(The)high speed response liquid crystal materials for TFT-LCD = TFT-LCD용 고속응답 액정 재료에 관한 연구

다국어 초록 (Multilingual Abstract)

Liquid crystals play an important role in fabricating of liquid crystal display (LCD) and they are model materials for organic chemists to investigate the connection between chemical structures and physical properties. For their applications, a complete understanding of the matter, the design and synthesis of liquid crystal, and the corresponding necessary general physical properties is required on the basis of some knowledge of the particulars of display technology.
The first part of this thesis includes synthesized liquid crystal compounds with core structures as follows; (1) CCP (bicyclohexylphenyl), (2) CPP (cyclohexylbiphenyl), (3) CECP or CCEP with ethylene linkage group and (4) CeP (cyclohexylbenzoate) with ester linkage group, where C stands for cyclohexane ring, P for benzene sing, E for ethylene linkage groups and e for ester linkage groups and e for ester linkage group. As a certain set of physicochemical requirements related to the optimal performance of AM-LCD measured in order to investigate relationship with structure-physical~properties. These specifications include the nematic phase range, dielectric anisotropy(Δε ) birefringence(Δn), kinematic viscosity(η) and elastic constatns(K_(1),K_3).
Also the thesis includes the calculations of not only the configuration and geometrical anisotropy of the molecule, but also the polarity and polarizability of the molecule using the MOPAC 5.0 package program in Chem 3D 5.0 POR version as empirical methods for the molecular design of high speed response liquid crystal material.
The final goal of the thesis work is aimed for the performance which was required in fast response display technology for TV/Monitor applications, via the electro-optic response exhibited by liquid crystals, to form a moving image on the screen at the time interval between two video frames (at 6OHz).
We have investigated how a certain chemical structure can be produced towards improved electro optical and viscoelastic properties of liquid crystal mixtures; on the other hand, for the increasing performance of TFT-LCDs be considered extremely stringent reliability demands on the liquid crystals. This work empirical trends concerning the relations between molecular structure and electro-optic response of thermotropic liquid crystals. This involves the following aspects (1) factors increasing the polarizability and polarity of a molecular structure, (2) factors leading to higher optical anisotropy, (3) factors favoring the formation of high-clearing liquid crystal materials and (4) factors influencing the packing density of the mesophase.
These factors are not only related to the configuration, conformation, and geometrical anisotropy of the molecule, but also to the polarity and polarizability of the molecule. The mutual effect of the electronic and the stereochemical factors are also discussed, ending up with suggestions for the molecular design of high-speed response liquid crystal materials with high birefringence and dielectric anisotropy, and high clearing temperatures.
This work has been a major part of the thesis and resulted in an advanced mixture with distinctly superior performance in comparison with the commercially available LC mixtures and ideally successful for research on TV/Monitor application for the addressing of AM-LCDs

목차 (Table of Contents)

