Stepped Sub-Pixel Electrode for LCD Viewing Angle and Aperture Ratio
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Solution Overview
Problem
The aperture ratio and transmittance of liquid crystal displays (LCDs) are compromised due to the definition of fine slits in pixel electrodes, leading to decreased display quality, especially in vertical alignment (VA)-mode LCDs, where the refractive index and transmittance of insulating layers can vary, affecting the viewing angle and overall image clarity.
Innovation Solution
A display device design featuring a first substrate with a passivation layer and overlapping sub-pixel electrodes, where one portion of the second sub-pixel electrode is closer to the first surface than the other, and a common electrode with varying distances to improve the alignment of liquid crystal molecules and reduce stress on underlying layers, thereby enhancing display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fine slits are defined in pixel electrodes to provide branch electrodes for widening viewing angle, then the viewing angle is improved, but the aperture ratio and transmittance decrease
Solution Approach 1:
The patent introduces a vertical dimension by forming the second sub-pixel electrode at different heights from the first substrate surface, creating a stepped configuration. This three-dimensional arrangement allows the electrode to provide viewing angle control functions while occupying less horizontal area, thereby preserving aperture ratio.
Solution Approach 2:
The pixel electrode is divided into multiple sub-pixel electrodes (first and second sub-pixel electrodes) with different vertical positions. This segmentation allows each sub-pixel electrode to contribute differently to the electric field distribution, achieving viewing angle control without requiring fine slits that would reduce aperture ratio.
2Adaptability or versatility
If fine slits are defined in pixel electrodes to provide branch electrodes, then the tilt direction of liquid crystal molecules is diversified, but the transmittance decreases
Solution Approach 1:
By utilizing the vertical dimension to position the second sub-pixel electrode at a different height, the patent achieves tilt direction control through three-dimensional electric field distribution rather than through planar slits, thereby maintaining high transmittance.
3Adaptability or versatility
If multiple branch electrodes or slits are provided in each pixel electrode to widen viewing angle, then the viewing angle is improved, but the refractive index and transmittance of insulating layers vary, deteriorating display quality
Solution Approach 1:
The patent avoids the need for multiple slits by using a vertical stepped structure. The second sub-pixel electrode is formed at a different height from the first substrate surface, creating a three-dimensional configuration that controls liquid crystal alignment without introducing variations in insulating layer properties.
Solution Approach 2:
The patent applies different vertical positions to different portions of the pixel electrode structure. The second sub-pixel electrode is localized at a specific height range (100-500 nm from the first substrate surface), creating localized electric field effects that control liquid crystal tilt without affecting the overall uniformity of insulating layers.
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 improves the display quality by maintaining high transmittance and aperture ratio, reducing light leakage, and enhancing side visibility while minimizing the need for additional light shielding members, thus providing a wider viewing angle.
Implementation Method 1
The LCD generates an electric field in the liquid crystal layer by applying a voltage to the field-generating electrodes so as to determine the alignment of liquid crystal molecules in the liquid crystal layer
Implementation Method 2
controls the polarization of light incident thereupon, thereby displaying an image
Data Source
AI summary
A display device includes a first substrate including a first base substrate, a first sub-pixel electrode, which is disposed on a first surface of the first base substrate, a passivation layer, which is disposed on the first sub-pixel electrode, and a second sub-pixel electrode, which is disposed on the passivation layer and partially overlaps the first sub-pixel electrode, a second substrate facing the first substrate, and a liquid crystal layer disposed between the first substrate and the second substrate, where the second sub-pixel electrode includes a first portion, which is apart from the first surface of the first base substrate by a first distance, and a second portion, which is apart from the first surface of the first base substrate by a second distance which is less than the first distance.