withperformance and cost points that simply could not be met by using glass.

The ultimate target of flexible-substrate manufacturing is, for many, the migrationto a complete roll-to-roll (R2R) process, where most if not all of the manufacturingcan be executed in a continuous or semi-continuous fashion. The promise of signifi-cantly increased throughput and reduced manufacturing cost is alluring, and indeedR2R manufacturing on flex has been demonstrated for certain applications such ascholesteric displays and electronic skins. However, for most flexible-display applica-tions, there are many technical challenges preventing widespread migration to R2R,not the least of which is the difficulty in maintaining dimensional control and patternregistration accuracy on flexible plastic, and the general challenge of integrating awide range of processes into a continuous line.

Flexible substrates can also be processed in a single-substrate manner, using either acarrier plate or in a free-sheet form. By using the carrier plate approach, the flexiblesubstrate is attached to (or built on top of) a rigid glass carrier panel. This carrier plate(CP) is typically display glass that is matched to a standard AMLCD Gen size, thustaking advantage of the wide range of process equipment that is already available fordisplay processing. Even so, the manufacturing equipment, and the processes per-formed, must be adapted to the unique characteristics of the laminated-carrier-panel/flexible-substrate assembly. In addition, there are special requirements for theultimate separation of the flex substrate from the carrier and the final assembly of theflexible-display device. Despite these challenges, the CP approach offers the advan-tage of maintaining reasonable dimensional stability and overlay accuracy during

(continued on page 27)

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president’s corner

6 Information Display 12/09

The Importance of Light

Paul DrzaicPresident, Society for Information Display

I’m a student of light. If that statement sounds confusing,please allow me to explain. One of my hobbies is photo-graphy, and particularly outdoor photography. I am fortu-nate enough to live only an hour or so from the CaliforniaBig Sur coastline, where the word “amazing” is an under-

statement when describing the views available along Highway 1. The same scene canlook very different from day to day; sometimes even from hour to hour. The positionof the sun in the sky changes the color of the illumination and the depth and positionof shadows. The absence or presence of clouds, fog, and rain, or even the wind kick-ing up ocean spray can change how light interacts with the ground and what I’m ableto see or photograph. Most of the time, the lighting is out of my control, other thanwhat I can do by paying attention to weather forecasts and what times the sun risesand sets.

Working in the electronic-display industry also makes me a student of light. In thecase of displays, though, the quality of the light provided by the display is determinedby a series of compromises inherent in whatever technology is being used in the dis-play. In most cases, the display just has to be good enough to provide the image thatthe user wants to see. Of course, what “good enough” means depends on the situationand setting. When watching a movie at home, I’d love a reasonable facsimile of whatI’d see if I paid my $9.50 to the local movie theater. When getting a text message, Ijust need to be able to read the message quickly and without hassle. In these varioussituations, the display is part of a system that I expect to function in a certain way.

Still, advances in display technology time and again have provided strong, emo-tional responses that have helped pull products out of the lab and into the mainstream.High-pixel-count televisions, providing image clarity that people had never seen intelevisions before; OLED displays in mobile devices, enabling a color gamut and con-trast totally unexpected in small-format displays; pico-projectors, presenting colorvideo imagery in places where one would never expect to see it. It is the extra benefitsin shaping light provided by new capabilities in displays that generate these emotionalresponses and drive new waves of products.

For my photographic hobby, as well as for my work on displays, there are a fewthings I am still waiting for that would improve my interaction with light. How abouta camera-viewing screen that I can actually use outdoors in bright sunlight? Maybethis is an application of that color e-paper product we are all waiting for. Or, a displaythat renders my photographs with a color gamut closer to the real scene, so the lasttemptation to print the photograph finally goes away – is this an OLED, LCD, PDP,plasma, or something else? These are products that would reach me on an emotionallevel and probably induce me to upgrade my equipment (once again!) before I reallyneed to. �

SID Executive CommitteePresident: P. DrzaicPresident-Elect: M. AnandanRegional VP, Americas: T. VoutsasRegional VP, Asia: S. NaemuraRegional VP, Europe: J-N. PerbetTreasurer: B. BerkeleySecretary: A. GhoshPast President: L. Weber

DirectorsBay Area: S. PanBeijing: B. P. WangBelarus: V. VyssotskiCanada: T. C. SchmidtDayton: D. G. HopperDelaware Valley: J. W. Parker IIIDetroit: J. KanickiFrance: J-P. ParneixHong Kong: H. LeungIndia: G. RajeswaranIsrael: G. GolanJapan: N. IbarakiKorea: K. W. WhangLatin America: A. MammanaLos Angeles: L. TannasMid-Atlantic: D. MortonMid-Europe: G. OversluizenNew England: S. AtwoodPacific Northwest: A. AbileahRussia: I. N. CompanetsSan Diego: T. StrieglerSingapore: C. C. ChaoSouthwest: S. O’RourkeTaipei: Y. T. TsaiTexas: Z. YanivU.K. & Ireland: I. SageUkraine: V. SerganUpper Mid-West: B. Bahadur

Committee ChairsAcademic: P. BosArchives/Historian: P. BaronBylaws: A. KmetzChapter Formation: Z. YanivConvention: D. EcclesDefinitions & Standards: J. MisceliHonors & Awards: C. KingLong-Range Planning: M. AnandanMembership: S. PanNominations: L. WeberPublications: B. GnadeSenior Member Grade: M. Anandan

Chapter ChairsBay Area: D. ArmitageBeijing: N. XuBelarus: V. VyssotskiCanada: A. KitaiDayton: F. MeyerDelaware Valley: J. BlakeDetroit: S. PalaFrance: J. P. ParneixHong Kong: H. S. KwokIndia: S. KauraIsrael: B. InditskyJapan: K. KondoKorea: Y. S. KimLatin America: V. MammanaLos Angeles: P. Joujon-RocheMid-Atlantic: Q. TanMid-Europe: A. JelfsNew England: B. HarkavyPacific Northwest: A. SilzarsRussia: S. PasechnikSan Diego: T. D. StrieglerSingapore/Malaysia: X. SunSouthwest: B. TritleTaipei: Y. TsaiTexas: S. PeanaU.K. & Ireland: S. DayUkraine: V. SerganUpper Mid-West: P. Downen

Executive DirectorT. Miller

Office AdministrationOffice and Data Manager: Jenny Bach

Society for Information Display1475 S. Bascom Ave., Ste. 114Campbell, CA 95008408/879-3901, fax -3833e-mail: office@sid.orghttp://www.sid.org

THE FIRST e-BOOKS, such as the Rocket and Softbook reader in the 1990s,were not major commercial successes. Thiswas probably due to a combination of limitedreading material being available, poor contentdistribution, and the fact that these devicesused active-matrix LCD screens that did notprove popular for immersive reading. In thelast few years, there have been major develop-ments that have led to wider acceptance of e-books. First, high-quality electrophoreticdisplays were created that closely mimickedthe visual appearance of printed paper. Then,Amazon, Sony, and other companies devel-oped the infrastructure to make large numbersof books, newspapers, and magazines quicklyand easily available, either by wireless or viathe Internet.

Electrophoretic displays had been underdevelopment by several groups since the1970s, but by the early 1990s they had largelyfallen out of favor because of the rise of LCDsand the many practical problems associatedwith making high-quality electrophoretic displays with acceptable performance andlifetime. In 1995, the Jacobson group at MITrevisited electrophoretic-display technology

and developed a foil with microcapsules containing black-and-white particles withopposite electrical charges on them in a clearliquid. The particles could be moved byexternal electrical fields, so that either theblack or white ones were toward the top, orthey could have different degrees of mixingwithin the capsule. An observer would thensee the capsule as black or white, dependingon which type of particle was uppermost, or ashade of gray that depended on the distribu-tion of mixed particles. Along with good con-trol of the surface chemistry of the chargedparticle, this approach solved many of the pre-existing problems of electrophoretic displays.1 The development of electrophoreticfoils was spun out from MIT just 2 years laterwhen the E Ink Company was formed in1997.

To make high-resolution e-book displaysthat can show pages of text and monochrome pictures, E Ink foils are laminated onto amor-phous-silicon (a-Si) TFT backplanes of thetype used in most active-matrix LCDs. Thefirst e-book to use E Ink foils was the SonyLIBRIé, which was launched in 2005. Ini-tially, TFT-backplane manufacturing andmodule integration were carried out byPhilips, but these activities were passed overto Prime View International (PVI) late in2005 when Philips decided to stop manufac-turing displays.

Currently, the e-paper market is one of the most dynamic in the display industry.

Market-research-company DisplaySearch estimates that it will grow from a value of$100 million in 2009 to $9 billion in 2018. Itis ironic that this dramatic growth is based ona technology that would seem like a backwardstep if we only consider the usual display metrics of brightness, contrast ratio, colorgamut, and speed of response. Electro-phoretic displays have slow response, a lowercontrast ratio than LCDs, and, at the moment,they are only monochrome. On the positiveside, they benefit from long battery lifebecause they only draw power when the pageis rewritten, but their major attraction is theirpaper-like appearance.

Although e-books have captured much ofthe visual experience of the printed page, theirfeel is very different. This can be importantfor immersive reading, which people typicallydo while holding a book, magazine, or news-paper. At the moment, the e-book displayshave a rigid, glass TFT backplane that mustbe enclosed in a metal case for protection.This makes them comparatively heavy, partic-ularly for larger displays, such as 8 in. andabove. They are well protected by the metalcase, but they can still sometimes break ifthey are dropped or if an object presses hardagainst them, as can happen in a bag. Theobvious solution to these issues is to replacethe glass backplane with an array of TFTs ona plastic substrate to make the display thinner,lighter, and more robust. In fact, it was soobvious that E Ink first started working

Flexible e-Book Displays Produced inStandard TFT and Module Factories

Thin, light, and robust flexible e-book displays are being prepared for mass production withmost of the same equipment and processes used for glass displays.

by Ian French

Ian French is principal scientist at PVI, concentrating on the industrialization ofEPLaR. He worked at Philips Research formany years on a range of display and sensorapplications. He can be reached at ianfrench@pvi.com.tw.

