Active Matrix
`Liquid Crystal
`Displays
`Fundamentals and
`Applications
`
`SAMSUNG, EXH. 1008, P. 1
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`

`

`Active Matrix Liquid Crystal Displays
`
`SAMSUNG, EXH. 1008, P. 2
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`

`

`Active Matrix Liquid Crystal Displays
`
`Willem den Boer
`
`Ne-...•ncs is an imprun of Elsevier
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`SAMSUNG, EXH. 1008, P. 3
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`

`

`Contents
`
`Preface ............... . .... . .................... . ............ xi
`Chapter One: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
`I. I Historical Perspective
`.. . . .. • ... • .. .. . . • . .. • . . . . . I
`l.2 Liquid Crystal Properties . . . . . . . . . .... . . . . . . . . . . . . . . • .. . . . . . . . . . . 7
`1.3 Polarization, Ok.hrohnu, anJ Birt·fring<.·nn· . ..... .. . .. . . . . . .. . . ..... 11
`1.4 The Twisred Nematic C'.ell
`. . . . . . .
`. . . . . ..• . .•...•.. . •. .. . . . . 14
`1.5 Limitations of Passive Matrix Addressing . . . . . . . . . . ...... . . . . . . . . . . 17
`References .. . . . . . . . . . . . . . . . .... . . . . . . . . . . • . . . • . . . . . . . . . . . . . . 21
`
`Chapter Two: Operating Principles of Active Matrix LCDs ..... .. .............. 23
`2. 1 The Case for Active Matrix ........ . . . . . . . . . . . .. . .. .. . . . . . . . . .. 23
`2.2 Requ irements for Active Matrix Switching Devices . . .... •. .. . ... . . . . 24
`2.3 The Thin Film Transistor . . .......... . . . . . . .................... 29
`2.4 Thin Film Silicon Properties ......... . . . . . . . . • ... . .. . ... • . . . . . . . 32
`2.5 Amorphous Silicon TFTs
`. . .... . ... . . . . . . . . ... .. . .. .. . . . . . . . . .. 34
`2.6
`l'oly-Silicon TFTs ......................... • ........ . . • ....... 36
`2.7 Basic Pixel Circuir and Addres5ing Merhods . . . . . . . . . • .. . . . . . . . . . . . . . l9
`2.8 Lliodc-1:lasc-..l Displays ... . .................. • ... ... . . .. • ....... 43
`2.9 Plasma-Addressed LCDs . . . . . . ...... • . . . • ... • .. .. .. • ... • . .. . . . . 47
`Refcrcnct-s ....... . . . ............ . . . . . . . . . . ...... .. . . . . . . . . .. 48
`Chapter Three: Manufacturing of AMLCDs . ......... . ............... . 49
`3. 1 B-asic Structure of AMLCDs ........ ... . . . . . ... .. . .. .. . ... . . . . . . 49
`3.2 T hin Film Processing . . . . . ... .. ... . . . . . . .... • ..... . • ... • . . . . . . . 50
`3.3 Thin Film Properties . . ................ . . . .......... . .......... 61
`3.4 Amorphous Silicon TFT Array Processes . . . • . . . • .... . . . . . . . . . . . ... 65
`3.5 Poly-Si TFT Army Processes ............ . . . . . . . .. ..... . ... . . . . .. 69
`3.6 Color Filter Array l'roccss . ......•... . ... . . . . • .......... . . . . .... 73
`1.7 1.C Cell Assembly . . . . . . . . . . • .. . . . . . . . . . . . . . . . . • . . . . . . • . . . . . . . 74
`.l.8 Module Assembly . . . . . . . . . ...... . . . . . . . . . ... . .. . ... . .•. . . . . . . 77
`
`Contents
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`3.9 Yield Improvements and O :msideracions ..... • . . . • ... . .. • ... • . . . . . 79
`.l. 10 Trends in Manufacturing . . . . . . . . .... . . . . . . . . . . . ...... . . . . . . . . . 83
`Chapter Four: AMLCD Electronics ................................. 87
`4.1 Drive Methods
`. . . . . . . . . . . . . . ...... . . . . . . . . . ...... . . . . . . . . . . 87
`4.2 Row Seit-cc and Column l>ata Drivers ....... . . . . . ...... •. ..... . . . 93
`4.3 Timing Controllers. Display Co,mollers, and Interfaces . . .. ... . . . . . . . 99
`4.4
`Integration of Electronics on Glass ... . . . . . . . . . ...... . . . . . . . ... . 102
`4.5 Backlights . . . . . . . . . ... . ...... . . . . . . • . . . . . . .. . . . . . . . . . . . . . . 105
`4.6 Power Consumption . .
