Multichromophoric Dye Mixture for Liquid Crystal Displays
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Solution Overview
Problem
Current dichroic fluorescent dyes used in guest-host liquid crystal mixtures face limitations in achieving high solubility, light stability, quantum efficiency, and dichroic ratio, particularly under high light intensity conditions, with rylene-type dyes like Lumogen IR 765 and IR 788 exhibiting poor fluorescence and low solubility.
Innovation Solution
Development of multichromophoric dyes with a rylene chromophore and a second chromophore connected by a spacer that interrupts conjugation, allowing for high dichroic ratios, excellent solubility (>0.2 wt %), and high quantum efficiency, along with the ability to extend wavelength range through Förster Resonance Energy Transfer (FRET).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If monochromophoric dyes are used in liquid crystal mixtures, then the dye can be aligned by the liquid crystal host, but the order parameter and dichroic ratio remain low
Solution Approach 1:
The dye molecule is divided into multiple chromophoric units (rylene chromophores) connected by spacers, creating a multichromophoric structure. This segmentation allows each chromophore to contribute to the overall dichroism while the spacers prevent conjugation between them, maintaining high order parameters and dichroic ratios.
Solution Approach 2:
The patent creates composite dye molecules by combining multiple chromophoric units with spacer groups. This composite structure integrates the advantages of individual chromophores while avoiding their limitations, achieving high solubility, high order parameter, and high dichroic ratio simultaneously.
2Use of energy by moving object
If dichroic fluorescent dyes are used to achieve high contrast in absorption or emission, then the quantum efficiency should be high, but light stability deteriorates under high intensity applications
Solution Approach 1:
By dividing the dye into multiple chromophores connected by spacers, the patent reduces aggregate formation and photodegradation pathways while maintaining high quantum efficiency. The spacers act as protective elements that isolate chromophores from each other, improving light stability.
3Quantity of substance
If dichroic dyes are mixed with thermotropic liquid crystals to achieve a useful temperature range, then the solubility should be high, but the concentration of dye is limited
Solution Approach 1:
The patent modifies the molecular parameters of the dye by introducing spacer groups with specific properties (flexibility, length, chemical composition) to optimize solubility in thermotropic liquid crystals. These parameter changes allow higher dye concentrations while maintaining mixture stability and desired temperature range.
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 multichromophoric dyes achieve a dichroic ratio exceeding 10, high solubility, and quantum yield of 50%-100%, enhancing the effectiveness of guest-host mixtures in applications like displays and lighting by maintaining high light stability and anisotropic fluorescence.
Implementation Method 1
extended wavelength range through Förster Resonance Energy Transfer
Implementation Method 2
Dichroism is the property whereby an oriented assembly of dye molecules exhibits relatively low absorption of a given wavelength of light in one state of orientation and a relatively high absorption of the same wavelength in another state of orientation with respect to the light source
Implementation Method 3
The term 'host' refers to the liquid crystal material, and the term 'guest' refers to an agent which may be aligned by the host to produce contrasting light absorptive states in response to selectively activeable external stimuli
Implementation Method 4
Nematic liquid crystals orient a beam of ordinary light into two polarized components whose transverse vibrations are at right angles to each other
Data Source
AI summary
A guest-host liquid crystal dye mixture comprising a calamatic, thermotropic liquid crystal as host and a dichroic fluorescent dye as guest, characterized in that the dichroic fluorescent dye is a multichromophoric dye containing at least a group with the general formula Ry-X1—C1, wherein Ry is a chromophore from the rylene family, C1 is a second chromophore and X1 is a spacer that interrupts the conjugation between Ry and C1, the spacer X1 is selected such that it introduces rigidity against bending or folding over an axis perpendicular to the length of the molecule.