VA LCD Polarizing Plate with λ/4 Phase Difference Plate
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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
Incorporating a polarizing plate with a λ/4 phase difference plate and compensating films like positive A-plates and negative C-plates, strategically positioned to adjust refractive indices and phase delays, reducing light leakage and improving viewing angles by optimizing the optical operation of the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a liquid crystal layer in VA mode is used, then the LCD apparatus achieves a high contrast ratio in front view, but light leakage occurs and contrast ratio varies at side viewing angles
Solution Approach 1:
The patent applies parameter changes by introducing a λ/4 phase difference plate with specific refractive index (1.65-1.75) and thickness (50-150 μm) to modify the optical path difference. This changes the phase relationship of light waves passing through the liquid crystal layer at different angles, compensating for the phase differences that cause light leakage and contrast ratio variation at side viewing angles.
Solution Approach 2:
The patent uses composite materials by combining the liquid crystal layer with a λ/4 phase difference plate made of optically compensating resin. This composite structure integrates the light modulation function of the liquid crystal with the phase compensation function of the resin material, achieving both high contrast ratio and improved viewing angle characteristics.
2Object-affected harmful factors
If the refractive index of the λ/4 phase difference plate is increased, then light leakage is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a refractive index range of 1.65-1.75 for the λ/4 phase difference plate, which is a carefully selected parameter range that balances light leakage reduction with manufacturing feasibility. This parameter range provides sufficient phase compensation while remaining achievable with conventional optical resin materials and manufacturing processes.
Solution Approach 2:
The patent employs a thickness range of 50-150 μm for the phase difference plate, which provides adequate phase compensation without requiring excessive precision. By using a thicker plate within this range, the patent achieves the necessary optical path difference while allowing for broader manufacturing tolerances, thus reducing the stringency of manufacturing precision requirements.
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 minimizes light leakage and enhances viewing angles, resulting in improved display quality and 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 1.65 and about 1.75
Implementation Method 2
the liquid crystal has an anisotropic refractive index, so that the liquid crystal induces a phase difference in light generated from the backlight assembly, where the magnitude of the phase difference depends on the incident angle of the light
Implementation Method 3
a polarizer and a λ/4 phase difference plate. The polarizer has a polarizing axis
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.