Retardation Layer for Transflective LCD Black Display
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Solution Overview
Problem
Existing liquid crystal display devices face challenges in achieving black display in reflective areas with increased liquid crystal layer thickness, making mass production difficult due to stringent retardation value requirements.
Innovation Solution
A liquid crystal display device with a retardation layer formed between the liquid crystal layer and the polarizer in the reflective area, where the retardation value of the liquid crystal layer exceeds a quarter wavelength and the retardation value of the retardation layer exceeds a half wavelength, allowing for achromatic dark display without voltage application, and the retardation layer's slow axis is angled between 20° and 75° relative to the polarizer's axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the retardation value of the liquid crystal layer is set to a quarter wavelength to achieve black display in reflective area, then the black display performance is improved, but the liquid crystal layer thickness becomes extremely thin (about 1.1 μm) making mass production difficult
Solution Approach 1:
The invention divides the retardation function into two separate components: the liquid crystal layer and an additional retardation layer. The liquid crystal layer provides a retardation value exceeding a quarter wavelength, while the retardation layer provides an additional retardation value exceeding a half wavelength. This segmentation allows the liquid crystal layer thickness to be increased for mass production while the combined retardation achieves the required black display performance.
Solution Approach 2:
The invention uses a composite structure combining the liquid crystal layer with an additional retardation layer made of a retardation material. This composite approach allows the system to achieve the required total retardation value (exceeding three-quarters of a wavelength) while using a thicker liquid crystal layer that is feasible for mass production, rather than relying solely on an extremely thin liquid crystal layer.
2Productivity
If the liquid crystal layer thickness is increased to improve mass productivity, then the manufacturing efficiency is improved, but the black display performance in reflective area deteriorates due to insufficient retardation value
Solution Approach 1:
The invention segments the retardation function between the liquid crystal layer and an additional retardation layer. This allows the liquid crystal layer to have a practical thickness for mass production while the combined system achieves the required total retardation value for black display performance.
Solution Approach 2:
The invention changes the parameter configuration by setting the liquid crystal layer retardation value to exceed a quarter wavelength and the additional retardation layer retardation value to exceed a half wavelength. This parameter configuration allows the liquid crystal layer thickness to be increased for mass productivity while maintaining the required black display performance through the cumulative retardation effect.
3Productivity
If the retardation value of the liquid crystal layer exceeds a quarter wavelength to allow increased thickness, then the mass productivity is improved, but the total retardation value may not be sufficient for achromatic dark display
Solution Approach 1:
The invention creates a composite retardation system where the liquid crystal layer (with retardation value exceeding a quarter wavelength) is combined with an additional retardation layer (with retardation value exceeding a half wavelength). This composite structure ensures the total retardation value exceeds three-quarters of a wavelength, achieving achromatic dark display quality while allowing the liquid crystal layer to have a thickness suitable for mass production.
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
Enables achromatic dark display in reflective areas with increased liquid crystal layer thickness, improving mass productivity by relaxing the retardation value constraints and allowing for efficient production.
Implementation Method 1
a liquid crystal layer which is homogeneously aligned between the first substrate and the second substrate
Implementation Method 2
liquid crystal is driven by a horizontal electric field by so called a fringe field switching (hereinafter, referred to as FFS) system
Implementation Method 3
a retardation layer which is formed between the liquid crystal layer and the first polarizer in the reflective display area, the retardation layer having a slow axis which makes an angle of not less than 20° and not more than 25° or not less than 60° and not more than 75° with respect to the polarization axis of the first polarizer
Implementation Method 4
a first polarizer provided on the first substrate, the first polarizer having a polarization axis parallel to or perpendicular to an initial alignment direction of the liquid crystal layer
Implementation Method 5
a pixel having a transmissive display area and a reflective display area
Data Source
AI summary
In a transflective type liquid crystal display device of an FFS system, a plurality of pixels has a transmissive display area for emitting transmissive display light and a reflective display area for emitting reflective display light, and the reflective display area is equipped with a retardation layer. Polarization axes of polarizers are perpendicular to each other and an alignment direction of the liquid crystal layer is parallel to or perpendicular to the polarization axis of the first polarizer. The angle of a slow axis of the retardation layer is not less than 20° and not more than 25° or not less than 60° and not more than 75° with respect to the polarization axis of the first polarizer. A retardation value of the liquid crystal layer in the reflective area exceeds a quarter wavelength, and a retardation value of the retardation layer exceeds a half wavelength.