`. ......... •. . .•. ...... . .. •. . . . . . ..... 109
`References . . . . . . . . . . . . . . . . . . . . . . . . . • . . . • . . . . . . • . . . . . . . . . . . 110
`
`Chapter Five: Performance Characteristics ...................... . ... 113
`5.1 Basics of Photometry and Colorimetry . . . . . . . . . . ...... . . . . . . . . . . . 11.l
`5. 2 Briglunc>.ss and Comrast Ratio ...... . . . . . ... . ... . . ... . . ... . . . . . 11 7
`5 . .l Viewing Angle Behavior . ........ . . . . . . . . .. ... . .. .. . . . . . . . . .. 121
`5.4 Color and Gray Scale l't·rfon nance .. . . ..... ... .. ..... . . ..... ... 123
`5.5 Respon.e Time and Flicker .. . . . . . . . . . . . . . . • ... . . . . . . . . . . . . . . . 129
`5.6 Resolution and Size:: .......... • ..... ... . .. • ............ . ..... 13 I
`5.7
`Image Artifacts . . . . . . . . . . .. . . . . . . . . . . ...... .. .. • . . . . . . . . . . . 134
`References . . . . . . . . . . . . ...... . . . . . . . . . . .......... . . . . . . . . .. 13 7
`Chapter SiK: Improvement of Image Quality in AMLCDs ....... . ........ 139
`6.1 Brightness Improvements
`. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
`6. 1.1
`Increased Color Filter Transmission ....................... 140
`6.1.2
`lligh -Aperture Rario Designs ... . ... . . . ....... . . ..... . . . . 140
`6.1.3 Alternative Color Filter Ammgements . .... ... . . . . . . . . .... 144
`. . . ... . . .... . ... . . ... . . . . . 145
`6.1.4
`Ilrighmess Enhancemem Films
`6.2 Readability Under High Ambient Lighting Conditions ... . . . . . . . . . .. 146
`6.3 Color Gamut Improvements .......................... • ....... 149
`. . 150
`6.4 Wide Viewing Angle Technologies . . . . . . . . . . . . . . • . . . . . . . . . .
`. .. . . . ... . . . . . . • ... . . . . . . . . ... . ... 151
`6.4. l Compensation Films
`6.4.2
`ln-Plane•Switching Mode ... . . . . . . . . . ... . .. • . . . • . . . . . . . 152
`6.4.3 Vertical Alignment .......... . . . .......... •. . . . . . . ... . 157
`6.4.4 A Comparison and Other Viewing Angle
`Improvement Methods ... . . . . . ................ . . . . .... 162
`6.5 Enhancement of Vidro Performance . . . . . . . . . . ......•.. . . . .. . . . . 166
`6.5.1 Response Time Compensation . . . . . . . . . . . ...... . . . . . . . . . . 167
`6.5.2 Emulation of an lmpulsc-Typt· Display . . . . . ...... . . . . . . . . . . 169
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`Contents
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`6.6 Large Size . .. .. . .. . ....... . ... • ... • ... . .. • . .. • ... • ... • ..... 172
`R~fcrcnct-s . , . . . . . , ....... , . . . . . . . . . . .. . , . , . . , , , , , . . , . , . , , , . 176
`Chapter Seven: Special AM LCD Configurations . ...................... 179
`7.1 U ltra-lligh-Resolution Monitors and Improved G ray Scale . . . . . . • ..... 179
`7.Z Rdkctivc and Transfiective Displays . . . . . . . . . .... . . . . . . . . . . • . . .. . 182
`7 .3 Field-Sequemial Color LCDs
`. . . . . . . . . , .. .. . . , . . . , . .. . . . .• ..... 185
`7.4 Stereoscopic AMLCDs . . .. , . . . . , . . , . . . ... .. . . . , . . . . . . . . . . , , , . 187
`7.5 Touch Screen Technologies . . . . . . . . . . . . . . . • .. . . . . . . . . . . . . • .... . 190
`References .......... .. . . ... . .... . .... .. ...... • . . . , ..... . . .. 196
`Chapter Eight: Alternative Flat Panel Display Technologies .. ........... . . 197
