Exo-Rich Norbornene Polymer for Liquid Crystal Alignment
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Solution Overview
Problem
Current liquid crystal display technologies face challenges in achieving high-quality dynamic images due to the inefficiencies in the rubbing process for liquid crystal alignment, which results in mechanical scratches, static electricity, and reduced productivity, and the optical alignment process using polycinnamate-based polymers has limitations in alignment property and process efficiency.
Innovation Solution
A norbornene polymer with at least 50 mol % exo isomers and a photoreactive functional group is developed, allowing for increased molecular weight and thermal stability, with a planar three-dimensional structure that enhances inter-chain cross-linking and anisotropic properties during photoreaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polycinnamate-based polymer is used for optical alignment, then liquid crystal alignment can be achieved through UV photopolymerization, but the polymer mobility is poor and photoreaction rate is slow requiring long exposure time
Solution Approach 1:
The patent changes the chemical structure parameters of the polymer by introducing norbornene backbone with specific stereochemistry (endo-exo ratio control) and incorporating photoreactive groups (cinnamate, coumarine, chalcone, fluorescein) at controlled ratios. This structural parameter optimization enables faster photoreaction kinetics while maintaining alignment quality, reducing exposure time from conventional levels to 5-30 seconds.
Solution Approach 2:
The patent creates composite polymer structures by copolymerizing norbornene derivatives with photoreactive groups. The composite nature combines the rigid norbornene backbone (providing thermal stability and structural integrity) with flexible photoreactive side groups (enabling rapid UV response). This composite approach resolves the contradiction between structural stability and photoreaction speed.
2Reliability
If rubbing process is used for liquid crystal alignment, then alignment can be achieved mechanically, but mechanical scratches and static electricity occur causing reduced productivity and yield
Solution Approach 1:
The patent replaces the mechanical rubbing process with a photochemical alignment system. Instead of using physical contact between rubbing cloth and alignment film, the invention uses UV light-induced photopolymerization to create molecular orientation. This substitution eliminates mechanical scratches, static electricity generation, and fiber contamination, thereby maintaining alignment quality while significantly improving productivity and production yield.
Solution Approach 2:
The patent utilizes the phase transition of photoreactive groups during UV irradiation. The photoreactive groups undergo conformational changes and photopolymerization reactions when exposed to UV light, transitioning from isotropic to anisotropic states. This phase transition mechanism creates liquid crystal alignment without mechanical contact, replacing the rubbing process with a non-contact optical method.
3Stability of the object's composition
If photoreactive groups are restricted by polymer main chain, then polymer structure is stable, but photoreaction rate decreases and network polymer formation is slow
Solution Approach 1:
The patent segments the polymer structure into distinct functional regions: a stable norbornene backbone providing structural integrity, and flexible side chains containing photoreactive groups. This segmentation allows the backbone to maintain stability while the side chains remain mobile and accessible for rapid photoreaction. The photoreactive groups are positioned at the periphery rather than being constrained within the main chain, enabling fast network polymer formation.
Solution Approach 2:
The patent extends the photoreactive groups into the spatial dimension by incorporating them as side chains protruding from the polymer backbone. This dimensional arrangement allows photoreactive groups to access UV light from multiple directions and reduces steric hindrance, enabling rapid photoreaction without compromising the stability of the polymer backbone structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The exo-rich norbornene polymer improves the alignment efficiency and stability of liquid crystals, increasing the anisotropic property and photoreaction rate, leading to enhanced optical alignment and improved liquid crystal display quality.
Implementation Method 1
The optical alignment is a mechanism in which a photoreaction of a photosensitive group that is connected to the polymer occurs due to linearly polarized ultraviolet rays
Implementation Method 2
a main chain of the polymer is unidirectionally aligned, thereby forming a photopolymerizable liquid crystal alignment film in which the liquid crystals are aligned
Implementation Method 3
the double bond [2+2] of cinnamate is subjected to the [2+2] cycloaddition reaction by using radiated UV to form cyclobutane
Data Source
AI summary
The present invention relates to a norbornene polymer that comprises a norbornene monomer having a photoreactive functional group, and a method of manufacturing the same. The norbornene polymer comprises at least 50 mol % of exo isomers among the norbornene monomers having the photoreactive functional group. Since the norbornene polymer according to the present invention comprises at least 50 mol % of exo isomers among the norbornene monomers having the photoreactive functional group, a molecular weight is significantly increased while the yield is not reduced during the manufacturing of the polymer. In views of the three dimensional structure, stability is ensured because the polymer has a planar structure in which the photoreactive groups between the molecules are close to each other. Therefore, the distance between the photoreactive groups is reduced, thus increasing the photoreaction rate.