Two-TFT LCD Pixel Structure with Capacitive Coupling
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Solution Overview
Problem
Conventional liquid crystal display (LCD) panels with bias-bending vertical alignment (BBVA) technology require three thin film transistors per pixel, reducing the aperture ratio and increasing manufacturing costs due to the need for precise alignment and additional ridges or bumps, which also results in a limited view angle and reduced manufacturing yield.
Innovation Solution
A pixel structure with two thin film transistor groups controlled by different scan lines and using at least one capacitor to create a coupling effect, allowing for a voltage difference between the control electrode and pixel electrode without the need for additional ridges or bumps, thereby reducing the number of transistors and simplifying the driving circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three thin film transistors are used per pixel in BBVA technology, then the liquid crystal molecule orientation can be controlled, but the aperture ratio decreases and manufacturing cost increases
Solution Approach 1:
The patent extracts and eliminates one of the three thin film transistors from the BBVA pixel structure, reducing the transistor count from three to two while maintaining the ability to control liquid crystal molecule orientation through the remaining transistors and capacitors
Solution Approach 2:
The two remaining thin film transistors are designed to perform multiple functions: controlling both the pixel electrode voltage and the control electrode voltage, thereby compensating for the removed transistor and maintaining full orientation control capability
2Reliability
If additional ridges or bumps are added to the color filter in MVA technology, then the liquid crystal molecule alignment is improved, but the manufacturing precision requirements increase and yield decreases
Solution Approach 1:
The patent removes the additional ridges or bumps from the color filter structure, eliminating the need for precise alignment between the color filter and active matrix substrate while maintaining liquid crystal molecule alignment through the bias-bending vertical alignment mechanism
Solution Approach 2:
The patent adopts a simpler color filter structure without additional ridges or bumps, reducing manufacturing complexity and yield requirements while achieving the same alignment effect through electrical field control rather than mechanical structure
3Reliability
If three thin film transistors are used in each pixel region, then the control electrode voltage can be written, but the RC delay increases and aperture ratio decreases
Solution Approach 1:
The patent removes one thin film transistor from each pixel region, reducing the transistor count from three to two, which directly reduces the RC time constant and minimizes RC delay while maintaining control electrode voltage control capability through the remaining transistors and capacitors
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 configuration increases the aperture ratio, reduces the RC delay, and lowers manufacturing costs by eliminating the need for precise alignment and additional features, while maintaining the ability to change liquid crystal molecule orientations, thus improving the view angle and yield.
Implementation Method 1
at least one capacitor is used to couple with the two TFT groups for providing a coupling effect to make sure the voltage in the two connection points simultaneously goes up and down
Implementation Method 2
A main electric field exists between the common electrode 108 and the pixel electrode 110 to make liquid crystal molecules 116 have oblique positions
Data Source
AI summary
A pixel region is surrounded in any adjacent scan lines and any adjacent data lines. Two thin film transistor (TFT) groups that are controlled by different scan lines are located in each pixel region. The two data lines respectively send different polarity data to the pixel region through the two TFT groups. At least one capacitor is used to couple with the two TFT groups for providing a coupling effect to make sure the voltage in the two connection points simultaneously goes up and down.