Twist Alignment LCD Reflective Layer Contrast
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Solution Overview
Problem
Reflective liquid crystal display devices in the transverse electrical field mode suffer from low reflectivity due to non-uniform electrical field distribution caused by comb-shaped electrodes, leading to reduced transmittance and reflection efficiency, making them unsuitable for practical use.
Innovation Solution
A liquid crystal display device configuration with a twist alignment mode, incorporating a polarizer, a phase difference layer with a λ/2 plate and a λ/4 plate, and specific optical axis settings to optimize the twist angle and retardation of the liquid crystal layer, enhancing contrast ratio and reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a comb-shaped electrode is used in transverse electrical field mode, then the device structure is simpler and manufacturing is easier, but the electrical field distribution becomes non-uniform causing low reflectivity and reduced transmittance
Solution Approach 1:
The pixel electrode is divided into multiple belt-shaped portions with slits between them, transforming the continuous comb-shaped electrode into segmented structures. This segmentation allows each portion to generate more uniform electrical fields while maintaining the overall comb electrode structure, thereby improving reflectivity without significantly complicating manufacturing
Solution Approach 2:
The electrode structure is designed with different local characteristics: belt-shaped portions with specific widths and slit widths are optimized to create uniform electrical fields in critical regions. The local geometry of electrodes is tailored to achieve consistent liquid crystal alignment across the pixel area, resolving the non-uniformity issue while preserving manufacturing simplicity
2Device complexity
If a comb-shaped electrode is used in transverse electrical field mode, then the device structure is simpler, but the transmittance and reflection efficiency are reduced
Solution Approach 1:
By segmenting the pixel electrode into belt-shaped portions, the device maintains the relatively simple comb electrode structure while significantly improving reflection efficiency. The segmentation enables more uniform electrical field distribution, allowing the liquid crystal layer to achieve better optical properties without adding complex multi-electrode configurations
Solution Approach 2:
The slit width is designed to be a specific proportion (5-20%) of the belt-shaped portion width, creating partial openings that allow electrical field lines to distribute more uniformly across the pixel. This partial action of removing material (slits) from the continuous electrode achieves excessive improvement in field uniformity, thereby enhancing reflection efficiency while keeping the overall device structure simple
3Reliability
If the liquid crystal layer is set to 1/4 wavelength condition for black display, then polarization conversion is achieved, but transmittance variation increases due to electrical field non-uniformity
Solution Approach 1:
The segmented belt-shaped electrode structure creates more uniform electrical fields across the pixel, which ensures consistent liquid crystal alignment when the layer is set to 1/4 wavelength condition. This uniformity reduces transmittance variation while maintaining the required polarization conversion function for black display
Solution Approach 2:
The electrode geometry parameters (belt width, slit width, spacing) are optimized to achieve uniform electrical field strength across the pixel area. This parameter optimization ensures that the liquid crystal molecules align uniformly under the 1/4 wavelength condition, reducing transmittance variation while maintaining polarization conversion reliability
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
The proposed configuration significantly improves the contrast ratio and reflectivity of reflective liquid crystal display devices, enabling them to achieve higher efficiency and performance comparable to vertical electrical field modes.
Implementation Method 1
the liquid crystal layer takes a twist alignment when no voltage is applied
Implementation Method 2
retardation Δn·d of the liquid crystal layer is set to a 1⁄4-wavelength condition (i.e., 138 nm) in order to achieve a polarization conversion of transmitted light from linear polarization to circular polarization or from circular polarization to linear polarization
Implementation Method 3
a phase difference layer disposed between the polarizer and the liquid crystal layer
Implementation Method 4
a first substrate includes a reflective layer configured to reflect light
Data Source
AI summary
A liquid crystal display device includes a first substrate, a second substrate disposed on a viewer side relative to the first substrate, a liquid crystal layer provided between the first substrate and the second substrate, a polarizer disposed on the viewer side relative to the liquid crystal layer, and a phase difference layer disposed between the polarizer and the liquid crystal layer, and also includes a plurality of pixels arrayed in a matrix shape. The first substrate includes a reflective layer that reflects light, a first electrode and a second electrode that can generate a transverse electrical field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer. The second substrate includes a second horizontal alignment film in contact with the liquid crystal layer. The liquid crystal layer takes a twist alignment when no voltage is applied.