Foldable Substrate Thickness Profile for Small Bend Radius

Solution Overview

Problem

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

Innovation Solution

The development of foldable substrates 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 are made thinner to achieve small minimum bend radii, then foldability is improved, but impact and puncture resistance deteriorate

Engineering Contradiction:

Improveminimum bend radiusVSAvoidimpact and puncture resistance

Core Design Contradiction:

ShapeVSStrength

Solution Approach 1:

The substrate has non-uniform thickness distribution with a thinner central portion (10-125 μm) for flexibility and smaller bend radius, and thicker first and second portions (80 μm to 2 mm) for impact and puncture resistance. This local variation in thickness allows each region to perform its specific function optimally.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The substrate is made of glass-based or ceramic-based materials with compressive stress regions introduced through chemical strengthening processes. The combination of material composition and stress distribution creates a composite structure that achieves both flexibility and strength.

Inventive Principle:

Principle #40Composite materials

2Strength

If glass-based substrates are made thicker to improve impact and puncture resistance, then strength is improved, but minimum bend radius increases

Engineering Contradiction:

Improveimpact and puncture resistanceVSAvoidminimum bend radius

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The substrate has non-uniform thickness distribution with a thinner central portion (10-125 μm) for flexibility and smaller bend radius, and thicker first and second portions (80 μm to 2 mm) for impact and puncture resistance. This local variation in thickness allows each region to perform its specific function optimally.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If uniform thickness is used throughout the substrate, then manufacturing is simplified, but stress concentration occurs at fold regions

Engineering Contradiction:

Improvesubstrate fabricationVSAvoidmechanical stability

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The substrate has non-uniform thickness distribution with a thinner central portion (10-125 μm) for flexibility and smaller bend radius, and thicker first and second portions (80 μm to 2 mm) for impact and puncture resistance. This local variation in thickness allows each region to perform its specific function optimally.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The substrate incorporates transition portions with continuously varying thickness that dynamically adapt to stress distribution during folding, reducing stress concentration at the fold regions while maintaining structural integrity.

Inventive Principle:

Principle #15Dynamics

4Shape

If abrupt thickness changes are introduced to reduce bend radius, then foldability is improved, but optical distortions increase

Engineering Contradiction:

Improvebend radiusVSAvoidoptical quality

Core Design Contradiction:

ShapeVSIllumination intensity

Solution Approach 1:

The substrate incorporates transition portions with continuously varying thickness that dynamically adapt to stress distribution during folding, reducing stress concentration at the fold regions while maintaining structural integrity.

Inventive Principle:

Principle #15Dynamics

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 solution provides foldable substrates with improved impact and puncture resistance, reduced optical distortions, and minimal mechanical deformation, enabling effective folding performance with small bend radii.

Implementation Method 1

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:

Implementation Method 2

Providing transition regions with continuously increasing thicknesses can reduce stress concentration in the transition regions and/or avoid optical distortions

Methodology Applied

Scientific EffectStress concentration reduction:

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

PatentUS20260056576A1Foldable apparatus, foldable substrate, and methods of making

Publication Date: 2026.02.26 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.