Glass Substrate Crack Mitigating Composite for Scratch Resistance
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Solution Overview
Problem
The application of scratch-resistant films to glass-based substrates often reduces the average flexural strength of the substrates, and this reduction is not mitigated by high temperature processing or thermal treatments, which can compromise the mechanical and optical properties of the substrates.
Innovation Solution
A glass-based article with a crack mitigating composite comprising an inorganic element and a polymeric element, where the composite has an elastic modulus greater than 30 GPa, and a hard film with an elastic modulus greater than or equal to the substrate, is used to maintain the flexural strength and optical properties of the substrate, even after high temperature exposures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a scratch-resistant film is applied to a glass-based substrate, then scratch resistance is improved, but average flexural strength is reduced
Solution Approach 1:
A crack mitigating composite layer is introduced as an intermediary between the hard scratch-resistant film and the glass substrate. This intermediate layer has an elastic modulus greater than 30 GPa and acts as a buffer to prevent stress concentration and crack propagation from the hard film from reaching the substrate, thereby maintaining the substrate's flexural strength while preserving the film's scratch resistance
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers with different mechanical properties: a hard film layer for scratch resistance, a crack mitigating composite layer with specific elastic modulus characteristics, and the glass substrate. This composite architecture allows each layer to perform its specific function while collectively maintaining both scratch resistance and structural strength
2Strength
If high temperature processing is applied to mitigate strength reduction, then thermal treatment is performed, but mechanical and optical properties are compromised
Solution Approach 1:
The patent converts the potentially harmful effect of the hard film on substrate strength into a benefit by introducing the crack mitigating composite layer. This layer transforms the stress concentration that would normally weaken the substrate into a controlled interface that absorbs and redistributes stress, thereby maintaining strength without requiring high temperature processing that could compromise other properties
3Object-affected harmful factors
If a hard film with high elastic modulus is applied, then scratch resistance is improved, but crack propagation risk increases
Solution Approach 1:
The crack mitigating composite layer serves as a pre-positioned cushioning layer between the hard film and substrate. This layer is designed with specific elastic modulus characteristics (greater than 30 GPa) to absorb and redistribute stresses before they can propagate as cracks through the substrate, thereby preventing crack propagation while maintaining the hard film's scratch 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 effectively retains the average flexural strength and optical properties of the glass-based substrates, preventing the degradation caused by scratch-resistant films and ensuring the substrates maintain their mechanical and optical integrity under various processing conditions.
Implementation Method 1
the composite is characterized by an elastic modulus of greater than about 30 GPa... preventing the degradation caused by scratch-resistant films
Implementation Method 2
a hard film with an elastic modulus greater than or equal to the substrate... ensuring the substrates maintain their mechanical and optical integrity
Data Source
AI summary
An article is described herein that includes: a glass-based substrate comprising opposing major surfaces; a crack mitigating composite over one of the major surfaces, the composite comprising an inorganic element and a polymeric element; and a hard film disposed on the crack mitigating composite comprising an elastic modulus greater than or equal to the elastic modulus of the glass-based substrate. The crack mitigating composite is characterized by an elastic modulus of greater than 30 GPa. Further, the hard film comprises at least one of a metal-containing oxide, a metal-containing oxynitride, a metal-containing nitride, a metal-containing carbide, a silicon-containing polymer, a carbon, a semiconductor, and combinations thereof.