Foldable Display Adhesive Segmentation for Folding Reliability

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Solution Overview

Problem

Existing flexible display devices face challenges in maintaining product reliability due to structural limitations during folding and unfolding, leading to potential damage and reduced durability.

Innovation Solution

A display device design incorporating a support layer with a barrier layer and cushion layer, featuring specific openings and adhesive layers to enhance structural integrity and flexibility, with the support layer having a higher elastic modulus than the cushion layer, and a barrier adhesive layer with controlled thickness and spacing to manage stress distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a foldable display device uses a continuous adhesive layer between the barrier layer and support layer, then the adhesive strength is improved, but stress concentration during folding increases leading to reduced reliability

Engineering Contradiction:
Improveadhesive strengthVSAvoidproduct reliability
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The barrier adhesive layer is divided into multiple discrete barrier portions spaced apart from each other, rather than using a continuous adhesive layer. This segmentation allows the structure to flex during folding while maintaining adequate adhesive bonding, reducing stress concentration and improving reliability.

Inventive Principle:
Principle #1Segmentation

2Strength

If the support layer is made rigid to provide structural support, then the structural integrity is improved, but flexibility during folding is reduced

Engineering Contradiction:
Improvestructural integrityVSAvoidflexibility
Core Design Contradiction:
StrengthVSAdaptability or versatility

Solution Approach 1:

The support layer is designed with non-uniform properties: it has higher rigidity in non-folding areas to provide structural support, and reduced rigidity (through openings) in folding areas to enable flexibility. This local differentiation allows the support layer to maintain structural integrity while accommodating folding movements.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The support layer includes openings that create a porous structure in the folding area. This porous design reduces the rigidity locally, allowing the support layer to flex during folding while maintaining overall structural support in non-folding areas.

Inventive Principle:
Principle #31Porous materials

3Ease of manufacture

If the barrier adhesive layer has uniform thickness, then manufacturing simplicity is improved, but stress distribution during folding is inadequate reducing durability

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoiddurability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The barrier adhesive layer is designed with varying thickness: thicker in non-folding areas to provide strong bonding, and thinner in folding areas to reduce stress concentration. This local variation in thickness improves durability during folding while remaining manufacturable.

Inventive Principle:
Principle #3Local quality

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 design improves product reliability by reducing stress concentration and enhancing the durability of foldable display devices, ensuring consistent performance and longevity.

Implementation Method 1

a barrier adhesive layer between the barrier layer and the support layer, the barrier adhesive layer including a first barrier portion and a second barrier portion spaced apart from each other along the first direction with the plurality of openings of the support layer therebetween

Methodology Applied
Scientific EffectStress distribution:

Implementation Method 2

the support layer may have an elastic modulus greater than that of the cushion layer

Methodology Applied
Scientific EffectElastic modulus: Elasticity

Implementation Method 3

a cushion layer facing the display panel with the support layer therebetween

Methodology Applied
Scientific EffectImpact absorption: Damping

Data Source

PatentEP3958339B1Display device and electronic device including the same
Publication Date: 2026.03.18 SAMSUNG DISPLAY CO LTD
  • EP3958339B1 patent drawingFigure 1A
  • EP3958339B1 patent drawingFigure 1B
  • EP3958339B1 patent drawingFigure 2

AI summary

A display device including a display panel including a folding area and a non-folding area adjacent along a first direction, a support layer facing the display panel with a barrier layer therebetween, openings defined in the support layer and corresponding to the folding area, a cushion layer facing the display panel with the support layer therebetween, and a barrier adhesive layer between the barrier layer and the support layer, the barrier adhesive layer including a first barrier portion and a second barrier portion spaced apart from each other along the first direction with the plurality of openings of the support layer therebetween.