Liquid Crystal Display Pixel Structure for Monotonic Transmittance
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Solution Overview
Problem
Liquid crystal displays, particularly multi-domain vertically aligned LCDs, suffer from color shift issues when viewed from oblique angles, where skin tones appear whitish due to non-monotonic transmittance-voltage characteristics, and residual image problems arise from voltage changes in sub-pixels.
Innovation Solution
A pixel structure incorporating a transistor and a capacitor with a metal-insulator-semiconductor (MIS) structure, where the capacitance is adjusted by varying the voltage difference between conductive layers and threshold voltage, and the area relationship between conductive and semiconductor layers, to achieve monotonic transmittance and reduce color shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MVA liquid crystal display structure is used to achieve wide viewing angle, then viewing angle characteristics are improved, but color shift occurs in oblique viewing direction causing skin tone to appear whitish
Solution Approach 1:
The patent modifies the T-V characteristics by changing the threshold voltage parameter. Specifically, it combines two different T-V curves with different threshold voltages (original threshold voltage and higher threshold voltage) to create a composite curve that maintains monotonicity in oblique viewing direction, thereby eliminating color shift while preserving wide viewing angle characteristics
2Object-affected harmful factors
If typical method divides pixel into two areas with different threshold voltages to achieve monotonic T-V characteristics, then color shift is reduced, but residual image problem occurs due to different voltage changes in sub-pixels
Solution Approach 1:
The patent applies local quality by creating different capacitor structures in different regions of the pixel. Specifically, it uses a first capacitor with a first dielectric layer and a second capacitor with a second dielectric layer having different capacitance values, allowing each region to be optimized for its specific function while maintaining overall image quality and monotonic T-V characteristics
3Reliability
If capacitor area is increased to improve holding capacitance, then voltage stability is improved, but pixel area is reduced leaving less area for liquid crystal
Solution Approach 1:
The patent employs thin film dielectric layers to create capacitors with high capacitance density. By using thin film structures for the dielectric layers, the capacitor achieves sufficient holding capacitance for voltage stability while occupying minimal area, thereby leaving adequate space for the liquid crystal region in the pixel structure
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, and each sub-pixel includes a thin film transistor, a liquid crystal capacitor and a storage capacitor. One of the storage capacitors is a tunable capacitor. The tunable capacitor includes a first conductive layer, an insulating layer, a semiconductor layer with a area Asem, and a second metal layer. The second conductive layer has a first region with a area Acon overlapping with the semiconductor layer. The area Acon is less than the area Asem.