Dichroic-Dye Liquid Crystal Elements for High-Temperature Transmittance
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Solution Overview
Problem
Existing liquid crystal elements struggle to effectively control the amount of transmitted light, especially in high-temperature environments, and have limited dynamic ranges in visible light transmittance due to issues with polymer matrix curing and refractive index mismatch, which affects their reliability and energy-saving capabilities.
Innovation Solution
A liquid crystal element with a polymer matrix and liquid crystal composition containing a liquid crystal component with positive dielectric constant anisotropy and refractive index anisotropy, along with a dichroic dye, is used to achieve a wide dynamic range and high light-shielding properties, maintaining performance even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If photopolymerization-induced phase separation is used to produce liquid crystal-polymer composite film, then the film structure can be obtained, but the dichroic dye absorbs light and inhibits photopolymerization causing poor curing and reduced reliability
Solution Approach 1:
The patent introduces a photopolymerization catalyst and uses a specific wavelength range light (380-780nm) that can penetrate the dichroic dye without being absorbed, enabling the light to reach and catalyze polymerization of the monomer while the dichroic dye maintains its light-absorbing function for the element's operation
Solution Approach 2:
The patent changes the parameters of the photopolymerization system by selecting a light wavelength range (380-780nm) that matches the transmission window of the dichroic dye, and by adjusting the catalyst concentration (0.01-10 wt%) to achieve effective polymerization despite the presence of light-absorbing dichroic dye
2Adaptability or versatility
If PDLC structure with liquid crystal droplets in polymer matrix is used, then flexibility and cutability are achieved, but forward scattering dominates making it almost impossible to control the amount of transmitted light
Solution Approach 1:
The patent creates a composite material system combining liquid crystal components, dichroic dyes, and polymer matrices, where the liquid crystal provides flexibility and the dichroic dye provides absorbance-based light control, achieving both mechanical versatility and optical control capability
Solution Approach 2:
The patent applies local quality by having the dichroic dye distributed within the liquid crystal droplets or polymer matrix, creating regions with different optical properties that collectively provide both scattering and absorbance mechanisms for effective light transmission control
3Reliability
If guest-host liquid crystal system with dichroic dye is used to control transmitted light amount, then light shielding property is improved, but a matrix is required to support the film structure reducing flexibility
Solution Approach 1:
The patent merges the functions of the matrix and liquid crystal by forming a liquid crystal-polymer composite film where the polymer matrix and liquid crystal components are intimately mixed, eliminating the need for a separate supporting matrix structure while maintaining both mechanical integrity and light shielding capability
4Ease of operation
If liquid crystal with low birefringence and high order parameter is used to achieve wide transmittance change, then dynamic range is improved, but haze in transparent state increases reducing clarity
Solution Approach 1:
The patent optimizes the liquid crystal component parameters by selecting compounds with specific refractive index anisotropy (0.05-0.20) and birefringence values, and by controlling the liquid crystal concentration (10-80 wt%) in the composite film to achieve the desired balance between transmittance modulation and transparency
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 liquid crystal element can electrically control light transmission, be cut and shaped, and maintain a wide dynamic range of visible light transmittance even under high temperatures, enhancing its reliability and energy-saving potential.
Implementation Method 1
When no voltage is applied to a PDLC of the normal mode driving liquid crystal molecules are oriented along walls of a polymer matrix. In this case, there is a refractive index mismatch between the liquid crystal regions and the polymer matrix. This mismatch causes light scattering and cloudiness
Implementation Method 2
When a voltage is applied to the PDLC, the liquid crystal molecules are oriented in the direction of the electric field. As a result, the liquid crystal region and the polymer matrix have the same refractive index and become transparent by transmitting light
Implementation Method 3
PTLs 1 to 3 disclose guest-host liquid crystal (GH liquid crystal) type smart glass in which a dichroic dye is added to the liquid crystal. Since the guest-host liquid crystal system is a system of switching between a transparent state and a colored state by electrically switching the absorbance of a liquid crystal element
Implementation Method 4
In PTL 4, a liquid crystal-polymer composite film is produced by polymerization-induced phase separation by photopolymerization. In the method of PTL 4, the dichroic dye in the liquid crystal absorbs light to inhibit photopolymerization. As a result, poor curing of the polymer matrix occurs
Data Source
AI summary
A liquid crystal element including: two substrates having a transparent conductive layer formed thereon, the substrates being arranged so that the transparent conductive layers face each other, and a liquid crystal-polymer composite film sandwiched between the two substrates having a transparent conductive layer, wherein the liquid crystal-polymer composite film includes a polymer matrix and a liquid crystal composition surrounded by the polymer matrix, the liquid crystal composition contains a liquid crystal component and a dichroic dye, the liquid crystal component has positive dielectric constant anisotropy, and has an NI point of 110° C. or higher and 150° C. or lower, the liquid crystal component has a refractive index anisotropy of 0.01 or more and 0.1 or less, and the liquid crystal-polymer composite film can be switched between a transparent state and a colored state by applying a voltage.