8 Information Display 12/090362-0972/12/2009-008$1.00 + .00 © SID 2009

frontline technology

with Lucent Technologies to make flexibledisplays with organic TFTs on a plastic sub-strate as long ago as 1999. Since then, E Inkhas demonstrated high-quality flexible displays, with more than 10 different compa-nies and research institutes using a range ofdifferent TFT types, flexible substrates, andfabrication techniques. Surprisingly, giventhat so many companies have successfullymade good demonstrators over the years, flexible displays have still not reached themarket. One of the main reasons for this isthat many of them were made using experi-mental techniques on small substrates thatwould have required large investments in newmachines and methods of handling in order toscale up to mass production. Organic or plastic TFTs also require new materials systems that have not yet made it into commercialproducts, despite having been in developmentfor use in TFTs for more than 10 years.

The EPLaR ProcessThe electronics on plastic by laser release process (EPLaR)2 is one method that can beused to produce flexible displays. (It is themethod that has been adopted by the author’scompany, Prime View International.) Thisprocess employs more than 95% of the samesteps and equipment that are used for making glass e-book displays, which minimizes invest-ment cost and development time because nonew factory is needed and relatively few newprocess machines have to be purchased.EPLaR displays also directly benefit fromyears of experience of manufacturing andusing glass displays in e-books.

The main steps in making active-matrixelectrophoretic displays on glass involve a-SiTFT-array fabrication, followed by display-module assembly. A field-shielded pixelstructure having a relatively thick polymerinsulator over the TFT is used. This allowsthe ITO pixel to lie over the TFT, rows, andcolumns, maximizing the ITO area and there-fore the area of the electrophoretic foil that isbeing controlled. This is the same TFT structure that is used in LCDs with large-optical-aperture pixels. The steps in modulemaking are scribe and break to separate thedisplays on the motherglass; lamination of anelectro-phoretic foil; attachment of row andcolumn drivers by a chip-on-glass process;and then, finally, attachment of a flexibleprinted circuit board (PCB) to provide con-nections to external driver electronics.

The EPLaR process closely follows that formaking glass electrophoretic displays, butwith some additions. The first extra step isinserted before TFT-array fabrication. A 10-µm-thick polyimide layer is applied to astandard glass substrate. This will eventuallybecome the plastic substrate. As long as thecorrect interface treatments are used in con-junction with the correct type of polyimideand curing schedule, then the polyimideadheres very strongly to the glass substrate.The polyimide can withstand all of the stan-dard processes used for making TFTs on glasssubstrates.

To reduce the level of particles and contam-ination, all TFT factories minimize the num-ber of workers inside them by using integratedautomated handling systems. These use cassettes on automated guided vehicles forcarrying the glass substrates between processmachines. The substrates are transferred fromthe cassettes to processing machines, andbetween adjacent process stations, by roboticarms. The glass substrates are so large, evenfor Gen 2 factories, that they sag in the cassettes, and the spacing must be very accu-rately controlled to obtain the maximum number of displays in a cassette while stillallowing the pick-up arm of the robots to getbetween the substrates. The automated handling is so precise and finely tuned that, inthe past, factories have not been able tochange glass-substrate thicknesses from 1.1 to 0.7 mm because all of the cassettes and

handling systems would have needed to bechanged. This illustrates the kinds of difficul-ties that should be expected if major changesare made to the size and weight of substratesin TFT factories. In the EPLaR process, thepolyimide increases the substrate thickness byonly about 1.4% and the weight of the sub-strate by less than 1%. These small changesallow EPLaR substrates to be used with all ofthe existing automated handling and mass-production equipment in TFT factories.

During processing, the polyimide layer isstrongly anchored to the glass substrate. Thismeans that the design rules for EPLaR displays can be kept exactly the same as forTFT arrays on glass, allowing use of the same mask sets for making glass and EPLaRdisplays. Figure 1(a) shows a photograph of apixel of a glass electrophoretic display andFig. 1(b) a pixel from a flexible display madeby the EPLaR process. It can be seen thatthey are identical, except for the color, whichcomes from the thin polyimide. In compari-son, flexible displays made on relatively thickpre-formed plastic substrates must use designrules that allow for shrinkage and swellingduring processing because the substrateabsorbs moisture and loses it during heating.For this reason, relatively thick pre-formedplastic substrates are generally not so well-suited for making high-resolution displays.

Electrophoretic foils, driver chips, and elec-trical interconnects are laminated onto thesubstrates after TFT-array fabrication with the

Information Display 12/09 9

(a) (b)

storagecapacitor

TFTs

Fig. 1: These photographs of electrophoretic-display pixels were taken through the substrate:(a) on glass and (b) taken through a laser-released EPLaR polyimide substrate.

same equipment and process settings that areused for glass electrophoretic displays. Atthis stage, there are fully working electro-phoretic displays on glass, but with a thinpolyimide layer between the glass and the bottom of the TFT array. To make them intoflexible displays, the second additionalEPLaR step is needed. The polyimide isreleased from the glass substrate using a laserprocess, and the polyimide becomes the plastic substrate for the flexible display. Figure 2 shows part of a batch of 9.7-in.EPLaR displays immediately after laserrelease at the PVI module factory inYangzhou, China.

Electrical CharacteristicsElectrical characteristics measured on testTFTs from a standard glass substrate and anEPLaR display after laser release are shown inFig. 3. The TFT characteristics are effectivelyidentical and no significant difference in ON-currents, threshold voltage, sub-thresholdslope, or OFF-currents are detectable. All ofthese characteristics are important becausetogether they determine the drive voltages andtiming needed to drive the display. Forinstance, TFTs with a small sub-thresholdslope have a wider voltage difference betweentheir OFF and ON states, so that more expen-sive driver chips with a larger voltage rangeare needed. The other TFT characteristics allaffect the driver voltages and timing in somemanner. The same drive electronics and driveschemes can be used for glass and EPLaR e-book displays because of their identicalcharacteristics, which is a significant advan-tage to a company that is manufacturing both.

DC-stability measurements at elevated tem-peratures and high gate fields were also madeon glass and EPLaR TFTs. Again, the resultswere identical for laser-released EPLaR TFTsand test devices on glass. The results showthat TFTs in EPLaR displays will have thesame performance, lifetime, and stability as a-Si TFTs in LCDs and e-books.

EPLaR Displays and Future PlansAll active-matrix displays that are already inmass production use glass as the TFT sub-strate. This includes TFT-LCDs, active-matrix OLEDs, and e-books. EPLaR displaysare called flexible to indicate that they are not rigid in the same way as glass displaysare; instead they are thin, light, and robust.Initially, EPLaR displays will be used in

10 Information Display 12/09

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Fig. 2: These 9.7-in. flexible displays have just gone through laser release. The ones on thetable and in the carriers are face-down while the one being held has the front face of the displaytoward the camera.

Fig. 3: The graph on the left shows the transfer characteristics of test a-Si TFTs on glass andthe graph on the right, on an EPLaR display.

applications where they are held flat or curvedto a fixed shape, rather than ones in whichthey are constantly rolled and unrolled. In thepast, E Ink has described displays that havethe feel and thickness of a mouse pad to con-vey the idea of a robust display that is nor-mally used flat, but that can withstand a cer-tain amount of bending. There is no reasonwhy EPLaR displays should not be made rol-lable in the future, but this would require aredesign of the module, especially the placingof the rigid row and column drivers, andextensive mechanical testing.

PVI has made EPLaR displays with 1.9-, 6-, and 9.7-in. diagonals, which are three ofthe standard sizes the company already usesfor glass electrophoretic displays. Figure 4 isa photograph of an EPLaR 9.7-in. displaywithout a case, showing the image of a news-paper page.

Although the EPLaR process has beendeveloped primarily for use in e-books and e-newspapers, it will also allow other applica-tions to benefit from having thin, light, androbust displays. One obvious possibility isincorporating a small display into a smart cardto show customers account information andmaybe alternate between the customer’s photograph and signature during payment.

Glass displays cannot be used in smart cardsbecause they are too thick and rigid, butEPLaR displays can be less than 0.4 mmthick. Small flexible displays could also beused as electronic shelf labels that do notbreak when knocked by a can or bottle, or forsecondary text displays on mobile phones.Figure 5 shows a photograph of a 1.9-in.EPLaR display having drive electronics on aflexible PCB that has been attached to ashaped holder to demonstrate that it can con-form to a curved shape. The image on theEPLaR screen has 16 gray levels, and it iseasy to see that it could act as an ID photo-graph in an electronic badge. The electronicsand drive scheme for this portable demonstra-tor were made by MpicoSys.3

EPLaR displays are currently being readiedfor commercial release, with production splitbetween the PVI TFT factory in Taiwan andthe module factory in China. The electricalcharacteristics and stability of the a-Si TFTson EPLaR displays are the same as TFTsmade on glass for LCDs, which have beenused in many millions of devices, rangingfrom mobile phones to LCD TVs. EPLaRdisplays can be used in a range of products,such as e-books, e-newspapers, smart cards,and electronic shelf labels. In the future, they

will benefit from planned improvements in electrophoretic displays on glass, such as thedevelopment of full-color displays and videorates, which will also be applicable to EPLaRdisplays.

References1J. Ritter, “The Promise of ‘Electronic Ink,’ ”Information Display 12/1, 22–25 (2001).2I. D. French, et al., “Thin Plastic Electro-phoretic Displays Fabricated by a Novel Process,” SID Symposium Digest 36, 1634-1637 (2005).3http://www.mpicosys.com. �

Information Display 12/09 11

Fig. 4: This 9.7-in. EPLaR display is flexible, though not rollable.

