Polarizing Plate with λ/4 Phase Difference Plate for LCD Viewing Angle
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Solution Overview
Problem
Liquid crystal display (LCD) panels with a vertical alignment (VA) mode suffer from light leakage and varying contrast ratios due to phase differences in light transmission, which worsen at different viewing angles, leading to suboptimal display quality.
Innovation Solution
The implementation of a polarizing plate comprising a polarizer, a λ/4 phase difference plate, and compensating films such as positive A-plates and negative C-plates, with specific refractive indices and phase delay values, is used to reduce light leakage and improve viewing angles by adjusting the refractive indexes of the λ/4 phase difference plates and incorporating compensating films between the polarizer and the λ/4 phase difference plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a liquid crystal layer in VA mode is used, then the LCD apparatus displays images with high contrast ratio in front views, but light leakage occurs and contrast ratio varies at side viewing angles
Solution Approach 1:
The patent applies parameter changes by carefully selecting and adjusting the refractive indices of the λ/4 phase difference plate (1.35-2.05) and compensating films (positive A-plate with phase delay 70-140 nm, negative C-plate with phase delay 30-80 nm). These parameter optimizations enable the polarizing plate to maintain high contrast ratio while improving viewing angle performance, resolving the contradiction between contrast ratio and viewing angle adaptability
Solution Approach 2:
The patent uses a composite structure consisting of multiple optical films with different properties: a polarizer, a λ/4 phase difference plate, a positive A-plate compensating film, and a negative C-plate compensating film. Each layer contributes specific optical characteristics that work together to reduce light leakage and improve viewing angle while maintaining high contrast ratio, effectively resolving the technical contradiction
2Adaptability or versatility
If the refractive index of the λ/4 phase difference plate is adjusted to reduce light leakage, then viewing angle performance improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for the λ/4 phase difference plate refractive index (1.35-2.05) and compensating film phase delays (positive A-plate: 70-140 nm, negative C-plate: 30-80 nm). These standardized parameter specifications make the manufacturing process more controllable and less sensitive to minor variations, reducing the practical impact of manufacturing precision requirements while still achieving improved viewing angle performance
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 configuration significantly reduces light leakage and enhances the viewing angle performance of LCDs, resulting in improved display quality and more consistent contrast ratios across various viewing positions.
Implementation Method 1
a λ/4 phase difference plate disposed over the polarizer and having a refractive index between about 1.35 and about 2.05 in a thickness direction
Implementation Method 2
The compensating film may be a positive A-plate, and a phase delay value of the positive A-plate is between about 70 nm and about 140 nm in a thickness direction
Implementation Method 3
The compensating film may be a negative C-plate, and a phase delay value of the negative C-plate is between about 30 nm and about 80 nm in a thickness direction
Implementation Method 4
The liquid crystal has an anisotropic refractive index, so that the liquid crystal induces a phase difference in light generated from the backlight assembly
Data Source
AI summary
A display apparatus comprises a display panel, a first polarizing plate and a second polarizing plate. The display panel comprises a first substrate including a pixel electrode, a second substrate opposite to the first substrate, and a liquid crystal layer disposed between a first surface of the first substrate and a first surface of the second substrate. The first polarizing plate comprises a first polarizer having a first polarizing axis, and a first λ/4 phase difference plate having a refractive index between about 1.35 and about 2.05 in a thickness direction. The second polarizing plate comprises a second polarizer having a second polarizing axis crossing the first polarizing axis, and a second λ/4 phase difference plate having a refractive index between about 1.35 and about 2.05 in a thickness direction. Accordingly, light leakage in a side view may be reduced and viewing angle may be improved.