OLED Protection Layer Thickness Variation for Leakage Current

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Solution Overview

Problem

Electroluminescent display apparatuses face challenges in preventing leakage current when emitting white light, leading to image quality degradation, and struggle with precise deposition of different colored light emitting layers in densely arranged subpixels when emitting colors like red, green, and blue.

Innovation Solution

The apparatus includes a substrate with subpixels emitting different colors, each with a first electrode, a bank to cover electrode edges, a protection layer on the electrodes and bank, and a light emitting layer, along with a second electrode, where the protection layer is designed to prevent short circuits and enable precise patterning of light emitting layers using varying thicknesses to achieve micro-cavity effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the light emitting layer emits light of the same color (white light) in each subpixel, then the device complexity is reduced, but leakage current occurs causing degradation in image quality

Engineering Contradiction:

Improvestructure complexityVSAvoidimage quality

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The light emitting layer is segmented into different colored layers (red, green, blue) in different subpixels, with electric charge blocking layers inserted between adjacent subpixels to prevent charge migration and leakage current, thereby maintaining image quality while managing device complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Electric charge blocking layers are introduced as intermediary elements between adjacent subpixels to prevent direct charge migration between subpixels emitting different colors, eliminating leakage current while maintaining the multi-color emission structure

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the light emitting layer emits lights of different colors (red, green, blue) in subpixels, then leakage current is prevented, but manufacturing precision becomes difficult due to dense arrangement of subpixels

Engineering Contradiction:

Improveleakage current preventionVSAvoiddeposition precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The light emitting layer is divided into separately deposited colored layers (red, green, blue) in different subpixels, with electric charge blocking layers between them, enabling precise control of each layer's deposition while preventing leakage current

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Electric charge blocking layers are deposited preliminary between adjacent subpixels before depositing the colored light emitting layers, establishing charge barriers in advance to prevent leakage current and guide subsequent precise layer deposition

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If a uniform protection layer is formed over all subpixels, then the manufacturing process is simplified, but light extraction efficiency is reduced

Engineering Contradiction:

Improveprocess simplicityVSAvoidlight extraction efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The protection layer is formed with different thicknesses in different regions: thicker over banks and boundaries for protection, and thinner over light emitting regions to maximize light extraction efficiency while maintaining manufacturing simplicity

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The thickness parameter of the protection layer is varied spatially across the display structure, being thicker in protective regions and thinner in light emitting regions, optimizing both protection and light extraction without complicating the manufacturing process

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

This configuration prevents leakage current, allows precise deposition of different colored light emitting layers in densely arranged subpixels, and enhances light extraction efficiency through micro-cavity effects, improving image quality and manufacturing precision.

Implementation Method 1

a protection layer on the first electrode and the bank... the protection layer includes a first portion overlapping the first subpixel, a second portion overlapping the second subpixel, a third portion overlapping the third subpixel, a fourth portion overlapping a boundary between any two of the first subpixel, the second subpixel, and the third subpixel

Methodology Applied

Scientific EffectMicro-cavity effect: Cavitation

Data Source

PatentUS11538867B2Organic electroluminescent display apparatus including continuous protection layer having different respective thicknesses formed among a plurality of sub-pixels

Publication Date: 2022.12.27 LG DISPLAY CO LTD

AI summary

The present disclosure provides an electroluminescent display apparatus including a substrate including a first subpixel, a second subpixel, and a third subpixel, a first electrode in each of the first subpixel, the second subpixel, and the third subpixel on the substrate, a bank provided in a boundary between any two of the first subpixel, the second subpixel, and the third subpixel to cover an edge of the first electrode, a protection layer on the first electrode and the bank, a light emitting layer on the protection layer, and a second electrode on the light emitting layer.