IPS LCD Electric-Field Shielding Layer Design
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Solution Overview
Problem
Conventional in-plane switching mode liquid crystal display devices with a color filter on the opposed substrate suffer from color non-uniformity due to electric fields leaking from scanning and signal lines, causing electrical charging of color layers and alignment disturbances in the liquid crystal layer, which results in brightness unbalance and display defects.
Innovation Solution
Incorporating an electric-field shielding layer on the substrate closer to the liquid crystal layer than the scanning line, which overlaps the scanning and data lines to prevent electric field leakage, and forming the shielding layer as part of the common electrode to simplify the fabrication process and avoid complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a color filter is formed on the opposed substrate without electrodes, then the device structure is simplified and manufacturing cost is reduced, but electric fields leak from scanning and signal lines causing color non-uniformity and display defects
Solution Approach 1:
The common electrode is segmented into two functional parts: a first common electrode region positioned closer to the liquid crystal layer that serves as an electric field shielding layer, and a second common electrode region positioned closer to the color filter that serves as the actual common electrode. This segmentation allows the same conductive layer to perform both shielding and electro-optical modulation functions, preventing color non-uniformity while maintaining manufacturing simplicity
Solution Approach 2:
The common electrode layer is designed to perform multiple functions simultaneously: it acts as both the electro-optical modulation element (common electrode) and the electric field shielding layer. By positioning different regions of the same continuous conductive layer at different distances from the liquid crystal layer, the structure achieves both display functionality and interference prevention without requiring separate shielding electrodes
2Power
If the common electrode is positioned closer to the color filter, then the electro-optical modulation is effective, but electric fields leak into the liquid crystal layer causing alignment disturbances
Solution Approach 1:
The common electrode structure exhibits spatially varying properties: the first common electrode region has a different spatial position (closer to liquid crystal layer) than the second common electrode region (closer to color filter). This local quality variation allows the structure to provide strong electro-optical modulation where needed while simultaneously providing electric field shielding where harmful leakage occurs
3Reliability
If an additional electric field shielding layer is added, then color non-uniformity is prevented, but fabrication complexity increases
Solution Approach 1:
The electric field shielding layer and the common electrode are merged into a single continuous conductive layer. The shielding function is achieved by positioning the first common electrode region closer to the liquid crystal layer, while the electro-optical modulation function is achieved by positioning the second common electrode region closer to the color filter. This merging eliminates the need for separate shielding electrode fabrication steps
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 solution effectively prevents color non-uniformity and display defects by shielding electric fields, ensuring high-quality and reliable image display with a wider chromaticity area without increasing fabrication steps or complexity.
Implementation Method 1
an electric-field shielding layer which overlaps the scanning line and is arranged closer to the liquid crystal layer than the scanning line
Implementation Method 2
an in-plane switching (IPS) mode in which liquid crystal molecules are rotated in parallel with transparent substrates
Implementation Method 3
By applying a voltage across the pixel and common electrodes, there is generated an electric field in parallel with the substrate. The thus generated electric field changes alignment direction of liquid crystal molecules
Data Source
AI summary
The liquid crystal display device includes a first substrate, a second substrate arranged in facing relation to the first substrate, and a liquid crystal layer sandwiched between the first and second substrates. The first substrate includes a thin film transistor, a pixel electrode associated with a pixel, a common electrode to which a reference voltage is applied, a data line, a scanning line, and a common electrode line. The second substrate is designed to include no electrodes thereon. The first substrate includes an electric-field shielding layer for preventing an electric field from leaking into pixels in which images are to be displayed, from the scanning line, the electric-field shielding layer being comprised of an electrically conductive layer and being formed in a layer located closer to the liquid crystal layer than an area in which the scanning line is arranged.