`8.1 Plasma Displays . . . . . . . . .. . . . . . . . . . . . . . . . .... . . • . .. • . . .• . . . . . 199
`8.Z Electroluminescent Displays ... . . . . . . . . . . . . . .. . . . . . . . . . . . . . .... 201
`8.2. 1 TFEL Displays ....... . . . . . . . . . ...... . . . . . . . . • . . . . .... . 202
`8.2.2 O rganic LED Displays . . . , . . . , . . . . . . . , .. . . . . . . . , . . . . .. , , 20.3
`8.Z.3 Passi vc Matrix Org,mic LEI) Oisplays
`. ... . . . . . . . . . . . . . . .... 205
`8.2.4 Acrive Matrix O rganic LED Displays . . . .... . . . . . . . . . . . ..... 206
`8.3 Electronic Paper and Flexible Displays ... . . . . .. . . . . ..... . . . . . .. . . Z09
`8.4 Organic Thin Film Transistors . . . . . . . . . . . . .. .. .. .. • . . . . . . .• ..... 213
`8.5 Front and Rear Projection Displays . , . , . . . , .. , , , . , , . . , , , . , , • , . , , , 214
`References . . . . . . . . .... . . . . . . . . . . . . . ... .. . . . . . . . . . . . . . • .... . 22 1
`Chapter Nine: Active Matrix Flat Panel Image Sensors . ....... . . . . . . . . . . 223
`9.1 Flat Panel Image Sensors . .. . . . . ....... . . . . .. . . ... . ..... . • ..... ZZ3
`9.2 Direct Omversion Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . .
`. 225
`9.3
`lmlirect Conversion Detectors
`. . . . . . . . . . . . .... . . . . . . . . . . . , . . , , . 228
`9.4 Applications of Rae Panel X-Ray Sensors . . . . • .... . ... . . • . . . • ..... 233
`Rdcrcnct-s . . . . . . . ........ . . . . . . . . . . . .. . . . .. . . . . . . . . . . . ... . . 234
`Index .... . .............. . . ................. .... . ....... . . . . 235
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`Preface
`
`Finally, I would like co chank che Elsevier Science organizacion for che opportunicy co
`write this lxx>k and for thl'ir supJX>rt <luring its production.
`
`Willem den Boer
`
`Preface
`
`The meteoric rise of the active matrix LCD over less than two decades to undisputed
`dominance as a flat panel display has been breathcaking. The technology behind this
`remarkable progress will he summarized in rhis book. Manufacn1ring of AMLCDs is a
`more than $40 billion inJusu,• and now plays an important role in the economy of
`several Asian counrries. Th is book will addre~s rhe fundamenra ls of LCD operation and
`the princip1es of active matrix addressing. The reader will become fomiliar with the
`construction and manufacturing methods of A.t\1LCDs, as well as with drive methods;
`performance characteristics; recent improvements in image quality; an<l applications in
`cellular phones, portable computers, desktop monitors, ,u,d LCD televisions.
`This book is on an introductory level and incended foe srndenrs, engineers, managers,
`educators, IP lawyers, research scientists, and technical professionals. Emphasis has been
`placed on explaining underlying principles in the simplest possible way without relying
`extensively on equations. Last, but not least, the lx>0k is intended for those inquiring
`minds who, for many hours every day, look at rhe LCD displays of notebook computers,
`flar panel monirors, and relevisions and simply wonder how rhey work.
`This book grl'w out of thl· course matnials from seminars 1 presl'ntl·d sl·veral times at
`UCLA, ar rhe gracious invitation of course organizer Larry ~1nnas. The course m:ueri:.11.s
`were further updated when the Society for Information Display kindly invited me to
`present Shorr Courses on AMLCDs ar che annual SID Symposiums in 2002 and 2003.
