Retardation Compensation Element for Reflective LCD Contrast
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Solution Overview
Problem
Reflective liquid crystal display devices with vertically aligned nematic (VAN) liquid crystals face challenges in maintaining high contrast and viewing angle due to pre-tilt of liquid crystal molecules and obliquely incident light, with existing retardation compensation elements lacking durability and mass productivity.
Innovation Solution
A reflective liquid crystal display device incorporating a biaxial birefringent medium with an optical axis inclined to the substrate surface, combined with a uniaxial birefringent medium, compensates phase differences caused by pre-tilt and obliquely incident light, improving contrast and viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a C-plate is used to compensate phase difference of obliquely incident light, then contrast is improved for front viewing, but phase difference caused by pre-tilt of liquid crystal molecules cannot be compensated
Solution Approach 1:
The patent combines a C-plate (uniaxial birefringent medium with optical axis perpendicular to substrate) and an O-plate (biaxial birefringent medium with optical axis inclined to substrate) into a composite retardation compensation element. This merging allows simultaneous compensation of phase differences from both oblique light incidence and pre-tilt effects, resolving the limitation of using a C-plate alone.
Solution Approach 2:
The invention uses a composite structure combining uniaxial and biaxial birefringent materials with specific optical axes oriented at different angles. The C-plate has its optical axis perpendicular to the substrate while the O-plate has its optical axis inclined at a predetermined angle, creating a composite material system that addresses multiple phase difference sources simultaneously.
2Illumination intensity
If A-plate and C-plate are used together to compensate phase difference, then contrast degradation from pre-tilt is prevented, but material choices are limited and durability is reduced
Solution Approach 1:
The patent changes the material parameters by replacing the traditional polymer film A-plate with a biaxial birefringent medium made from inorganic materials (such as glass or crystal) with specifically controlled refractive indices. This parameter change maintains the necessary optical compensation functionality while significantly improving durability and reliability.
3Adaptability or versatility
If two or more O-plates are layered to extend viewing angle, then TN-LCD contrast is improved, but the structure becomes complex and is not suitable for VAN-LCD
Solution Approach 1:
The patent designs a retardation compensation element that serves multiple functions: the C-plate component compensates for oblique light incidence effects while the O-plate component compensates for pre-tilt effects. This multi-functional design achieves wide viewing angle performance suitable for VAN-LCD without requiring complex multi-layer structures.
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 enhances contrast and viewing angle in VAN-LCDs by compensating phase differences, while being durable and cost-effective, and is applicable in reflective liquid crystal projectors.
Implementation Method 1
a biaxial birefringent medium made by obliquely depositing an inorganic material. This biaxial birefringent medium has an optical axis inclined to the substrate surface of the VAN liquid crystal cell
Implementation Method 2
a uniaxial birefringent medium which has an optical axis perpendicular to the surface of the VAN liquid crystal cell
Implementation Method 3
a biaxial birefringent medium made by obliquely depositing an inorganic material
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A retardation compensation element (56) is composed of a C-plate (85) and an 0-plate (86). The O-plate (86) is a biaxial birefringent medium made of an obliquely deposited organic material. A fast axis (L6) of the 0-plate (86) is parallel to the orthographic projection of a deposition direction (96) onto the surface of the O-plate (86). Between a liquid crystal display device (51) and a polarization beam splitter (48), the O-plate (86) is arranged such that the fast axis (L6) and a tilt direction (L8) of liquid crystal molecules (75) are parallel to each other, and that the deposition direction (96) and the tilt direction (L8) face the opposite direction with respect to a Z2 axis. The C-plate (86) is disposed together with the O-plate (85) between the liquid crystal display device (51) and the polarization beam splitter (48).