FFS Liquid Crystal Display Dummy Pixel Capacitance Matching
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Solution Overview
Problem
Fringe field switching (FFS) liquid crystal displays face issues with image quality and yield due to variations in electric field around the display region, particularly caused by reduced storage capacitance and resistance in dummy pixels, leading to peripheral unevenness and line failures.
Innovation Solution
The design reduces the size of dummy pixels by optimizing the overlap area of pixel and common electrodes, eliminating slits in dummy pixels to match capacitance with display pixels, thereby minimizing frame width without impairing dummy pixel functions and reducing peripheral unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the size of dummy pixels is reduced to narrow frame width, then the frame width is reduced, but the storage capacitance and capacitance of lines in dummy pixels change, causing discontinuous variation in electrical and optical characteristics
Solution Approach 1:
The patent applies local quality by making the dummy pixels have the same structural characteristics as display pixels specifically in the electrode overlap region. The pixel electrode and common electrode in dummy pixels are designed to create the same overlap area as in display pixels, ensuring local electrical characteristics match despite the overall smaller pixel size. This localized design ensures uniform capacitance values across both dummy and display pixels.
Solution Approach 2:
The patent changes the electrical parameters of dummy pixels by adjusting the overlap area of pixel and common electrodes to maintain the same capacitance value as display pixels. By controlling the electrode geometry and overlap dimensions, the patent modifies the electrical characteristics of dummy pixels to match display pixels, preventing discontinuous variation in the display region.
2Length of stationary object
If the size of dummy pixels is reduced to narrow frame width, then the frame width is reduced, but variations in potential of signal lines increase due to reduced storage capacitance
Solution Approach 1:
The patent applies local quality by specifically designing the electrode structure in dummy pixels to maintain appropriate capacitance values. By ensuring the pixel electrode and common electrode have sufficient overlap area in dummy pixels, the patent locally compensates for the reduced storage capacitance that would otherwise occur due to smaller pixel size, thereby reducing potential variations in signal lines.
Solution Approach 2:
The patent applies beforehand cushioning by pre-designing the electrode overlap structure in dummy pixels to provide sufficient capacitance before potential variations can occur. The increased overlap area in dummy pixels acts as a preventive measure, cushioning against potential variations caused by reduced pixel size before they can affect signal line stability.
3Length of stationary object
If the size of dummy pixels is reduced to narrow frame width, then the frame width is reduced, but the width of the frame cannot be sufficiently narrowed due to image quality degradation
Solution Approach 1:
The patent applies local quality by making the electrode overlap characteristics in dummy pixels match those in display pixels. By ensuring the pixel electrode and common electrode have the same overlap area in both regions, the patent creates uniform electrical and optical characteristics across the entire display, enabling high manufacturing precision even with reduced frame width.
Solution Approach 2:
The patent changes the geometric parameters of electrodes in dummy pixels to maintain the same overlap area as display pixels. By adjusting the electrode dimensions and positioning in dummy pixels, the patent modifies the electrical characteristics to match display pixels, ensuring uniform display quality while allowing smaller dummy pixel sizes for narrower frames.
4Length of stationary object
If the size of dummy pixels is reduced to narrow frame width, then the frame width is reduced, but line failures due to short circuit between gate lines and source lines increase
Solution Approach 1:
The patent applies local quality by ensuring the electrode structure in dummy pixels maintains appropriate spacing and overlap characteristics. By designing the pixel electrode and common electrode to have the same overlap area as display pixels, the patent creates uniform electrical fields that prevent abnormal charge accumulation and reduce the risk of short circuits between gate lines and source lines.
Solution Approach 2:
The patent applies beforehand cushioning by pre-designing the electrode overlap structure to provide sufficient capacitance in dummy pixels. This preventive design ensures stable electrical characteristics before potential short circuit conditions can develop, reducing yield losses from line failures.
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 approach enhances display quality by maintaining equal capacitance between dummy and display pixels, reducing line failures and peripheral unevenness, and allowing for a narrower frame in FFS liquid crystal displays.
Implementation Method 1
The FFS liquid crystal display performs display by applying a fringe electric field (oblique electric field including both components of a lateral electric field and a vertical electric field) on the liquid crystal layer
Implementation Method 2
Each of the pixels includes gate lines (scan lines) for controlling ON and OFF of the TFT and source lines (signal lines) for input of image data. A region surrounded by the gate lines and the source lines usually corresponds to each of the pixels
Data Source
AI summary
In an FFS liquid crystal display in which a dummy pixel in a dummy pixel region is smaller than a display pixel in a display region, a slit is formed in a common electrode in the display pixel while no slit is formed in the common electrode in the dummy pixel.