Photoreactive Mesogens for Liquid Crystal Alignment
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Solution Overview
Problem
Current liquid crystal display technologies face challenges in achieving optimal viewing angle dependence, contrast, and response times due to the complexity and cost of producing polyimide layers, particularly in VA displays, which also require a separate self-assembly step and are prone to alignment reversibility under light exposure.
Innovation Solution
Development of photoreactive mesogens that enable in-situ photoalignment of liquid crystals using linearly polarized light, eliminating the need for polyimide layers and allowing for improved dark state and voltage holding ratios, while being compatible with mass production processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide layers are used for liquid crystal alignment, then alignment stability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent removes the polyimide alignment layer from the display structure entirely. Instead of using a separate polyimide layer for alignment, the invention uses photoreactive mesogenic compounds that directly provide alignment functionality through photoinduced self-assembly, eliminating the need for polyimide deposition and rubbing processes
Solution Approach 2:
The patent combines the alignment function and the liquid crystal medium into a single integrated system. The photoreactive mesogenic compounds are mixed with the liquid crystal molecules, allowing the alignment function to be embedded within the liquid crystal layer itself rather than being provided by a separate polyimide layer
2Manufacturing precision
If separate self-assembly steps are used for alignment, then alignment precision is improved, but production time increases
Solution Approach 1:
The patent incorporates photoreactive mesogenic compounds into the liquid crystal mixture before filling the cell. The alignment function is prepared in advance through chemical composition design rather than requiring post-filling self-assembly processes, enabling alignment to occur naturally when the liquid crystal is introduced
Solution Approach 2:
The patent replaces mechanical alignment methods (polyimide deposition and rubbing) with photoinduced self-assembly of photoreactive mesogenic compounds. This substitution eliminates complex mechanical processing steps while maintaining alignment precision through optical field control
3Reliability
If polyimide layers are used for alignment, then alignment stability is improved, but production cost increases
Solution Approach 1:
The patent replaces expensive polyimide materials and complex deposition equipment with inexpensive photoreactive mesogenic compounds that can be simply mixed into the liquid crystal formulation. This substitution dramatically reduces material costs and eliminates the need for expensive vacuum deposition equipment and rubbing machinery
Solution Approach 2:
The photoreactive mesogenic compounds serve multiple functions simultaneously: they act as liquid crystal molecules, provide alignment functionality, and enable photocontrol. This multi-functionality eliminates the need for separate polyimide alignment layers and reduces the overall complexity of the display structure
4Device complexity
If photoreactive mesogens are used for in-situ photoalignment, then manufacturing complexity is reduced, but viewing angle dependence may worsen
Solution Approach 1:
The patent achieves wide viewing angle by controlling the photoalignment process parameters, including using linearly polarized light with specific orientations and controlling the photoinduced self-assembly conditions to create the desired liquid crystal orientation patterns that provide wide viewing angle characteristics
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 solution provides liquid crystal displays with enhanced viewing angle independence, improved contrast, and reduced production costs by enabling photoalignment within the display assembly, maintaining stability and performance without the need for polyimide layers.
Implementation Method 1
irradiating the liquid crystal mixture with linearly polarised light causing photoalignment of the liquid crystal
Implementation Method 2
curing the polymerizable compounds of the liquid crystal mixture by irradiation with ultraviolet light or visible light having a wavelength of 450nm or below
Data Source
AI summary
The invention relates to a compound of formula I, wherein R11, R21, A11, A, Z, X11, X21, Y11, Y12, Sp11, Sp21, o and p have one of the meanings as given in claim 1. The invention further relates to method of production of a compound of formula I, to the use of said compounds in LC media and to LC media comprising one or more compounds of formula I. Further, the invention relates to a method of production of such LC media, to the use of such media in LC devices, and to LC device comprising a LC medium according to the present invention. The present invention further relates to a process for the fabrication such liquid crystal display and to the use of the liquid crystal mixtures according to the invention for the fabrication of such liquid crystal display.