Fringe Field Switching LCD Counter Electrode Shielding
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Solution Overview
Problem
Fringe-field switching mode liquid crystal display devices face challenges in increasing aperture ratio and transmittance due to light leakage and non-transmitting regions caused by the structure of pixel and counter electrodes, which affects display quality.
Innovation Solution
The liquid crystal display device design includes a pixel electrode directly overlapping the drain electrode, an interlayer insulating layer covering the pixel electrode, and a counter electrode with slits that overlap the gate line, allowing for improved fringe electric field generation and reduced light leakage by shielding the electric field from the source line, thus eliminating the need for a black matrix and minimizing non-transmitting regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pixel electrode is placed away from the source line to reduce capacitance, then display quality is improved, but light leakage occurs in the vicinity of the source line
Solution Approach 1:
The patent introduces a black matrix as an intermediary element positioned between the source line and the pixel electrode. This black matrix serves as a mediator that blocks the electric field lines from the source line, preventing them from reaching the liquid crystal and causing light leakage, while allowing the pixel electrode to maintain its optimal position away from the source line for reduced capacitance.
Solution Approach 2:
The patent converts the harmful electric field from the source line into a beneficial configuration by using the black matrix to redirect and contain the field lines. The electric field that would otherwise cause light leakage is now channeled through the black matrix structure, which blocks it from affecting the liquid crystal while maintaining the necessary electrical connections.
2Object-generated harmful factors
If a black matrix is placed to cover the source line and vicinity to block leakage light, then light leakage is reduced, but the aperture ratio decreases
Solution Approach 1:
The patent applies the black matrix only in specific local regions where it is most needed - primarily along the source line and in areas where electric field lines are concentrated. Rather than covering large areas, the black matrix is strategically positioned to block harmful fields while leaving the majority of the pixel area transparent for light transmission, thus minimizing the impact on aperture ratio.
3Productivity
If the pixel electrode and counter electrode are formed by transparent conductive layers to improve aperture ratio, then light use efficiency is improved, but capacitance between source line and pixel electrode increases
Solution Approach 1:
The patent segments the electrode structure by introducing the black matrix as a dividing element between the source line and pixel electrode. This segmentation physically separates the regions, reducing the overlapping area and thus the capacitance between the source line and pixel electrode, while maintaining the transparent conductive layer structure for high light use efficiency in the active display areas.
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 design enhances the aperture ratio and transmittance by reducing light leakage and eliminating the need for a black matrix, resulting in improved display quality and efficiency.
Implementation Method 1
liquid crystal is driven by a fringe electric field that is generated between the pixel electrode having a slit placed in an upper layer and the counter electrode placed in a lower layer
Implementation Method 2
the counter electrode is placed to overlap the gate line in at least part of area and connected to the counter electrode in an adjacent pixel across the gate line
Data Source
AI summary
The liquid crystal display device, in which liquid crystal is filled between a TFT array substrate having a TFT and a counter substrate placed opposite to the TFT array substrate, includes a pixel electrode placed at least partly directly over or under a drain electrode of the thin film transistor so as to directly overlap the drain electrode, an interlayer insulating layer placed to cover the pixel electrode, and a counter electrode placed on the interlayer insulating layer and having a slit to generate a fringe electric field with the pixel electrode, wherein the counter electrode is placed to overlap a gate line connected to a gate electrode of the TFT in at least part of area and connected to the counter electrode in an adjacent pixel across the gate line.