TFT Protrusions for LCD Brightness and Transmittance
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Solution Overview
Problem
In small-sized liquid crystal display devices, the reduction in pixel size leads to decreased transmittance and brightness due to the limited ability to decrease the size of TFTs and through holes, while maintaining the performance and manufacturing margin of the liquid crystal display device.
Innovation Solution
The configuration includes a TFT substrate with trapezoidal protrusions and continuous banks, allowing the pixel electrode and source electrode to be directly connected on the inclined surfaces, eliminating the need for through holes and maximizing the pixel electrode area, which can be applied to IPS, TN, and VA systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel size is decreased to maintain high definition in small-sized liquid crystal display devices, then the screen definition is improved, but the transmittance and brightness are reduced
Solution Approach 1:
The pixel electrode is extended onto the inclined surface of the trapezoidal protrusion, utilizing the vertical dimension (height of protrusion) to increase the effective pixel electrode area without increasing the horizontal pixel footprint. This dimensional extension allows more light to pass through the pixel region while maintaining the same pixel pitch for high definition.
Solution Approach 2:
The invention changes the geometric parameters of the pixel structure by introducing trapezoidal protrusions with specific height (0.5-2.0 μm) and top width (0.5-2.0 μm) dimensions. These parameter changes increase the pixel electrode area ratio without compromising the TFT performance or manufacturing margins.
2Measurement precision
If the pixel size is decreased to maintain high definition, then the screen definition is improved, but the pixel electrode area is reduced
Solution Approach 1:
The pixel electrode is extended onto the inclined surface of the trapezoidal protrusion, utilizing the vertical dimension (height of protrusion) to increase the effective pixel electrode area without increasing the horizontal pixel footprint. This dimensional extension allows more light to pass through the pixel region while maintaining the same pixel pitch for high definition.
Solution Approach 2:
The pixel electrode area is segmented into two parts: the horizontal area at the top of the protrusion and the vertical area on the inclined surface. This segmentation allows the electrode to utilize both the planar region and the vertical surface, effectively increasing the total electrode area within the constrained pixel dimensions.
3Reliability
If through holes are used to connect the TFT and pixel electrode, then the electrical connection is achieved, but the transmittance is reduced
Solution Approach 1:
The invention extracts and eliminates the through hole structure from the pixel region. By using the inclined surface of the trapezoidal protrusion for direct electrode connection, the harmful through holes that block light are removed, thereby increasing transmittance while maintaining electrical connectivity.
Solution Approach 2:
The inclined surface of the trapezoidal protrusion serves as an intermediary structure that enables direct contact between the pixel electrode and source electrode. This intermediary surface replaces the need for through holes, providing both mechanical support and electrical connection while allowing light to pass through.
Data Source
AI summary
A liquid crystal display device includes a TFT substrate with gate lines and drain lines, and pixel electrodes each formed in a region surrounded by the gate lines and drain lines. Protrusions are formed below the gate lines, each of the protrusions having an upper surface and at least one inclined side surface. A gate insulating film is formed over the gate lines, a semiconductor layer formed on the gate insulating film, and drain electrodes formed and source electrodes formed over the semiconductor layer. Channel portions are defined by the space between the drain electrodes and the source electrodes, each of the channel portions being formed covering the upper surface and at least one of the at least one inclined side surface of one of the protrusions, the pixel and source electrode being in contact with each other on at least one inclined side surface of the protrusion.