Fig. 5: This 1.9-in. EPLaR display in acurved holder can hold this shape indefinitely.

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THE RAPID INCREASE in functionalityof handheld electronic devices has put signifi-cant pressure on standard keypad interfacesto the point that touch-screen interfaces onmobile devices are now a common feature. Inaddition, the release of Microsoft Windows 7,with its strong touch-application focus, looksready to make touch screens pervasive atlarger screen sizes.

Attractive features of any touch-screentechnology include low power consumption,double-touch-pen and/or gloved-finger opera-tion, and freedom from distortion of the liquid-crystal-display (LCD) optical performance through absorbing overlays or films. Oneclass of technology that exhibits all of thesefeatures is optical or infrared (IR) touch.1 Inthis approach, a grid of IR light beams is con-structed, propagating just above the top surface of the LCD. Any touch event breaks the beams, casting a shadow that can be detected by elec-tronic means. Figure 1 shows the typical con-figuration for an IR touch screen, in which thebeams are set on a Cartesian grid and discreteemitters and receivers are mounted in one-to-one correspondence around the edge of the LCD.

An alternative approach, developed byNextWindow, uses point-source corner-mounted emitters to create a spherical coordi-nate system for IR light beams and camera-based detection. More recently, RPO, Inc.,

has introduced Digital Waveguide Touch(DWT), in which a series of densely packedlight pipes, or optical waveguides, areemployed to route LED-generated IR lightfrom the touch-screen grid on the perimeter of

High-Volume Manufacturing of PhotonicComponents on Flexible Substrates

The penetration of photonic technologies into the low-cost consumer-electronics marketplacehas so far been limited. This article details several flexible-substrate-based manufacturingprocesses that have been developed for the high-volume low-cost production of opticalwaveguides – key components of a specific optical touch-screen system.

by Robbie Charters

Robbie Charters is Founder and Chief Tech-nical Officer of RPO, Inc. He can be con-tacted at Innovations Building, 124 EgglestonRoad, Acton ACT 0200, Australia; telephone+61 2 6125 3918, e-mail: r.charters@rpo.biz.

12 Information Display 12/090362-0972/12/2009-012$1.00 + .00 © SID 2009

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Fig. 1: In this typical optical-touch-technology configuration, LEDs arranged along two edgescreate a grid of IR light and discrete receivers (photoreceptors) are mounted in one-to-one cor-respondence around the opposite edges of the display. Illustration courtesy Elo TouchSystems.

Edge of activedisplay area

Opto-matrix frameinside bezel

Photoreceptors

Inside and outsideedges of infraredtransparent bezel

LEDs create gridof infrared light

the LCD to remotely mounted cameras. Theelements of a DWT-based touch screen,shown in Fig. 2, are described below.

The DWT touch-screen module is assem-bled around a central rectangular LCD panelwith the waveguides mounted to the bottomand left edge of the touch-screen assembly.Infrared light is emitted by two LEDs, witheach divergent IR light beam striking aparabolic reflector on the opposite side of theassembly. The light beams are collimated bythe reflector along the top and left edges ofthe assembly and reflected back over the topof the LCD panel as a 300-µm thin sheet of IR light projected over the glass surface. Thecollimated light is captured by the waveguideson the opposite sides of the assembly. Eachwaveguide channels an independent light pathto one or more pixels on an application-specific integrated circuit (ASIC) based light-sensor camera.

This waveguide-based light-distribution circuit offers a distinct advantage over exist-ing optical touch systems by reducing thenumber of emitters and receivers, thereby dramatically reducing costs and power con-sumption. In addition, the miniaturization of the optical components afforded by thewaveguide-based approach results in nar-rower, more aesthetically pleasing borders(bezels) around the LCD. However, the keyadvantage of DWT lies in its ability to accu-rately pattern waveguide and micro-optic lenscomponents in a single photolithographic step.This simple mask-based process completelydefines the touch-screen resolution, ambientlight rejection, and sunlight operation of the

system. A change in touch-screen perfor-mance or screen size is simply a matter ofchanging the mask design layout, a routineCAD operation. A description follows of howthe DWT waveguide components can be manufactured in high volume on flexible substrates and of how different techniqueshave been applied for the automated handlingof these substrates.

Waveguide ManufacturingThe basic processing steps for manufacturingwaveguides for DWT are shown in Fig. 3.

In the first step, a planarization layer oflow-refractive-index waveguide buffer mate-rial is applied with high uniformity to a flexi-ble substrate. This layer is flood-exposedunder UV light to form both a mechanicallyflat surface for subsequent coatings and alsothe base section of low-refractive-index mate-rial that forms the waveguide cladding. In asecond step, a high-refractive-index wave-guide material is coated directly onto thebuffer and is selectively exposed to UV lightthrough a photomask. The unexposed mate-rial is then removed through a simple wet-develop process.

As mentioned above, the waveguides andmicrolens components formed in this singlephotopatterning step completely define theDWT touch-screen performance. The result-ing photopatterned waveguide core featuresenable the guiding of light in the same manneras the familiar optical fiber through total inter-nal reflection of light at the interface betweenthe core and cladding materials.

In a final step, another low-refractive-indexcladding material is overcoated, which planarizes and encapsulates the core features.For DWT, this third layer is also aligned andphotopatterned with large-area features thatopen air gaps over core-patterned microlenssurfaces. In a final processing step, individualwaveguide die are singulated from the sub-strate using a dicing process, at which pointthey are ready for assembly into DWT touch-screen modules. By design, the waveguidemanufacturing process itself is similar to aphotoresist photolithography line.

Polymer WaveguidesPolymer waveguides have been an active areaof research for many years. The pioneeringwork of a group at Allied Signal laid the

Information Display 12/09 13

Fig. 2: An optical waveguide approach totouch uses just two LEDs (bottom and left) forIR light. (Drawing components are not toscale.)

Fig. 3: A polycarbonate substrate (lower right) is the foundation for the waveguide manufac-turing process, which ends with individual waveguide strips (upper right). IPG stands forRPO’s Inorganic Polymer Glass.

WaveguidesParabolicReflectors

Waveguides

Coat core IPGlayer

Pattern transferby UV exposure

Wet development

Coat cladding IPGlayer

and UV exposeSingulate individual

waveguide strips

layer & UVCoat buffer IPG

expose

Polycarbonatesubstrate

LED

LED

ImageSensor

ground rules for the design of polymer materi-als for optical applications, with a strongfocus on long-haul telecommunications.2 Inthat case, highly fluorinated acrylate-basedmaterials were used with silicon-wafer sub-strates and standard semiconductor processingtools to manufacture high-performancewaveguide components. In addition, the largethermo-optic coefficient of these materialsallowed highly efficient, electrically tunabledevices such as space switches and variableoptical attenuators to be demonstrated.Today, polysiloxane-based material systemsare also recognized as well-suited to opticalwaveguide and thermo-optic tuning applica-tions, due to their low optical loss and highenvironmental stability.3

Designed and manufactured by RPO, Inor-ganic Polymer Glass (IPG) coat materials arepolysiloxane-based systems, originally devel-oped with long-haul telecommunicationsapplications in mind. These materials exhibit,among other desirable features, low opticalloss at telecommunications wavelengths, anaccurately tunable refractive index over awide range, matched thermo-optic coeffi-cients, and low glass-transition temperature(Tg). Of these, a low Tg outside the operatingtemperature range of the waveguide compo-nent is vitally important to negate the buildupof internal stresses and possible micro-cracking within the materials during any thermal cycling in product use. Indeed, IPGmaterials are designed to have no materialphase transitions within the DWT operatingand storage temperature ranges. The IPGmaterials are therefore always in a rubberystate, also a very important feature for wave-guides manufactured on flexible substrates.

IPG materials are manufactured as anoligomeric mixture such that the materials canbe coated as films from a viscous, solvent-freeresin. By controlling the IPG synthesis pro-cess and molecular design, the molecular-weight distribution of the resin can be tuned tocombine effective coating properties and highenvironmental stability with low-volatile out-gassing. The solvent-free nature of the coatfluids is a key feature for use with plastic flex-ible substrates – swelling of the substrate dueto the presence of a carrier solvent, even forshort periods of time, is never encountered.Indeed, since there is no solvent to bake out, asoft bake step is completely unnecessary. Inaddition, since there is no solvent evaporationduring coating, very high-quality optical films

with low surface roughness can be easilyformed through techniques such as extrusioncoating, spin coating, or extrude-and-spin. Onthe flipside of these positive features, IPGmaterials remain a viscous liquid even in filmform until exposed to UV light, which pre-sents challenges from a substrate-handlingperspective, particularly for fully automatedproduction lines.

Flexible Substrate RequirementsThe application of optical waveguides andphotonics to consumer-electronics products,such as DWT, requires careful considerationof manufacturing costs, certainly compared to the typical telecommunications productsthat polymer waveguides have historically targeted. DWT waveguide chips are generallylarge, rectangular die, a couple of millimeterswide and many tens of millimeters long,dependent on LCD screen size. The packingdensity of DWT die onto round wafers,whether they are silicon or a cheaper alterna-tive, is severely limited both by geometry andoverall substrate size. The use of the rectan-gular, large-area substrate sizes commonlyfound in the LCD industry are far better suitedto DWT waveguide production, as a signifi-cantly higher volume throughput is achievablefor the same processing time as a wafer-basedprocess. The current RPO waveguide produc-tion process uses 400 × 500-mm-sized sub-strates (Gen 2.5).

The choice of substrate material is unusualin the flexible substrate world in that the sub-strate itself has no obvious functionality otherthan as a carrier, and, in fact, DWT does notuse the flexible nature of the substrate at all.The sole reason that RPO chose flexible

plastic substrates was to keep product costslow. In addition, the substrate and wave-guides only reside in the bezel of the LCD,with no requirement for substrate optical clarity or quality.

