Bendable Glass Stack Assembly for Puncture-Resistant Flexing
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Solution Overview
Problem
Conventional flexible glass materials lack suitable fatigue resistance and mechanical reliability upon bending, limiting their use in flexible substrate and display applications, particularly for flexible electronic devices that require high puncture resistance and optical transparency.
Innovation Solution
A glass element with a thickness ranging from 25 μm to 125 μm, featuring a compressive stress region of at least 100 MPa at the surface, which provides puncture resistance and maintains structural integrity at bend radii from 3 mm to 20 mm without failure, combined with a low modulus adhesive and PET support, and a pencil hardness of 8H or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If glass substrate thickness is reduced to achieve flexibility and small bend radii, then flexibility and bendability are improved, but puncture resistance and mechanical reliability deteriorate
Solution Approach 1:
The patent applies composite material principles by combining glass substrates with polymer layers (PET, PEN, PI) to create a hybrid structure. The glass provides puncture resistance and optical properties, while the polymer provides flexibility and fatigue resistance. This composite approach resolves the contradiction between thin glass flexibility and puncture resistance.
Solution Approach 2:
The patent uses thin polymer films (25-50 μm) as flexible support structures that enable the glass to bend at small radii without breaking. These thin films act as compliant layers that accommodate bending while the glass maintains its structural integrity and resistance to puncture.
2Adaptability or versatility
If glass substrate thickness is reduced to achieve flexibility, then bendability is improved, but fatigue resistance deteriorates
Solution Approach 1:
The composite structure combines brittle glass with ductile polymer materials that have high fatigue resistance. The polymer layers can withstand repeated bending cycles without failure, protecting the glass from fatigue-induced cracking while maintaining flexibility.
Solution Approach 2:
The polymer layers serve as cushioning elements that absorb and distribute stresses before they can concentrate at glass defects or edges. This pre-cushioning effect prevents stress concentration that would lead to fatigue failure during repeated bending.
3Strength
If glass substrate thickness is increased to improve puncture resistance, then puncture resistance is improved, but flexibility and bendability deteriorate
Solution Approach 1:
The patent segments the substrate system into distinct functional layers: a relatively thin glass layer (50-150 μm) for puncture resistance and optics, and separate polymer layers for flexibility. This segmentation allows each material to optimize its function without compromising the other.
Solution Approach 2:
The composite construction allows the glass to maintain adequate thickness for puncture resistance while the overall assembly achieves flexibility through the compliant polymer layers. The glass doesn't need to be thin to provide flexibility since the polymer handles that function.
4Reliability
If glass substrate thickness is increased to improve mechanical reliability, then strength is improved, but optical transparency and flexibility deteriorate
Solution Approach 1:
The composite structure uses thin glass (50-150 μm) that maintains excellent optical transparency while the polymer layers provide the mechanical reliability needed for flexible applications. The polymer's high tensile strength and ductility compensate for the glass's brittleness.
Solution Approach 2:
The thin polymer films (25-50 μm) act as flexible support structures that enhance mechanical reliability without compromising optical properties. These thin films are sufficiently transparent to maintain display quality while providing the mechanical strength needed for flexible device reliability.
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 glass element exhibits high puncture resistance and mechanical reliability at small bend radii, suitable for flexible electronic devices, including foldable displays and wearable devices, with improved optical transparency and thermal stability.
Implementation Method 1
a compressive stress region extending from the first primary surface of the glass layer to a first depth in the glass layer, the region defined by a compressive stress of at least about 100 MPa at the first primary surface of the layer
Data Source
AI summary
A glass element having a thickness from 25 μm to 125 μm, a first primary surface, a second primary surface, and a compressive stress region extending from the first primary surface to a first depth, the region defined by a compressive stress σI of at least about 100 MPa at the first primary surface. Further, the glass element has a stress profile such that it does not fail when it is subject to 200,000 cycles of bending to a target bend radius of from 1 mm to 20 mm, by the parallel plate method. Still further, the glass element has a puncture resistance of greater than about 1.5 kgf when the first primary surface of the glass element is loaded with a tungsten carbide ball having a diameter of 1.5 mm.