Alignment Technologies and Applications of Liquid Crystals

✍ Scribed by Kohki Takatoh, Masanori Sakamoto, Ray Hasegawa, Mitsushiro Koden, Nobuyuki Itoh, Masaki Hasegawa

• Publisher: CRC Press
• Tongue: English
• Leaves: 269
• Edition: 1
• Category: Library

✦ Synopsis

Written by a group of authors, who have published extensively in the international research literature, the book takes a detailed look at a critical aspect of Liquid Crystal technology - the alignment characteristics and properties of the materials used in the construction and use of LCDs. The book examines the chemical, physical and mechanical properties of the materials and relates them to practical performance issues in the modern Liquid Crystal. This authoritative sourcebook will be of great value for all concerned with the practical and theoretical issues of alignment phenomena in Liquid Crystals.

✦ Table of Contents

Alignment Technologies and Applications of Liquid Crystal Devices......Page 3
Contents......Page 5
Preface......Page 9
Acknowledgements......Page 11
Notations......Page 16
1.1 Development of the LCD Market......Page 17
1.3 Ferroelectric and Antiferroelectric Liquid Crystals......Page 18
1.4 Development of Novel Alignment Method......Page 19
1.5 The Characteristics of this Book......Page 20
2.1 Introduction......Page 22
2.2.1 Observations of rubbed surfaces......Page 23
2.2.1.1 AFM observations of microgrooves......Page 24
2.2.1.2 Chemical observations......Page 25
2.2.1.3 SHG measurements......Page 27
2.2.1.4 Optical retardation measurements......Page 30
2.2.1.5 X-ray scattering and absorption......Page 33
2.2.2 Definition of rubbing strength......Page 38
2.2.3 Alignment mechanisms......Page 45
2.2.4 Pretilt mechanisms......Page 47
2.3.1 Alignment defects of actual devices......Page 51
2. Tilt-reverse......Page 52
3. Twist-reverse......Page 53
1. Impurity attached to surface......Page 54
2.3.1.3 Defects around spacer beads......Page 55
1. Static electricity and dust......Page 58
2. Uniformity......Page 59
3. Limited viewing angle caused by unidirectional alignment......Page 60
2. Baking......Page 62
1. Voltage holding ratio......Page 64
2.3.3.3 Rubbing cloth......Page 65
References......Page 66
3.1 Introduction......Page 70
3.2.1 Introduction......Page 72
3.2.2.1 Photoisomerization......Page 74
1. Photodimerization......Page 76
2. Photodecomposition......Page 77
4. Hybrid (decomposition and crosslinking)......Page 78
3.2.2.3 Progress in photoalignment materials......Page 79
3.2.3.1 Experimental results......Page 80
3.2.3.3 Alignment mechanism......Page 81
3.2.4 Influence of UV light on display device characteristics......Page 85
3.2.5 Light source......Page 87
2. Photoalignment......Page 88
2. Photoalignment......Page 89
3.2.7 Current status of photoalignment......Page 90
3.3.1 Alignment mechanism......Page 91
3.3.3 Material scientific view point......Page 93
3.4.2 Control of the pretilt direction by a ‘‘hybrid cell’’......Page 94
3.4.3 Microgroove surface control of pretilt angle direction......Page 98
3.5.1 LB membranes for the alignment layer......Page 99
3.5.3 Structure of polyimide LB films and liquid crystalline alignment on the film......Page 100
3.6 PTFE Drawn Films for Alignment Layers......Page 102
3.7 Liquid Crystalline Alignment on Chemically Treated Surfaces......Page 104
3.7.2 Treatment of the substrate surface by active surface agents......Page 105
3.1–3.2 Introduction......Page 110
3.4–3.6 Liquid Crystal Alignment on Microgroove Surfaces–PTFE Drawn Films for Alignment Layers......Page 112
3.7 Liquid Crystalline Alignment on Chemically Treated Surfaces......Page 113
4.1.1 Molecular alignment in nematic phases......Page 114
4.2 Twisted Nematic (TN)......Page 117
4.2.1 Basic operation......Page 118
4.2.2 OFF state......Page 119
