Grooved Glass Cover Window for Repeated-Folding Durability

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Solution Overview

Problem

Flexible display devices, particularly foldable displays, suffer from deformation and damage due to repeated folding, leading to issues like buckling and cracking in bending areas.

Innovation Solution

A cover window with a glass substrate featuring grooves filled with a multi-layered resin layer, where the inner surface is compressed and outer surface is stretched, with specific layers having varying storage moduli and elongation properties to enhance folding durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a glass substrate is used for the cover window, then transmittance and durability are improved, but folding characteristics deteriorate due to rigidity and resistance to bending

Engineering Contradiction:

ImprovedurabilityVSAvoidfolding characteristics

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The glass substrate is divided into a folding portion and a non-folding portion, with grooves introduced into the folding portion. This segmentation allows the glass to be more flexible in the folding area while maintaining integrity in the non-folding area, resolving the contradiction between rigidity for durability and flexibility for folding characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the glass substrate are given different properties: the folding portion has grooves and is thinner to enable bending, while the non-folding portion remains thick and intact to maintain strength and transmittance. This local differentiation resolves the contradiction by optimizing each region for its specific function.

Inventive Principle:

Principle #3Local quality

2Strength

If the glass thickness is increased to improve strength and transmittance, then durability is improved, but folding characteristics deteriorate due to increased resistance to bending

Engineering Contradiction:

ImprovestrengthVSAvoidfolding characteristics

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The glass substrate is segmented by thickness, with the folding portion having reduced thickness (about 30 μm or less) compared to the non-folding portion (about 150 μm or more). This thickness segmentation allows the folding area to be flexible while maintaining overall strength through the thicker non-folding regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The glass substrate exhibits local quality variation in thickness: thinner in the folding portion to enable bending and thicker in the non-folding portion to maintain strength. This resolves the contradiction by applying different thickness characteristics to different functional regions.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If a single-layer resin is used to fill the groove, then manufacturing complexity is reduced, but folding durability deteriorates due to inability to simultaneously satisfy compression and elongation requirements

Engineering Contradiction:

Improvemanufacturing complexityVSAvoidfolding durability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The groove is filled with a multi-layered resin layer consisting of at least two layers with different properties: a first layer with high storage modulus (≥0.046 MPa) to resist compression, and a second layer with high elongation (≥120%) to accommodate stretching. This composite structure resolves the contradiction by combining materials with complementary properties to simultaneously satisfy both compression and elongation requirements during folding.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different layers within the resin filling exhibit different mechanical properties: the first layer provides compression resistance with high storage modulus, while the second layer provides elongation capacity with high elasticity. This local differentiation of material properties within the groove filling resolves the contradiction between compression and elongation requirements for folding durability.

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 cover window design improves folding characteristics by reducing damage and maintaining transmittance, ensuring durability and stability even with repeated folding.

Implementation Method 1

The glass which is folded at the folding portion includes an inner surface that is compressed and an outer surface that is stretched

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 2

elongation of a layer of the multi-layered resin layer which is closest to the outer surface being largest

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS12461285B2Cover window, method of providing cover window, and display device including cover window

Publication Date: 2025.11.04 SAMSUNG DISPLAY CO LTD

AI summary

A cover window includes a glass including a folding portion and a non-folding portion, and a groove in the folding portion of the glass. The glass which is folded at the folding portion includes an inner surface that is compressed and an outer surface that is stretched, the groove filled with a multi-layered resin layer, a storage modulus of a layer of the multi-layered resin layer which is closest to the inner surface being largest, and elongation of a layer of the multi-layered resin layer which is closest to the outer surface being largest.