The obvious requirements of DWT wave-guide substrates are that they are flat enoughto enable high-resolution photolithographicprinting, have sufficient surface quality toallow a planarizing layer to be coated ontoone surface, and, most importantly, are inexpensive. The very-high-performanceflexible substrates, such as PEN, developedspecifically for flexible-display applications,are unnecessary for DWT; low-cost standardsubstrate film materials such as PET, poly-imide (PI), or polycarbonate (PC) are sufficient.

On closer inspection, however, there areadditional features that need to be added to thesubstrate to allow successful production pro-cessing and also provide high-performanceDWT operation. First, the photolithographicprocessing of IPG waveguides for high-volume production requires high-intensity UVlight of a specific wavelength spectrum, toachieve high throughput but also to counteractdetrimental oxygen-inhibition processeswithin the IPG photochemistry. RPO hasworked directly with a photolithography-toolmanufacturer to develop a customized projec-tion scanning tool for DWT waveguide com-ponent manufacture. These production sys-tems operate at high UV intensities, and underthese conditions, the photosensitivity of thesubstrate as well as that of the IPG materialsmust be taken into account. By correct speci-fication of the substrate material properties, itis possible to control the substrate photo-sensitivity. Figure 4 shows the large improve-

14 Information Display 12/09

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Fig. 4: At left is shown photopatterning of IPG materials coated onto a substrate with correctly specified properties, and, at right, with a poor substrate choice.

ment in photolithographic resolution of IPGphotopatterned features that can be achievedwith a correctly specified substrate.

Secondly, the sunlight performance of theDWT system as a whole is dictated by theamount of stray light that can reach the cam-era. This light is non-directional and thereforeacts as a large background noise signal. Themain source of this noise is ambient light thatcan travel through the substrate material to thecamera rather than via the waveguide-definedpath. Again, correct specification of the flexible substrate material properties allowscontrol of stray light and can improve systemperformance markedly.

For DWT waveguides, however, the choiceof base-substrate material is ultimately drivenby the cutting process in which individualoptical chips are singulated from the Gen 2.5substrate, as shown earlier in Fig. 3. Unlikemicroelectronics components, in which sur-face contacts and pads located on the top sur-face of the die are usual, the most efficient useof photonic chips generally requires light tobe injected or captured from the edges of thedie. For polymer waveguides to be viable forconsumer-electronics products, the singulationprocess must therefore provide an optical-quality chip endface in a single step – additionalpost-processes such as polishing are not viable.

Through judicious choice of substrate mate-rial, RPO has developed a single-step dicingprocess using high-speed diamond-impreg-nated blades similar to those used for dicingsilicon wafers. When employed with a poly-carbonate substrate material, very high-qualityoptical endfaces are achievable on wave-guides with acceptably fast throughputs forvolume production. This is in contrast toPET-type materials, in which the semi-crystalline nature of the substrate leads to high internal stress build-up and shattering/delamination of the waveguide layers duringcutting. While PC is not as robust an indus-trial plastic as either PET or PEN, for exam-ple, the low temperatures involved in DWTwaveguide processing, and the solvent-freenature of the IPG coat fluids, mean that PC is sufficiently well specified for the DWTapplication.

Automated Flexible SubstrateHandling for DWTWhile the manufacture of waveguides on flex-ible substrates is simple to achieve in a pilot-line process, the scale-up to fully automated

production is dictated by cost requirements. Specifically, product cost structures dictate that it is not possible to handle the flexible sub-strates by the more usual approach of laminat-ing to a rigid carrier such as FPD motherglass,5

or by using rigid perimeter frames – rather, the flexible substrates need to be robotically han-dled as-is. Combined with the wet nature ofsome of the in-process IPG-coated substrates,this places restrictions on the type of robotichandling schemes that can be employed, andalso on the design of the process-tool vacuumchucks that hold the substrate in place duringprocessing. Of importance here is the choiceof substrate thickness – the thicker the sub-strate, the less it will flex. However, it shouldbe borne in mind that DWT waveguidesoccupy a space inside the LCD bezel, andwith current LCD trends pushing to narrowerand thinner bezels, keeping substrate volumeto a minimum is important. Balancing thesetwo counteracting effects leads to an optimumpolycarbonate substrate thickness that is read-ily available in roll form.

Development projects between RPO andindividual tool suppliers have resulted in acohesive set of solutions for the handling of

RPO flexible substrates. For all tools, the design of any substrate vacuum hold-down systemrequires that vacuum holes to the rear of theflexible substrate do not cause an appreciabledistortion. This is particularly important forlithography tools where distortion of the sub-strate out of the focal plane can result in areduction in resolution or changes in criticaldimension of the waveguides. In addition,any through-holes in the substrate chuck thatallow access for lift pins or pads must be care-fully designed to avoid any resonant oscilla-tion of the flexible substrate during processing.

Based on detailed finite-element analysissimulations, robot end effectors, cassettes, andspin-coat/develop chucks with integrated liftpads have been successfully designed, manu-factured, and tested under continuous produc-tion conditions. Figure 5 shows a spin chuckwith integrated lift pads in the raised position,allowing access for a robot end effector.

Extrusion coating is well established as thecoating method of choice for large-area LCDscreen manufacturing and is a key part ofRPO’s manufacturing strategy to minimizeIPG material consumption. However, it pre-sents further challenges for IPG coating of

Information Display 12/09 15

Fig. 5: Above is an example of a flexible-substrate transfer paddle and spin chuck with inte-grated lift pads

flexible substrates. During the IPG extrusioncoating process, there is a measurable forcefrom the fluid exiting the extrusion die downonto the flexible substrate; indeed, the prox-imity of the substrate itself causes a back pressure into the die cavity.

Additionally, the polysiloxane nature of theIPG materials necessitates a high-precisionextrusion-coating process with accuratelydesigned wetting surfaces and gaps. The flex-ible substrate must therefore be held flat withrespect to the extrusion die with tight toler-ances. These tight tolerances, and the potential of the fluid force to distort the flexible sub-strate over lift pad or vacuum holes, negates the ability to use the integrated handling solutionsused for the spin tools. As a solution to thisproblem, a flexible substrate load station hasbeen designed, using air to levitate the sub-strate and float it onto an interdigitated stationwhere the end effector can raise the substrateand move it to the next process module. Animage of the load station is shown in Fig. 6.

SummaryThe high-volume manufacture of polymerwaveguides on flexible substrates for DWTtouch-screen applications is already under

way. In particular, the choice of flexible sub-strate material allows for integration into acomplete high-volume production solution foroptical waveguides and planar photonic com-ponents for consumer electronics. Althoughpilot-production development work has beenbased on Gen 2.5 substrate sizes, all the tech-niques developed scale readily to larger sub-strate sizes and therefore greatly increasedvolumes. With minor detail modification tosome of the process steps, this manufacturingprocess should be eminently suitable for scal-ing to roll-to-roll production.

References1I. Maxwell, “An overview of optical-touchtechnologies,” Information Display 12, 2–6(2007).2L. Eldada, L. W. Shacklette, R. A. Norwood,and J. T. Yardley, “Next-generation polymericphotonic devices,” SPIE CR68, 207 (1997).3T. Watanabe, N. Ooba, S. Hayashida, T. Kurihara, and S. Imamura, “Polymericoptical waveguide circuits formed using sili-cone resin,” IEEE Journal of Lightwave Tech-nology 16, No. 6, 1049–1055 (1998).4R. Charters, G. Atkins, D. Kukulj, C. Zha, G. Gordon, B. Cornish, B. Luther-Davies,

R. Friedrich, R. Jarvis, W. Li, and M. Krowlikowska, “Inorganic polymer glasses(IPG) for integrated optics,” Australian Con-ference on Optical Fiber Technology, 13–14(2002).5J. Mills, “High volume, high throughputmanufacturing of flexible active matrix dis-play modules,” USDC Flexible Electronicsand Displays Conference, paper 9.1 (2008).�

16 Information Display 12/09

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Fig. 6: This extrusion-coater flexible-substrate load station uses air to levitate the substrate.

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Speakers:Ken Werner, The LCD MarketplaceDave Soberanis, Thin Film CoatingsTodd Winter, Touch Screen Technology

Bill Kennedy, LED BacklightsLarry Tannas, LCD Resizing

Frank Evagues, LCD PackagingTBA, Smart LCD Controllers

DESPITE THE FACT that TFT-LCDsuse less power than similarly sized CRTs, theconversion to LCD TV has led consumers tochoose larger and brighter TVs and is drivingfaster unit growth, which means the totalpower consumed by TVs is increasing.Worldwide, LCD TVs consumed an estimated83 TWh of electricity in 2008, equivalent tothe output of 11 nuclear power plants. Thatmuch electricity produced from coal-firedpower plants would result in the creation of 66 million tons of CO2. Much closer to homefor electronics manufacturers, regulatoryauthorities in Asia, Europe, and the UnitedStates are writing and implementing power-consumption regulations for flat-panel TV sets.

At the same time, reducing costs is anessential goal for panel manufacturers to keepup with relentless price declines while tryingto maintain positive margins. For larger TVs,average year-to-year cost changes during2009–2015 are expected to range from –23%to –8%.

Backlight EmphasisIn conventional LCDs, most of the light gen-erated by the backlight is lost due to polarizerabsorption, shading by the TFT-array aperture,color-filter absorption, as well as other factors,so that only about 5% of the light emittedreaches the front of the screen. Thus, evensmall improvements in transmission canenable significant backlight lamp reduction.For example, a 400-nit panel with a 5% trans-mission rate requires an 8000-nit luminance atthe backlight; if transmission is increased to10%, the same amount of brightness can beachieved with a 4000-nit backlight.

The backlight unit is the most expensivecomponent of a display and accounts for 90%of the power consumption in large LCDs.This is the case regardless of whether thebacklight uses cold-cathode fluorescent lamps(CCFLs) or light-emitting-diode (LED)lamps. Because LEDs are still substantiallymore expensive than CCFLs, increasing trans-mission is critical to enabling wider LED adoption for LCD-TV applications and istherefore currently a key theme in LCD manu-facturing. Given the transmission’s potentialto reduce both cost and power consumption, alarge variety of manufacturing technologiesthat target transmission increases are beingdeveloped and adopted for mass production.