`
`A book 1ike this would not have been possible without frequent interaction and
`<liscussions with colleagu~s in the field. Working with them has always been a great
`pleasure and I wou ld like to mention speclfic.1lly some of my former coworkers at OIS
`Optical Imaging Systems, Inc. and at Planar Systems, Inc. They include Adi Abileah,
`Steve Aggas, Tom Baker, Yair Baron, Bill Barrow, Mike Boyd, Young Byun, Vin Ca1lllella,
`Mark Friends, Pat Green, Tieer Gu, Chris King, Terrance Lirss<m, A lan Lien, Darrin
`Lowe, Yiwei Lu, Fan Luo, 11.n Nguyen, Cheng-bin Qiu, Seate Robinson, Score Smith,
`Scott Thomsen, Dick li,enge, Vicror Veernsamy, Mimi Wang, Moshe Yang, Mei Yen,
`Zvi Yaniv, auJ John Zhong.
`
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`CHAPTER 1
`
`Introduction
`
`1.1 Historical Perspective
`Electronic displai•s have, for many years, been d1e window to the world in television as
`well as the primary human interface to computers. In today's information society, they
`play an increasing ly impo rtant and in<lispcnsablc role in conununkati<.m , computing, and
`cntcrtairunc1u devices.
`The venerahle carhode ray n,be (CRT) has heen around for more rhan 100 years and has
`been the workhorse for television displays and, umil recently, for computer screens. As
`one of the few surviving electronic devices based on vacuum tubes, the CRT can ooast
`an unrivaled success as a low,cost color display with good image quality. Its large depth,
`weight, and power consumption, however, have limited its use ro nonportable
`applications.
`From tl1e early days of electronic display development, a rtat panel display was considered
`a very t1trracrive alternative ro rhe hu lky CRT. For decades, display eng ineers searched for
`flat panel display technologies to replace the CRT in many applications. Jn spite of many
`attempts to develop flat CRTs, plasma displays, and other low-profile displays,
`commercial success remained elusive for many years. Finally, by the I 990s several
`tcchnologil-.s wen.· 1naking ~igniCic.ant inroaJs to achieve this goal. ln particular, active
`marrix liquid crystal displays (AMLCDs) and plasma displays demonsrrared large sizes
`and high image quality comparable to CRTs.
`The success of AMLCDs, the subject of this oook, is the culmination of two significant
`developments: liquid crystal cell techno logy and large .. area microelectro nics o n glass.
`For more than cwo decades these technologies have been refined and an extensive
`infrastructure for manufucturing equipmenr and marerials has heen established, especfr,lly
`in Asia.
`Liquid c,ysrals were discovered in 1888 by rhe Ausrrian horanist Friedrich Reinirzer. I le
`experimenr.e<l with r.he cholesterol .. type organic fluid cholesteryl henzoate and found r.har .•
`
`Active Matrix Liquid Crystal Displays
`
`upon hearing, it undetwent a phase transition from a milky fluid to a mostly trans~>arent
`fluid. This was later explained as a transition from an optically and ekctrically
`anisotropic fluid to an isotropic rtuid. The anisotropy (i.e., the difference in dielectric
`co n:mmt and refractive index for differe nt o rienrnrio ns of rhe molec ules in the fluid) led
`to d1e analogy with the anisotropy of solid crystals, hence the name lk1uid crystal. The
`teclu1ological and commercial potential of liquid crystal was not realized until the 1960s,
`when RCA developed the first liquid crystal displays (LCDs) b:tsed on the dynamic
`scattering effect [I]. T he cwisced t1ematic (TN) mode of operation, on which many
`current LCDs are based, was first described by Schadt and Helfrich f2) in 1971 and,
`independently around the same rime, by Fergason (3). Twisted nematic LCDs appeared
`on the scene in the early I 970s in electronic wrist watches and in calculators.
