Photoaligning Copolymer for Liquid Crystal Alignment

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Solution Overview

Problem

Current photo-aligning materials for liquid crystals face challenges such as solubility issues, phase separations, and undesirable electro-optical property changes, limiting their flexibility and effectiveness in optical and electro-optical applications.

Innovation Solution

A copolymer is developed comprising a first monomer with photoreactive groups and a second monomer with either non-photoreactive or photoreactive groups, specifically designed to improve alignment and stability, with a molar ratio and specific structural features that enhance solubility and electro-optical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If homopolymers are used for photoalignment, then the structure is simple and easy to manufacture, but the flexibility in fine-tuning chemical and electro-optical characteristics is limited

Engineering Contradiction:

Improvesimplicity of structureVSAvoidflexibility in fine-tuning properties

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent employs copolymer composition comprising first monomer units with photoreactive groups and second monomer units with terminal polar groups. This composite structure combines the advantages of different monomer types to achieve both ease of manufacture and flexibility in property tuning, resolving the contradiction between structural simplicity and adaptability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The copolymer structure assigns different functional roles to different monomer units: first monomer units provide photoreactive functionality for alignment, while second monomer units provide terminal polar groups for electro-optical property control. This local differentiation enables independent optimization of various properties without compromising overall performance.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If blends or formulations are composed to access desired properties, then flexibility in fine-tuning characteristics is improved, but solubility problems and phase separations occur

Engineering Contradiction:

Improveflexibility in fine-tuning propertiesVSAvoidhomogeneity of alignment layer surface

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent merges multiple functional monomers into a single copolymer structure through co-polymerization. This integration ensures molecular-level mixing and uniform distribution of different functional groups throughout the material, eliminating phase separation and solubility problems while maintaining the flexibility to tune properties by adjusting monomer ratios.

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If blends or formulations are composed to access desired properties, then flexibility in fine-tuning characteristics is improved, but inhomogeneities on the alignment layer surface occur

Engineering Contradiction:

Improveflexibility in fine-tuning propertiesVSAvoidhomogeneity of alignment layer surface

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

By combining different monomer units into a copolymer structure, the patent ensures uniform molecular composition throughout the alignment layer. This molecular-level homogeneity prevents surface inhomogeneities and achieves consistent alignment properties across the entire layer, while still allowing property tuning through monomer ratio adjustment.

Inventive Principle:

Principle #5Merging (Combining)

4Adaptability or versatility

If blends or formulations are composed to access desired properties, then flexibility in fine-tuning characteristics is improved, but changes in electro-optical properties occur which are undesirable

Engineering Contradiction:

Improveflexibility in fine-tuning propertiesVSAvoidstability of electro-optical properties

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The copolymer structure localizes electro-optical functionality to specific second monomer units with terminal polar groups, while first monomer units provide stable photoreactive framework. This separation of functions allows independent optimization: the photoreactive framework maintains stable electro-optical properties, while the polar groups provide the desired flexibility for property tuning.

Inventive Principle:

Principle #3Local quality

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 copolymer provides improved solubility, stability, and electro-optical performance, addressing the drawbacks of existing materials by maintaining desired properties and preventing undesirable changes in electro-optical characteristics.

Implementation Method 1

The copolymer comprises a photoreactive group as given below in formula (I), wherein the copolymer is used for the photoalignment of liquid crystals

Methodology Applied

Scientific EffectPhotoalignment: Photochromism

Implementation Method 2

Methodology Applied

Scientific EffectSolubility enhancement: Solvation

Data Source

PatentUS9765235B2Photoaligning material

Publication Date: 2017.09.19 ROLIC AG

AI summary

The present invention relates to a copolymer for the photoalignment of liquid crystals comprising a photoreactive group as given below in formula (I), compositions thereof, and its use for optical and electro optical devices, especially liquid crystal devices (LCDs).