LCD Pixel Structure with Changeable Capacitor for Viewing Angle
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Solution Overview
Problem
Liquid crystal displays, particularly MVA-LCDs, suffer from poor viewing angle characteristics, causing skin tones of Asian individuals to appear whitish when viewed obliquely due to non-monotonic transmittance-voltage characteristics, and residual image issues from voltage changes in sub-pixels.
Innovation Solution
A liquid crystal display structure with two sub-pixels per pixel unit, each with a transistor and a changeable storage capacitor, optimizing threshold voltage and capacitance to achieve monotonic transmittance-voltage characteristics and symmetrical data voltage between frames, improving image quality and viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MVA liquid crystal display is used to achieve wide viewing angle, then viewing angle characteristics are improved, but skin color appears whitish from oblique viewing direction due to non-monotonic transmittance-voltage characteristics
Solution Approach 1:
Each pixel is divided into two distinct areas (first area and second area), where each area has different threshold voltage characteristics. This segmentation allows combining two different T-V characteristics to achieve monotonic transmittance-voltage behavior while maintaining wide viewing angles
Solution Approach 2:
Different regions within the same pixel are assigned different threshold voltage characteristics (one area with original threshold voltage, another with higher threshold voltage). This local differentiation enables each region to contribute differently to the overall transmittance-voltage response, achieving monotonic characteristics across the full viewing angle range
2Manufacturing precision
If pixel is divided into two areas with different threshold voltages to improve transmittance characteristics, then monotonic T-V characteristics are achieved, but residual image problem occurs due to different voltage changes in adjacent frames
Solution Approach 1:
The capacitance value of at least one storage capacitor is made changeable rather than fixed. By adjusting the capacitance parameter dynamically, the voltage change in each area can be equalized across adjacent frames, eliminating residual images while maintaining monotonic T-V characteristics
Solution Approach 2:
The storage capacitor's capacitance is made variable to dynamically adjust voltage distribution between the two pixel areas. This dynamic adjustment ensures that voltage changes in both areas are equalized during frame transitions, preventing residual image formation while preserving the improved transmittance characteristics
3Reliability
If different capacitance values are used in sub-pixels to equalize voltage changes, then residual images are reduced, but device complexity increases
Solution Approach 1:
The capacitance modification is applied locally to only one of the two pixel areas rather than uniformly to both areas or to all pixels. This selective local modification achieves voltage equalization and residual image reduction while minimizing the increase in device complexity
Data Source
AI summary
The present invention provides a liquid crystal display with a plurality of pixel units. Each pixel unit includes two sub-pixels. Each sub-pixel includes a thin film transistor, a liquid crystal capacitor and a storage capacitor. One of the storage capacitors is a changeable capacitor. By the changeable capacitor, two different data voltages are generated in respective sub-pixels during adjacent frames. The different data voltages are symmetrical with respect to a common voltage to improve image quality.