Methods such as low-resistance bus lines, Cst-less pixels, SHA, OA, PSA, thinner blackmatrix, and color-filter-on-array (all explainedlater in this article) are being implemented inthe array, cell, and color-filter processes toincrease efficiency.

Array ProcessesStorage-Capacitor-Less Pixel Design: InTFT-LCDs, storage capacitors (Cst) are typi-cally fabricated at each pixel to hold the volt-age between writing data signals to the pixel.Without a Cst, the voltage can leak and changethe state of the liquid crystal (LC). To preventthis, conventional pixel designs use an extragate metal or wider gate line to increasecapacitance. The trade-off is that the extraarea for the gate line blocks illumination fromthe backlight. Samsung developed what itcalls “Cst-less” pixels, which eliminate thestorage capacitor and increase aperture ratio.Samsung has not publicly disclosed all thedetails on how it was able to achieve this, butit is likely that it was though a combination ofimproved LC and TFT performance. Thecompany claims that transmission can beincreased up to 10% with new pixel design.

Low-Resistance Bus-Line Materials:Adoption of low-resistance gate and data linesenables a reduction in the RC delay, which

Charles Annis is Vice President, Manufactur-ing Research, and Paul Semenza is SeniorVice President, Analyst Services, with DisplaySearch. They can be reached atcharles.annis@displaysearch.com andpaul.semenza@npd.com.

18 Information Display 12/090362-0972/12/2009-018$1.00 + .00 © SID 2009

Better Transmission: TFT-LCD ManufacturingAdvances Reduce Cost and Energy Consumption

Much attention has focused on advances in TFT-LCD panel technology such as LED backlights,120/240-Hz frame rates, wide viewing angle, and other technologies leading to performanceimprovements. But behind the scenes, TFT-LCD manufacturing continues to evolve, leadingto increased manufacturing productivity, lower costs, and improved power efficiency. Recentdevelopments include color filters, liquid-crystal alignment, and TFT design.

by Charles Annis and Paul Semenza

display marketplace

improves performance and can potentiallyeliminate requirements for dual-scan driving.In addition, due to lower resistivity, the widthof the bus line can be reduced, whichincreases the aperture ratio without sacrificingperformance. Because copper has a very lowresistance, it is the material of choice. LGDisplay is already mass producing the major-ity of its larger panels using copper, and overthe next 5 years copper and copper-alloy applications are expected to grow substantially.

Super High Aperture (SHA) with OrganicPassivation: SHA pixel designs use a thickorganic passivation layer to move the indiumtin oxide (ITO) pixel electrode further awayfrom the data line. Compared to conventionalpixels, in which the ITO pixel electrode is separated only by a thin passivation layer, TFT capacitance is reduced. This allows the ITO pixel electrode to be extended over the bus lines, increasing the aperture ratio at each pixel. The technology has been used in mass pro-duction for a while, but is tricky to implement.

Cell ProcessesThe performance of LCDs is strongly affectedby the orientation of the LC molecules, andLC molecules can be aligned in a variety ofways, depending on the LC mode. The LCmolecules should be aligned orderly in theOFF-state and with an appropriate orientationor pre-tilt angle to facilitate switching to theON-state when the drive voltage is applied tothe pixel. Conventional LC alignment isachieved through the use of a thin polyimidelayer (about 100 nm) on both the array andcolor-filter (CF) side of the cells. In thetwisted-nematic (TN) and in-plane switching(IPS) modes, rubbing is used to create a preferred alignment direction during the cellprocess. In the PVA mode, patterning of theCF ITO common electrode is used to align thearray pixel ITO electrodes in order to createfringe fields. In the multi-domain viewing-angle (MVA) mode, a protrusion is patternedon the CF to physically align the molecules,and a slit is created on the TFT side of theITO pixel electrode.

Each approach has advantages and dis-advantages. The viewing angle of the TNmode is limited. The TN and IPS modes offerhigher transmittance, but rubbing is problem-atic because it generates particles and staticelectricity and is not easily scaled to largersubstrates. The PVA and MVA modes are

relatively fast and have good viewing-angleperformance, but transmittance is lower, theLC material is more expensive, and the num-ber of CF manufacturing steps must beincreased.

For these reasons, developing new align-ment technologies that enable higher transmit-tance, generate faster response times, avoidrubbing, improve contrast, allow a wide view-ing angle, and offer more general productivitythan conventional approaches have been long-standing goals for LCD makers. PSA and OAare two methods that achieve proper liquid-crystal pre-tilt angles without rubbing, protru-sions, or patterned common electrodes.

Polymer-Sustained Alignment (PSA):Typically, MVA panels use a protrusion to aidalignment of the LC; however, protrusionsrequire an extra mask step in the CF process,which drives up cost and increases manufac-turing time. Furthermore, the inactive area ofthe protrusion restricts transmittance of thepanel and creates some light leakage thatreduces the dark level and contrast ratio.

In polymer-sustained alignment (PSA) –also known as polymer-stabilized alignmentor phase-separated alignment) – a polymer-alignment layer is formed over a convention-ally coated polyimide by mixing a UV-curablemonomer into the LC. The monomer is thenactivated by UV radiation while applying anAC voltage. The monomer reacts with thepolymer layer to form a surface that fixes thepre-tilt angle of the LC. By removing the pro-trusion and achieving excellent LC pre-tiltalignment, the aperture ratio is increased, lightleakage reduced, and LC switching perfor-mance is improved. Because this eliminates a

protrusion from the CF side of the display, thecontrast ratio is increased and the panelbrightness can be improved by more than20%. At the same time, costs are reducedbecause the protrusion mask step can be elim-inated from the CF process and backlightlamps can be reduced.

PSA technology was originally developedby Fujitsu and is being used in mass produc-tion by AU Optronics Corp. (AUO), whichhas reported the development of a “protru-sion-less” MVA-LCD that increases transmit-tance and reduces cost and process time. Thecompany is calling the technology AdvancedMVA (AMVA). The key PSA-relatedAMVA improvements are achieved by adopt-ing a new “fishbone”-shaped pixel electrodein the array process and polymer-sustainedalignment in the cell process to eliminate theprotrusions of the conventional MVA mode(Fig. 1). When a drive voltage is applied tothe fishbone electrode, LC molecules alignalong the direction of each domain.

In addition to the fishbone electrode, theother key PSA process modification is to adda monomer to the LC, which is then polymer-ized by UV curing in the cell process. Thisprovides LC molecules with the proper pre-tiltangle for smooth and fast switching. The pre-tilt angle is fixed by simultaneously applyinga voltage and UV exposure (Fig. 2). The pre-tilt angle of the LC can be controlled by thecuring recipe by varying the applied voltageand UV dose.

The performance of AMVA is stronglyaffected by the material science of the poly-mer-alignment layer, monomer mixture, andLC. AUO has developed unique and propri-etary materials to enable this new technology.

Information Display 12/09 19

Fig. 1: Above is a top view of an AMVA3 pixel electrode; below is the cross section. Source:AUO, SID 2009.

(a) (b)

Optical Alignment: Optical alignment(OA) is the process of the interaction of lightwith a material that generates light-inducedanisotropic properties. The anisotropy isdetermined by the intrinsic characteristics ofthe material and the direction of theanisotropy is related to the incident angle ofthe polarized light. For the material

researched here, photoalignment involvesphoton absorption and interaction on a molec-ular scale, and the effects are observed interms of the parameters of LC tilt angle, alignment direction, and azimuthal anchoringenergy.

In optical alignment, UV exposure througha mask made of a special polyimide film

creates an anisotropic feature that generatesthe pre-tilt angle. There are a variety of mate-rials that have been researched that includeazobenzene dyes or azo-dyes, poly (vinyl cinnamate), coumarin dye, poly-siloxanebased polymers, and polyimides with addi-tives such as cyclobutane. The basic principleinvolves the absorption of photons in the200–365-nm UV range by the material thatcauses alignment of the polymer chains form-ing the layer through several processes,including isomerization, dimerization, anddecomposition.

Some manufacturers have pursued a photo-decomposition approach. The advantage ofthis approach is that polyimides similar tothose used in conventional processing can beadopted. UV light of sufficient energy breaksthe organic bonds within the polyimidemolecules, which create an anisotropy in theLC molecule alignment or a pre-tilt angle ofabout 2° (Fig. 3). The actual mechanism andphotochemistry is apparently not well under-stood, but some sources have suggested it is atype of photo-oxidation. Historically, opticalalignment approaches have been susceptibleto long-term stability problems where the pre-tilt angle degrades over time. Overcomingthis problem appears to be more closelyrelated to the material composition of thepolyimide alignment film rather than the process itself.

The benefits of OA are quite similar tothose for PSA. Additionally, OA is assumed

20 Information Display 12/09

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Polyimide

OO

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Dangling bonds enable orderly LCmolecule pre-tilt angles @ about 2°

Fig. 3: The OA process (left to right) results in LC molecules with a pre-tilt angle of about 2º. Source: Sharp Corp., adapted by DisplaySearch.

Fig. 2: Steps 1–4 show the PSA polymerization process. Source: AUO, SID 2009.

to be highly productive and flexible, offeringa wide process margin. The modifications tomanufacturing are relatively simple. A photo-sensitive alignment film replaces the moreconventional polyimides; the film is patternedon both the array and CF substrates in the cellprocess. Multi-domain structures can beachieved by patterning and the maskapproach. The material is cured, then the sub-strates are conventionally aligned, scribed,and sent to module processing.Sharp began mass-producing 32-in. eco-

model TVs having OA in early 2009. InOctober 2009, the company announced that itwill apply this technology to panel productionat its plants in Sakai and Kameyama.1 Ref-ered to as UV2A (ultraviolet-induced multi-domain vertical alignment), the technologyuses a combination of proprietary materialsdeveloped by Sharp and its partners with UV-exposure equipment and processing technolo-gies. Sharp stated that its approach resultsin aperture ratios 20% larger than those ofconventional panels.

