Liquid Crystal Display Panel with Dual λ/4 Retardation Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional liquid crystal display panels experience low contrast ratios due to deteriorated retarders, leading to increased luminance during black display and coloration issues, particularly in outdoor environments with strong external light.
Innovation Solution
A horizontal electric field mode liquid crystal display panel is designed with a pair of λ/4 retardation layers having in-plane slow axes perpendicular to each other, where the second λ/4 retardation layer is formed from a different material and has varying thicknesses to match the retardation values across different color filters, ensuring optimal cancellation of retardation effects to prevent light leakage and coloring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional retarder is used to reduce internal reflection, then the light transmittance during black display is decreased, but the contrast ratio becomes low after heat resistance test due to deteriorated retarder
Solution Approach 1:
The patent divides the single retarder into multiple retardation layers (first λ/4 retardation layer and second λ/4 retardation layer) with different materials and thicknesses. Each layer is positioned at specific locations (overlapping red, green, and blue color filters) to independently control retardation for different wavelengths, preventing deterioration-related contrast ratio loss while maintaining low light transmittance during black display.
Solution Approach 2:
Different regions of the retardation layers have different thicknesses tailored to specific color filter locations. The first λ/4 retardation layer has thicknesses of 1.375μm, 1.400μm, and 1.425μm over red, green, and blue filters respectively, while the second layer has corresponding thicknesses of 1.400μm, 1.425μm, and 1.450μm. This local variation optimizes retardation control for each wavelength range, ensuring durable contrast ratio performance across the visible spectrum.
2Reliability
If a highly durable retarder is used to increase durability, then the heat resistance is improved, but the internal reflection cannot be reduced throughout the visible light wavelength range and the screen becomes colored during black display
Solution Approach 1:
The patent employs composite material structure with two different retardation layers made from different materials. The first λ/4 retardation layer and second λ/4 retardation layer have different wavelength dispersion characteristics, allowing their combination to achieve broadband internal reflection reduction across the entire visible spectrum while preventing coloration during black display, all while maintaining high durability.
Solution Approach 2:
The patent adjusts the thickness parameters of the retardation layers to precisely control the retardation values for different wavelengths. By setting specific thicknesses (e.g., 1.375μm to 1.450μm range) for each layer over different color filters, the system achieves optimal internal reflection reduction across the visible spectrum while preventing coloration, demonstrating parameter optimization for multi-wavelength control.
3Device complexity
If a single λ/4 retardation layer is used to simplify the structure, then the device complexity is reduced, but the black display becomes colored and internal reflection is not adequately reduced
Solution Approach 1:
Instead of using a single uniform retardation layer, the patent segments the retardation function into two distinct λ/4 retardation layers with different materials and thickness profiles. Each layer targets specific wavelength ranges, and their combined effect achieves comprehensive internal reflection reduction across the visible spectrum without causing coloration, while maintaining a relatively simple overall structure.
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 solution effectively reduces internal reflection and achieves favorable black display without coloring, enhancing the contrast ratio and visibility of the liquid crystal display device, especially in bright environments.
Implementation Method 1
a first λ/4 retardation layer whose in-plane slow axis extends in a first direction... a second λ/4 retardation layer whose in-plane slow axis extends in a second direction perpendicular to the first direction
Implementation Method 2
a liquid crystal layer containing liquid crystals horizontally aligned with no voltage applied... a pair of electrodes configured to generate a horizontal electric field in the liquid crystal layer upon voltage application
Data Source
AI summary
A liquid crystal display panel includes a first λ/4 retardation layer, a first substrate, a color filter layer, a liquid crystal layer containing horizontally aligned liquid crystals, and a second λ/4 retardation layer that is formed from a different material from the first λ/4 retardation layer between the first substrate and the color filter layer or between the color filter layer and the liquid crystal layer. The second λ/4 retardation layer has a smaller thickness in a region overlapping the blue color filter than in a region overlapping the green color filter. The first λ/4 retardation layer provides a retardation Rout(λ) to light having a wavelength of λ nm. The second λ/4 retardation layer provides a retardation Rin(λ). The retardation Rout(λ) and the retardation Rin(λ) satisfy the following formula (1) in the region overlapping the blue color filter.−1.0 nm<Rin(450)−Rout(450)<10.0 nm (1)