4.2.4 Dynamic response......Page 120
4.3 Super Twisted Nematic (STN)......Page 121
4.4 The IPS (In-Plane Switching) Mode......Page 125
4.5.1 Vertical alignment (VA) mode......Page 126
4.5.2 MVA method (Multi-domain vertical alignment method)......Page 127
4.6 Pi Cell......Page 132
4.6.1 LC configuration......Page 133
4.6.2 Dynamics......Page 135
4.7.1 Improvement of the viewing angle dependence of TN-LCDs......Page 136
4.7.2 Mechanism of viewing angle dependence of TN-LCDs......Page 137
4.7.3 Reduction of the viewing angle dependence by the multi-domain mode......Page 138
4.7.4 Formation of two kinds of regions possessing different alignment directions in one pixel......Page 140
4.7.5 Formation of two kinds of region with different pretilt angles in one pixel......Page 142
4.7.5.2 Control of pretilt angle by photoradiation......Page 145
4.8 Polymer Dispersed Liquid Crystals (PDLC)......Page 147
4.2 Twisted Nematic (TN)......Page 149
4.6 Pi Cell......Page 150
4.7 Multi-domain Mode......Page 151
4.8 Polymer Dispersed Liquid Crystals (PDLC)......Page 152
5.1.2 Ferroelectric SmC* liquid crystals......Page 153
(b) Memory effect......Page 155
5.1.4.1 Smectic layer structures in various alignments......Page 156
5.1.4.2 Relationship between molecular tilt angle and chevron layer tilt angle......Page 157
5.1.5.2 Observed phenomena and considerations......Page 163
5.1.6 Summary......Page 176
5.2.2 Driving scheme of SSFLCs......Page 177
5.2.3 FLC materials for excellent alignment and bistability......Page 179
Thermoplastic Polymers and Thermosetting Polymers......Page 180
5.2.4.3 Crystallographic class......Page 182
Polyimides (PI)......Page 183
5.2.4.5 Odd–even effect......Page 184
5.2.5.1 Polarity on polymer surface and alignment of SSFLC......Page 186
5.2.5.2 Sign of the surface polarity, S......Page 189
5.2.6.2 Annealing process......Page 191
5.2.7 Electric double layer influence......Page 193
5.1 Layer Structure and Molecular Orientation of Ferroelectric Liquid Crystals......Page 198
5.2 Alignment and Bistability of Ferroelectric Liquid Crystals......Page 199
6.1.1 Introduction......Page 201
6.1.2 The DHF mode......Page 202
6.1.3 The bookshelf orientation......Page 203
6.1.4 C1-uniform (C1U) orientation......Page 209
6.1.5 C2-uniform (C2U) orientation......Page 211
6.1.6 Shock stability of FLC displays......Page 216
6.1.7 The layer-rotation phenomenon......Page 220
6.1.8 Summary......Page 222
6.2.1 AFLC materials and Devices......Page 223
6.2.2.1 Polymer molecular structure for alignment layers......Page 226
6.2.2.2 Surface energy......Page 228
6.2.2.5 Rubbing conditions......Page 229
6.2.3.1 Symmetry of alignment layers......Page 230
6.3.1 Introduction......Page 233
6.3.2 Specifications of liquid crystalline materials with spontaneous polarization for TFT driving......Page 234
6.3.2.1 The relationship between spontaneous polarization and saturated voltage......Page 235
6.3.3.1 Active matrix driving for SSFLC......Page 239
6.3.3.2 Deformed-Helix FLC (DHF) mode......Page 242
6.3.3.3 Twisted FLC mode......Page 245
Parallel stripe textures......Page 250
6.3.3.4 The ‘‘Texture Mode’’ for simple matrix driving......Page 251
6.3.3.5 Short pitch bistable ferroelectric (SBF) liquid crystal [59] for simple matrix driving......Page 252
6.3.3.6 Alternating Polarization Domains (APD) mode for active matrix driving......Page 253
6.3.3.7 Monostable SSFLC mode with tilted bookshelf structure......Page 254
6.3.3.8 Continuous Director Rotation (CDR) mode......Page 255
6.3.3.9 The application of the frustoelectric phase......Page 257
Random model......Page 258
Collective model......Page 260
6.1 Molecular Orientations and Display Performance in FLC Displays......Page 262
6.3 Application of FLC/AFLC Materials to Active matrix Devices......Page 265