Color FilterBlack-Matrix (BM) Width Reduction: In theCF process, panel manufacturers are reducingthe width of the black matrix (BM). (Somewidth of black matrix is needed between thesubpixels to block the light that leaks acrossfrom one subpixel its neighbor.) Similar to areduction in the width of gate and data lines,a narrower BM translates into to a wideraperture ratio. Interestingly, the focus onimproved transmission through thinner BMrequirements has challenged other CF cost-saving technologies, such as ink-jet printingand BM ablation. Both of these have thepotential to lower the total costs by reducinglithography-related-equipment and maskcosts, but neither offer the same preciseresolution and overlay performance asconventional photolithography that is requiredfor very thin BM patterning.Color Filter on Array (COA): COA is

another CF-related manufacturing technologythat moves RGB pixels from the commonelectrode glass to the array glass. There are

multiple variations of this technology, but allincrease transmission and improve contrast bywidening the aperture ratio. However, movingcolor pixels to the array creates multiple pro-cess challenges – specifically, yield loss. Forthis reason, COA is not yet widely adopted.TMDisplay and Samsung are currently the twomain producers of COA-based LCDs.

Greener Operation Equals More Green forManufacturers: In order to continue prof-itable growth in an environment of continuouscost pressure and more-stringent environmen-tal controls, TFT-LCD makers must simulta-neously drive down manufacturing costs andreduce power consumption. The technologiesthat directly address these issues include thosethat aim to improve the historically low opticaltransmission of TFT-LCDs. Manufacturersthat can bring such improvements into massproduction will have a competitive advantage.

References1http://sharp-world.com/corporate/news/090916.html �

LOW-TEMPERATURE-POLYSILICON(LTPS) appeared on the manufacturing sceneabout 10 years ago with the promise ofenabling new generations of faster, higher-resolution slimmer LCDs. Since that time,LTPS has not exactly taken over from itscounterpart, amorphous-silicon (a-Si), but ithas developed a substantial position in theoverall LCD market. Here’s a look at howLTPS works, what it’s currently being usedfor, and how it fits into the general LCD land-scape, now and in the future.

The Promise of LTPSLTPS technology enables the manufacture ofactive-matrix LCDs (AMLCDs) that are fasterthan displays using a-Si. “Fast” refers to theaddressing speed: how quickly can a cell beaccessed and receive a charge, and then howquickly can the process be repeated with thenext cell? All this affects the frame rate, resolution and drive-complexity factors in apanel design. LTPS has many additionaladvantages: integration, smaller transistors,lower power consumption, and ruggedness.However, it is important to note that all thesebenefits are available on a sliding scale ofsorts: LTPS allows smaller pixels, or fasterlarge pixels, or lower power consumption, butnot necessarily all at the same time.

LTPS transistors can be fabricated byrecrystallizing amorphous silicon (a-Si) usinglaser annealing. With LTPS, you can achieveeither a much greater current density com-

pared to a-Si for the same size transistors, orhave much smaller transistors for the samecurrent density. These features enable designsin which polysilicon drivers are integrated onthe glass, unlike a-Si, which generally cannotachieve this integration. This added capabil-ity of LTPS arises from the fact that its elec-tron mobility can be as much as 100 timeshigher than that of a-Si, and hole mobility canbe much higher than a-Si as well. Polysiliconconsists of many small crystallites of silicon,with the crystal structure enabling high mobil-ity. In contrast, the silicon lattice in a-Si hasno crystal structure, so mobility is reduced.

The following discussion of polysilicon isfrom the article “Flexible Transistor Arrays”

by Peter Smith, David Allee, Curt Moyer, andDouglas Loy, in the June 2005 issue of Infor-mation Display: “Another advantage [ofpolysilicon] is that CMOS circuits can bemade in poly-Si because it is possible to fabri-cate both N-and P-type TFTs. Since CMOS is the dominant technology in the integrated-circuit (IC) industry, there is substantial expe-rience in designing sophisticated integratedcircuitry in CMOS. In stark contrast, only N-type transistors are possible in a-Si, makingcircuit design more complicated. N-type-onlycircuits have not been widely built in the ICindustry since the 1970s, although N-typeactive-matrix backplanes are the mainstay ofthe display industry.” (Readers are strongly

Overview: Low-Temperature Polysilicon

Low-temperature-polysilicon (LTPS) technology is an important part of the active-matrix-LCD manufacturing environment. Will its role expand or has it found its niche?

by Jenny Donelan

Jenny Donelan is the Managing Editor ofInformation Display Magazine.

22 Information Display 12/090362-0972/12/2009-022$1.00 + .00 © SID 2009

enabling technology

Fig. 1: These LTPS TFT-LCDs for notebook PCs from Toshiba Mobile Display range in sizefrom 8.9-in. WXGA to 13.3-in. WXGA. Image courtesy TMD.

encouraged to review this and many other ref-erences for a complete technical summary ofpoly-Si technology).

Integration is key in that LTPS allowsdriver circuitry to be made part of the display.Because of its lower electron mobility, a-Sirequires more extensive external driver circuitry that, in turn, must be made from con-ventional silicon. These driver types requireexternal connections, although sometimes thedriver chips can be put on glass without a separate PC board. Consequently, discretelogic chips must be mounted on printed circuitboards (PCBs) around the edge of the panel, adesign that contributes to the overall bulk andexpense of the display. The use of LTPSenables a smaller and more elegant panel lay-out (note the narrow rims on the displaysshown in Fig. 1.)

Smaller transistors are possible for eachsubpixel due also to LTPS technology’shigher electron mobility. The higher mobilityreduces the size of the transistor for a givenaddressing time, and this feature can be usedto increase the aperture ratio of the subpixel;i.e., the ratio of transparent area to total areain each subpixel. This allows higher light-transmission efficiency that, in turn, enablesbrighter and higher-resolution displays (withlower power consumption).

The option of making a device rugged is oneother distinct advantage of LTPS. Because thedrive circuit can be integrated directly onto theglass surface, the number of potentially break-able connectors is decreased and the resultingLCD is vibration- and impact-resistant.

It is also important to note that when used asa backplane, LTPS is highly compatible withAMOLED displays. As Jennifer Colegrove,Director of Display Technology at Display-Search, puts it: “OLEDs are a current-driventype of display, and they need a lot of current.”This is a requirement that is well-matched bythe high electron mobility of LTPS.

High-Temperature and Low-Temperature PolysiliconWhen display designers first began workingwith polycrystalline silicon, the standardmethodology was to deposit a silicon layer onquartz, then heat it (using temperatures over1000°C). The silcon would melt, and as itcooled, the crystals would reform in a uniformmode, creating a quartz semiconductor withmuch higher performance than a-Si. One ofthe drawbacks to this method, however, is that

it is only possible to make a quartz substrateto a size of about 8 in., and it cannot be put onglass. High-temperature polysilicon (HTPS)has its place, however. Some manufacturers,such as Epson, use it for high-quality displaysin projectors.

In the late 1990s, manufacturers beganexperimenting with using lasers in low-temperature annealing processes to replace thehigh-temperature annealing (the melting process described above). This allowed forthe creation of larger displays that still had thebasic electron mobility of the high-tempera-ture process. And the low-temperature pro-cess had the added benefit of being usablewith either glass or plastic. (While glass fordisplays can withstand about 500°C, plasticsubstrates are limited to about 200°C or less.)

LTPS products, most of them portabledevices, began to be produced around 1998.In 1999, for example, Toshiba announced theworld’s first 4-in. VGA-resolution LTPSLCD. The “big three” manufacturers in LTPS today, according to Vinita Jakhanwal,Principal Analyst, Small/Medium Displays,with market-research-firm iSuppli Corp., areSharp, Toshiba Mobile Display (TMD), andTPO Displays.

The Current State of LTPSJakhanwal notes that according to iSuppli,LTPS technology represents about 32% of themarket share for active-matrix displayssmaller than 10 in. (see Fig. 2).

Although a variety of large-screen LTPSTFTs have been produced, the technology

Information Display 12/09 23

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Fig. 3: The LTPS-LCD shipment market by application shows overall units increasing through2013, and mobile handsets retaining the lion’s share. Source: iSuppli Corp.

Fig. 2: Through 2013, LTPS, along with a-Si, is predicted to gain in terms of overall LCD volumes shipped. Source: iSuppli Corp.

seems to have found its main niche in portable active-matrix devices. These includenotebooks, but also mobile phones, smart-phones, and cameras (see Fig. 3). “In terms of overall volume for 2009,” says Jakhanwal,“mobile phones represent 65%.” The othermain applications, she continues, are digitalcameras (21%) and portable media players(11%).

The mobile-phone application is a logicalone, as consumers are requiring devices todisplay an ever-wider range of content. “Themobile market is really being challenged toprovide higher-resolution displays,” saysSteve Vrablik, Business Development Director, LCDs, with Toshiba America Electronic Components, Inc. As mentionedearlier, LTPS is very suitable for creatinghigh-resolution displays. Vrablik notes thatin 2008 TMD created 3.0-in.-diagonalWVGA displays that were used in manymobile phones in the Japanese market, andthat this resolution trend is now catching onelsewhere. “This is very, very denseimagery.” Not all LTPS displays are diminu-tive, however. In 2004, TMD came out witha 32-in. panel and currently focuses its larger-size production for notebook display applica-tions in sizes up to 15.4 in.

