Watch Coating Using ALD Semi-Transparent Layers for Interference Colors
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Solution Overview
Problem
Current coating processes for watch components are limited in achieving a wide range of interference colors, particularly in blues, and fail to provide uniform coloration on components with complex geometries.
Innovation Solution
A method involving a first opaque layer deposited by PVD, followed by a stack of semi-transparent layers using ALD, where the thickness and refractive indices of the layers are carefully chosen to achieve a wide range of interference colors, including blues, by modifying the L*a*b* parameters of the coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single transparent thin layer is deposited by ALD to obtain interference colors, then uniformity on complex geometries is improved, but the range of interference colors remains limited
Solution Approach 1:
The patent divides the single-layer approach into multiple ALD layers with different refractive indices (first layer with refractive index n1, second layer with refractive index n2 where n1 < n2). This segmentation allows independent control of optical properties while maintaining uniform deposition on complex geometries, thereby expanding the range of achievable interference colors.
Solution Approach 2:
The patent uses composite multi-layer structures combining materials with different refractive indices (such as Al2O3, TiO2, SiO2, Ta2O5, HfO2, ZrO2) deposited by ALD. This composite approach enables tuning of optical interference effects to achieve a broader spectrum of colors while preserving the uniformity advantage of ALD on complex surfaces.
2Ease of manufacture
If PVD is used to deposit coatings on metal parts, then a shiny or matte appearance can be obtained, but the range of colors remains limited and uniformity on complex geometries is poor
Solution Approach 1:
The patent replaces the PVD physical vapor deposition process with ALD (Atomic Layer Deposition), a chemical vapor deposition method. This substitution enables precise control of film thickness at the nanometer scale, ensuring uniform coverage on complex geometries while allowing tuning of optical properties through multi-layer structures with different refractive indices.
Solution Approach 2:
The patent changes the deposition method from PVD to ALD, fundamentally altering the process parameters to achieve atomic-level control over film thickness and composition. This parameter change enables uniform deposition on complex surfaces and allows precise control of interference colors through the multi-layer ALD structure.
3Manufacturing precision
If ALD is used to deposit uniform layers on parts with complex geometry, then uniform color is achieved, but the range of interference colors is not extended
Solution Approach 1:
The patent segments the single ALD layer into multiple layers with different refractive indices, allowing each layer to contribute differently to the overall optical interference effect. This segmentation maintains the uniform thickness advantage of ALD while expanding color range through the combined optical properties of the multi-layer structure.
Solution Approach 2:
The patent changes the optical parameters of the ALD structure by introducing layers with different refractive indices (n1 and n2 where n1 < n2). This parameter change enables tuning of the interference conditions to achieve a broader range of colors while preserving the uniform thickness deposition characteristic of ALD on complex geometries.
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 method allows for a broad spectrum of interference colors with varying shades, ensuring uniformity and applicability to components with complex geometries, independent of the substrate's nature or initial color, while maintaining low-temperature deposition to preserve the component's structure.
Implementation Method 1
a first step of depositing a first opaque layer on the substrate
Implementation Method 2
the thickness of the stack being chosen so as to obtain a color with an interference phenomenon
Implementation Method 3
a first step of depositing a first opaque layer on the substrate
Implementation Method 4
a second step of depositing by an ALD method (atomic layer deposition) a stack of at least two semi-transparent layers
Data Source
Figure 1~3
AI summary
One aspect of the invention relates to an article (1) comprising a substrate (10) and a coating having a color with an interference effect for the decoration and/or protection of said article (1), said coating comprising: a first opaque layer (11) covering at least partially at least one surface of the substrate (10); a stack (20) of at least two semi-transparent layers (12, 13) deposited by an ALD process covering said first layer (11); the stack (20) having a thickness (e2) as a function of said color with an interference phenomenon of said coating.