Coatings with Interrupting Layers for Controlled Roughness
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Solution Overview
Problem
There is a need for methods to control the microstructure and surface roughness of polycrystalline or semi-crystalline hardcoatings while maintaining optical transparency, particularly for applications in displays, touch screens, and eyeglasses, where mechanical toughness and piezoelectric properties are beneficial.
Innovation Solution
A multi-layered structure is applied to a substrate, comprising a first portion, one or more interrupting layers with a different microstructure, and a second portion, where the interrupting layers have an optical transmittance greater than 85% over the visible wavelength range and a thickness of 100 nm or less, allowing for controlled crystallite size and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the coating is made polycrystalline or semi-crystalline to improve mechanical toughness and piezoelectric properties, then mechanical strength is improved, but surface roughness increases and optical transparency deteriorates
Solution Approach 1:
The coating is divided into multiple layers with different microstructures. The first and second portions have polycrystalline or semi-crystalline microstructures providing mechanical toughness, while the interrupting layers have amorphous microstructures providing optical transparency. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the coating are assigned different microstructural qualities. The first and second portions are engineered with crystalline structures for mechanical performance, while the interrupting layers are engineered with amorphous structures for optical performance. This local differentiation resolves the contradiction by optimizing each region for its primary function.
2Reliability
If the coating is made polycrystalline or semi-crystalline to improve mechanical properties, then durability is improved, but surface roughness increases causing increased contact events
Solution Approach 1:
The coating structure is segmented into mechanical function layers (first and second portions with crystalline microstructures) and optical function layers (interrupting layers with amorphous microstructures). This segmentation allows the crystalline layers to provide durability while the amorphous layers maintain surface smoothness, reducing fictive contact events.
3Illumination intensity
If the interrupting layers are made thinner to improve optical transmittance, then optical transparency is improved, but mechanical durability may deteriorate
Solution Approach 1:
The interrupting layers are designed with amorphous microstructure and optimized thickness (50-200 nm) to provide sufficient optical transparency while maintaining adequate mechanical durability. The amorphous structure inherently provides smooth surface properties, and the thickness is carefully controlled to balance optical and mechanical requirements.
Data Source
AI summary
An article includes a glass, glass-ceramic or ceramic substrate including a primary surface. A functional coating is disposed over the primary surface of the substrate. The coating includes a first portion disposed over the primary surface. One or more interrupting layers are disposed over the first portion. A second portion is disposed over the one or more interrupting layers. The one or more interrupting layers includes a microstructure different than one of the first and second portions and the coating has an average optical transmittance greater than about 10% over the visible wavelength range from about 450 nm to about 650 nm.