Liquid Crystal Alignment Layer Using Soft Rubbing and Polarized UV

Solution Overview

Problem

Existing methods for aligning liquid crystals in LCD devices, such as rubbing and photo-alignment, face issues like contamination, light leakage, low anchoring energy, and afterimage effects, which affect the response rate and stability of the alignment layer.

Innovation Solution

A method involving a soft rubbing process to align the main chain of an alignment material in a predetermined direction, followed by irradiation with polarized UV rays to align the side chain, enhancing the photo-response rate and anchoring energy by increasing the anisotropic characteristics of the alignment layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If rubbing alignment method is used, then liquid crystal alignment is achieved, but contaminant materials attach to substrate surface due to static electricity

Engineering Contradiction:

Improvealignment stabilityVSAvoidcontaminant attachment

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical rubbing system with a photo-alignment system using polarized ultraviolet rays. Instead of physically rubbing the alignment layer with a cloth that generates static electricity, the invention uses optical energy to induce molecular orientation in the alignment material, thereby eliminating contaminant attachment while achieving reliable liquid crystal alignment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the alignment mechanism from mechanical contact to photochemical reaction. By controlling the polarization direction and wavelength of UV rays, the alignment layer's molecular orientation is controlled without physical contact, changing the fundamental parameter of how alignment is achieved from mechanical force to optical energy.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If rubbing alignment method is used, then liquid crystal alignment is achieved, but light leakage occurs when rubbing cloth arrangement is misaligned

Engineering Contradiction:

Improvealignment consistencyVSAvoidlight leakage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical rubbing system with a photo-alignment system using polarized ultraviolet rays. Instead of physically rubbing the alignment layer with a cloth that generates static electricity, the invention uses optical energy to induce molecular orientation in the alignment material, thereby eliminating contaminant attachment while achieving reliable liquid crystal alignment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the alignment mechanism from mechanical contact to photochemical reaction. By controlling the polarization direction and wavelength of UV rays, the alignment layer's molecular orientation is controlled without physical contact, changing the fundamental parameter of how alignment is achieved from mechanical force to optical energy.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If photo-alignment method is used, then contamination and light leakage are avoided, but anchoring energy is low causing afterimage effects

Engineering Contradiction:

Improvecontaminant-free surfaceVSAvoidanchoring energy

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent employs a dual-component alignment material system: (1) a polymer main chain that provides structural framework and high anchoring energy through its rigid structure, and (2) photo-reactive side chains that respond to polarized UV irradiation to establish molecular orientation. This composite structure combines the advantages of both mechanical stability and photo-alignment capability, achieving high anchoring energy while preventing afterimage effects.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The alignment material is segmented into distinct functional components: the main chain provides structural support and anchoring energy, while the side chains containing photo-reactive groups (such as cinnamoyl, azo, or coumarin groups) are responsible for light-responsive orientation. This segmentation allows each component to perform its specialized function optimally.

Inventive Principle:

Principle #1Segmentation

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

This approach improves the response rate and anchoring energy of the alignment layer, reducing afterimage effects and ensuring stable liquid crystal alignment, suitable for mass production even with larger substrates.

Implementation Method 1

irradiating polarized ultraviolet (UV) rays onto the alignment material whose main chain has been aligned in the predetermined direction to form an alignment layer

Methodology Applied

Scientific EffectPhoto-reaction: Photopolymerisation

Data Source

PatentUS8530008B2Liquid crystal display device and method of fabricating the same

Publication Date: 2013.09.10 LG DISPLAY CO LTD

AI summary

A liquid crystal display (LCD) device includes at least one substrate; and an alignment layer over the substrate, wherein the alignment layer includes material having a main chain adapted to be aligned by a rubbing process and a photo-reactive side chain adapted to be aligned by irradiation.