Variable Transmittance Optical Device Using Guest-Host Mixture
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Solution Overview
Problem
Current liquid crystal guest-host devices for eyewear applications lack wideband absorption and high transmission swing due to limitations in substrate materials and performance parameters, leading to unacceptable optical performance and visibility issues.
Innovation Solution
A variable transmission optical device using a guest-host mixture of negative dielectric anisotropy liquid crystal host and dichroic guest dye between plastic substrates, with specific parameters such as a cell gap greater than 3 microns, a thickness to pitch ratio of less than 0.9, and dichroic dyes with a positive dichroic ratio, achieving wide absorption bands and high transmission swings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional guest-host liquid crystal systems are used with plastic substrates, then the device can be manufactured for eyewear applications, but the absorption band is limited to less than 175nm and transmission swing is insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the cell gap to greater than 3 microns and adjusting the thickness-to-pitch ratio to less than 0.9, which enables wideband absorption greater than 175nm while maintaining plastic substrate compatibility for eyewear manufacturing
Solution Approach 2:
The patent uses a composite guest-host mixture comprising dichroic dyes dissolved in liquid crystal host material, where the specific combination of materials with optimized concentrations enables both wideband absorption and compatibility with plastic substrates
2Device complexity
If traditional guest-host liquid crystal systems are used, then the device structure is simpler, but the transmission swing is less than 30% and optical performance is unacceptable
Solution Approach 1:
The patent achieves a transmission swing of at least 30% by optimizing parameters including the cell gap greater than 3 microns, the thickness-to-pitch ratio less than 0.9, and the guest-host mixture composition, while maintaining the relatively simple guest-host device structure without additional polarizers
Solution Approach 2:
The patent applies local quality by using dichroic dyes with specific absorption characteristics that target particular wavelength ranges, enabling the device to achieve high transmission swing and wideband absorption through localized optical properties of the dye molecules within the liquid crystal host
3Quantity of substance
If the cell gap is increased to improve wideband absorption, then the absorption band width increases, but the device thickness and weight increase
Solution Approach 1:
The patent optimizes the cell gap to be greater than 3 microns (a specific parameter change) which provides sufficient path length for wideband absorption greater than 175nm while keeping the thickness increase manageable for eyewear applications
4Reliability
If dichroic dyes with high dichroic ratio are used to improve transmission swing, then the transmission swing increases, but the solubility in liquid crystal host decreases
Solution Approach 1:
The patent selects dichroic dyes with positive dichroic ratios and optimizes their concentration in the liquid crystal host to achieve at least 30% transmission swing while maintaining adequate solubility, balancing optical performance with mixture stability
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 provides a wideband absorption greater than 175nm and a transmission swing of over 30%, enhancing optical performance and minimizing visibility issues by reducing polarization dependence and optical distortions.
Implementation Method 1
The liquid crystal 'host' includes non-polarizing liquid crystal material having an axis of orientation that is alterable by adjustment of voltage applied across the substrates
Implementation Method 2
The dye 'guest' mixture comprises dichroic dyes which are dissolved within the liquid crystal host and which align with the orientation of the liquid crystal material
Data Source
AI summary
We describe a wide band variable transmission optical device, mixtures for use in such a device, and methods of making the same. The wide band optical device includes a cell comprising a guest-host mixture of a liquid crystal host and a dichroic guest dye material contained between a pair of plastic substrates. The optical device does not use polarizers. The liquid crystal host has an axis orientation that is alterable between a clear state orientation and a dark state orientation perpendicular thereto and the dichroic guest dye material includes one or more dichroic dyes. The optical device is characterized in that it exhibits a wide absorption band that is greater than 175nm within a visible wavelength range of 400-700nm and has a clear state transmission equal to or above 30% and a dark state transmission equal to or below 40%.