OLED Thin Film Encapsulation Layer Stress Relief

Solution Overview

Problem

The increased thickness of inorganic layers in thin film encapsulation (TFE) for organic light-emitting display apparatuses leads to higher film stress, which can cause peeling, allowing external humidity and oxygen to intrude and reduce the lifespan of the devices.

Innovation Solution

An organic light-emitting display apparatus with an improved sealing force using a thin film encapsulation layer comprising sequentially stacked first and second inorganic layers of different materials, with a first organic layer covering the first inorganic layer and a second inorganic layer contacting the interlayer insulating layer, and additional layers to alleviate stress and prevent peeling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the thickness of the inorganic layer is increased to prevent intrusion of external humidity and oxygen, then the sealing effectiveness is improved, but the film stress increases and the inorganic layer may be peeled off

Engineering Contradiction:

Improvesealing effectivenessVSAvoidfilm stress

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The encapsulation layer is divided into multiple inorganic layers (first inorganic layer, second inorganic layer, third inorganic layer) with organic layers in between. This segmentation allows each layer to be thinner, reducing film stress and peeling risk, while the combined structure maintains effective sealing against humidity and oxygen intrusion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The encapsulation structure uses a composite of inorganic and organic materials stacked alternately. The inorganic layers provide barrier properties against moisture and oxygen, while the organic layers provide flexibility and stress relief, creating a composite structure that balances sealing effectiveness with reduced film stress.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the thickness of the inorganic layer is increased to prevent intrusion of external humidity and oxygen, then the sealing effectiveness is improved, but the inorganic layer may be peeled off reducing the life span

Engineering Contradiction:

Improvesealing effectivenessVSAvoidlife span

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The encapsulation layer is divided into multiple inorganic layers (first inorganic layer, second inorganic layer, third inorganic layer) with organic layers in between. This segmentation allows each layer to be thinner, reducing film stress and peeling risk, while the combined structure maintains effective sealing against humidity and oxygen intrusion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Organic layers are inserted between the inorganic layers to act as cushioning layers that absorb and relieve film stress before it can cause peeling. This beforehand cushioning prevents the peeling issue that would otherwise occur with thick inorganic layers, thereby extending the device lifespan.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Length of stationary object

If a thin film encapsulation is used to make the display apparatus thinner, then the device thickness is reduced, but the sealing force may be insufficient

Engineering Contradiction:

Improvedevice thicknessVSAvoidsealing force

Core Design Contradiction:

Length of stationary objectVSReliability

Solution Approach 1:

The encapsulation structure uses a composite of inorganic and organic materials stacked alternately. The inorganic layers provide barrier properties against moisture and oxygen, while the organic layers provide flexibility and stress relief, creating a composite structure that balances sealing effectiveness with reduced film stress.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The encapsulation layer extends not only horizontally but also vertically to cover side surfaces of the display unit. This multi-dimensional coverage enhances sealing effectiveness without requiring increased thickness of individual layers, maintaining thin profile while improving protection.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9496518B2Organic light-emitting display apparatus and method of manufacturing same

Publication Date: 2016.11.15 SAMSUNG DISPLAY CO LTD

AI summary

An organic light-emitting display apparatus includes a substrate; a display unit which defines an active area on the substrate and includes a thin film transistor and an organic light-emitting device electrically connected to each other; and an encapsulation layer disposed on a top surface and a side surface of the display unit, the encapsulation layer including at least a first inorganic layer, a first organic layer, and a second inorganic layer that are sequentially stacked, and the first organic layer covers the first inorganic layer.