Silver-Plated Substrate with Al2O3/TiO2 Nanocoating for Tarnish Protection
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Solution Overview
Problem
Existing methods for protecting silver-plated horological elements against tarnishing, such as Zapon varnishing and ALD, either conceal fine details, alter the appearance, or provide inadequate adherence, leading to reduced brightness and aesthetic issues.
Innovation Solution
A substrate with a silver-plated surface protected by a dual-layer coating of Al2O3 and TiO2, applied in specific thicknesses between 0.5 nm and 100 nm, combined with a porosity-free silver or silver-copper alloy layer, to enhance brightness and maintain aesthetic appearance while preventing tarnishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Zapon varnish is applied to protect the silver-plated surface, then tarnishing protection is improved, but fine details are concealed and appearance is altered
Solution Approach 1:
The invention changes the parameter of coating thickness from micrometers (10 μm) to nanometers (1-200 nm, preferably 5-50 nm). This drastic reduction in thickness allows the protective coating to preserve fine details and surface structuring while still providing effective tarnishing protection against sulfur-containing atmospheres.
Solution Approach 2:
The invention uses composite material systems: a silver-plated surface (Ag) combined with an aluminum oxide (Al2O3) protective coating deposited by ALD. This composite structure provides both the aesthetic properties of silver and the chemical resistance of aluminum oxide, preventing tarnishing while maintaining fine detail visibility.
2Reliability
If ALD method is used to deposit protective coat, then tarnishing protection is improved, but adherence to silver-plated surface is poor
Solution Approach 1:
The invention applies a preliminary action by depositing a thin layer of aluminum (Al) or aluminum oxide (Al2O3) on the silver-plated surface before depositing the final protective coating. This preliminary layer creates a nucleation substrate that enhances the adherence of subsequent ALD-deposited protective layers, preventing delamination during stress or decoration operations.
Solution Approach 2:
The invention introduces an intermediary layer (aluminum or aluminum oxide) between the silver-plated surface and the protective coating. This intermediary layer acts as a bonding interface that improves adhesion, allowing the protective coating to withstand mechanical stress and decoration processes without delaminating.
3Reliability
If ALD method is used to deposit protective coat, then tarnishing protection is improved, but brightness of silver is reduced
Solution Approach 1:
The invention optimizes the thickness parameter of the protective coating to the nanometer range (1-200 nm, preferably 5-50 nm). At this extremely thin scale, the coating provides sufficient chemical protection against tarnishing while remaining optically transparent, thus preserving the brightness and aesthetic appearance of the underlying silver-plated surface.
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 silver tarnishing while preserving the bright, white appearance and structural details of the silver-plated surface, ensuring strong adhesion and maintaining the aesthetic integrity of the substrate.
Implementation Method 1
depositing on at least a part of said final silver-plated surface from step a) at least one protective coat against silver tarnishing
Implementation Method 2
depositing on at least a part of said final silver-plated surface from step a) at least one protective coat against silver tarnishing
Implementation Method 3
capable of being coated with a thin coat of silver... coating a substrate with a thin coat of silver, deposited preferably galvanically
Data Source
AI summary
A substrate includes a final silver-plated surface protected against silver tarnishing by a protective coat having a thickness between 1 nm and 200 nm, the protective coat includes a first coat of Al2O3 deposited on said final silver-plated surface and having a thickness between 0.5 nm and 100 nm, and on the first coat of Al2O3, a second coat of TiO2 having a thickness between 0.5 nm and 100 nm, the substrate including a coat of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy, forming said final silver-plated surface, said coat of a silver and copper alloy having a thickness between 1000 nm and 3000 nm. Embodiments also relate to a method for manufacturing such a substrate.