Alignment Technologies and Applications of Liquid Crystal Devices

269 Pages·2007·5.62 MB·English

by  Masanori Sakamoto

Alignment Technologies and
Applications of Liquid Crystal
Devices
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
THE LIQUID CRYSTALS BOOK SERIES
Editedby
G.W.GRAY,J.W.GOODBY&A.FUKUDA
TheLiquidCrystalsbookseriespublishesauthoritativeaccountsofallaspectsof
thefield,rangingfromthebasicfundamentalstotheforefrontofresearch;from
the physics of liquid crystals to their chemical and biological properties; and,
fromtheirself-assembling structures totheirapplications in devices.The series
willprovidereadersnewtoliquidcrystalswithafirmgroundinginthesubject,
whileexperiencedscientistsandliquidcrystallographerswillfindthattheseries
isanindispensableresource.
IntroductiontoLiquidCrystals
ChemistryandPhysics
P.CollingsandM.Hird
TheStaticandDynamicContinuumTheoryofLiquidCrystals
I.W.Stewart
CrystalsThatFlowClassicPapersfromtheHistoryofLiquidCrystals
T.J.Sluckin,D.A.DunmurandH.Stegemeyer
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
Alignment Technologies
and Applications of Liquid
Crystal Devices
KohkiTakatoh, Masaki Hasegawa,
Mitsuhiro Koden, Nobuyuki Itoh,
Ray Hasegawa and
Masanori Sakamoto
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
Firstpublished2005
byTaylor&Francis
2ParkSquare,MiltonPark,Abingdon,OxonOX144RN
SimultaneouslypublishedintheUSAandCanada
byTaylor&FrancisInc,
270MadisonAve,NewYork,NY10016
Taylor&FrancisisanimprintoftheTaylor&FrancisGroup
(cid:1)2005KohkiTakatoh,MasakiHasegawa,MitsuhiroKoden,
NobuyukiItoh,RayHasegawaandMasanoriSakamoto
TypesetinCenturySchoolbookby
IntegraSoftwareServicesPvt.Ltd,Pondicherry,India
PrintedandboundinGreatBritainby
MPGBooksLtd,Bodmin
Allrightsreserved.Nopartofthisbookmaybereprintedor
reproducedorutilisedinanyformorbyanyelectronic,
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invented,includingphotocopyingandrecording,orinany
informationstorageorretrievalsystem,withoutpermissionin
writingfromthepublishers.
Everyefforthasbeenmadetoensurethattheadviceand
informationinthisbookistrueandaccurateatthetimeofgoingto
press.However,neitherthepublishernortheauthorscanaccept
anylegalresponsibilityorliabilityforanyerrorsoromissionsthat
maybemade.Inthecaseofdrugadministration,anymedical
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ISBN0^748^40902^5
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
Contents
Preface ix
Acknowledgements xi
Notations xvi
1 Overview 1
KOHKITAKATOH
1.1 DevelopmentoftheLCDMarket 1
1.2 ImprovementofViewingAngleDependenceofthe
ContrastRatio 2
1.3 FerroelectricandAntiferroelectricLiquidCrystals 2
1.4 DevelopmentofNovelAlignmentMethod 3
1.5 TheCharacteristicsofthisBook 4
2 RubbingTechnologies:MechanismsandApplications 7
MASAKIHASEGAWA
2.1 Introduction 7
2.2 RubbingMechanisms 8
2.2.1 Observationsofrubbedsurfaces 8
2.2.2 Definitionofrubbingstrength 23
2.2.3 Alignmentmechanisms 30
2.2.4 Pretiltmechanisms 32
2.3 Applications 36
2.3.1 Alignmentdefectsofactualdevices 36
2.3.2 Characteristicsoftherubbingprocess 43
2.3.3 Alignmentmaterial 47
3 Non-rubbingMethods 55
3.1 Introduction 55
MASAKIHASEGAWA
3.2 Photoalignment 57
MASAKIHASEGAWA
v
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
vi Contents
3.2.1 Introduction 57
3.2.2 Overview 59
3.2.3 Photoalignmentusingpolyimide 65
3.2.4 InfluenceofUVlightondisplaydevicecharacteristics 70
3.2.5 Lightsource 72
3.2.6 Comparisonofphotoalignmentandrubbing 73
3.2.7 Currentstatusofphotoalignment 75
3.3 ObliqueEvaporationMethod 76
MASANORISAKAMOTO
3.3.1 Alignmentmechanism 76
