VA LCD Color Wash-Out Mitigation via Common Voltage Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid crystal display (LCD) devices using the vertically aligned mode (VA mode) suffer from a color wash-out phenomenon when viewed at oblique angles, particularly affecting skin tones, which existing half-tone technologies attempt to address but often result in low reliability, non-uniform images, and increased power consumption.
Innovation Solution
The solution involves modulating a common voltage to differentiate the coupling voltage of a first pixel capacitor from that of a second pixel capacitor, using a specific capacitor configuration and voltage levels to generate distinct 'data signal-transmittance' curves for each sub-pixel, thereby improving color accuracy without requiring additional scan lines or increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If half-tone technology is implemented by dividing the pixel unit into two areas with different gamma characteristic curves, then the color wash-out phenomenon is eliminated, but the device complexity increases due to additional circuit requirements
Solution Approach 1:
The pixel unit is divided into two sub-pixels (first sub-pixel and second sub-pixel) with different gamma characteristic curves. The first sub-pixel uses a first gamma characteristic curve while the second sub-pixel uses a second gamma characteristic curve, allowing different gray-scale voltages to produce different transmittance values and eliminate color wash-out.
Solution Approach 2:
The common electrode serves multiple functions: it acts as a reference for both sub-pixels and enables the generation of different gamma characteristic curves through voltage modulation. By modulating the common voltage, the system can differentiate between the first and second pixel capacitors without requiring separate reference electrodes.
2Area of stationary object
If the voltage of the second sub-pixel capacitor is determined by coupling method through serially connected storage capacitor, then the aperture ratio is maintained, but the reliability decreases due to voltage shifting when electric charges are captured
Solution Approach 1:
The common electrode acts as an intermediary that enables voltage differentiation between sub-pixels without requiring floating capacitors. By modulating the common voltage, the system can control the voltage of the second sub-pixel capacitor without relying on coupling methods that cause voltage shifting.
3Object-affected harmful factors
If two different gamma characteristic curves are directly assigned from the system to sub-pixel capacitors through transistors and scan lines, then the color wash-out is eliminated, but the power consumption doubles
Solution Approach 1:
The first and second sub-pixels share common circuit elements including the common electrode, scan lines, and data lines. This merging approach allows both sub-pixels to be driven using the same circuit infrastructure, eliminating the need for separate driving circuits and reducing power consumption while maintaining different gamma characteristic curves.
Data Source
AI summary
A liquid crystal display and a driving method thereof are provided. A pixel of the liquid crystal display includes a first pixel capacitor, a second pixel capacitor, a first transistor, and a second transistor. A first terminal and a second terminal of the first pixel capacitor are respectively coupled to the first transistor and a common voltage. A first terminal and a second terminal of the second pixel capacitor are respectively coupled to the second transistor and the common voltage. A voltage between the first and the second terminals of the first capacitor is differentiated from a voltage between the first and the second terminals of the second capacitor by modulating the common voltage. A coupling voltage of the first pixel capacitor is differentiated from a coupling voltage of the second pixel capacitor by modulating the common voltage. Thereby, the phenomenon of color wash-out is reduced.