Liquid Crystal Display Optically Anisotropic Layer Retardation
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Solution Overview
Problem
Liquid crystal display devices, particularly in the VA mode, suffer from light leakage and color shift issues when viewed at oblique angles, limiting their viewing angle range and contrast ratio.
Innovation Solution
A liquid crystal display device configuration featuring a first and second polarizing element with their transmission axes perpendicular, a liquid crystal layer, and optically anisotropic layers with specific retardation properties to optimize in-plane and thickness-direction retardation, ensuring positive and negative retardation values at different wavelengths, thereby reducing color shift and enhancing viewing angle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an optically-biaxial retardation plate is used to improve viewing angle characteristics in VA-mode devices, then light leakage is reduced within a specific wavelength range (e.g., green light at 550 nm), but color shift occurs in other wavelength ranges (e.g., blue light at 450 nm, red light at 650 nm) when observed obliquely
Solution Approach 1:
The patent divides the optical compensation function into multiple wavelength-specific retardation plates. Each plate is designed to compensate for light leakage at specific wavelength ranges (e.g., blue, green, red) rather than using a single biaxial plate that only works for one wavelength. This segmentation allows independent optimization of compensation for each color channel.
Solution Approach 2:
The patent applies different optical properties to different parts of the spectrum by using multiple retardation plates with specific retardation values tailored to each wavelength range. Each plate has locally optimized retardation characteristics (e.g., Re(450), Re(550), Re(650)) to address light leakage at specific wavelengths while minimizing color shift in others.
2Reliability
If a VA-mode liquid crystal display is used to achieve high contrast and good producibility, then normal viewing angle performance is improved, but viewing angle range is narrowed and light leakage occurs when observed obliquely
Solution Approach 1:
The patent introduces multiple optically anisotropic layers (retardation plates) as intermediary elements between the liquid crystal layer and the observer. These layers act as mediators that modify the polarization state of light passing through the VA-mode liquid crystal, compensating for the light leakage and viewing angle limitations inherent in the VA mode while preserving its high contrast ratio.
3Object-affected harmful factors
If an optically-compensatory sheet is applied to a TN-mode liquid crystal cell to enlarge viewing angle, then viewing angle is improved, but the serious requirement for large-size television applications is not satisfied
Solution Approach 1:
The patent uses a composite structure of multiple optically anisotropic layers with different retardation characteristics. This composite approach combines the effects of multiple materials/layers to achieve broad-spectrum optical compensation that works across the entire visible wavelength range, providing superior viewing angle characteristics suitable for large-size television applications.
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 configuration significantly improves the viewing angle range and contrast ratio by effectively compensating for light leakage and color shift, providing a broader viewing angle with minimal color change when observed obliquely.
Implementation Method 1
a first optically anisotropic layer disposed between the first or the second polarizing element and the liquid crystal layer, showing a positive in-plane retardation (Re) at λ1 and a negative Re at λ2
Data Source
AI summary
A novel liquid crystal display device is disclosed. The device comprises a first polarizing element and a second polarizing element which are disposed with their transmission axes perpendicular to each other, a liquid crystal layer disposed between the first and the second polarizing elements, and a first optically anisotropic layer disposed between the first or the second polarizing element and the liquid crystal layer, showing a positive in-plane retardation (Re) at λ1 and a negative Re at λ2, both of λ1 and λ2 (λ1≠λ2) are within a visible wavelength range, and its absolute value of a thickness-direction retardation at 550 nm, |Rth(550)|, is equal to or more than 50 nm.