Drawbacks and ChallengesAlthough LTPS is highly useful technology, itdoes not appear poised to take over from a-SiTFTs. One reason for this is that “It is moreexpensive,” says Colegrove, noting that theannealing process is expensive because thelasers themselves are costly, and the processitself takes extra time. And, as in all things,manufacturing, overhauling existing produc-tion lines, or creating entirely new fab lines toaccommodate a different technology is nosmall matter. The question of scale comesinto play – the more a company can produce,the more it stands to save from making suchchanges, but it has to have conviction in thelong-term viability of the technology.

Toshiba’s Vrablik says that TMD has beenable to offset expenses incurred by LTPSthrough garnering savings in component costs.TMD built its AFPD, at the time the world’slargest production plant for LTPS TFT-LCDsin Singapore in 2002. And in 2006, itannounced plans to invest approximately $270million in a new production line to produceLTPS LCD panels in its Ishikawa Works inJapan.

What’s Ahead for LTPSAs mentioned earlier, another prominent andpromising application for LTPS is as a back-plane for AMOLED products. “Currently,about 100% of AMOLED products useLTPS,” says Colegrove. Samsung is a majorplayer in this area, notes Jakhanwal. In 2007,Samsung SDI introduced a 31-in. OLEDpanel with an LTPS backplane. In 2008, itshowed a 40-in. model at FPD International,and in 2009 demonstrated a 21-in. OLED TVwith a 1,000,000:1 contrast ratio.

Where will LTPS be in a few years?Jakhanwal points to its current market share:“LTPS is doing really well,” she says.“There’s been tremendous growth.” WillLTPS eventually wrest the bulk of marketshare from a-Si? Probably not, according toColegrove: “We would forecast that it willgrow, but it will be limited. LTPS is onlyabout 3% vs. a-Si of the total TFT substratemarket now and over the next several years.”For a technology that might take on a-Si atsome point in the future, “Besides LTPS, Iwould look for some other technology, per-haps oxide-TFT,” she says. �

24 Information Display 12/09

enabling technology

Also this year, LG invested heavily (overUS$500 million) in low-temperature poly-silicon (LTPS) TFT-LCD production, with thegoal of having 20K-sheets/month glass startcapacity by 2010. That’s a lot of cash to tieup during a recession. Many smaller compa-nies invested in LED-backlight retro-fit sys-tems, and white-LED manufacturers achievedremarkable gains in light efficiency in thesame time frame. New investments were alsoseen in handheld touch screens, overlays, andnumerous portable display systems. Large-area LED display technology saw several newinnovations, including distributed tiles or“meshes,” as they are called, that can be usedas distributed building blocks of addressablespace. Not a new concept, but a very newembodiment. Finally, this was certainly ayear in which OLED technology proved itwill be worth waiting for, with heavy spend-ing on commercialization at Samsung and itsR&D partners combined with impressivetechnical announcements and demonstrationsat all the major shows.

Countless other examples exist, many ofthem featured throughout the year in this magazine – proof enough that there are coura-geous companies are out there. We believethey will be rewarded.

Even more encouraging is the fact thatmany companies have recently made signifi-cant manufacturing investments, includingbuilding out new fab lines for LCDs, startingthe world’s first large-volume lines for OLEDdisplays, making large-scale innovations inLTPS and flexible substrates, and achievingdramatic gains in capacity for eletrophoreticdisplays. Manufacturing is, of course, theobvious end game for almost all of the devel-opment work that we chronicle. A technologythat cannot be manufactured in high volumefor a reasonable cost rarely gets past theresearch phase at most companies. Some-times new developments require new manu-facturing methods to be realized, and it is frequently at this last stage where the largestpart of the investment gets consumed. In thiscurrent economic climate, the fact that theseinvestments are being made at all is a symbolof real courage and leadership.

The final thing I want to talk about thismonth is mentoring. The late ProfessorRandy Pausch talked and wrote aboutenabling dreams; his own and those of his students. It’s not enough for each of us to“do;” we also need to be willing to impart our

experiences on the next generation. By teach-ing and mentoring the next generation of engi-neers. We are enabling their dreams as wellas giving them the tools to build the dreams ofcountless more people in other disciplines.We can’t know in advance how each littlepiece of technology we touch will fit into thegiant web of the future, but it is awesome tothink that the things we do with displays cancreate unbelievable leverage for many kindsof growth in the future. From simple televi-sions came the tools for a whole new type ofsurgical discipline, as well as the windows fordeep-space exploration, and other productsthat went on to spur the amazing economicdevelopments of whole countries. All of thesediscoveries came about through the minds ofstudents who were mentored until theybecame the mentors. Each generation growson the knowledge of the previous and just afew minutes of your time could lead to aninspiration in someone else that becomes thenext great achievement.

So, for the next few weeks, it’s OK to have alittle bit of “awe” in your work attitude – look at things less analytically and more emotionally.Share that energy and awe with those aroundyou. Teach as you were taught and enable thedreams of as many people as you can!

It’s a pleasure to introduce this month’sissue focused on manufacturing technologyand guest edited by our colleague, industryexpert Greg Gibson. Greg has brought us twoFrontline Technology features that highlightinnovative manufacturing developmentsinvolving flexible substrates and I suggest youread his guest editorial first to appreciate thebackground for both articles and how theyrepresent significant achievements in the flex-ible substrate space.

In our monthly Display Marketplace fea-ture, Charles Annis and Paul Semenza fromDisplaySearch provide us with a very compre-hensive survey of the various technologiesbeing employed by LCD manufacturers toimprove light transmission, reduce power con-sumption, and improve manufacturing yields.Taken together, these various techniques, allat some level of commercial implementationtoday, are driving the next generation of high-efficiency LCD TVs.

This month we also have another install-ment in our continuing coverage of “green”technology examining the complicated issuessurrounding recycling of electronic devicessuch as TVs and cell phones. There are

numerous challenges to both implementingthe many growing regulations as well aseffectively enforcing them and it has leftmany manufacturers struggling to find theright balance between commercial interest,environmental responsibility, and limitation ofliability.

From the Enabling Technology file comesanother homework assignment we gave toJenny Donelan, this time to report on the stateof the art for low-temperature-polysilicontechnology. As I mentioned earlier, LG hasinvested heavily in manufacturing capacity forLTPS and is betting on its unique characteris-tics to enable advanced display designs formobile devices. In the mobile-display marketplace (screens 10-in. and less), about32% are made with LTPS TFTs rather than a-Si. About 65% of all LTPS applications aremobile phones. While this is not a technologypoised to skyrocket, because of the expenseand difficulty of converting existing produc-tion lines, it has its space in enabling small-sized high-resolution LCDs as well as reduc-ing power consumption and footprint.

We also have our regular departments thismonth, including a message from SID Presi-dent Paul Drzaic, and some SID news on arecent honor bestowed on Dr David Fyfe andProfessor Sir Richard Friend. I hope you enjoythis issue as much as we did assembling it. �

25 Information Display 12/09

editorial

continued from page 2

Submit Your News ReleasesPlease send all press releases and new productannouncements to:

Jenny DonelanInformation Display Magazine411 Lafayette Street, Suite 201

New York, NY 10003Fax: 212.460.5460

e-mail: jdonelan@pcm411.com

Visit Information

Display On-Line

www.informationdisplay.org

NEW!NNEEWW!!

The following papers appear in the January 2010 (Vol. 18/1) issue of JSID. For a preview of the papers go to sid.org/jsid.html.

Optical performance of in-plane electrophoretic color e-paper (pages 1–7)Alwin R. M. Verschueren, et al., Philips Research, The Netherlands; Jack J. van Glabbeek, et al., MiPlaza, Philips

Research, The Netherlands

Analysis of angular dependence of 3-D technology using polarized eyeglasses (pages 8–12)HyungKi Hong, et al., LG Display Co., Ltd., Korea

Achromatic quarter-wave film using two chromatic wave plates and a twisted-nematic liquid-crystal cell (pages 13–16)Di Wu, et al., Sichuan University, China

Size matters: Improved color-difference estimation for small visual targets (pages 17–28)Robert C. Carter, Retired, USA; Louis D. Silverstein, VCD Sciences, Inc., USA

A novel low-power-consumption all-digital system-on-glass display with serial interface (pages 30–36)Kenji Harada, et al., Toshiba Mobile Display Co., Ltd., Japan

Investigation of the interaction between rubbing cloth and pattern structure on in-plane-switching liquid-crystal displays (pages 37–42)

Kyung-Mo Son, et al., LG Display Co., Ltd., Korea

Analysis and inhibition of progressive photomask contamination in long-term use for liquid-crystal panel production(pages 43–49)

Yoshinori Yanagita, et al., Asahi Kasei E-Materials Corp., Japan; Hiroyuki Shinchi, et al., Hoya Corp., Japan

Wearable 4-in. QVGA full-color-video flexible AMOLEDs for rugged applications (pages 50–56)Ruiqing Ma, et al., Universal Display Corp., USA; Juhn-Suk Yoo, et al., LG Display Co., Ltd., Korea; Keith Tognoni, et al.,

L3 Communications, USA

Evaluation of LCD local-dimming-backlight system (pages 57–65)Hanfeng Chen, et al., Samsung Electronics, Co., Ltd., Korea

Birefringent properties of cyclic block copolymers and low-retardation-film development (pages 66–75)Weijun Zhou, et al., The Dow Chemical Co., USA; Shin-Tson Wu, University of Central Florida, USA

Flexible inverted bottom-emitting organic light-emitting devices with a semi-transparent metal-assisted electron-injection layer (pages 76–80)

Chang-Yen Wu, et al., National Chiao Tung University, Taiwan, ROC

Color-tuning projection system for adaptive combination of high brightness and wide color gamut (pages 81–90)Makoto Maeda, et al., SANYO Electric Co., Ltd., Japan

High-efficiency red-phosphorescent organic light-emitting diode with the organic structure of 2-TNATA/Bebq2:SFC-411/SFC-137 (pages 92–96)

Ji Geun Jang and Won Ki Kim, Dankook University, Korea

Efficient white organic light-emitting diodes based on a balanced split of the exciton-recombination zone using a graded mixed layer as an electron-blocking layer (pages 97–102)

C. K. Kim, et al., Soonchunyang University, Korea

Displacement-current analysis of organic light-emitting diodes (pages 103–107)Soonseok Lee, Sun Moon University, Korea; Jeongwook Hur, Lumiette Korea, Korea; Sungkyoo Lim, Dankook University,

Korea

Instability dependent upon bias and temperature stress in amorphous-indium gallium zinc oxide(a-IGZO) thin-film transistors (pages 108–112)

Kwang-Il Choi, et al., Chungnam National University, Korea; Jae-Kyeong Jeong, Inha University,Korea

SOCIETY FOR

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SIDSOCIETY FOR INFORMATION DISPLAY

Journal of the

Information Display 12/09 27

suming to pull them apart. A promising startin this area, according to Allen, are Design forDisassembly initiatives, in which electronicsare designed from the beginning to be takenapart quickly and safely. Such design featuresmight include low or no-lead solder, modularelectronics boards, and pieces that snaptogether (or apart) without glue. In mostcases, such items would be disassembled byrecycling specialists rather than consumers,but the latter alternative is possible as well.

