Chiral Nematic Liquid Crystal Display Haze Reduction
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Solution Overview
Problem
Chiral nematic liquid crystal display devices face challenges in maintaining low haze across a wide range of viewing angles due to refractive index mismatch between the polymer matrix and liquid crystal, leading to increased haze as the viewing angle increases, which is critical for applications like smart windows where clear visibility is required.
Innovation Solution
The use of microencapsulated chiral nematic liquid crystal with a spherulite morphology, where the liquid crystal is enclosed in a spherical polymer shell, minimizing the interface area with the polymer matrix and allowing for a stable light scattering or absorbing state without compromising the transparent state, achieved by optimizing the helical pitch length and using dichroic dyes for enhanced light scattering or absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid crystal is dispersed as a discontinuous phase in a continuous polymer matrix, then the device provides containment for the liquid crystal fluid and forms a solid liquid crystal film, but haze increases with viewing angle due to refractive index mismatch between the polymer matrix and birefringent liquid crystal
Solution Approach 1:
The patent changes the physical state of liquid crystal from discontinuous dispersed phase to continuous phase by inducing phase separation. This parameter change eliminates the refractive index mismatch issue at interfaces, thereby reducing haze while maintaining containment stability through the polymer network structure.
Solution Approach 2:
The patent creates a composite material system where liquid crystal and polymer form a phase-separated structure with interconnected domains. This composite approach allows the liquid crystal to remain contained within the polymer matrix while achieving a continuous phase morphology that minimizes optical scattering and haze.
2Object-affected harmful factors
If the maximum discrete liquid crystal volume is increased to minimize interface area, then haze is reduced, but the polydomain texture becomes unstable beyond a certain dimension
Solution Approach 1:
The patent changes the texture state from polydomain to monodomain through phase separation. This parameter change allows liquid crystal volumes to extend throughout the device thickness without the stability limitations of polydomain textures, enabling larger effective volumes that minimize interface area and reduce haze.
Solution Approach 2:
Instead of trying to stabilize polydomain textures in large volumes, the patent inverts the approach by creating monodomain regions through phase separation. This inversion allows the liquid crystal to form stable, large-scale continuous phases that naturally minimize interfaces with the polymer matrix.
3Illumination intensity
If the liquid crystal is oriented to achieve transparent state, then light transmission is improved, but haze increases at wider viewing angles due to extraordinary refractive index
Solution Approach 1:
The patent changes the morphological parameter from discontinuous dispersed droplets to continuous phase domains. This parameter change eliminates the viewing angle dependence of haze because the continuous phase eliminates interfaces where refraction and scattering occur, allowing wide viewing angle transparency while maintaining high light transmission.
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 approach minimizes haze across various viewing angles, maintains stability over time, and allows for efficient light scattering or absorption, meeting the requirements for transparent and translucent states in display devices without introducing polymer networks or additives that could compromise the transparent state.
Implementation Method 1
a helical superstructure, wherein the chiral nematic liquid crystal molecules form concentric helices with a helical pitch length
Implementation Method 2
the liquid crystal is birefringent
Implementation Method 3
Strong scattering of incident light in a chiral nematic liquid crystal body in the light scattering state is created by: a) the spherulite morphology
Implementation Method 4
said discrete bodies are microencapsulated by a polymer shell
Implementation Method 5
In light absorbing embodiments of the present invention, the liquid crystal comprises dichroic-dye doped, chiral nematic, liquid crystal
Data Source
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Figure 4
AI summary
A cholesteric, liquid crystal device comprises a plurality of discrete spheroidal bodies of chiral nematic, liquid crystal, microencapsulated by a polymer shell and arranged in an electro-optical layer sandwiched between electrodes. The bodies of liquid crystal are selectively operable in at least two states, a first state that transmits light through a liquid crystal body and a second state that scatters or absorbs light in a liquid crystal body. Each body in the second state has an ordered liquid crystal texture that minimizes disclinations or domains within the liquid crystal body. The liquid crystal texture comprises a superstructure of helices of chiral nematic, liquid crystal.