Liquid Crystal Composition with Azo Dyes for High Contrast and Solubility

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Solution Overview

Problem

Current liquid crystal compositions with dichroic dyes face challenges in achieving high contrast, solubility, nematic-isotropic transition temperature, and low birefringent anisotropy for high light and thermal resistance, particularly at low temperatures, due to issues with dye solubility and molecular weight differences.

Innovation Solution

A liquid crystal composition containing specific azo dichroic dyes, such as disazo and trisazo compounds, combined with compounds represented by general formulas (L) and (N), which enhance solubility, transition temperature, and birefringent anisotropy, allowing for high light and thermal resistance and improved display quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a large amount of dichroic dye is added to achieve a large dichroic ratio, then the contrast is improved, but the solubility deteriorates causing precipitation of dichroic dye and liquid crystal compound

Engineering Contradiction:

ImprovecontrastVSAvoidsolubility

Core Design Contradiction:

Illumination intensityVSStability of the object's composition

Solution Approach 1:

The invention changes the chemical structure parameters of the liquid crystal compound by introducing specific groups (sulfone, sulfonylurea, carbamoyloxy, or cyanocarboxy groups) that enhance solubility of the dichroic dye without requiring a large amount of dye addition, thus achieving high contrast while maintaining solubility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite liquid crystal composition containing specific liquid crystal compounds with dichroic dyes, where the specially designed liquid crystal compound acts as a solubility-enhancing matrix that allows high dye concentration without precipitation, resolving the contradiction between contrast and solubility

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If dichroic dye with high molecular weight is used, then the dichroic ratio is improved, but the solubility at low temperature deteriorates

Engineering Contradiction:

Improvedichroic ratioVSAvoidlow-temperature solubility

Core Design Contradiction:

Illumination intensityVSStability of the object's composition

Solution Approach 1:

The invention modifies the liquid crystal compound structure to include specific functional groups that lower the freezing point and enhance solubility at low temperatures, allowing high molecular weight dichroic dyes to remain dissolved in the liquid crystal composition across a wide temperature range including low temperatures

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the nematic liquid crystal phase is maintained in a wide temperature range, then the device reliability is improved, but the birefringent anisotropy increases which reduces light resistance

Engineering Contradiction:

Improvetemperature range stabilityVSAvoidlight resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention carefully balances the liquid crystal compound parameters by selecting specific molecular structures with appropriate birefringent anisotropy values (0.05-0.15) that maintain nematic phase stability across wide temperature ranges while keeping light resistance acceptable, achieving a optimal compromise between reliability and light resistance

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 composition achieves high contrast, solubility, and stability across a wide temperature range, ensuring high-quality display performance with improved light and thermal resistance, preventing dye precipitation and maintaining a sharp black color.

Implementation Method 1

the liquid crystal composition exhibits a nematic phase in a wide temperature range

Methodology Applied

Scientific EffectLiquid crystal phase transition: Phase Change

Implementation Method 2

a liquid crystal composition containing one or two or more compounds represented by general formula (L) and three or four or more dichroic dyes selected from azo compounds

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 3

low birefringent anisotropy (Δn) effective for high light resistance and high thermal resistance

Methodology Applied

Scientific EffectBirefringence: Birefringence

Data Source

PatentUS11174431B2Liquid crystal composition and liquid crystal display device

Publication Date: 2021.11.16 DIC CORP

AI summary

There are provided a liquid crystal composition containing one or two or more compounds represented by general formula (L) and three or four or more dichroic dyes selected from azo compounds, and a guest-host liquid crystal display device or light-controlling device that uses the liquid crystal composition. The liquid crystal composition according to the present invention contains dichroic dyes that satisfy high contrast, high solubility, high nematic-isotropic transition temperature (TNI), and low birefringent anisotropy (Δn) effective for high light resistance and high thermal resistance at the same time. The use of the liquid crystal composition according to the present invention provides a liquid crystal display device or a light-controlling device that exhibits a good-looking black color and has high contrast, high display quality, and high practicality.