Consumer Caring is KeyThe recycling situation as it now stands is atough challenge not only for the environmentbut for consumers and manufacturers.Progress has to start somewhere, however,and there are bright spots. First, companiessuch as Staples have made some headway indeveloping recycling programs that actuallywin customer follow-through. The office-supply chain received the EnvironmentalLeadership Award from the National Recy-cling Coalition this year for initiatives recog-nized as an industry model. By making iteasy for customers to return any brand of inkcartridges at any store, and offering a financialincentive ($3 a cartridge) to do so, the chainhas made strides and reports that it is on trackto recycle 50 million cartridges in 2009.

As long as bottom-line responsibility forrecycling is hard to pinpoint (should it belong tothe manufacturer, the waste hauler, the con-sumer?), the legislation remains difficult toenforce, but in the meantime, public opinionseems to be doing some of the work, both inalerting end users to the importance of recyclingand in pointing out which companies are for-warding the cause. The very fact that so manyelectronic devices are stockpiled in homes andoffices indicates that many people are not com-fortable just tossing them into a dumpster.“Watchdog” agencies such as Greenpeace alsoreport the names of companies not involved inrecycling or not living up to their recyclingclaims. Greenpeace publishes a monthly rankingof the 18 top manufacturers of personal comput-ers, mobile phones, TVs, and games consolesaccording to their policies on toxic chemicals,recycling, and climate change (http://www.greenpeace.org/international/campaigns/toxics/electronics/how-the-companies-line-up). Noneof them get “perfect” scores, but as of Septem-ber 2009, Nokia, Samsung, and Sony Ericssonreceived the highest marks.

Time will tell whether such messages willreach beyond those who follow the news frompolitical activists. Like other fundamental

consumer behavior changes - consider howAmericans began using fewer plastic shoppingbags for the first time this year - electronicsrecycling will be most successful when endusers’ awareness and manufacturers’ ability tomake it easy for them to act on that awarenessmeet in the middle somewhere. �

industry news

continued from page 3

processing, with the potential of producingmanufacturing quantities of rugged, flexible,plastic displays as the end product. This issuecontains an interesting overview of one suchapproach to the flexible-display market,“Flexible E-Book Displays Produced in Standard TFT and Module Factories,” by IanFrench of PVI.

Free sheet or sheet-to-sheet (S2S) process-ing is also an emerging manufacturing processfor certain applications. This technique usesflexible plastic in cut sheet form that is pro-cessed on highly modified (or completelyunique) versions of display-manufacturingequipment. Due to the absence of a rigid carrier plate, there are limitations to overlayaccuracy and registration using this approach,which will therefore limit the use for high-resolution displays. However, for certainapplications, this approach offers uniqueadvantages, such as the absence of a lamina-tion/delamination step and the ability to produce units at very low cost. This approachalso allows the use of many of the base technology and existing toolsets that havebeen developed for “conventional” displaymanufacturing and avoids the integrationchallenges of moving completely to R2R production. In “High-Volume Manufacturingof Photonic Components on Flexible Substrates,” Dr. Robbie Charters of RPO provides a detailed description of the imple-mentation of S2S processing for the manufac-ture of RPO’s digital waveguide devices,which are being commercialized for touch-screen applications.

Flexible-substrate manufacturing, using thecarrier plate or sheet-to-sheet approach, couldbe an important transitional technology forproducts that are ultimately produced on aroll-to-roll line. Alternately, the uniqueadvantages of these approaches could offerlong-term benefits and product characteristicsthat cannot be realized with any other method.Either way, the end products made possible bythese methods should offer a compelling addi-tion to the range of products based on theirglass-based display cousins. �

Greg Gibson is Chief Technology Officer forFAS Holdings Group, LLC.

guest editorial

continued from page 4

SID News

Dr. David Fyfe and Professor SirRichard Friend Awarded the 2009Institute of Physics Business and Innovation Medal

Dr. David Fyfe, CEO of Cambridge DisplayTechnology and Professor Sir Richard Friendof Cambridge University were awarded theInstitute of Physics’ Business and InnovationMedal in October 2009 for “guiding the com-pany Cambridge Display Technology (CDT)to a pre-eminent position in the developmentof light-emitting polymers and in the develop-ment of the technology for flat-panel displaysand lighting.” The prize was one of four goldmedals awarded annually by the Institute ofPhysics (IOP) and is for outstanding contribu-tions to the organization or application ofphysics in an industrial or commercial context.

Fyfe commented, “I am honored to receiveand share this award with Sir Richard in recogni-tion of our efforts in developing and commer-cializing this technology platform. The award isalso recognition of the many scientists, investors,and supporters of CDT who have helped drivethe technology to its leading position for thefuture of the displays and lighting markets.”

The discovery that certain polymers can emit light when an electric current is passedthrough them was made by Jeremy Burroughes(Chief Technology Officer for CDT) under theguidance of Professor Richard Friend withassistance from Professor Donal Bradley at theUniversity of Cambridge in the late 1980s.Realizing the potential for the technology,Friend and colleagues promoted the spinout ofthe intellectual property into CDT, which wasinitially funded by the University, as well asvarious business “angels” and local venturecapitalists. Fyfe joined CDT in 2000, leadingits expansion from a laboratory-based researchcompany to one that built a manufacturing process development line near Cambridge andentered the manufacture of ink-jet printers inCalifornia to enable CDT’s technology to beapplied on an industrial scale. �

sustaining members index to advertisers

AdvitechApplied ConceptsApplied PhotonicsAstra Products, Inc.AU Optronics Corp.autronic–Melchers GmbH

BigByte Corp.

California Micro DevicesCDT, Ltd.Chi Mei Optoelectronics Corp.Chunghwa Picture Tubes, Ltd.Corning Japan K.K.Cytec Industries

Dawar Technologies, Inc.DisplaySearchDontech, Inc.DTC/ITRI

Endicott Research Group, Inc.ENEAEpoxy Technology

FIMI

Global Display Solutions

IGNIS Innovation, Inc.Industrial Electronic Engineers, Inc.

(IEE)Industrial Technology Research

InstituteInstrument Systems GmbHIST (Imaging Systems Technology)

Japan Patent Office

Kent Displays, Inc.Kuraray Co., Ltd.

LXD, Inc.

Micronic Laser Systems ABMicrovisionMitsubishi Chemical Corp.Mitsubishi Electric Corp.

Nano-Proprietary, Inc.NEC Corp.Nippon Seiki Co., Ltd.Nitto Denko America, Inc.Noritake Itron Corp.Novaled AGNovatek Microelectronics Corp., Ltd.

Optical Filters, Ltd.

Parker Chomerics/Silver CloudPlanar SystemsPlaskolite, Inc.Polytronix, Inc.

QualCommQuantum Data, Inc.

Radiant ImagingReflexite Display Optics

Schott North America, Inc.Sharp Corp.

Tannas ElectronicsTechnology Research Association for

Advanced Display Materials(TRADIM)

Teijin DuPont Films Japan, Ltd.TFD, Inc.TLC InternationalToshiba America Electronic

Components, Inc.TPO Displays Corp.Trident Microsystems, Inc.

Universal Display Corp.

Vestal Electronics A.S.

Westar Display TechnologiesWINTEK Corp.

3M ................................................C2,C4Aixtron................................................C3Display of the Year Awards ..................5EIS Optics (Formerly Oerlikon Optics) .................................................17

ELDIM S.A. .......................................21EuropTec .............................................24LA Chapter Conference.......................17OSD Displays ........................................7

Business and Editorial OfficesPalisades Convention Management411 Lafayette Street, 2nd FloorNew York, NY 10003Jay Morreale, Managing Editor212/460-8090 x212 fax: 212/460-5460jmorreale@pcm411.com

Sales Office – EuropeGeorge Isaacs12 Park View CourtThe Paddock, Eaton FordSt. Neots, CambridgeshirePE19 7SD U.K.+44-(0)-1480-218400george@gandg.demon.co.uk

Sales Office – China & TaiwanJoy WangACE Forum, Inc.3F-2, No. 5, Sec. 1, Pa-Te Rd.Taipei 100, Taiwan+886-2-2392-6960 x204fax: +886-2-2393-0667joy@aceforum.com.tw

Sales Office – U.S.A.Palisades Convention Management411 Lafayette Street, 2nd FloorNew York, NY 10003Michele Klein, Director of Sales212/460-8090 x216fax: 212/460-5460mklein@pcm411.com

Sales Office – Korea Jung-Won SuhSinsegi Media, Inc.Choongmoo Bldg., Rm. 110244-13, Yoido-dongYoungdung-gu, Seoul, Korea+82-2-785-8222 fax: +82-2-785-8225sinsegi-2@sinsegimedia.info

28 Information Display 12/09

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