TFT Array Substrate Drain Electrode Overlap Storage Capacitor
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Solution Overview
Problem
Conventional TFT array substrates face reduced storage capacitance due to decreased aperture ratio and charging time, leading to issues like crosstalk and image sticking, as the area of the drain electrode is limited, preventing expansion of the storage capacitor.
Innovation Solution
The TFT array substrate design includes a drain electrode overlapping a portion of the common electrode to form a first storage capacitor, with the pixel electrode and common electrode forming a second storage capacitor, connected in parallel, increasing the storage capacitor capacity without reducing the aperture ratio by varying the thickness of the planarization layer in overlapping and non-overlapping areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the aperture ratio is reduced to increase definition and resolution, then display quality is improved, but storage capacitance is reduced
Solution Approach 1:
The storage capacitor is segmented into two separate capacitors: a first storage capacitor formed by the drain electrode overlapping the common electrode, and a second storage capacitor formed by the pixel electrode overlapping the common electrode. This segmentation allows independent optimization of each capacitor's area and positioning, enabling increased total capacitance without requiring a larger overall pixel area, thus maintaining high definition and resolution while compensating for reduced storage capacitance caused by reduced aperture ratio.
Solution Approach 2:
The patent utilizes the vertical dimension by varying the thickness of the planarization layer in different regions. The planarization layer is made thicker in non-overlapping areas and thinner in overlapping areas, creating different insulation layer thicknesses for the two storage capacitors. This dimensional change allows optimization of electric field distribution and capacitance values without affecting the planar aperture ratio, enabling increased storage capacitance while maintaining high resolution display quality.
2Quantity of substance
If the area of the drain electrode is increased to expand storage capacitor capacity, then storage capacitance is improved, but the aperture ratio is reduced
Solution Approach 1:
The storage capacitor function is segmented into two separate capacitors with different electrode configurations. The first storage capacitor uses the drain electrode overlapping the common electrode, while the second uses the pixel electrode overlapping the common electrode. This segmentation allows the drain electrode to be enlarged for increased capacitance without compromising the aperture ratio, as the pixel electrode area remains optimized for light transmission.
Solution Approach 2:
The planarization layer serves as an intermediary element between the electrodes. By controlling its thickness in different regions, it enables the formation of two distinct storage capacitors with optimized electric fields. The planarization layer acts as a mediator that allows the drain electrode to overlap the common electrode without directly interfering with the pixel electrode's optical function, thus enabling increased storage capacitance while maintaining aperture ratio.
3Speed
If the charging time is reduced for faster display response, then response speed is improved, but the amount of charges retained in the storage capacitor is reduced
Solution Approach 1:
The storage capacitor is divided into two separate capacitors that can be independently optimized. The first storage capacitor (drain electrode and common electrode) can be designed with larger area for increased charge retention, while the second storage capacitor (pixel electrode and common electrode) can be optimized for faster charging. This segmentation allows the system to retain more total charges while maintaining fast response times, as each capacitor can be tuned for its specific function.
Solution Approach 2:
The patent changes the parameters of the two storage capacitors differently to optimize their respective functions. The first storage capacitor is designed with larger area and optimized insulation layer thickness for maximum charge retention, while the second capacitor is optimized for rapid charging. By changing parameters (area, thickness, positioning) of each capacitor independently, the system achieves both fast response speed and high charge retention capacity.
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 design enhances storage capacitor capacity, alleviates crosstalk and image sticking, and improves display quality without reducing the aperture ratio, by effectively increasing the area of the drain electrode within a light-shielding zone.
Implementation Method 1
the drain electrode and the common electrode constituting a first storage capacitor
Implementation Method 2
the pixel electrode and the common electrode constituting a second storage capacitor
Implementation Method 3
a corresponding electric field is generated between the pixel electrode and a common electrode. The liquid crystal molecules contained in the liquid crystal layer is acted upon by the electric field to change direction
Data Source
AI summary
Provided is a TFT array substrate, which increases the area of a drain electrode of a TFT within a light-shielding zone to have the drain electrode overlapping a portion of a horizontal projection of a common electrode, wherein the drain electrode and the common electrode constitute a first storage capacitor and a pixel electrode and the common electrode constitute a second storage capacitor. The pixel electrode and the drain electrode are electrically connected and thus are of the same potential. The first storage capacitor and the second storage capacitor are connected in parallel and collectively form a storage capacitor such that the storage capacitor has a capacity that is equal to the sum of capacities of the first storage capacitor and the second storage capacitor, whereby, without reducing aperture ratio, the capacity of the storage capacitor is increased, crosstalk and image sticking are alleviated, and product display quality is enhanced.