Glass Substrate Crack Mitigating Stack for Scratch Resistance
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Solution Overview
Problem
The application of scratch-resistant films to glass-based substrates often results in a reduction of the average flexural strength of the substrate, which is not mitigated by existing technologies, especially after high temperature processing, and there is a need to retain both the strength and optical properties of the substrate and film.
Innovation Solution
A glass-based article with a crack mitigating stack comprising bi-layers of organosilicate materials disposed between the substrate and the scratch-resistant film, where the scratch-resistant film includes metal-containing oxides or nitrides, and the stack is designed to maintain at least 70% of the substrate's average flexural strength and retain optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a scratch-resistant film is applied to the glass-based substrate, then scratch resistance is improved, but the average flexural strength of the substrate is reduced
Solution Approach 1:
A crack mitigating layer is introduced as an intermediary between the scratch-resistant film and the glass-based substrate. This layer has intermediate elastic modulus properties that bridge the mismatch between the stiff film and the substrate, preventing stress concentration and crack propagation at the interface while maintaining scratch resistance.
Solution Approach 2:
The system is designed as a composite structure consisting of multiple layers with different material properties: the glass-based substrate, the crack mitigating layer with intermediate elastic modulus, and the scratch-resistant film with high elastic modulus. This composite approach allows each layer to contribute its optimal properties to the overall performance.
2Object-affected harmful factors
If the scratch-resistant film has high elastic modulus to maintain scratch resistance, then functional properties are improved, but the adhesion to the substrate deteriorates causing strength reduction
Solution Approach 1:
The crack mitigating layer provides locally optimized properties at the critical interface region. It has lower elastic modulus than the film but higher than the substrate, creating a gradient that improves adhesion locally at the interface while maintaining the high elastic modulus of the film for scratch resistance.
Solution Approach 2:
The elastic modulus parameter is varied through the layer structure. The crack mitigating layer has an intermediate elastic modulus value that changes the stress distribution parameters at the interface, preventing the stress concentration that would occur with a direct film-substrate interface.
3Illumination intensity
If thin film is used to maintain other functional properties, then optical properties are improved, but the film becomes more susceptible to cracking and strength reduction
Solution Approach 1:
The crack mitigating layer is placed beforehand between the thin film and substrate to cushion against stress concentrations. This protective layer prevents cracks from initiating in the thin film during processing or use, while the film remains thin to maintain optical properties.
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 prevents the reduction in flexural strength of the glass-based substrate while maintaining the scratch resistance and optical properties, even after high temperature exposures, by using a crack mitigating stack that deflects cracks and maintains interfacial properties.
Implementation Method 1
a modified interface between the film and the glass-based substrate such that the glass-based substrate substantially retains its average flexural strength
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An article that includes: a glass-based substrate having opposing major surfaces; a crack mitigating stack disposed on one of the major surfaces; and a scratch-resistant film disposed on the crack mitigating stack that has an elastic modulus greater than or equal to the elastic modulus of the substrate. The stack comprises one or more bi-layers defined by: (a) a first layer comprising an organosilicate material, and (b) a second layer comprising an organosilicate material over the first layer, the first layer having a lower elastic modulus than the elastic modulus of the second layer. The 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. In addition, the article is characterized by an average flexural strength that is at least 70% of an average flexural strength of the substrate.