3.3.2 Evaporationapparatus 78
3.3.3 Materialscientificviewpoint 78
3.4 LiquidCrystalAlignmentonMicrogrooveSurfaces 79
KOHKITAKATOH
3.4.1 Liquidcrystalalignmentonmicrogroovesurfaces 79
3.4.2 Controlofthepretiltdirectionbya‘‘hybridcell’’ 79
3.4.3 Microgroovesurfacecontrolofpretiltangledirection 83
3.5 LBMembranesfortheAlignmentLayer 84
KOHKITAKATOH
3.5.1 LBmembranesforthealignmentlayer 84
3.5.2 PolyimideLBalignmentfilm 85
3.5.3 StructureofpolyimideLBfilmsandliquidcrystalline
alignmentonthefilm 85
3.6 PTFEDrawnFilmsforAlignmentLayers 87
KOHKITAKATOH
3.7 LiquidCrystallineAlignmentonChemicallyTreatedSurfaces 89
KOHKITAKATOH
3.7.1 Additionofsurfaceactiveagentsintoliquidcrystalline
materials 90
3.7.2 Treatmentofthesubstratesurfacebyactivesurfaceagents 90
4 ApplicationsofNematicLiquidCrystals 99
4.1 SummaryofMolecularAlignmentandDeviceApplications 99
RAYHASEGAWA
4.1.1 Molecularalignmentinnematicphases 99
4.1.2 Deviceapplications 102
4.2 TwistedNematic(TN) 102
RAYHASEGAWA
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
Contents vii
4.2.1 Basicoperation 103
4.2.2 OFFstate 104
4.2.3 ONstate 105
4.2.4 Dynamicresponse 105
4.2.5 Reversedomains 106
4.3 SuperTwistedNematic(STN) 106
NOBUYUKIITOH
4.4 TheIPS(In-PlaneSwitching)Mode 110
MITSUHIROKODEN
4.5 VerticalAlignment(VA)ModeandMulti-domainVertical
Alignment(MVA)Mode 111
KOHKITAKATOH
4.5.1 Verticalalignment(VA)mode 111
4.5.2 MVAmethod(Multi-domainverticalalignmentmethod) 112
4.6 PiCell 117
MASAKIHASEGAWA
4.6.1 LCconfiguration 118
4.6.2 Dynamics 120
4.7 Multi-domainMode 121
KOHKITAKATOH
4.7.1 Improvementoftheviewingangledependenceof
TN-LCDs 121
4.7.2 MechanismofviewingangledependenceofTN-LCDs 122
4.7.3 Reductionoftheviewingangledependencebythe
multi-domainmode 123
4.7.4 Formationoftwokindsofregionspossessingdifferent
alignmentdirectionsinonepixel 125
4.7.5 Formationoftwokindsofregionwithdifferentpretilt
anglesinonepixel 127
4.8 PolymerDispersedLiquidCrystals(PDLC) 132
RAYHASEGAWA
5 AlignmentPhenomenaofSmecticLiquidCrystals 139
5.1 LayerStructureandMolecularOrientationofFerroelectric
LiquidCrystals 139
NOBUYUKIITOH
5.1.1 Introduction 139
5.1.2 FerroelectricSmC*liquidcrystals 139
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
viii Contents
5.1.3 Surface-StabilizedFerroelectricLiquidCrystals(SSFLCs) 141
5.1.4 Smecticlayerstructurestudy 142
5.1.5 Molecularorientationalstatesandopticalproperties 149
5.1.6 Summary 162
5.2 AlignmentandBistabilityofFerroelectricLiquidCrystals 163
KOHKITAKATOH
5.2.1 Introduction 163
5.2.2 DrivingschemeofSSFLCs 163
5.2.3 FLCmaterialsforexcellentalignmentandbistability 165
5.2.4 Polymercrystallinity,linearityandmolecularstructures 166
5.2.5 Polarityonpolymersurfaces 172
5.2.6 Rubbingandannealingprocess 177
5.2.7 Electricdoublelayerinfluence 179
6 ApplicationsofFerroelectricandAntiferroelectric
LiquidCrystals 187
6.1 MolecularOrientationsandDisplayPerformancein
FLCDisplays 187
MITSUHIROKODEN
6.1.1 Introduction 187
6.1.2 TheDHFmode 188
6.1.3 Thebookshelforientation 189
6.1.4 C1-uniform(C1U)orientation 195
6.1.5 C2-uniform(C2U)orientation 197
6.1.6 ShockstabilityofFLCdisplays 202
6.1.7 Thelayer-rotationphenomenon 206
6.1.8 Summary 208
6.2 AlignmentandPerformanceofAFLCD 209
KOHKITAKATOH
6.2.1 AFLCmaterialsandDevices 209
6.2.2 AlignmentofAFLC 212
6.2.3 Drivingmarginhysteresisandthresholdproperties 216
6.3 ApplicationofFLC/AFLCMaterialstoActivematrixDevices 219
KOHKITAKATOH
6.3.1 Introduction 219
6.3.2 Specificationsofliquidcrystallinematerialswith
spontaneouspolarizationforTFTdriving 220
6.3.3 ActivematrixdrivingforFLCorAFLCmaterials 225