`LCDs quickly dominated in small portable applications due to the compatibility of the
`simple reflecrive-rype LCD with low-power CMOS driving circuitry and therefore with
`harrery opernrion. In addirion, high .. volume manufacruring led ro very low cost. The
`mark<,t for small, direct-driven, segmented, TN LCDs in portable devices increased
`rapidly during rhe 19 70s. They were initially mostly used in a reflecr_ive mode, relying on
`ambient light for legibility. Since each segment in a direct~driven alphanumeric display
`needs to be separately connected to the control electronics, rhe information content of
`this type of display is very limited, usually to one or two lines of text or nmnbcrs. Other
`drawbacks of the reflective mode included the difficulty of implementing color, the
`dependence on ambient lighting, and the parallax caused by the separation of about
`0.5-1 mm between rhe back reflector and the LC layer.
`The mass market for electronic wrist watches, calculators, and other applications,
`however, allowed invcsttncnts in manufacturing and further development.
`For displays with higher information content, the large number of picture elements
`(pixels) precluded rhe individual addressing of eveiy pixel. This led ro rhe developmenr
`of matrix addressing in which an array of M x N pixels is addrc-;sed by applying pubes to
`each of irs M rows and N columns. It reduces rhe number o f inrerconnecr..s ro the
`external addressing circuitry from lvl x N to M + N. For example, a 100 X 100,pixcl display
`now requ ired 100 + 100 • 200 interconnections instead of 100 x 100 s 10,000. Such
`passive matrix displays arc usually operated with a one .. Jine .. ar .. a .. timc addressing method
`called multiplexing. The TN LCD was limited to only about 10 rows of pixels because of
`its gradual tr.-msmission .. voltage curve. Many improveme nts in passive matrix addressing
`have been proposed and implemented over the last fifteen years, notably the super(cid:173)
`twisted nernacic (STN) LCD. However, rheir performance in terms o f viewing angle,
`response tim4:, gr.ty scak-, and <.:.ontr.ist ratio has gl'n<:mlly fallen short of what was
`possible with a single direcr~driven pixe l.
`
`2
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`

`Introduction
`
`Active Matrix Uquld Crystal Displays
`
`Early during the developme,u of LCD technology, the limitations of direct multiplexing
`or passive matrix a<l<lressing Wl're rl'CObrnizl'd. A solution was proposed by Lechner ct al.
`(4) and bl' Marlowe and Nester (5). il)' incorporating a switch at each pixel in a matrix
`display, rhe volr.age across each pixel could he controlled independently. The same high(cid:173)
`contrast ratio of more than 200, obtained in simple, dirccI-driven backlit displays, could
`then also be achieved in high-information-concenc displays.
`
`Peter Brody and coworkers [6] constructed the first so-called active matrix LCDs
`(AMLCDs) with CdSe thin film transistors (TFTs) as the switching elements. The TFTs
`in rhe array act merely as ON/OFF switches and do not have an amplifying function. For
`an electronic engineer, the term "active matrix" may therefore be inappropriate. It is
`now, however, commonly used :-md irs definition has been exr.ended to include arrays of
`switching cll'mcnt.s other than TFTs, such as diodes.
`The CdSe TFTs used for the first AMLCDs turned out co be a temporary solution.
`Semiconducrors such as C'.dSe are nor compmihle wirh srnndard processing in rhe
`microdl'Ctronic industry, which uS('s mainly silicon as the semiconductor material.
`Advanced phorolirhogrnphic and etch ing processes have been developed over rhe years
`for silicon devices and this technology is not readily applicable to CdSe T IT,. Dr. Brody
`has, nonetheless, remained a strong and vocal ptoponent of CdSe-based AMLCDs
`over the years, even in the face of the overwhelming success of silicon thin film-based
`TFT LCDs.
`
`Polycrystalline Si materials and devices are more fam iliar to semiconducror process
`engineers a,KI were developed for use in AMLC[)s in the early I 980s. The first LC
`pocket television markered by Seiko Epson in 1983 used a poly-Si TFT active matrix [?J
`and was the very first commerc ial application of AMLCDs. T he early poly-Si T IT,
`required high-remperature processing and therefore used expensive quartz sull5trares.
`
`A color LCD was obtained by subdivid ing the pixel into three subpixels with red, green,
`and blue color filters. Since the color filt<·rs absorb a large portion of the light, these
`color LCOs required a backlighc to operate in a transmissive rather chan a reflective
`mode r.o be useful in most ambient lighting conditions.
