Dual-functional photoalignment materials with chalcone moieties and LC mixtures for negative dispersion retarder film

다국어 초록 (Multilingual Abstract)

Negative-dispersion liquid crystals (ND-LCs) are essential for broadband phase compensation in advanced display optics. Despite their importance, ND-LC retarder films often suffer from a narrow processing window because the alignment layer cannot sufficiently anchor sterically bulky ND-LC molecules. This interfacial mismatch leads to alignment instability and pronounced exposure-dose-dependent optical non-uniformity. To overcome these limitations, this thesis proposes a single-exposure hybrid photoalignment strategy based on a chalcone–methacrylate copolymer (PM6-CMA2) incorporating a high-anisotropy reactive mesogen (LC242). Unlike dual-exposure schemes (e.g., UVB+UVA) that can induce thermal buildup and alignment relaxation, the proposed approach employs linearly polarized UVA (LPUV) to simultaneously trigger chalcone photodimerization and radical-mediated crosslinking between methacrylate groups and the mesogen. During this process, a liquid-crystal-like anisotropic scaffold is formed in situ at the interface, reinforcing the rigidity and anchoring strength of the alignment layer and thereby significantly improving ND-LC alignment stability and process margin without degrading optical performance. Polarized UV–Vis analysis showed that the hybrid system achieved a substantially higher orientational order parameter than the control (0.0769 vs. 0.00937) and maintained excellent color stability even at low exposure doses (∆E_ab* ≈ 0.27), confirming an expanded processing window. Overall, this single-exposure hybrid photoalignment strategy provides a practical and reproducible route for manufacturing high-performance ND-LC retarder films for OLED display applications.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• Chapter 2. Basic theories 3
• 1. Principles of Anti-Reflection and Circular Polarization 3
• 2. Retardation 5
• 3. Structure and Operation of Retarder Films by LC Type 7
• 4. Alignment method of liquid crystal 9
• 5. Mechanism of photo-alignment 11
• Chapter 3. Experimental 14
• 1. Materials 14
• 2. Synthesis of photoalignment polymers 15
• 2.1 Synthesis of Poly(hydroxyalkymaleimide)(PM6) 15
• 2.2 Synthesis of Chalcone 16
• 2.3 Synthesis of PM6chF 17
• 2.4 Synthesis of PM6-CMA2 18
• 3. Preparation of photoalignment layers 20
• 4. Retarder film fabrication process 21
• 5. Characterization 23
• Chapter 4. Results and Discussion 25
• 1. Molecular Design and Overall Strategy 25
• 2. Synthesis of photopolymer 26
• 2.1 Synthesis of Poly(hydroxyalkymaleimide)(PM6) 26
• 2.2 Synthesis of Chalcone 28
• 2.3 Synthesis of PM6chF 30
• 2.4 Synthesis of PM6-CMA2 32
• 2.5 1H-NMR integrals as a function of chalcone content 35
• 3. Casting solvent selection of photopolymer 37
• 4. Thickness and Cross-sectional Morphology 39
• 5. Surface and Film-Forming Characteristics of Photoalignment layers 41
• 6. Photoreactivity of PM6chF under Pulsed LPUV Irradiation 43
• 7. Formulation Optimization for Single-Exposure Hybrid Photoalignment 44
• 7.1 Photoreactivity under LPUV Irradiation 44
• 7.2 Effect of LC242 Content on Orientation and Phase Retardation 48
• 7.3 Effect of Photoinitiator Content on Orientation and Phase Retardation 51
• 7.4 Content-Dependent Orientation of PM6chF Films: Optimization of Film Composition 54
• 7.5 Comparative Conversion Analysis of PM6chF and PM6-CMA2 Formulations 57
• 8. Photoinduced Anisotropy and Alignment Capability 59
• 8.1 Polarized UV-Vis 59
• 8.2 Order parameter 61
• 9. ND retarder Film Performance and Process Window 63
• 10. Structural Characterization and Interfacial Stabilization Analysis 67
• Chapter 5. Conclusion 70
• References 71