Bilayer Multispectral DLC Coating for Adhesion and Optical Transmission
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Solution Overview
Problem
Diamond-like carbon (DLC) coatings face challenges with adhesion to underlying materials and limited optical transmissivity, particularly in multispectral applications requiring dual or multiple wavelength operation, due to high internal stress and limited spectral bandwidth.
Innovation Solution
A bilayer DLC coating with varying modulus of elasticity and sp3/sp2 ratios, combined with multi-layer dielectric films, to enhance adhesion and spectral transmission across multiple wavelength bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single layer DLC coating is applied, then the coating provides durable protection, but adhesion to underlying materials deteriorates
Solution Approach 1:
The single layer DLC coating is divided into multiple layers with different sp3/sp2 ratios. The first layer has a higher sp3/sp2 ratio for durability, while the second layer has a lower sp3/sp2 ratio for improved adhesion to the substrate, resolving the contradiction between coating strength and adhesion reliability
Solution Approach 2:
The invention uses a composite DLC coating structure where layers with different carbon bonding ratios (sp3/sp2) are combined. This composite approach allows the coating to simultaneously achieve high durability from sp3-rich layers and good adhesion from sp2-rich layers, resolving the contradiction between these two properties
2Ease of manufacture
If a single layer DLC coating is applied, then the coating is easy to manufacture, but optical transmissivity deteriorates
Solution Approach 1:
The coating is segmented into multiple layers with different optical properties. By controlling the thickness and sp3/sp2 ratio of each layer, the coating achieves improved optical transmissivity while maintaining manufacturing feasibility through sequential deposition processes
Solution Approach 2:
The invention changes the sp3/sp2 ratio parameter across different layers to optimize optical transmissivity. The second layer with lower sp3/sp2 ratio has better optical transmission characteristics, resolving the contradiction between manufacturing simplicity and optical performance
3Strength
If DLC coating thickness is increased for durability, then coating strength improves, but internal stress worsens
Solution Approach 1:
The thick DLC coating is segmented into multiple layers with different sp3/sp2 ratios. This segmentation distributes and reduces internal stress while maintaining overall coating thickness for durability, resolving the contradiction between coating strength and internal stress
Solution Approach 2:
The composite DLC structure with varying sp3/sp2 ratios across layers creates a stress-balanced coating system. The different layers compensate for each other's stress, allowing thick coatings to maintain high strength without excessive internal stress
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 provides a durable, low-stress DLC coating with improved adhesion and multispectral transmission capabilities, suitable for thermal imaging and other optical applications.
Implementation Method 1
first multi-layer dielectric film disposed on the first surface of the substrate and constructed and arranged to transmit light in a first band of wavelengths, a second multi-layer dielectric film disposed on the second surface of the substrate and constructed and arranged to transmit light in a second band of wavelengths
Implementation Method 2
Diamond-like carbon (DLC) coatings typically comprise an amorphous combination of carbon and hydrogen that is capable of providing a durable protective coating for optical and other surfaces
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Multispectral optical interference coatings and methods. In one example, an optical element includes a substrate having a first surface and a second surface disposed opposite the first surface, a first multi-layer dielectric film disposed on the first surface of the substrate and constructed and arranged to transmit light in a first band of wavelengths, a second multi-layer dielectric film disposed on the second surface of the substrate and constructed and arranged to transmit light in a second band of wavelengths, the first and the second bands of wavelengths at least partially overlapping, and a bilayer diamond-like carbon (DLC) coating disposed on the first multi-layer dielectric film, the bilayer DLC coating including a first layer and a second layer, the first layer having a modulus of elasticity of a first value, and the second layer disposed on the first layer and having a modulus of elasticity of a second value that is greater than the first value.