`In parallel to the early development of LC cell technology and CdSe TFTs, thin film
`amorphous silicon (a-Si) was investigllted in the 1970s. The rationale behind this
`interest was initially not its potential use for LCDs, but rather its promise for low~cost
`solar cells. A major development occurred ac the U niversity of Dundee in Scotland in
`1979, when LcComber ct al (8) devd op<'<I the first TrT with a -Si as the semiconductor
`material and suggested the active matrix LCD as one of its applications. Interestingly, a
`patent on the hasic ,1 .. S i TIT wns never filed, since r.his work was performed at an
`
`academic institution. The University of Dundee had been a pioneer in che development
`and understanding of amorphous silicon materials under the leadership of Profe,;,;or W.E.
`Spear and Or. 1'.G. Lc-C:Ombcr. Unfortunately, Or. LcCombcr witnessed onl)' the start of
`the tremendous growth in AMLCDs based on a-Si TFTs; he died ar the age of 51 of a
`fatal heart au ack whik• vacationing in Switzerland in 1992.
`
`Amorphous silicon can be deposited on low-cost, large-area glass substrates at a
`temperature below 300~C . It was more attractive than the early polycrystalline
`technology for active matrix LCDs, which needed much higher process temperatures and
`more process steps. A pocket television with a,Si TFTs was pur on the market hy
`Matsushita in 1984 [9).
`
`Soon after the first TFT LCO wirh amorphous silicon T Ffs was inrroduced, rhea-Si TFT
`overshadowed poly-Si T IT,:« the semiconductor device of choice for AM LC:Ds. The
`first TFT LCDs had a diagonal size of 2-3 in. and were mainly used in small portable
`relevisions. The pe,formance of rhe color AMLCO was inirially improved for high-end
`applications such as aircraft cockpit displays. Jn avionics, c«:nit was a Sl'Condar)' conC('n1
`and emphasis was placed on rhe highest possible performance in terms of legibiliry under
`any lighting cond itions.
`While a market was established, volume production capability was gradually increased at
`several Japanese companies. T his was accompanied by a scale,up in glass substrate size
`from wafer-like sizes to around 300x400 mm. A significant br<:akthrough occurred in rhe
`late 1980s, when the first lapcop computers wirh I 0-in. diagonal she TFT LCOs were
`marketcti by several companies, including IBM, NEC, Sharp, Toshiba, a1'Cl Hitachi. T h is
`scale-up was made possible by the gradual increase in manuf-acturing yields by process
`improvement. mctho<.l~ borrowed from the .scmicom.luctor industry. Laptop an<l notebook
`computers turned out to be the killer application for active matrix liquid crystal displays.
`They addressed rhe need of traveling businessmen for lighrweighr computers with high
`image qualit)', and thin and low-power flat panel displays.
`
`By 1996 the manufacturing substrate size had grown co 550x650 mm and many
`improvements in processing and materials were implemenr.ed. ln the mid~ l 990s Ko rean
`companies started mass production of AMLCD modules, followed a few years later by
`massive investments by several companies in Taiwan.
`The late 1990s also witnessed a revival of poly-Si TFT LCDs for small displays. Several
`compan ies succeeded in producing low-temperature poly-Si TFTs processed ac
`tcmp('r..ttur('S bdow 600°C1 co1npatiblc with lower-cost glass. T he main attraction o(
`pol)'-S i TFTs is their l1igher current-carrying capability, aUowi1~ rhe integration of some
`of the <lrive electronics o n the glass.
`
`3
`
`4
`
`SAMSUNG, EXH. 1008, P. 8
`
`

`

`Introduction
`
`Active Matrix Liquid Crystal Displays
`
`be amibuted to supply-demand cycles. Based on an extrapolation of chis plot, rhe
`AMLCD industry will achieve $100 billion in ann ual revenues around the year 2010.
`
`The market for AMLCDs is usually subdivided into small di,;plays with a diagonal size of
`less chan 10 in. (in POAs, cell phones, digital cameras, camcorders, etc.), med ium
`displays of 10-20 in. ( in noteb<><>k computers and desktop monitors), and large displays
`exceeding 20 in. (mostly in televisions). Figure 1.2 shows the recent rapid ,mir growch in
`all applications. A lthough the small displays have the largest unit sales, the larger
`displays obviously represem a large pare of the total revenues.
