Cholesteric Liquid Crystal Display Brightness via Light Recovery
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Solution Overview
Problem
Cholesteric liquid crystal displays suffer from insufficient brightness due to the reflection and transmission characteristics of circularly polarized light, which limits their visibility and effectiveness as non-self-emitting displays.
Innovation Solution
The integration of a cholesteric liquid crystal device, a color filter element, and a light recovery structure, including a quarter-wave plate and a polarizer, enhances the brightness by optimizing the polarization and reflection of stray light, allowing circularly polarized light to pass through while reflecting the opposite polarization direction, and utilizing a light-absorbing substrate to manage contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If cholesteric liquid crystal is used to reflect circularly polarized light in one rotation direction, then the display achieves non-self-emitting operation and power saving, but the brightness is insufficient because only reflected circularly polarized light is utilized
Solution Approach 1:
A quarter-wave plate is introduced as an intermediary optical element between the cholesteric liquid crystal layer and the color filter. This quarter-wave plate converts linearly polarized light into circularly polarized light, enabling the system to utilize both left-handed and right-handed circularly polarized light components, thereby doubling the effective light utilization while maintaining the power-saving bistable operation of the cholesteric liquid crystal
Solution Approach 2:
The patent changes the polarization state parameter of the incident light by introducing a quarter-wave plate that transforms linearly polarized light from the backlight into circularly polarized light. This parameter change enables the cholesteric liquid crystal to reflect both rotation directions of circularly polarized light, effectively doubling the brightness while maintaining low power consumption
2Illumination intensity
If a light recovery structure is added to improve brightness, then the brightness and contrast are enhanced, but the device complexity increases
Solution Approach 1:
The light recovery structure is nested within the existing display stack by integrating the quarter-wave plate between the cholesteric liquid crystal layer and the color filter layer. This nested configuration allows the additional functional element to be incorporated without significantly increasing the overall device footprint or structural complexity, while still achieving the brightness enhancement goal
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
This configuration significantly improves the brightness and contrast of the cholesteric liquid crystal display, enabling better visibility and performance by effectively utilizing external light sources.
Implementation Method 1
the circularly polarized light in one rotation direction will be reflected by the cholesterol liquid crystal, and the circularly polarized light in the other rotation direction will pass through the cholesterol liquid crystal
Implementation Method 2
A first quarter-wave plate and a color filter element are disposed to overlap the cholesteric liquid crystal device
Data Source
AI summary
A cholesteric liquid crystal display includes a cholesteric liquid crystal device, a color filter element, a first quarter-wave plate, and a light recovery structure. The cholesteric liquid crystal device includes a cholesteric liquid crystal. The color filter element and the first quarter-wave plate overlap the cholesteric liquid crystal device. The first quarter-wave plate and the color filter element are located between the cholesteric liquid crystal and the light recovery structure.