Multi-domain Vertical Alignment LCD Gamma Compensation
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Solution Overview
Problem
Multi-domain vertical alignment LCDs suffer from non-uniform gamma values due to the birefringence effect, leading to poor picture quality when viewed from the edges, as all pixels in the same electric field environment have similar tilt angles.
Innovation Solution
The design includes unequal overlapping sizes of coupling electrode lines with different voltages applied to each, allowing for adjustment of liquid crystal tilt angles to compensate gamma values, with specific voltage control for each color to achieve uniformity across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If all pixels are placed in the same electric field environment with uniform tilt angles, then the device structure is simple and easy to manufacture, but the gamma values of red, green and blue colors become non-uniform due to birefringence effect, degrading picture quality
Solution Approach 1:
The patent introduces different coupling electrode line overlapping sizes for different color sub-pixels (red, green, blue) within the same pixel. This creates local variations in the electric field environment for each color channel, allowing independent gamma value adjustment. The different overlapping sizes compensate for the birefringence effect specific to each color, achieving uniform gamma values across all colors while maintaining a relatively simple overall structure.
2Manufacturing precision
If coupling electrode lines have unequal overlapping sizes with pixel electrodes, then gamma values can be compensated for different colors, but the device structure becomes more complex
Solution Approach 1:
Instead of making all coupling electrode lines different, the patent selectively varies the overlapping sizes only where needed for different color sub-pixels. The coupling electrode lines maintain a regular overall layout, with local modifications only in the overlapping regions with pixel electrodes. This minimizes structural complexity while achieving the required gamma compensation.
3Manufacturing precision
If different voltages are applied to coupling electrode lines to adjust liquid crystal tilt angles, then picture quality at display edges is improved, but the control system becomes more complex
Solution Approach 1:
The patent adjusts the overlapping sizes of coupling electrode lines to change the capacitance parameters of different color sub-pixels. This structural parameter change allows the system to achieve different effective voltages across color channels without requiring complex external voltage control circuitry. The capacitance differences created by varying overlapping sizes naturally produce the required voltage variations for gamma compensation.
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 approach results in uniform gamma values for red, green, and blue colors, enhancing picture quality and contrast, particularly when viewed from the edges by varying the liquid crystal tilt angles based on applied voltages.
Implementation Method 1
negative type liquid crystals and a vertical alignment film are used such that a black picture is displayed as liquid crystal molecules stand vertically due to no voltage. When a voltage is applied, liquid crystal molecules tend to orientate horizontally
Implementation Method 2
due to birefringence effect, the non-uniform of gamma values of red, green and blue colors in the multi domain vertical alignment LCD is easily more serious
Implementation Method 3
The overlapping size of the first coupling electrode and the coupling electrode lines is unequal to the overlapping size of the third coupling electrode and the coupling electrode lines. A voltage is applied respectively on the coupling electrodes to adjust liquid crystal tilt angles
Data Source
AI summary
A multi-domain vertical alignment liquid crystal display and a lower substrate thereof are disclosed. The voltage provided by coupling electrode lines is swung between a high voltage level and a low voltage level. Therefore, with different coupling of a large pixel electrode and of a small pixel electrode that both receive the same color displaying data, the voltage on the large pixel electrode is different from that on the small pixel electrode. The tilt angle of the liquid crystal between the large pixel electrode and the upper electrode is different from the tilt angle of the liquid crystal between the small pixel electrode and the upper electrode for compensating the gamma value of the color. Besides, through adjusting the value of the voltage respectively on the coupling electrode lines to compensate the gamma values of different colors and the gamma values of different colors will tend to be uniform.