`
`AMLCOs are also increasingly used in medica l. industrial, and recail applications, often
`with a touch panel includc·d.
`
`1000 ~ - -~ - -~ - -~ - -~
`
`100 vr-:
`" t--Jd=-1
`- i 1==--1
`/
`1'---~--~--~---'
`
`1981
`
`19Qi
`Yea,
`Figure 1.1: Growth of the semiconductor IC and
`LCD market.
`
`2002
`
`2001
`
`ooos of AMLCD panels
`
`~
`
`1,000.000
`900,000
`800,000
`700,000
`600,000
`S00.000
`400,000
`300,000
`200,000
`100,000
`
`4
`
`,,
`,,
`,,
`,,
`,., ;;;; -
`-
`,.,
`-
`,.,_
`
`/
`
`-
`-
`-
`-
`
`-
`
`-
`-
`-
`
`-----
`-
`-
`-
`-
`-
`-
`-
`-
`-
`-
`-
`I - 1 - 1
`
`·-·-
`
`- -"
`
`0<10"
`a Notebook PC$
`(cid:127) tCO Monitors
`(cid:127) LCD TVS
`
`
`
`2003 2004 2005 2006 2007 2008
`Figure 1.2: Market forecast for TFT LCDs (courtesy of
`Ois~aysearch).
`
`Applicacion of a-Si TFT LCDs in nocebook compucers facilitated large investments in
`their manufacturing infrastructure. This, in tum , ma<le possible the introduction of space.(cid:173)
`and power-saving, !ht-panel desktop monitors based on AMLCD palids with improv<xl
`v iewing ;angles.
`
`Sevt·ral 1nc:thods to i1nprovc the viewing angk 1 including compen!)ation filnis and
`different LC modes (ili•plane-switching and multi-domain vertical alignment) were
`introduced after 1995 and implemented in 17 ,in. and larger monitors. In 2003 T FT
`LCDs surpassed CRTs in terms of revenue for computer monicors.
`
`Recent furcher improvements in brightness. color performance, viewing angle. and
`response time have le"<.! to the development of LCD television with superior image quality
`and progres~ively larger screens, now well beyond 40 in. in diagonal size. LCD relevisio n
`is the final frontier for the AM LCD and a number of companies have started production
`on glass substrates with 1-4 m2 size to participate in chis rapidly growing marker.
`Another applic:ition where AMLCDs have attained a large market sh:ire is handheld
`tkvkes ( i.e., in PDAs, digital camerJS, camcor<li:rs, an<l mobile phones). With the
`introduction of 3G cellular phone service and built-in cameras, the demand for high,
`contrast, video-rate color displays haw allowed the AMLCD to replace many of the
`poorer-performing passive matrix LCDs.
`
`Paralle l to the development of direct,view displays, microdisplays for projection have
`been developed since the late I 970s. Ir was realized early on that the LCD is a light valve
`that can ace as an electronically concrolled slide in a slide projector. Rusiness•grade front
`projectors app<."Jm! on the. scene in the early 1990s with three high-resolution poly-Si
`TFT LCDs. T hey are now commonplace in many meering rooms and cJ;assrooms acro.ss
`the world and c.an weigh less than J lhs. Rear--pmjection, high--definition television hased
`on reflective microdisplays (liquid crysral on silicon [LCOSJ) have emered rhe
`marketplace as well .
`Micro<lisplays arc al.so usc<l in personal viewers such as vicwfin<lcrs for digital earner.is
`and camcorders.
`
`The success of AM LCD technolOb'Y is the result of many years of close c<><>peration
`among scientists and engineers from different disciplines. They include organic chemists,
`physicists, optical, e lectrical, electronic, mechanical, p;.1ckaging, and manufacruring
`engineers, all supported by increasing revenues from sales of LCDs.
