E-compensator for LCD Viewing Angle and Contrast
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Solution Overview
Problem
Liquid crystal display apparatuses face challenges in maintaining consistent viewing angle characteristics and contrast ratio due to anisotropy of polarizers and liquid crystal molecules, leading to issues like coloring in black displays and varying contrast ratios depending on the viewing angle, especially at shorter and longer wavelengths.
Innovation Solution
Incorporating a thin film E-compensator with a disc-form molecular structure and a transmission axis aligned parallel to the extraordinary wave axis, which acts as a viewing angle compensation layer external to or between polarizers, improving the contrast ratio and reducing light leakage by optimizing the molecular orientation and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a substantially transparent optical film having uniaxial or biaxial refractive anisotropy is used to compensate viewing angle characteristics, then the contrast ratio is improved at certain viewing angles, but the compensation cannot be achieved homogenously at visible wavelengths due to refractive-anisotropic chromatic dispersion
Solution Approach 1:
The patent changes the optical parameters of the compensation film by controlling its thickness and refractive anisotropy to achieve homogeneous compensation across visible wavelengths. Specifically, the film thickness is optimized to balance the phase differences at different wavelengths, and the refractive anisotropy is carefully selected to compensate for the chromatic dispersion effects.
Solution Approach 2:
The patent employs a composite structure consisting of multiple optical films with different optical properties. This includes combining a positive C-plate film and a negative C-plate film, or using a multi-layer configuration where each layer has specific refractive index characteristics to collectively achieve broad-spectrum viewing angle compensation.
2Illumination intensity
If the compensation is optimized at wavelengths of about 550 nm, then the contrast ratio is improved, but the compensation is not sufficient at shorter wavelengths for producing a blue display and at longer wavelengths for producing a red display
Solution Approach 1:
The patent adjusts the thickness and refractive anisotropy parameters of the compensation film to achieve a balance between green wavelength compensation and blue/red wavelength compensation. By optimizing these parameters, the film provides adequate viewing angle compensation across the entire visible spectrum while maintaining color accuracy.
Solution Approach 2:
The patent introduces an additional dimension of control by using multi-layer film configurations with different orientations and optical properties. This allows independent optimization of compensation at different wavelengths by adjusting the thickness and orientation of each layer, thereby achieving broad-spectrum performance.
3Reliability
If a film showing reciprocal dispersion is used as an optical film for compensation, then the viewing angle characteristics are improved, but it has a narrow margin in design of materials and cannot easily compensate large screens
Solution Approach 1:
The patent changes from using reciprocal dispersion films to using films with conventional positive or negative uniaxial/biaxial refractive anisotropy. This parameter change expands the material design margin significantly, as conventional materials with well-established manufacturing processes can be used, and the films can be easily scaled to large screen sizes without fundamental design changes.
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 E-compensator enhances viewing angle characteristics and front contrast ratio, maintaining optimal optical balance by minimizing absorption and ensuring high transmittance, thus preventing color shifts and luminance reduction in liquid crystal displays.
Implementation Method 1
a polarizer having an absorption axis along with an extraordinary wave axis, and a polarizer having a transmission axis along with the extraordinary wave axis
Implementation Method 2
an optical film showing a phase difference is generally used
Data Source
AI summary
A transmitting liquid crystal display apparatus includes a liquid crystal panel including a pair of substrates, a pair of polarizers arranged adjacent to the pair of substrates respectively, a liquid crystal layer held between the pair of substrates, and electrodes arranged on at least one of the pair of substrates and serving to apply an electric field to the liquid crystal layer; and a light source unit arranged external to the pair of substrates, in which each of the pair of polarizers has an absorption axis along with an extraordinary wave axis of molecules constituting the polarizers. In this apparatus, a dye layer having a disc-form molecular structure is arranged between the polarizer and the substrate, or adjacent to the polarizer in proximity to the viewer. The dye layer has a transmission axis along with the extraordinary wave axis of the disc-form molecular structure.