Flexible OLED Display Structure for Folding-Induced Peeling

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Solution Overview

Problem

Flexible organic light emitting display devices experience peeling defects due to tensile and compressive stress from folding, particularly affecting the organic light emitting layer, which is vulnerable to stress and has weak adhesion.

Innovation Solution

A flexible display device with an inverse-tapered structure is designed, featuring a spacer with an inverse taper shape to distribute stress and improve adhesion, reducing peeling defects and lateral current leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a flexible organic light emitting display device is folded, then the device can be made portable and compact, but tensile stress and compressive stress are applied causing peeling defects in the organic light emitting layer

Engineering Contradiction:

ImproveflexibilityVSAvoidpeeling defect

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies an inverse taper structure where the width of the support structure increases from top to bottom (opposite to conventional tapers). This inverted geometry reverses the stress distribution pattern, creating compressive stress in the organic light emitting layer that counteracts the tensile stress generated during folding, thereby preventing peeling defects while maintaining flexibility

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the geometric parameters of the support structure by implementing an inverse taper shape with specific width variations at different heights. This parameter change transforms the stress distribution characteristics, converting a structure that would normally concentrate stress into one that distributes stress favorably to prevent layer separation during flexing

Inventive Principle:

Principle #35Parameter changes

2Strength

If a spacer with conventional taper shape is used, then the structure provides support, but it increases the overall thickness of the display device

Engineering Contradiction:

Improvesupport structureVSAvoidthickness

Core Design Contradiction:

StrengthVSLength of moving object

Solution Approach 1:

By inverting the taper direction, the support structure achieves its mechanical strength and stress distribution function with a more compact vertical profile. The expanded base width at the bottom provides structural support while the reduced top width minimizes the overall thickness contribution of the support element

Inventive Principle:

Principle #13The other way round (Inversion)

3Length of moving object

If the organic light emitting layer is made thinner to reduce device thickness, then the package becomes more compact, but the adhesion strength decreases making it more vulnerable to peeling

Engineering Contradiction:

ImprovethicknessVSAvoidadhesion

Core Design Contradiction:

Length of moving objectVSStrength

Solution Approach 1:

The inverse taper structure creates a stress field that compensates for the reduced adhesion strength of thinner organic light emitting layers. By generating compressive stress in the layer during folding, the structure counteracts the tensile forces that would otherwise cause peeling, enabling thin-layer designs without sacrificing reliability

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The inverse taper structure pre-establishes a compressive stress state in the organic light emitting layer before folding occurs. This preliminary anti-action counterbalances the tensile stress that will be generated during subsequent folding operations, preventing peeling defects even in thinner layers with inherently lower adhesion strength

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS12402488B2Flexible display device and method of manufacturing the same

Publication Date: 2025.08.26 LG DISPLAY CO LTD

AI summary

The present disclosure relates to a flexible display device including: a substrate over which a thin film transistor is disposed, an intermediate layer disposed to cover the thin film transistor, a first electrode located on the intermediate layer and connected to the thin film transistor, a bank located on the intermediate layer and the first electrode and defining a first region exposing a part of the intermediate layer, a second region exposing a part of the first electrode, and a third region excluding the first and second regions, a first structure located in the first region defined by the bank and tapered toward the substrate, an organic light emitting layer located on the first electrode exposed in the second region, and a second electrode disposed on the organic light emitting layer. Both lateral surfaces of an inverse-tapered structure are disposed to contact the bank, and as a result, corresponding adhesion can be improved, and peeling defects can be reduced or corrected.