`Figure 1.1 illumares the exponential increase in the total marker for AMLCDs. The
`development shows a remarkable parallel with the semiconductor industry in the 1980s
`and 1990s, also indicated in the plot. Some fluctuations in the LCD revenue curve can
`
`5
`
`6
`
`SAMSUNG, EXH. 1008, P. 9
`
`

`

`Introduction
`
`Active Matrix Liquid Crystal Displays
`
`The AMLCD manufacnirers are supported by a large infrastructure of equipment aod
`material suppliers, which continue to improve efficiency and reduce cost. They include
`color filter, polarizer, and opLical (iln, rnanufacLurers, dri vcr IC and controller IC wndors,
`packaging firms, rnlcklighr manufucturers, and supplie~ of materials such as LC fluids and
`alig1unem layers.
`The momentum the LCD industry has gained is difficult to supplant by alternative flat
`panel display technologies, even if, on paper, they may have advantages over LCDs.
`
`1.2 Liquid Crystal Properties
`After their discovery hy Reinitzer in 1888, liquid crystals were, for many decades,
`consi<lctt<l int(•rcsting o nly from an acadc·mic point of view. Li<.luiJ crystals arc an
`inrermediare phase herween crysrnlline solids ;:incl isorropic liquids, an<l combine cerrain
`d1aractc·ristic properties of the crystal structure with those of a deformable fluid. Di,play
`devices utilize both their fluidiry and the anisotropy associated with their crystalline
`character. T he anisotropy causes the dielectric constant and refractive index of the LC
`fluid to depend on the orientation of its molecules.
`Nematic liquid crystals are commercially the most interesting type. Upon heating, most
`crystalline solids undergo a phase transition to an isotropic liquid. The nematic
`im:ermediate phase (mesopha.se) occurs in certain, mostly organic, subsrances in a
`temperature range between the solid and isotropic liquid state. Figure 1.3 shows an
`example of the molecular mucture of a liquid crystal, p-methoxyben.ylidene•p•n(cid:173)
`butylaniline (MBBA), with its nematic temperature range.
`The liquid crystal (LC) molecules arc gcncr-Jlly elongated in shape and have a length of
`around 2 nm. Because of their "cigar" shape they tend to line up more or less 1,ara llel to
`each otht·r in the lowest cnt·rgy state. T he avt-rJ.gc orientation axis along the molecules is
`a unit vector n, called the director. Nematic LC molecules are not polar, so there is no
`differentiation between n and -n . T he dielectric constant and refractive index of the LC
`is different along the director and perpendicular to the director, as shown in Fig. 1.4,
`giving rise to dielectric and optical anisotropy, respectively. The d ielectric anisotropy
`
`O~N~C ,H ,
`H3C/ ~ '
`Figure 1.3: Example of molecular structure
`of LC - MBBA, with a nematic range of
`21-48"C.
`
`n
`
`~=?< i=
`==~c::::=::,
`~<== ,~~~
`=
`c::=>
`
`;fi3
`
`(B)
`(C)
`(A)
`Figure 1.4: Orientation of LC molecules in (A)
`smectic, (B) nematic, and (C} isotropic phas e .
`
`makes ir possible to change the orientation of rhe LC molecules in an electric field,
`crucial for application in electro..-optical devices. The o ptical anisotropy leads to
`birefringence effects (described later in this chapter) and is essential for the modulation
`of polari zed light in display operation.
`In bulk, liquid crystal tends to form microdroplets. Within the droplets there is one
`dirccLOr orientation, but the director can Ix· difforcnt for adjacem droplets. Although
`most high-purity liquid crystals are transparent, this explains the milky appearance of
`bulk LC, as scattering of light occurs at d,e boundaries of the microdroplets.
`When nematic LC is heated beyond a certain temperature, a phase transition occurs to
`an isotropic liquid. T he nematic.-isotropic transition temperature is often referred to as
`the clearing point or clearing temperature because of rhe drastic teductioo in light
`scattering that occurs when the fluid no lo nger consists of microdroplets with different
`directors. Just below the clearing point, the optical and dielectric anisotropy of the LC
`fluid srnrrs to decline, until at the clearing point there is a single d ielectric com;rnnr. and
`refractive index in the isotropic state. Above the clearing point, the LC fluid no longer
`has the desirable optical and dielectric anisotropy, and display operatio11 fails.
`When the tempcmture is lowered, the LC fluid undcrgot.>s another phase transition from
`the nematic to the smectic phase. In the sniectic phase, the LC molecul