TFT Array Panel Pixel Electrode Oblique Edges
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Solution Overview
Problem
Existing liquid crystal display (LCD) technologies face challenges in enlarging the viewing angle without compromising display quality, as methods to increase viewing angle, such as using vertically aligned LC layers with cutouts or protrusions, lead to reduced transmittance and parasitic capacitance issues, causing light leakage and luminance differences across the screen.
Innovation Solution
A thin film transistor (TFT) array panel design featuring pixel electrodes with oblique edges and data lines that overlap each other, with specific geometrical configurations to minimize parasitic capacitance and maintain uniformity, including bent and linear oblique portions that equidistantly overlap pixel electrodes, thereby reducing unwanted electric fields and luminance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the size of pixel electrodes is increased to compensate for reduced transmittance, then transmittance is improved, but parasitic capacitance between pixel electrodes and data lines increases
Solution Approach 1:
The pixel electrode is designed with different regions having different properties: a first region with larger area for high transmittance and a second region with smaller area for reduced parasitic capacitance. This local differentiation allows the electrode to simultaneously achieve high light transmission while minimizing capacitive coupling with data lines.
Solution Approach 2:
The pixel electrode is divided into multiple regions (first region and second region) with different areas and positions. The first region is positioned farther from the data line to reduce parasitic capacitance, while the second region is positioned closer to maintain aperture ratio. This segmentation resolves the contradiction between transmittance and parasitic capacitance.
2Illumination intensity
If the size of pixel electrodes is increased to compensate for reduced transmittance, then transmittance is improved, but lateral electric fields between pixel electrodes increase causing light leakage
Solution Approach 1:
Different regions of the pixel electrode are designed with different areas and positions relative to the data line. The first region with larger area is positioned to maximize light transmission, while the second region with smaller area is positioned to minimize lateral electric field interference with adjacent pixels, thus reducing light leakage.
3Reliability
If a wide black matrix is used to screen textures and light leakage, then display quality is improved, but aperture ratio is reduced
Solution Approach 1:
The invention extracts and eliminates the need for a wide black matrix by addressing the root cause of light leakage through proper pixel electrode design. By positioning the first region farther from the data line and optimizing the electrode geometry, lateral electric fields are minimized, making extensive black matrix coverage unnecessary and thus preserving aperture ratio.
4Productivity
If step-and-repeat process is used for exposure, then manufacturing capability is improved, but alignment accuracy deteriorates causing stitch defects
Solution Approach 1:
The design ensures that parasitic capacitances are uniform across different shots by maintaining consistent geometric relationships between pixel electrodes and data lines. This uniformity compensates for alignment variations in step-and-repeat exposure, preventing luminance differences and stitch defects at shot boundaries.
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
This design enhances the viewing angle of LCDs while maintaining high transmittance and uniformity, reducing parasitic capacitance and light leakage, and preventing stitch defects, thus improving overall display quality.
Implementation Method 1
The LC layer is subject to an electric field generated by the electrodes, and variations in the field strength change the molecular orientation of the LC layer
Implementation Method 2
A change in the molecular orientation of the LC layer, in turn, changes the polarization of light passing through the LC layer
Data Source
AI summary
A liquid crystal display with improved viewing angle and uncompromised transmittance is provided, along with a thin film transistor (TFT) array panel usable for such liquid crystal display. The TFT array panel includes a substrate, a plurality of gate lines formed on the substrate, a plurality of data lines formed on the substrate and intersecting the gate lines, and a plurality of thin film transistors. Each of the thin film transistors includes a gate electrode connected to one of the gate lines, a source electrode connected to one of the data lines, and a drain electrode. The TFT array panel also includes a plurality of pixel electrodes, each of the pixel electrodes connected to one of the drain electrodes and having a pair of oblique edges parallel to each other, and covering at least a portion of the drain electrodes.