Foldable Display Cover Layers for Thermal Shrinkage Control

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Solution Overview

Problem

Foldable display devices experience unwanted bending due to thermal shrinkage of protective films or cover members, which can lead to damage when in a spread-out state.

Innovation Solution

Incorporating a cover member and a circularly polarizing plate with controlled thermal shrinkage rates, aligned to minimize thermal shrinkage in the bending direction, to prevent or reduce unwanted bending of the display panel.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a polyester film or cover member is used to protect the display panel, then the display panel is protected from damage, but the protective film undergoes thermal shrinkage along the bending direction causing unwanted bending of the display panel

Engineering Contradiction:

Improveprotection of display panelVSAvoidbending of display panel

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The patent changes the thermal shrinkage parameters of the protective film by selecting specific materials (polyimide film, cyclic olefin copolymer film) with controlled thermal shrinkage rates. The film is designed to have a thermal shrinkage rate of 1% or less in the bending direction and 5% or less in the perpendicular direction, preventing unwanted bending while maintaining protection functionality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite material structures where the protective film is combined with the display panel and other components. The selective orientation of the protective film with different thermal shrinkage rates in different directions creates a composite system that compensates for thermal expansion differences, preventing bending while maintaining protection

Inventive Principle:

Principle #40Composite materials

2Shape

If the display panel is pulled tight to prevent unwanted bending, then the display panel maintains its shape, but the display panel may be damaged

Engineering Contradiction:

Improveflatness of display panelVSAvoidintegrity of display panel

Core Design Contradiction:

ShapeVSReliability

Solution Approach 1:

The patent converts the harmful thermal shrinkage effect into a beneficial one by designing the protective film with controlled thermal shrinkage characteristics. The film's thermal shrinkage in the perpendicular direction (5% or less) compensates for the thermal expansion of the display panel, while the limited shrinkage in the bending direction (1% or less) prevents unwanted bending, thus eliminating the need to pull the panel tight

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Prevents or reduces unwanted bending of the display panel while minimizing the risk of damage, by ensuring the thermal shrinkage rates of the cover member and polarizing plate are lower in the bending direction, thus maintaining the display's integrity in a spread-out state.

Implementation Method 1

A thermal shrinkage rate of the cover member in a bending direction along which the display panel is bent when the display panel is rolled up is smaller than a thermal shrinkage rate of the cover member in a perpendicular direction

Methodology Applied

Scientific EffectThermal shrinkage: Thermal Contraction

Implementation Method 2

A thermal shrinkage rate of the circularly polarizing plate in a bending direction along which the display panel is bent when the display panel is rolled up is smaller than a thermal shrinkage rate of the circularly polarizing plate in a perpendicular direction

Methodology Applied

Scientific EffectThermal shrinkage: Thermal Contraction

Data Source

PatentUS12477894B2Folded or rolled display device having thermal shrinkage rates

Publication Date: 2025.11.18 MAGNOLIA BLUE CORP

AI summary

A display device includes a display panel capable of being rolled up or folded and a cover member that is placed upon the display panel and that is capable of being rolled up or folded together with the display panel. A thermal shrinkage rate of the cover member in a bending direction along which the display panel is bent when the display panel is rolled up is smaller than a thermal shrinkage rate of the cover member in a perpendicular direction that is perpendicular to the bending direction, or a thermal shrinkage rate of the cover member in a bending direction along which the display panel is bent when the display panel is folded is smaller than a thermal shrinkage rate of the cover member in a perpendicular direction that is perpendicular to the bending direction.