Shielding Electrode for Liquid Crystal Display Aperture Ratio
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Solution Overview
Problem
In liquid crystal display devices, particularly in the fringe-field switching (FFS) mode, the aperture ratio is limited due to light leakage near the source line, which reduces transmittance and overall display quality, as the electric field from the source line cannot be effectively shielded, necessitating a black matrix that increases the non-transmitting region.
Innovation Solution
A liquid crystal display device structure incorporating a thin film transistor with a second counter electrode overlapping the source line to shield the electric field generated by the source line, combined with a pixel electrode and first counter electrode generating an oblique electric field, allowing for improved aperture ratio and reduced light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a black matrix is placed to cover the source line and the vicinity of the source line to block leakage light, then light leakage is reduced, but the invalid region increases causing a decrease in aperture ratio
Solution Approach 1:
The patent extracts the shielding function from the black matrix and assigns it to a dedicated shielding electrode. This separates the light-blocking function from the general counter electrode structure, allowing the black matrix to cover only the minimum necessary area while the shielding electrode handles the electric field shielding specifically in the source line vicinity.
Solution Approach 2:
The patent segments the counter electrode into two distinct functional parts: a first counter electrode for generating the primary electric field and a second counter electrode (shielding electrode) specifically for shielding the source line electric field. This segmentation allows each electrode to be optimized for its specific function without compromising the other.
2Reliability
If the pixel electrode is placed away from the source line to reduce capacitance, then capacitance between source line and pixel electrode is reduced, but the electric field from the source line cannot be shielded causing light leakage
Solution Approach 1:
The patent introduces a shielding electrode as an intermediary element between the source line and the liquid crystal display area. This shielding electrode acts as a mediator that blocks the harmful electric field from the source line without requiring the pixel electrode to be repositioned, thus maintaining both low capacitance and effective shielding.
3Area of stationary object
If transparent conductive layers are used for pixel electrode and counter electrode to improve aperture ratio, then aperture ratio and transmittance are increased, but electric field shielding becomes more difficult
Solution Approach 1:
The patent employs a composite electrode structure where transparent conductive layers are used for the pixel electrode and first counter electrode to maintain high aperture ratio, while a separate shielding electrode (which can be opaque or transparent) is added specifically for electric field shielding. This composite approach allows both high transmittance and effective shielding to coexist.
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 configuration enhances the aperture ratio by minimizing light leakage and eliminating the need for a wide black matrix, thereby improving the display's light use efficiency and viewing angle characteristics.
Implementation Method 1
a first counter electrode placed below and opposite to the pixel electrode with an insulating layer interposed therebetween to generate an oblique electric field with the pixel electrode
Implementation Method 2
a second counter electrode formed in the same layer as the pixel electrode and placed overlapping the source line in a given area to generate an in-plane electric field with the pixel electrode
Implementation Method 3
a liquid crystal display device including a thin film transistor placed above a substrate
Data Source
AI summary
A liquid crystal display device includes a gate line placed above a substrate, a gate insulating layer to cover the gate line, a source line placed above the gate insulating layer, an interlayer insulating layer to cover the source line, a comb-shaped or slit-shaped pixel electrode electrically connected a drain electrode of a TFT through a contact hole penetrating the interlayer insulating layer, a first counter electrode placed below and opposite to the pixel electrode with an insulating layer interposed therebetween to generate an oblique electric field with the pixel electrode, and a second counter electrode formed in the same layer as the pixel electrode and placed overlapping the source line in a given area to generate an in-plane electric field with the pixel electrode.