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
Preface
Theaimofthisbookistopresentasystematicdiscussionofthealignmenttech-
nologies of liquid crystalline materials forliquid crystal displays (LCDs).These
technologiesdeterminethemolecularorientationandconformationofliquidcrystal
phases on surfaces, and by understanding the technologies, both the structure
andthepropertiesoftheLCDscanbebetterunderstood.Thereaderwillobtain
essentialknowledgeofLCDsthroughthediscussionofthealignmenttechnologies
giveninthetext,whichasfarastheauthorsknowisthefirsttobewrittenfrom
thisstandpoint.
Originally,thebookwasplannedtobeintwoparts,theoreticalandpractical.
However, as writing progressed, we came to the conclusion that the chapters
based upon discussions and descriptions of actual devices could provide the
reader with the most useful and comprehensive information to cover most
requirements.Althoughdiscussions fromthetheoreticalpointofview maybe a
littlelimited, eachchapter does provide indispensable theoreticalexplanations,
supplementedandsupportedbyreferencesandthebibliography.
Thefirsthalfofthebookdealswithalignmenttechnologiesfornematicliquid
crystals, and in the second half those for smectic liquid crystals are covered.
Almost allcommerciallyavailable LCDs use nematicliquid crystals, and so the
firstchaptersprovideinformationthatispracticalanduseful.However,alignment
ofsmecticliquidcrystalswithalltheir variations isavery fruitfulareaofstudy,
and with developments that are possible in the future, a knowledge of smectic
liquidcrystalalignment couldbeeven moreimportant. It istherefore one of the
keyfeaturesof thebookthat the alignments forbothsmecticand nematicliquid
crystalsarepresented.
Thebookprovidesusefulinformationandreferencesforresearchersandengi-
neersworkingondevelopmentsandproductionprocessesforLCDs.Italsoprovides
averyappropriateintroductionforstudentsjuststartingtostudyliquidcrystals
orbeginningtoworkintheLCDindustry.ItalsoprovidesaguidetoLCDscience
and the related industries, and as such, establishes a good introduction to the
field,withreferencesandbibliography,forresearchersandengineersfromother
fields.
TheauthorshaveallworkedintheLCDindustryfromthe1980stothetimeof
writing, in the followingcompanies: Sharp, IBMJapan andToshiba.Their pro-
jects duringtheseyearswere concernedwith managingalignmenttechnologies
ix
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto
x Preface
forLCDs.DuringtheseyearstheLCDindustryhas developed rapidlyinJapan.
Fromthefirstproposalforthisbookin1996,itsaccomplishmentwithappropri-
ate translation into English has taken time. Some of the verylatest topics may
not be discussed as fully as would be desired, but the basic concepts for these
topicshaveallbeenintroduced.Theauthorswillbe delightedifthisbookoffers
notonly information, but also clues and ideas for solving theproblems of those
studyingandworkinginthefieldofLCtechnologies.
WewouldliketorecordoursincerethankstoProfessorHiroshiYokoyamaand
ProfessorYukioOuchifortheirusefulsuggestionsanddiscussionsattheinitial
planningstageofthisbook.Wealsowishtothanktheeditorsoftheseries,Profes-
sor George Gray, FRS, ProfessorJohn Goodbyand ProfessorAtsuo Fukuda, for
theopportunityandinvitationtowritethisbookandfortheirhelpfulsuggestions
andguidance.WearealsogratefultoGrantSoanes,FrancesHorrocksandJanie
Wardlefortheireditorialassistanceduringthedifferentstagesofpreparationof
this book. In addition, we would like to extend our heartfelt thanks to our
familiesfortheirconstantsupport.
© 2005 Kohki Takatoh, Masaki Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanori Sakamoto