Adhesive Layer Design for Uniform Curvature in Foldable Displays

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Solution Overview

Problem

The curvature of the folding area in foldable electronic devices is not uniform, leading to potential damage and surface deformation when folded, which can reduce the device's lifespan.

Innovation Solution

A display module with a uniform curvature is achieved by correcting length changes along the folding axis in the folded state, using a specific configuration of housing structures and an adhesive layer with varying adhesive forces to maintain the display's flatness and curvature consistency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the flexible display is folded along a folding axis, then the device achieves portability and compact form factor, but the curvature of the folding area becomes non-uniform causing surface deformation and potential damage

Engineering Contradiction:
Improvecompact form factorVSAvoiduniform curvature
Core Design Contradiction:
Volume of moving objectVSShape

Solution Approach 1:

The adhesive layer is designed with spatially varying adhesive force characteristics - stronger adhesive force in regions prone to delamination and weaker adhesive force in regions that require flexibility. This local differentiation allows the display module to maintain structural integrity while achieving uniform curvature during folding, preventing surface deformation without compromising the compact form factor.

Inventive Principle:
Principle #3Local quality

2Ease of manufacture

If the adhesive layer uses uniform adhesive force across the folding area, then manufacturing is simplified, but surface deformation and delamination occur during folding

Engineering Contradiction:
Improveadhesive layer fabricationVSAvoidbonding strength
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The adhesive layer incorporates regions with different adhesive force characteristics tailored to local structural requirements. Areas with higher stress concentration during folding receive stronger adhesive bonding, while flexible regions maintain appropriate adhesion levels. This localized approach ensures reliable bonding throughout the folding area while preventing surface deformation, addressing both manufacturing feasibility and operational reliability.

Inventive Principle:
Principle #3Local quality

3Adaptability or versatility

If the display module is repeatedly folded, then the device provides flexible usability, but the non-uniform curvature causes cumulative damage reducing lifespan

Engineering Contradiction:
Improveflexible usabilityVSAvoiddisplay module lifespan
Core Design Contradiction:
Adaptability or versatilityVSDuration of action of stationary object

Solution Approach 1:

The adhesive layer's spatially varying adhesive force distribution is specifically engineered to accommodate repeated folding cycles. By providing enhanced adhesive support in high-stress regions and maintaining appropriate flexibility in other areas, the structure distributes mechanical stresses more uniformly during each folding cycle. This prevents cumulative damage accumulation and surface deformation, thereby extending the display module's operational lifespan while preserving flexible usability.

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

This solution ensures a uniform curvature in the folding area, preventing damage and surface deformation, thereby extending the lifespan of the display module and maintaining its functionality across different states.

Implementation Method 1

an adhesive layer 330, between the first plate 321 and the second plate 322

Methodology Applied
Scientific EffectAdhesive: Adhesive

Data Source

PatentEP3997689B1Display module and electronic device including the same
Publication Date: 2023.11.01 SAMSUNG ELECTRONICS CO LTD
  • EP3997689B1 patent drawingFigure 1
  • EP3997689B1 patent drawingFigure 2
  • EP3997689B1 patent drawingFigure 3

AI summary

A display module and an electronic device including the same are provided. The display module includes a display panel including a first edge and a second edge facing the first edge, a support plate on a rear surface of the display panel, and an adhesive layer between the display panel and the support plate. The adhesive layer includes first and second areas providing a first adhesive force and a third area providing a second adhesive force different from the first adhesive force and disposed between the first area and the second area, the third area extending from the first edge to the second edge. The third area has a first width in a central area between the first edge and the second edge and a second width in areas adjacent to the first edge and the second edge, the second width being different from the first width.