TFT Drain Electrode C-Shape Reduces Parasitic Capacitance
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Solution Overview
Problem
The power consumption of liquid crystal displays is increased due to capacitance generated by the overlap between data lines and thin film transistor (TFT) channels, leading to higher current requirements and inefficiencies.
Innovation Solution
The design of the liquid crystal display includes a thin film transistor with a gate electrode, a source electrode partially overlapping the gate electrode, and a drain electrode with specific shaped end portions that minimize overlap with the data line, reducing parasitic capacitance and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the overlap between data line and TFT channel is increased, then the capacitance is increased, but the power consumption of the liquid crystal device is increased
Solution Approach 1:
The patent extracts and eliminates the harmful overlap between the data line and TFT channel by redesigning the electrode configuration. Specifically, the source electrode is designed to overlap the gate electrode while the data line is positioned to avoid overlapping the gate electrode, thereby removing the parasitic capacitance source while maintaining necessary electrical connections.
Solution Approach 2:
The patent changes the spatial arrangement of electrodes from a conventional planar layout to a multi-layered configuration where the source electrode extends in one dimension to overlap the gate electrode, while the data line is positioned in a different spatial dimension (layer) to avoid overlap with the gate electrode, thus reducing parasitic capacitance.
2Reliability
If the current magnitude of data signal is increased, then the capacitance effect is compensated, but the power consumption is increased
Solution Approach 1:
The patent converts the potential harm of reduced overlap (which might affect signal transmission) into a benefit by designing the source electrode to maintain necessary overlap with the gate electrode for proper transistor operation, while the data line avoidance of gate electrode overlap eliminates parasitic capacitance. This ensures reliable signal transmission without requiring increased current magnitude.
3Reliability
If the overlap between source electrode and gate electrode is maintained, then the transistor operation is ensured, but the data line overlap with gate electrode increases capacitance
Solution Approach 1:
The patent applies different spatial configurations to different components: the source electrode is designed with local overlap with the gate electrode to ensure proper transistor operation and electrical connection, while the data line is positioned with local avoidance of the gate electrode to minimize parasitic capacitance. This localized differentiation of spatial relationships resolves the contradiction between operational reliability and energy efficiency.
Data Source
AI summary
A liquid crystal display including a plurality of pixels that display an image, each pixel includes a thin film transistor that includes a gate electrode, a source electrode having a bar-shape and partially overlapping the gate electrode, and a drain electrode facing the source electrode at a location corresponding to the gate electrode, the drain electrode includes a first end portion having a C-shape that surrounds a distal end of the bar-shaped source electrode. This design eliminates an overlap between a data line and the gate electrode, which eliminates an overlap between the data line and the channel area of a semiconductor layer, which reduces a parasitic capacitor of the data line, resulting in less current to drive the data line, resulting in reduced power consumption of the display.