Optical Hardcoating Scratch Resistance on Textured Glass
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Solution Overview
Problem
Existing anti-reflective coatings on transparent substrates are susceptible to wear and abrasion, leading to compromised optical performance, and are more prone to scratch damage than the underlying substrates, which affects the durability and reliability of display devices and other applications.
Innovation Solution
A combination of a textured light-scattering chemically strengthened glass surface with a uniform, color-controlled, low-reflectance optical hardcoating is used, where the optical coating has a thickness greater than 300 nm to achieve high hardness and minimize scratch formation, while the light scattering surface helps hide scratches and reduce glare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If anti-reflective coatings are applied to improve optical performance, then light transmittance and reflectance are improved, but the coating becomes susceptible to wear and abrasion
Solution Approach 1:
The patent applies a composite coating structure consisting of multiple layers with different refractive indices and mechanical properties. The coating includes at least one layer comprising silicon nitride (SiNx) or silicon oxynitride (SiOxNy) providing high hardness and scratch resistance, combined with other dielectric materials optimized for optical performance. This composite approach allows simultaneous achievement of low reflectance and high wear resistance.
Solution Approach 2:
Different layers of the coating are designed with locally optimized properties: some layers are optimized for minimum reflectance through specific refractive indices and thicknesses, while other layers are optimized for mechanical durability and scratch resistance. The gradient structure allows each layer to perform its specialized function, resolving the contradiction between optical performance and wear resistance.
2Illumination intensity
If optical filters are made from multilayer coatings with differing refractive indices, then optical performance is improved, but the materials lack requisite mechanical properties such as hardness
Solution Approach 1:
The patent combines dielectric materials with different refractive indices in a multilayer structure, where at least one layer uses silicon nitride or silicon oxynitride to provide high hardness (exceeding 8 GPa). This composite material approach ensures that optical performance is maintained through refractive index optimization while mechanical strength is enhanced by the hard ceramic layers.
Solution Approach 2:
The patent controls the composition and thickness of each layer to optimize both optical and mechanical parameters. By adjusting the nitrogen content in silicon nitride layers and controlling layer thicknesses, the coating achieves the desired balance between optical performance and mechanical properties including hardness and scratch resistance.
3Duration of action of stationary object
If abrasion damage occurs over longer term, then coating materials oxidize, but this further degrades the durability of the coating
Solution Approach 1:
The patent employs silicon nitride and silicon oxynitride materials that inherently resist oxidation and chemical degradation. These materials form a stable, inert environment within the coating structure that prevents oxidative damage to underlying layers, thereby maintaining coating durability and preventing degradation over extended periods of use.
Solution Approach 2:
The multilayer composite structure includes oxidation-resistant barrier layers that protect the underlying substrate and other coating layers from environmental degradation. The combination of materials creates a synergistic effect where the most oxidation-resistant layers serve as protective barriers, extending the overall coating lifespan.
4Reliability
If known scratch and abrasion damage solutions are applied, then durability is improved, but the optical properties are compromised
Solution Approach 1:
The patent applies scratch-resistant materials specifically in layers where mechanical durability is most critical, while maintaining optically optimized layers for light management. The localized application of hard coatings in strategic positions allows scratch resistance enhancement without significantly impacting optical performance, as the hard layers are designed with appropriate thickness and refractive index to maintain optical coherence.
Solution Approach 2:
The composite coating structure integrates materials with complementary properties: some layers optimized for scratch resistance and others for optical performance. The careful selection and arrangement of materials in the composite structure allows both scratch resistance and optical properties to be maintained simultaneously through proper layer design and thickness optimization.
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 enhances display readability, reduces glare, and maximizes apparent brightness and color gamut by combining light scattering and low reflectance features, providing improved scratch resistance and maintaining optical coherence even on rough surfaces.
Implementation Method 1
a textured or rough surface inducing light scattering
Implementation Method 2
an optical coating disposed on the major surface... the optical coating having a physical thickness of greater than 300 nm
Data Source
AI summary
According to one or more embodiments described herein, a coated article may comprise: a transparent substrate having a major surface, the major surface comprising a textured or rough surface inducing light scattering; and an optical coating disposed on the major surface of the transparent substrate and forming an air-side surface, the optical coating comprising one or more layers of material, the optical coating having a physical thickness of greater than 300 nm, wherein the coated article exhibits a maximum hardness of about 10 GPa or greater as measured on the air-side surface by a Berkovich Indenter Hardness Test along an indentation depth of about 50 nm or greater.