Preformed Curvilinear Foldable Substrate for Low-Stress Flexible Displays

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Solution Overview

Problem

Foldable electronic devices with flexible displays face mechanical stress and failure when folded due to the hinge interrupting the display, limiting the size and durability of clamshell devices.

Innovation Solution

A flexible display is designed with a preformed foldable substrate that maintains a predefined curvilinear three-dimensional shape, minimizing stress loads by simulating the contours of the device housing, thereby reducing mechanical strain and extending the lifespan of the display layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If the display is made larger in clamshell devices, then the display area increases, but the mechanical stress and failure risk increase due to folding

Engineering Contradiction:
Improvedisplay areaVSAvoidmechanical reliability
Core Design Contradiction:
Area of moving objectVSReliability

Solution Approach 1:

The substrate is preformed into a curvilinear three-dimensional shape that anticipates the folding configuration, placing the display in a neutral state before actual folding occurs. This preliminary shaping reduces the mechanical stress that would otherwise occur during folding operations.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The substrate is formed with a curvilinear three-dimensional shape featuring rounded contours and curved surfaces rather than flat or sharp edges. This curvature distributes mechanical stress more evenly during folding, preventing stress concentration points that would lead to failure.

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Volume of moving object

If the display is folded about a hinge, then the form factor is reduced, but the display size is limited by the hinge interruption

Engineering Contradiction:
Improveform factorVSAvoiddisplay size
Core Design Contradiction:
Volume of moving objectVSArea of moving object

Solution Approach 1:

The curvilinear substrate shape allows the display to fold along curved paths rather than sharp hinge lines. This enables the display to maintain its visual continuity while achieving compact folding, effectively removing the visual and functional interruption caused by traditional hinges.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The substrate transitions from a two-dimensional flat surface to a three-dimensional curvilinear form that can accommodate folding. By adding the third dimension through curvature, the display achieves both compact form factor and large display area without the limitations of traditional hinge-based folding.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Reliability

If the substrate is preformed into a curvilinear shape, then stress loads are minimized, but the manufacturing complexity increases

Engineering Contradiction:
Improvestress resistanceVSAvoidsubstrate fabrication
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The substrate is preformed into its final curvilinear shape during the manufacturing process itself, rather than requiring post-manufacturing adjustments or complex assembly steps. This preliminary forming integrates the stress-reducing geometry into the base manufacturing flow.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The substrate manufacturing process utilizes controlled changes in physical parameters (such as temperature, pressure, or forming tool geometry) to achieve the curvilinear shape. By adjusting these parameters during standard manufacturing operations, the complex shape is achieved without requiring fundamentally different manufacturing processes.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP3816763B1Flexible display with preformed curvilinear foldable substrate and corresponding electronic devices and methods
Publication Date: 2023.03.01 MOTOROLA MOBILITY LLC
  • EP3816763B1 patent drawingFigure 1
  • EP3816763B1 patent drawingFigure 2~4
  • EP3816763B1 patent drawingFigure 5~6

AI summary

A flexible display includes a foldable display coupled to a foldable substrate. The foldable substrate is preformed to maintain a curvilinear three-dimensional shape when in a neutral, force-free state. The curvilinear three-dimensional shape can simulate one or more contours of an electronic device housing to which the flexible display is attached, thereby reducing or minimizing stress loads on the flexible display as the electronic device housing transitions between an axially displaced open position and a closed position.