• Abstract = ⅰ
• Overview = ⅳ
• Contents = ⅶ
• Chapter 1. Introduction = 1
• 1.1. Liquid Crystal Displays = 1
• 1.2. Liquid Crystal Phase = 2
• 1.2.1.The nematic and cholesteric phase = 4
• 1.2.2.The smectic A and C phases = 5
• 1.3. Molecular Structures of Calamitic Liquid Crystals = 6
• 1.4. Liquid Crystal Materials : Applications = 11
• 1.4.1. Low optical anisotropy = 11
• 1.4.2. High dielectric anisotropy = 12
• 1.4.3. Low viscosity = 12
• 1.4.4. High elastic constant ratio = 12
• 1.4.5. High optical anisotropy = 12
• 1.5. Material Requirements for Active Matrix Displays = 13
• 1.6. Materials for TV Applications = 14
• References = 16
• Chapter 2. Super Fluorinated Materials (SFM) for AM-LCD Applications = 19
• Abstract = 19
• 2.1. Introduction = 20
• 2.2. Material Study = 21
• 2.2.1. Material requirements for active matrix displays = 25
• 2.3. Synthesis = 26
• 2.4. Mesomorphic Properties = 28
• 2.5. Physical Properties = 35
• 2.5.1. Voltage holding ratio = 38
• 2.5.2. Viscosity = 39
• 2.5.3. Optical anisotropy = 39
• 2.6. Practical Mixtures = 41
• 2.7. Experimental = 48
• 2.7.1. Preparation of 4'-trans-n-pentylbicyclohexyl-4-one(9) = 49
• Method A = 52
• Method B = 55
• Method C = 56
• 2.7.2. Preparation of 4'-trans-pentyl-4-(3,4-difluorophenyl)bicyclohexyl (2-12) = 57
• 2.7.3. Preparation of 4'-trans-pentyl-4-(2-(3,4-difluorophenyl)ethyl)bicyclohexyl (3-6) = 59
• 2.7.4. Preparation of 4-n-trans-pentyl-(2-(4-(3,4-difluorophenyl)cyclohexyl)ethyl)cyclohexane (4-10) = 60
• 2.7.5. Preparation of 2,3-difluorophenyl-4-trans-n-pentylcyclohexylate (5-3) = 65
• 2.7.6. Preparation of 4'-(4-trans-alkylcyclohexyl)-3,4,5-trifluorbiphenyl (6-5) = 67
• 2.8. Conclusion = 69
• References = 70
• Chapter 3. 2,3,4-Trifluoro Phenylbicyclohexane Liquid Crystal with the Low Viscosity and Small Dielectric Anisotropy = 73
• Abstract = 73
• 3.1. Introduction = 74
• 3.2. Equations for Dielectric and Optical Anisotropies = 77
• 3.3. Experimental = 82
• 3.4. Measurements = 84
• 3.5. Result and Discussion = 87
• 3.5.1. Mesophase = 87
• 3.5.2. Quantum chemical calculation = 100
• 3.5.3. Physical properties = 101
• 3.6. Synthesis = 116
• 3.6.1. Preparation of 4'-trans-n-alkyl-4-2,3,4-trifluorophenylbicyclohexyl (4-6) = 118
• 3.6.2. Preparation of 4'-trans-butyl-4-(2,4-difluoro-3-isothiocyanatophenyl)bicyclohexane = 120
• 3.7. Conclusion = 120
• References = 122
• Chapter 4. Physical and Electro-Optical Properties of 3,(5)-(di)fluoro-4-isothiocyanato Phenyl Liquid Crystals with Large Birefringence = 125
• Abstract = 125
• 4.1. Introduction = 126
• 4.2. Synthesis = 127
• 4.2.1. Characterization = 128
• 4.2.2. General scheme of synthesis = 128
• 4.2.3. Preparation of 4-brome-2,6-difluoro-N,N-dibenzylaniline (4) = 130
• 4.2.4. Preparation of 4'-alkyl-4-(3,5-difluoro-4-isothiocyanato-phenyl)bicyclohexane (13) = 131
• 4.2.5. Preparation of (4'-trans-pentylbicyclohexyl-4-yl)carbaldehyde (18) = 134
• 4.3. Liquid Crystalline Properties = 136
• 4.3.1. Characterization = 136
• 4.3.2. Thermodynamic properties = 136
• 4.3.3. Dielectric and optical anisotropy = 141
• 4.4. Conclusion = 144
• References = 146
• Chapter 5. Voltage Holding Ratio Characteristics of Fluoro-, Cyano-and Isothio-cyanatated Liquid Crystal Materials = 147
• Abstract = 147
• 5.1. Introduction = 148
• 5.2. Experimental = 149
• 5.3. Model of Charge Density on an Electrode of TN Cells = 151
• 5.4. Result and Discussion = 153
• 5.4.1. Molecular parameter - assisted prediction of VHR = 153
• 5.4.2. The voltage holding ratio characteristics of polar liquid crystal compounds = 157
• 5.4.3. Frequency and temperature dependence of the voltage holding ratio = 159
• 5.5. Conclusion = 161
• References = 163
• Chapter 6. High Speed Response LC Mixtures for TV/Monitors of TFT-LCDs = 165
• Abstract = 165
• 6.1. Introduction = 166
• 6.2. Experimental = 167
• 6.3. Results and Discussion = 169
• 6.3.1. Blending of liquid crystal mixtures containing fluoroisothiocyanatophenyl compounds = 169
• 6.3.2. Liquid crystal mixtures for high response time = 169
• 6.3.3. High birefringence and elastic constant LC mixture for LCD TV application = 173
• 6.3.4. Switching times vs. switching parameters = 177
• 6.3.5. Bias voltage effect = 182
• 6.3.6. High △n mixtures = 187
• 6.4. Conclusion = 189
• References = 190
• Chapter 7. Concluding Remarks = 191
• 7.1. Conclusions = 191
• 7.2. The Research Progress in this work = 194