Pixel Electrode Shielding Layout for TFT Display Off-Current Control
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Solution Overview
Problem
The increasing number of thin film transistors (TFTs) in display devices leads to a higher number of wirings, which complicates the accurate control of light emission and results in issues such as parasitic capacitance and off-currents, affecting the display quality.
Innovation Solution
A display device design that includes a shielding layer between the first electrode layer and the pixel electrode, overlapping the node connection line, and connected to a driving voltage line, which helps in preventing parasitic capacitance and off-currents by applying a constant voltage, thereby improving the control of light emission and display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of TFTs and wirings is increased to accurately control light emission, then the control precision is improved, but the device complexity and parasitic capacitance increase
Solution Approach 1:
The patent extracts the harmful parasitic capacitance effect by introducing a shielding layer that is electrically connected to a reference potential (ground or power supply line). This shielding layer is positioned between the node connection line and the pixel electrode to isolate and eliminate the parasitic capacitance between these conductive elements, thereby resolving the contradiction by removing the harmful electrical coupling while maintaining the necessary wiring structure for control precision
Solution Approach 2:
The shielding layer acts as an intermediary element between the node connection line and the pixel electrode. By introducing this intermediate conductive structure connected to reference potential, the patent mediates the electrical interaction between the signaling line and the pixel electrode, preventing direct parasitic capacitance formation while allowing the control signals to reach the pixel electrode through the intended path
2Measurement precision
If the number of TFTs and wirings is increased to accurately control light emission, then the control precision is improved, but the off-currents increase
Solution Approach 1:
The patent extracts and eliminates the source of off-currents by removing the parasitic capacitance between the node connection line and pixel electrode through the shielding layer. By isolating these conductive elements, the patent prevents the generation of displacement currents that would otherwise flow during voltage transitions, thereby reducing off-currents while maintaining the necessary control wiring structure
Solution Approach 2:
The shielding layer serves as an intermediary that blocks the generation of off-currents by preventing direct electrical coupling between the node connection line and pixel electrode. This intermediate structure connected to reference potential acts as a barrier that stops parasitic current paths while allowing the control signals to function properly through the intended circuit paths
3Reliability
If a shielding layer is added to reduce parasitic capacitance, then the display quality is improved, but the device complexity increases
Solution Approach 1:
The patent merges the shielding layer function with existing structural elements by positioning the shielding layer to also serve as part of the pixel electrode structure or adjacent conductive layers. The shielding layer is integrated into the existing multi-layer structure, sharing space and functional roles with other components, thereby reducing the net increase in device complexity while maintaining the parasitic capacitance reduction benefit
Solution Approach 2:
The shielding layer is designed to serve multiple functions: it provides electrostatic shielding to reduce parasitic capacitance, maintains structural integrity of the pixel electrode assembly, and can be electrically connected to reference potential through existing wiring infrastructure. This multi-functionality approach allows the shielding function to be achieved without proportionally increasing device complexity
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
The shielding layer effectively reduces parasitic capacitance and off-currents, ensuring a constant driving current and preventing color deviations, thereby enhancing the display quality and maintaining intended brightness levels.
Implementation Method 1
the shielding layer effectively reduces parasitic capacitance and off-currents
Data Source
AI summary
A display device includes: a plurality of pixels each including a driving thin film transistor and a storage capacitor, wherein each of the pixels further includes: a driving semiconductor layer including a driving channel region, a driving source region, and a driving drain region; a first electrode layer, a portion of the first electrode layer overlapping the driving channel region; a second electrode layer overlapping the first electrode layer; a node connection line having a first side connected to the first electrode layer; a pixel electrode overlapping the first electrode layer and the second electrode layer; and a shielding layer between the first electrode layer and the pixel electrode and overlapping the first electrode layer, the node connection fine, and the pixel electrode.