Compensating TFT Structure for High Aperture Ratio LCD
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Solution Overview
Problem
In ultra high-resolution liquid crystal displays, the inclusion of compensating thin film transistors (TFTs) reduces the aperture ratio, as the non-transmittance area increases, which is exacerbated in high-density displays over 300 PPI, where the size of each pixel is smaller and the TFTs' characteristics must be maintained.
Innovation Solution
The implementation of a compensation TFT structure where the gate electrode of the compensation TFT is formed using a portion of the gate line, and the TFTs are connected in a serial configuration to minimize the area ratio within the pixel, ensuring high aperture ratios in fringe field type liquid crystal displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compensating TFT is added to each pixel to maintain TFT characteristics, then the reliability is improved, but the aperture ratio deteriorates due to increased non-transmittance area
Solution Approach 1:
The gate electrode of the compensation TFT is merged with the gate line structure, where the gate line is divided into first and second gate electrodes. This integration eliminates separate gate electrode structures and reduces the overall area occupied by TFT components, thereby maintaining aperture ratio while providing compensation functionality.
Solution Approach 2:
The gate line serves dual functions: it acts as the gate electrode for the main TFT and simultaneously provides the gate electrode for the compensation TFT by being divided into segments. This multi-functionality reduces the need for additional dedicated structures, minimizing area consumption.
2Productivity
If the pixel size is reduced to achieve ultra high-resolution over 300 PPI, then the productivity is improved, but the aperture ratio deteriorates as TFT area becomes significant relative to pixel area
Solution Approach 1:
By merging the compensation TFT gate electrode with the gate line structure, the patent minimizes the area consumed by control electronics. This allows smaller pixel dimensions to be achieved while maintaining sufficient aperture ratio, enabling ultra high-resolution displays over 300 PPI.
Solution Approach 2:
The patent optimizes the spatial arrangement of TFT components within the pixel structure, utilizing vertical stacking and layered configurations. This dimensional optimization allows compact integration of compensation TFTs without proportionally increasing the horizontal footprint, enabling higher pixel density.
3Reliability
If the gate line is divided into first and second gate electrodes for compensation TFT connection, then the reliability is improved through better TFT characteristic control, but the device complexity increases
Solution Approach 1:
The patent combines the gate line function with the gate electrode function for both main and compensation TFTs. By dividing the existing gate line into segments rather than adding completely separate gate structures, the solution maintains reliability through improved control while limiting the increase in structural complexity.
Data Source
AI summary
The present disclosure relates to an ultra high-resolution liquid crystal display having a compensating thin film transistor at each pixel. The present disclosure suggests a thin film transistor substrate comprising: gate lines running in horizontal direction and data lines running in vertical direction which define a plurality of pixel area on a substrate; a first gate electrode and a second gate electrode formed by dividing any one gate line disposed at any one of an upper side and a lower side; a first thin film transistor connected to the first gate electrode; and a second thin film transistor connected to the first thin film transistor and the second gate electrode. The flat panel display according to the present disclosure has an ultra high-density resolution over 300 PPI with the high aperture ratio.