Benzotriazole Derivatives for Smart Window Lightfastness

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Solution Overview

Problem

There is a need for dichroic dye compounds and media that offer improved performance and reliability in guest-host type applications, specifically with high lightfastness, favorable dichroic ratio, and low fluorescence, while providing broad and stable liquid crystal phase ranges and low-temperature stability, particularly for smart switchable windows.

Innovation Solution

The use of benzotriazole derivatives in mesogenic media, specifically compounds of formulae Ia, Ib, and Ic, which exhibit high dichroic ratios, excellent solubility, and stability, allowing for tailored color options and reduced fluorescence, particularly in blue hues, and are suitable for guest-host applications in electro-optical and electronic devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cyanobiphenyl derivatives and dichroic dyes are used in liquid crystal media, then the device can regulate energy passage effectively, but the lightfastness and stability under prolonged sunlight exposure are insufficient

Engineering Contradiction:

ImprovelightfastnessVSAvoiddegradation under sunlight

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by modifying the chemical structure of liquid crystal compounds through specific substitutions (fluorine atoms at defined positions, cyano groups, and alkyl chains) to achieve enhanced photostability and lightfastness while maintaining the desired liquid crystal properties and energy regulation functionality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by formulating liquid crystal media that combine multiple components including the novel benzotriazole derivatives, dichroic dyes, and other liquid crystal compounds in specific ratios to achieve synergistic effects that improve both lightfastness and energy regulation performance

Inventive Principle:

Principle #40Composite materials

2Reliability

If dichroic dyes are added to liquid crystal media for guest-host applications, then the dichroic ratio and color purity improve, but the fluorescence increases which reduces aesthetic stability

Engineering Contradiction:

Improvedichroic ratioVSAvoidfluorescence

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by introducing specific fluorine substitutions at defined positions (R1, R2, R3) of the benzotriazole derivative structure, which locally modifies the electronic properties to enhance dichroic ratio while suppressing fluorescence through electron-withdrawing effects that alter the dye's photophysical behavior

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the potentially harmful fluorescence effect into a benefit by using fluorine substitutions that not only reduce unwanted fluorescence but also enhance the dichroic ratio and overall photostability, turning a negative property into a positive design feature

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Temperature

If liquid crystal media are designed for broad phase ranges and low-temperature stability, then the operational temperature range expands, but the solubility and homogeneity of components may be compromised

Engineering Contradiction:

Improvephase rangeVSAvoidsolubility

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by systematically varying the alkyl chain lengths (R4-R10), substitution patterns, and molecular weights of liquid crystal components to optimize the balance between phase range breadth and solubility, ensuring homogeneous mixing while achieving the desired low-temperature stability and broad operational phase ranges

Inventive Principle:

Principle #35Parameter changes

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 benzotriazole derivatives provide enhanced performance and reliability in regulating energy passage through smart windows by offering high lightfastness, stable liquid crystal phases, and low fluorescence, ensuring effective energy regulation and aesthetic stability under prolonged sunlight exposure.

Implementation Method 1

a temperature-induced transition from an isotropic state of the liquid-crystalline medium to a liquid-crystalline state

Methodology Applied

Scientific EffectLiquid crystal phase transition: Phase Change

Implementation Method 2

Owing to the directional dependence of the absorption by the dye molecules, the transmissivity of the dye-doped liquid crystal to light can be modulated

Methodology Applied

Scientific EffectDichroism: Dichroic Filter

Data Source

PatentUS11667845B2Liquid crystalline medium

Publication Date: 2023.06.06 MERCK PATENT GMBH

AI summary

The present invention relates to benzotriazole derivatives selected from the group of compounds of formulae Ia, Ib and Ic as defined in claim 1, to mesogenic media comprising the compounds of formulae Ia, Ib and Ic, and to the use of these compounds and mesogenic media in optical, electronic and electro-optical applications, in particular in devices for regulating the passage of energy from an outside space into an inside space, for example in windows.