Foldable Substrate Thickness Zoning for Tight Bending and Puncture Resistance
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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 minimum bend radii.
Innovation Solution
The development of foldable substrates comprising glass-based and/or ceramic-based portions with compressive stress regions and recesses, along with controlled thermal expansion and chemical strengthening, to enhance impact and puncture resistance and facilitate good folding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If glass-based substrates with small minimum bend radii are used, then foldability is improved, but impact and puncture resistance deteriorates
Solution Approach 1:
The substrate thickness is varied locally across different regions: the central portion has a first thickness while the edge portions have a second thickness greater than the first. This local quality variation allows the center to bend easily for foldability while the thicker edges provide enhanced impact and puncture resistance.
Solution Approach 2:
The substrate is segmented into distinct regions with different thickness characteristics - a central portion and edge portions - each optimized for specific functions. The central portion enables folding while edge portions provide structural strength.
2Strength
If thicker glass-based sheets are used, then impact and puncture resistance is improved, but minimum bend radius increases
Solution Approach 1:
The substrate thickness is varied locally across different regions: the central portion has a first thickness while the edge portions have a second thickness greater than the first. This local quality variation allows the center to bend easily for foldability while the thicker edges provide enhanced impact and puncture resistance.
Solution Approach 2:
The substrate is segmented into distinct regions with different thickness characteristics - a central portion and edge portions - each optimized for specific functions. The central portion enables folding while edge portions provide structural strength.
3Ease of manufacture
If uniform thickness substrate is used, then manufacturing is simplified, but mechanical instabilities occur during folding
Solution Approach 1:
The substrate thickness is varied locally across different regions: the central portion has a first thickness while the edge portions have a second thickness greater than the first. This local quality variation allows the center to bend easily for foldability while the thicker edges provide enhanced impact and puncture resistance.
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 reduced bend-induced strain, improved mechanical stability, and increased resistance to impact and puncture, enabling small effective minimum bend radii and minimizing mechanical instabilities and optical distortions.
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
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 increased puncture resistance
Implementation Method 3
the substrate thickness can be sufficiently large (e.g., from about 80 micrometers (microns or μm) to about 2 millimeters) to further enhance impact resistance and puncture resistance
Implementation Method 4
providing a first recess opposite a second recess can reduce a maximum bend-induced strain of the foldable apparatus, for example, between a central portion and a first portion and/or second portion
Data Source
AI summary
Foldable substrates comprise a first outer layer comprising a first major surface, a second outer layer comprising a second major surface, and a core layer positioned therebetween. The core layer may comprise a first central surface area positioned between a first portion and a second portion of the first outer layer, and the core layer comprising a second central surface area positioned between a third portion and fourth portion of the second outer layer. Some foldable substrates comprise a first portion comprising a first depth of compression, a first depth of layer, and a first average concentration. The central portion may comprise a first central depth of compression, a first central depth of layer, and a central average concentration. Methods comprise chemically strengthening a foldable substrate. Some methods comprise etching the foldable substrate and then further chemically strengthening the foldable substrate.