Hydrogen Collection Layer in Light Emitting Display Apparatus

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Solution Overview

Problem

In light emitting display apparatuses, prolonged use at high temperatures causes hydrogen diffusion from the encapsulation layer to shift the threshold voltage of transistors, leading to defects such as smears in the displayed image.

Innovation Solution

Incorporating a hydrogen collection layer around the transistors to collect and block hydrogen diffused from the encapsulation layer, preventing it from flowing into the pixel driving circuit and maintaining the quality of the display.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the encapsulation layer covers the light emitting device for protection, then the device is protected from environmental damage, but hydrogen diffuses from the encapsulation layer to the transistors causing threshold voltage shift and display defects

Engineering Contradiction:

Improveprotection of light emitting deviceVSAvoidhydrogen diffusion to transistors

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A hydrogen collection layer is introduced as an intermediary component between the encapsulation layer and the transistor. This layer selectively collects and traps hydrogen atoms that diffuse from the encapsulation layer, preventing them from reaching the transistor channels. The hydrogen collection layer acts as a mediator that protects the transistor from hydrogen-induced threshold voltage shifts while allowing the encapsulation layer to maintain its protective function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The encapsulation layer, which was originally a source of harmful hydrogen diffusion, is recontextualized as having a beneficial function through the addition of the hydrogen collection layer. The hydrogen that would otherwise damage the transistor is now collected and concentrated in a specific layer, converting the harmful diffusion process into a controlled collection mechanism that protects the device.

Inventive Principle:

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

2Device complexity

If the transistor is exposed to hydrogen from the encapsulation layer, then the structure remains simple, but the threshold voltage shifts causing smears in the displayed image

Engineering Contradiction:

Improvestructure simplicityVSAvoidthreshold voltage stability

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The hydrogen collection layer serves as a mediator that adds minimal structural complexity while effectively addressing the threshold voltage stability issue. By placing this intermediate layer between the encapsulation layer and the transistor, the solution prevents hydrogen-induced threshold voltage shifts without requiring fundamental redesign of the device architecture.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If hydrogen collects in the transistor region, then the encapsulation layer structure is simple, but display defects such as smears occur over time

Engineering Contradiction:

Improveencapsulation layer structureVSAvoiddisplay quality over time

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The hydrogen collection layer acts as a mediator that maintains the simplicity of the encapsulation layer structure while preventing display defects. By collecting hydrogen in a dedicated layer rather than allowing it to reach the transistor, the system maintains structural simplicity while ensuring long-term display quality and reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 hydrogen collection layer effectively prevents the shift in threshold voltage, thereby reducing the occurrence of smears and maintaining the quality of the light emitting display apparatus over time.

Implementation Method 1

threshold voltages of the transistors may be changed by hydrogen diffused from an encapsulation layer covering the light emitting device

Methodology Applied

Scientific EffectHydrogen diffusion: Diffusion

Implementation Method 2

a hydrogen collection layer surrounding the first planarization layer

Methodology Applied

Scientific EffectHydrogen collection/absorption: Absorption (physical)

Data Source

PatentUS20230217708A1Light emitting display apparatus

Publication Date: 2023.07.06 LG DISPLAY CO LTD

AI summary

A light emitting display apparatus includes a base substrate, a buffer provided in the base substrate, a pixel driving circuit layer provided on the buffer, the pixel driving circuit layer including transistors, a first planarization layer surrounding the pixel driving circuit layer, a hydrogen collection layer surrounding the first planarization layer, a second planarization layer covering the hydrogen collection layer, a light emitting device provided on the second planarization layer and connected to a driving transistor of the transistors, and an encapsulation layer covering the light emitting device.