Optical Coating Transition Layer for Plastic Substrates
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Solution Overview
Problem
Existing vacuum coating processes for optical coatings, such as CVD and sputtering, face challenges with contamination and adhesion issues due to the brittleness of inorganic layers on substrates with different mechanical and thermal properties, particularly on plastic materials like spectacle lenses, leading to reduced adhesion and potential flaking off.
Innovation Solution
A process combining physical sputtering with a transition layer that matches the mechanical properties of the substrate, using precursors in a controlled vapor phase to create a directional coating that prevents contamination and enhances adhesion, allowing for the application of layers like Si oxide/Si nitride systems without a separate hard lacquer layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic layers are applied by vacuum coating processes, then optical quality and abrasion resistance are improved, but adhesion to plastic substrates deteriorates due to brittleness and mechanical property mismatch
Solution Approach 1:
A transition layer is introduced as an intermediary between the plastic substrate and the inorganic optical layers. This transition layer has intermediate mechanical properties that bridge the gap between the flexible substrate and the brittle inorganic coating, improving adhesion while maintaining optical quality and abrasion resistance.
Solution Approach 2:
The mechanical properties of the coating system are optimized by changing the composition and thickness parameters of the transition layer. By adjusting these parameters, the transition layer achieves optimal compliance with the substrate while providing sufficient support for the inorganic layers.
2Manufacturing precision
If CVD processes are used to apply coatings, then coating uniformity is improved, but contamination of other chamber surfaces increases due to vapor phase deposition
Solution Approach 1:
The harmful vapor phase deposition is extracted or removed from the system by using sputtering instead of CVD. The sputtering process confines the coating material primarily to the substrate surface through directional ion bombardment, preventing contamination of other chamber surfaces while maintaining coating uniformity.
Solution Approach 2:
The chemical deposition mechanism of CVD is replaced with a physical sputtering mechanism. This substitution changes the deposition process from a chemically reactive vapor phase process to a physically driven ion bombardment process, which provides better directional control and reduced contamination.
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
This approach results in high-quality, cost-effective coatings with improved adhesion and reduced contamination, ensuring the optical quality and mechanical compatibility of the layers with the substrate, even under high mechanical and thermal stresses.
Implementation Method 1
The term sputtering is used to describe removal of material by ion bombardment, during which extremely small particles of a bombarded solid-state target are detached (sputtered) and, if appropriate after reaction with sputtering gases present in the vacuum chamber, condense on a front surface located directly opposite the target, of a substrate, resulting in the formation of a solid layer.
Implementation Method 2
The term sputtering is used to describe removal of material by ion bombardment, during which extremely small particles of a bombarded solid-state target are detached (sputtered)
Implementation Method 3
The material in the vapor phase then condenses on a cooler surface of the substrate which is to be coated, where it forms a layer.
Implementation Method 4
In this variant, a plasma is generated above the substrate surface to be coated. Some of the components within the vapor which is introduced are brought into a chemically reactive state in the plasma, so that they are capable of undergoing a chemical reaction in the vicinity of the substrate surface
Data Source
AI summary
A process and apparatus for applying an optical coating to a substrate, wherein a transition layer 12, which is used to match mechanical properties of a substrate 10 to mechanical properties of a layer system 16 to be applied upon the transition layer 12, is deposited on a front surface 20 of the substrate 10. For this purpose, during a sputtering process carried out in a vacuum chamber 18, reaction products 14 are incorporated at least virtually exclusively in the transition layer 12 on the substrate. This prevents other surfaces of the vacuum chamber 18 and the rear side 34 of the substrate 10 from being contaminated with the reaction products 14 and/or their precursors.