Foldable Substrate Thickness Transitions for Tight Bending Strength

Solution Overview

Problem

Existing foldable displays and covers face challenges in achieving small minimum bend radii while maintaining good impact and puncture resistance, with conventional glass-based substrates either having poor resistance or large bend radii.

Innovation Solution

A foldable substrate design comprising glass-based and/or ceramic-based portions with compressive stress regions, transition regions, and controlled thickness variations to minimize mechanical instability and stress concentration, allowing for small bend radii and enhanced resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If glass-based substrates with small minimum bend radii are used, then foldable displays and covers can achieve small bend radii, but impact and puncture resistance deteriorates

Engineering Contradiction:

Improveminimum bend radiusVSAvoidimpact and puncture resistance

Core Design Contradiction:

ShapeVSStrength

Solution Approach 1:

The substrate employs different thicknesses in different regions: a first thickness in the first and second portions and a second thickness in the central portion. This local variation allows the central region to achieve small bend radii while the thicker first and second portions maintain impact and puncture resistance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention transitions from a uniform thickness design to a variable thickness design along the length dimension of the substrate. By introducing thickness as a varying parameter along the length, the substrate can simultaneously satisfy the conflicting requirements of small bend radius and high impact resistance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Strength

If thicker glass-based sheets are used, then impact and puncture resistance is improved, but minimum bend radius increases

Engineering Contradiction:

Improveimpact and puncture resistanceVSAvoidminimum bend radius

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The substrate employs different thicknesses in different regions: a first thickness in the first and second portions and a second thickness in the central portion. This local variation allows the central region to achieve small bend radii while the thicker first and second portions maintain impact and puncture resistance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention transitions from a uniform thickness design to a variable thickness design along the length dimension of the substrate. By introducing thickness as a varying parameter along the length, the substrate can simultaneously satisfy the conflicting requirements of small bend radius and high impact resistance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of manufacture

If uniform thickness substrates are used, then manufacturing is simplified, but stress concentration occurs in folded regions

Engineering Contradiction:

Improvesubstrate manufacturingVSAvoidstress distribution

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The substrate employs different thicknesses in different regions: a first thickness in the first and second portions and a second thickness in the central portion. This local variation allows the central region to achieve small bend radii while the thicker first and second portions maintain impact and puncture resistance.

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 provides foldable substrates with improved impact and puncture resistance, reduced optical distortions, and increased durability by minimizing stress and strain, enabling effective folding performance.

Implementation Method 1

The portions can comprise glass-based and/or ceramic-based portions, which can provide good dimensional stability, reduced incidence of mechanical instabilities, good impact resistance, and/or good puncture resistance

Methodology Applied

Scientific EffectMaterial property:

Implementation Method 2

The first portion and/or the second portion can comprise glass-based and/or ceramic-based portions comprising one or more compressive stress regions, which can further provide increased impact resistance and/or puncture resistance

Methodology Applied

Scientific EffectCompressive stress: Compression

Implementation Method 3

Providing a foldable substrate comprising a central portion comprising a central thickness that is less than a substrate thickness of the first portion and/or the second portion can enable small effective minimum bend radii (e.g., about 10 millimeters (mm) or less) based on the reduced thickness in the central portion

Methodology Applied

Scientific EffectBending:

Data Source

PatentUS12481316B2Foldable apparatus, foldable substrate, and methods of making

Publication Date: 2025.11.25 CORNING INC

AI summary

Foldable apparatus comprise a foldable substrate foldable about an axis and a substrate thickness defined between a first major surface and a second major surface. The foldable substrate comprises a central portion positioned between a first portion and a second portion. The first portion comprising a substrate thickness. The central portion comprises a central thickness that is less than the substrate thickness. In some embodiments, a width of central portion is about 45 millimeters or less. Methods of making a foldable apparatus comprise forming a recess in a first major surface of the foldable substrate. In some embodiments, methods comprise chemically strengthening the foldable substrate.