TFT Substrate Symmetrical Slanted Electrodes Prevent Color Shift
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Solution Overview
Problem
In-plane switching (IPS) mode liquid crystal displays (LCDs) suffer from color shift issues due to refractive index anisotropy, leading to degradation in picture quality, and existing solutions compromise aperture ratio by requiring domain division and black matrix overlap.
Innovation Solution
A thin film transistor (TFT) substrate design with alternately arranged unit pixels and electrodes slanted relative to gate and data lines, forming symmetrical in-plane fields to compensate for refractive index anisotropy differences without domain division, thereby preventing color shift and enhancing aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If domain division is implemented to compensate for refractive index anisotropy, then color shift is prevented, but aperture ratio is reduced due to black matrix overlap
Solution Approach 1:
The pixel electrode is divided into multiple domains with different rubbing directions to compensate for refractive index anisotropy. Each domain is assigned a specific orientation (e.g., 0°, 60°, 120°) to balance the optical properties across the pixel, preventing color shift while maintaining high aperture ratio through optimized domain boundaries
Solution Approach 2:
The patent employs asymmetric domain configuration where the rubbing directions and widths of different domains are intentionally made asymmetric to counterbalance the symmetric refractive index anisotropy of the liquid crystal molecules. This asymmetric design allows color compensation without requiring symmetric black matrix patterns that would reduce aperture ratio
2Device complexity
If liquid crystal molecules are uniformly arranged according to rubbing axis, then alignment is simplified, but color shift occurs due to refractive index anisotropy
Solution Approach 1:
The uniform alignment is segmented into multiple domains with different rubbing directions. Instead of a single uniform rubbing axis, the alignment film is divided into domains with rubbing directions at specific angles (e.g., 0°, 60°, 120°), maintaining alignment simplicity through standardized angular relationships while preventing color shift through directional diversity
Solution Approach 2:
Different regions of the pixel are assigned different local alignment properties through varying rubbing directions in each domain. The local rubbing direction in each domain is optimized to compensate for the refractive index anisotropy in that specific region, while the overall pattern maintains global consistency for manufacturing
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 TFT substrate design effectively compensates for refractive index anisotropy differences between sub-pixels, preventing color shift and improving aperture ratio by eliminating domain division, thus enhancing the display's image quality and efficiency.
Implementation Method 1
The LCDs are devices for displaying images by using electro-optical characteristics of liquid crystal molecules and can be divided into a twisted nematic (TN) mode LCD, a vertically aligned (VA) mode LCD, and an in-plane switching (IPS) mode LCD.
Implementation Method 2
Liquid crystal molecules 10 in the liquid crystal layer have a dielectric constant anisotropy (Δε) and a refractive index anisotropy (Δn).
Implementation Method 3
Liquid crystal molecules 10 in the liquid crystal layer have a dielectric constant anisotropy (Δε) and a refractive index anisotropy (Δn).
Data Source
AI summary
A thin film transistor (TFT) substrate for a liquid crystal display is provided. The thin film transistor substrate includes: a plurality of gate lines and a plurality of data lines that cross each other and define a plurality of sub-pixels; and a plurality of unit pixels in which first and second unit pixels are alternately formed in a direction of the gate lines and first and second unit pixels are formed vertically in a direction of the data lines, wherein the first unit pixel includes three sub-pixels and the first electrodes are slanted with respect to the gate lines and the data lines in each sub-pixel, the second unit pixel includes three sub-pixels and the second electrodes are a slanted with respect to the gate lines and the data lines in each sub-pixel, and the slant of the second electrodes is symmetrical to the slant of the first electrodes.