LCD Alignment Layer Defect Removal via UV Etching

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Solution Overview

Problem

The existing methods for forming alignment layers in liquid crystal displays (LCDs) suffer from rubbing defects such as vertical lines, scratches, and mura, which lead to non-uniform alignment of liquid crystal molecules, resulting in degraded image quality and reduced production yield, especially in larger substrates.

Innovation Solution

A method involving a primary alignment process using a rubbing technique followed by a secondary alignment process where non-polarized UV light is irradiated onto the alignment layer to etch the surface, removing defects and improving alignment uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a rubbing process is used to form the alignment layer, then the alignment direction is established and the process is easy to implement, but rubbing defects such as vertical lines, scratches, and mura occur degrading image quality

Engineering Contradiction:

Improveease of alignment layer formationVSAvoidalignment uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The alignment layer formation is divided into two separate processes: a rubbing process to establish the alignment direction, and a subsequent light irradiation process to remove surface defects. This segmentation allows each process to optimize for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Light irradiation is introduced as an intermediary process between the rubbing step and the final alignment layer formation. This intermediary step selectively removes rubbing-induced defects while preserving the alignment direction established by the rubbing process.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the rubbing process is performed with direct contact, then the alignment direction is imparted effectively, but particles contaminate the liquid crystal cells and cause defects

Engineering Contradiction:

Improvealignment stabilityVSAvoidparticle contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The rubbing process is allowed to create surface defects, and then light irradiation is used to convert these defects into removable byproducts. The harmful rubbing artifacts become temporary intermediates that can be selectively eliminated without compromising the beneficial alignment direction.

Inventive Principle:

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

Solution Approach 2:

The light irradiation process selectively extracts and removes rubbing-induced defects and particles from the alignment layer surface, separating the harmful contaminants from the beneficial alignment structure.

Inventive Principle:

Principle #2Taking out (Extraction)

3Productivity

If a rubbing cloth is used for mass production, then the process is stable and efficient, but electrostatic discharge damages TFTs and additional cleaning is required

Engineering Contradiction:

Improvemass production efficiencyVSAvoidelectrostatic discharge

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The mechanical rubbing process is supplemented with a light irradiation process that eliminates the need for additional cleaning steps. The light energy replaces the need for mechanical removal of contaminants, reducing further mechanical interaction and associated electrostatic risks.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Area of stationary object

If the substrate size is increased for large screen displays, then the display area is expanded, but rubbing defects become more frequent and yield decreases

Engineering Contradiction:

Improvedisplay screen areaVSAvoidalignment uniformity

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The solution moves from a purely mechanical two-dimensional rubbing process to a three-dimensional approach by adding light irradiation from above. This additional dimension allows uniform treatment across large substrate areas without increasing mechanical complexity or defect probability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 secondary alignment process effectively reduces rubbing defects, enhancing the image quality and manufacturing efficiency by thinning the alignment layer and eliminating surface imperfections, thereby improving the overall performance of the LCD.

Implementation Method 1

irradiating a non-polarized ultraviolet light onto the alignment layer material having the alignment direction to form the alignment layer

Methodology Applied

Scientific EffectPhotodecomposition: Photodissociation

Data Source

PatentUS7414687B2Method of forming alignment layer in LCD

Publication Date: 2008.08.19 LG DISPLAY CO LTD

AI summary

A method of forming an alignment layer in a liquid crystal display includes depositing an alignment layer material on a substrate; rubbing the alignment layer material to impart an alignment direction onto the alignment layer material; and irradiating a non-polarized ultraviolet light onto the alignment layer material having the alignment direction to form an alignment layer.