Norbornene Photoalignment Layer for LCD Stability
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Solution Overview
Problem
Conventional liquid crystal alignment methods, such as the rubbing process, face challenges including static charge damage to TFTs, poor alignment in complex pixel structures, dust issues, and inability to form multi-domains, while photopolymerizable alignment layers suffer from low alignment stability and image sticking due to unreacted photoreactive groups and low anchoring energy.
Innovation Solution
A liquid crystal alignment layer comprising a photo-alignment polymer with norbornene-based repeating units and a mesogen layer, where the photoreactive groups are partially aligned and cured, enhancing interaction with liquid crystals and reducing image sticking by forming a multidirectional pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a photopolymerizable liquid crystal alignment layer is applied to achieve wide viewing angle and contrast ratio characteristics, then alignment speed and liquid crystal alignment property are improved, but alignment stability decreases and image sticking occurs due to unreacted photoreactive groups and low anchoring energy
Solution Approach 1:
The patent changes the chemical structure parameters of the photoalignment polymer by introducing norbornene-based repeating units with specific photoreactive groups. This structural modification enables partial photoreaction and photoalignment while maintaining stability, resolving the contradiction between fast alignment and stable performance
Solution Approach 2:
The patent creates a composite alignment layer system combining photoalignment polymer with specific functional groups (norbornene-based structure) that provide both rapid photopolymerization capability and long-term alignment stability. The composite structure integrates the benefits of fast alignment with the stability needed to prevent image sticking
2Ease of manufacture
If conventional rubbing process is used for liquid crystal alignment, then alignment can be achieved, but static charges are generated that damage TFT, particles or dust are generated that deteriorate screen quality, and multi-domains cannot be formed
Solution Approach 1:
The patent replaces the mechanical rubbing process with a photochemical alignment method. Instead of using physical contact with a rubbing cloth that generates static charges and dust, the invention uses UV light irradiation to induce photoreaction and photoalignment in the polymer layer, eliminating all mechanical contact and its associated harmful effects
Solution Approach 2:
The patent introduces a photoalignment polymer layer as an intermediary medium that absorbs UV light and translates it into molecular orientation. This intermediary converts optical energy into alignment force, replacing the need for mechanical rubbing while achieving the same alignment function without harmful side effects
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 proposed solution improves alignment stability and reduces image sticking, maintaining excellent contrast ratio and wide viewing angle characteristics in liquid crystal display devices.
Implementation Method 1
a photoreaction is generated by irradiation of the alignment layer with linearly polarized UV light
Implementation Method 2
the main chains of the photo-alignment polymer are unidirectionally aligned, and thus liquid crystals included in the liquid crystal layer can be aligned due to the effect of the alignment layer thus photoaligned
Data Source
AI summary
The present invention relates to a photoalignment layer, for example, a liquid crystal alignment layer, which is able to realize the wide viewing angle and contrast ratio characteristics of a photopolymerizable alignment layer, and to facilitate interaction with the liquid crystal layer, thereby improving alignment stability and reducing image sticking, and a liquid crystal cell including the same. The liquid crystal alignment layer includes a photo-alignment layer including a photo-alignment polymer having at least partially photo-aligned photoreactive groups; and a mesogen layer including a cured product of a reactive mesogen that is liquid crystal-aligned by the photo-aligned photoreactive group, in which the photo-alignment polymer include a norbornene-based polymer having a particular structure.