Optically Anisotropic Layer for Liquid Crystal Panel Light Leakage
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Solution Overview
Problem
Conventional liquid crystal display devices face challenges in reducing light leakage in the oblique direction during black displays, leading to compromised image quality and increased power consumption due to trade-offs between coloring and transmittance.
Innovation Solution
A liquid crystal panel design incorporating a first and second polarizing plate, a liquid crystal layer with horizontally aligned molecules, and an optically anisotropic layer with specific refractive index properties and dichroic characteristics to compensate for polarized light across various wavelengths, reducing light leakage while maintaining high transmittance in white displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a phase difference layer with birefringence characteristics is used to reduce light leakage in the oblique direction, then light leakage is reduced at a specific wavelength (550 nm), but light leakage occurs at other wavelengths (400-500 nm blue range and 600-700 nm red range) due to chromatic dispersion, causing conspicuous coloring
Solution Approach 1:
The patent uses a composite optically anisotropic layer combining two different materials with complementary birefringence characteristics. The first material has positive birefringence (no=1.50, ne=1.70) and the second material has negative birefringence (no=1.60, ne=1.55), creating a composite structure that compensates for chromatic dispersion effects across the visible spectrum while maintaining effective light leakage suppression in the oblique direction
Solution Approach 2:
The patent changes the optical parameters of the compensation layer by using materials with different birefringence signs and magnitudes. The specific refractive index values (no and ne for each material) and their combination ratios are optimized to achieve wavelength-independent compensation, transforming the single-wavelength compensation approach into a broadband solution
2Object-affected harmful factors
If a dichroic dye is used to compensate for viewing angle characteristics, then light leakage is reduced, but transmittance in white display decreases, resulting in increased power consumption
Solution Approach 1:
The patent introduces an intermediary optically anisotropic layer that mediates between the polarizing plates and the liquid crystal layer. This intermediate layer provides viewing angle compensation and light leakage suppression through its birefringence properties without the strong light absorption characteristics of dichroic dyes, thereby maintaining high transmittance and low power consumption
Solution Approach 2:
The patent substitutes the dichroic dye mechanism (which relies on strong light absorption) with a birefringence-based optical compensation mechanism. This substitution replaces an absorptive system with a refractive/phase-difference system, achieving the same light leakage suppression function through optical path manipulation rather than light absorption, thus preserving transmittance and reducing power consumption
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 suppresses light leakage in the oblique direction during black displays, enhancing image quality and reducing power consumption by optimizing the liquid crystal panel's optical properties to achieve better viewing angles and luminance.
Implementation Method 1
optimal characteristics of a phase difference plate for reducing viewing angle dependence of the polarizing plate by theoretically determining birefringence characteristics for equalizing a polarized state of light that has passed through a polarizer in the case of oblique incidence to the polarized state in the case of perpendicular incidence
Implementation Method 2
a technology of reducing light scattering by pigment particles of a color filter or the liquid crystal layer is reported as a technology for improving a contrast ratio in the vertical direction (front direction)
Data Source
AI summary
Provided is a liquid crystal display device, in which a pretilt angle of liquid crystal molecules in a liquid crystal layer (21) is smaller than 2° and a first optically anisotropic layer (10) is formed between a first polarizing plate (12) and the first substrate (31). When a polar angle of the first optically anisotropic layer with respect to an in-plane vertical direction is denoted by φ, the first optically anisotropic layer compensates for a polarized state of light having a wavelength of 550 nm that enters the first optically anisotropic layer, the first optically anisotropic layer has a dichroic maximum value in a range of 430 nm or larger and 470 nm or smaller and has a dichroic maximum value in a range of 600 nm or larger and 650 nm or smaller when φ≠0 is satisfied.