TFT-LCD Array Substrate Storage Capacitor Aperture Ratio
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Solution Overview
Problem
In TFT-LCD array substrates, it is challenging to simultaneously achieve sufficient capacitance and high aperture ratio, as existing designs often compromise on one or the other due to the light shielding effect of metal common electrodes and the need for large capacitance values.
Innovation Solution
The introduction of a second storage capacitor formed by a first conductive layer and a second conductive layer, with the second conductive layer being electrically connected to the potential of the transparent common electrode and the pixel electrode within the pixel unit, allowing for reduced size and increased aperture ratio while meeting capacitance requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal common electrode is used to form a storage capacitor, then the capacitance requirement is satisfied, but the aperture ratio is reduced due to light shielding effect
Solution Approach 1:
The patent extracts the common electrode function from a separate metal layer and integrates it into the transparent conductive layer that forms the pixel electrode. This allows the storage capacitor to be formed using the transparent conductive layer itself rather than requiring a separate metal common electrode, thereby eliminating the light shielding effect while maintaining capacitance functionality
Solution Approach 2:
The transparent conductive layer is designed to serve multiple functions: it acts as both the pixel electrode and the common electrode for the storage capacitor. By making the transparent conductive layer extend across the pixel region and connecting it to both the pixel electrode and the storage capacitor, the structure achieves multi-functionality without requiring separate metal electrodes
2Reliability
If the transparent common electrode is extended across the entire pixel unit to connect to external potential, then the storage capacitor function is achieved, but the aperture ratio is significantly reduced
Solution Approach 1:
The patent segments the common electrode connection into two parts: the transparent conductive layer within the pixel unit that forms part of the storage capacitor, and the separate external connection path. The transparent conductive layer does not need to extend across the entire pixel unit to an external connection point, as it is electrically connected to the pixel electrode which provides the external potential reference
Solution Approach 2:
The pixel electrode acts as an intermediary that connects the transparent conductive layer (storage capacitor component) to the external potential. Instead of requiring the transparent common electrode to directly extend to external connections, the pixel electrode mediates the electrical connection, allowing the storage capacitor to function without the transparent electrode spanning the entire pixel unit
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 enables a TFT-LCD array substrate with both large capacitance and high aperture ratio, improving display quality by maintaining stable voltage at pixel electrodes without the need for extensive metal common electrodes, thus enhancing the overall performance of the TFT-LCD array substrate.
Implementation Method 1
each pixel unit in the TFT-LCD typically has a storage capacitor to maintain a stable voltage at the pixel electrode of the pixel unit within a predetermined time period
Implementation Method 2
apply an electric field between the array substrate and the color filter substrate to control the orientation of liquid crystal molecules of the liquid crystal layer
Implementation Method 3
control the orientation of liquid crystal molecules of the liquid crystal layer, thereby controlling an amount of light penetrating through the liquid crystal molecules
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
The present invention provides a TFT-LCD array substrate, in which an additional second storage capacitor is introduced to satisfy the capacitance requirement. The second storage capacitor is formed by a first conductive layer, a second conductive layer, and a second insulating layer disposed between the first conductive layer and the second conductive layer, wherein the first conductive layer and the second conductive layer are respectively electrically connected, inside the pixel unit, to the potential of the transparent common electrode and that of the pixel electrode, that is, the first conductive layer and the second conductive layer that form the second storage capacitor is not required to extend across the entire pixel unit in order to be connected to the potential outside the pixel unit, but are merely required to be electrically connected to the potential of the transparent common electrode and that of the pixel electrode, respectively, inside the pixel unit. Thereby, under the condition that the capacitance is satisfying, the size of the second conductive layer are reduced, that is, the aperture ratio of the pixel unit is increased, so that the pixel unit has both a relatively large capacitance and a relatively high aperture ratio.