Pixel Unit Multi-Domain Electrode Alignment for Liquid Crystal Displays
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Solution Overview
Problem
Liquid crystal display panels face issues with low contrast ratio and transmittance due to irregular alignment of liquid crystal molecules caused by contamination and static electricity in rubbing processes, and the continuum arrangement of liquid crystal molecules at pixel electrode intersections leads to discontinuous alignment and reduced efficiency.
Innovation Solution
A pixel unit design with a specific configuration of gate lines, data lines, active devices, and pixel electrodes, including sub-pixel electrodes and connecting electrodes, that control the orientation of liquid crystal molecules through a multi-domain alignment structure, using a polymer-stabilized alignment (PSA) method to stabilize pretilt angles and reduce contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rubbing processes are used to form alignment layers, then liquid crystal molecules can be aligned in specific directions, but the alignment layers become contaminated by impurities and generate static electricity, resulting in low yield and low contrast ratio
Solution Approach 1:
The patent replaces the mechanical rubbing process with a photo-alignment process using optical fields. Specifically, a photopolymer alignment layer is formed by irradiating a photopolymer composition with polarized light, causing the liquid crystal molecules to align in specific directions determined by the polarization direction of the light, thereby eliminating mechanical contact and its associated contamination and static electricity problems
Solution Approach 2:
The patent changes the alignment mechanism from mechanical friction to photo-induced molecular orientation. By controlling parameters such as the polarization angle of irradiation light and the photopolymerization conditions, precise alignment of liquid crystal molecules can be achieved without the harmful effects of rubbing processes
2Device complexity
If liquid crystal molecules are arranged in continuum at pixel electrode intersections, then the electrode structure can be simplified, but the liquid crystal molecules show discontinuous arrangement, decreasing liquid crystal efficiency
Solution Approach 1:
The patent segments the pixel electrode into multiple sub-pixel electrodes (red, green, blue sub-pixels) with distinct alignment directions. Each sub-pixel electrode is further divided into multiple domains with different liquid crystal orientation directions, ensuring continuous and efficient liquid crystal alignment even at intersections, thereby maintaining high liquid crystal efficiency while achieving the desired electrode structure
3Object-affected harmful factors
If four domains are used in PSA liquid crystal display panel, then light leakage at dark state is reduced, but dark fringes appear on pixels and transmittance decreases due to discontinuous liquid crystal arrangement at electrode intersections
Solution Approach 1:
The patent applies different alignment directions to different local regions (domains) within each sub-pixel electrode. By optimizing the number and orientation of domains in each local region, the patent achieves both reduced light leakage at dark states and maintained transmittance, eliminating the trade-off between these two parameters
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 design enhances the contrast ratio and transmittance by stabilizing liquid crystal molecule orientation, reducing dark fringes and improving display quality by maintaining efficient liquid crystal alignment and minimizing light leakage.
Implementation Method 1
irradiating the liquid crystal material by ultra-violet light so as to fix the pretilt angle of the light crystal molecules and achieve the stabilization of the polymers
Implementation Method 2
applying voltages to the liquid crystal material to make the liquid crystal molecules have a pretilt angle
Data Source
AI summary
A pixel unit includes a gate line, a first data line, a second data line, a first active device, and a pixel electrode. The first active device is electrically connected to the gate line and the first or second data line. The pixel electrode is electrically connected to the first active device. The pixel electrode includes a first sub-pixel electrode, a second sub-pixel electrode, and a first connecting electrode. Each of the first sub-pixel electrode and the second sub-pixel electrode includes a trunk electrode, a traverse trunk electrode, and branch electrodes. The first connecting electrode connects the first sub-pixel electrode to the second sub-pixel electrode.