Ceramic Trim Coating That Preserves Color Under Wear
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Solution Overview
Problem
Existing protective layers for ceramic watch parts are either too thin to withstand mechanical stress or too thick to maintain visual appearance, and none provide effective protection against chemical and mechanical aggressions while being transparent.
Innovation Solution
A transparent inorganic protective coating with a refractive index matching that of the substrate, typically 300 nm to 5 µm thick, is applied using vacuum deposition methods to provide mechanical resistance and chemical protection without visible interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a thin protective layer (less than 5 μm) is deposited to preserve visual appearance, then transparency and visual appearance are maintained, but mechanical resistance to friction and impacts is insufficient
Solution Approach 1:
The patent applies a composite protective coating consisting of multiple layers with different properties. The first layer is a dense inorganic coating providing chemical resistance, while the second layer is a crosslinkable organic coating providing mechanical resistance. This composite structure allows each layer to contribute its specific strength, achieving both transparency and mechanical protection simultaneously.
Solution Approach 2:
The patent changes the parameters of the protective coating by using a two-layer system with different thicknesses and material compositions. The first layer has controlled thickness (1-5 μm) and specific refractive index matching the substrate, while the second layer provides mechanical cushioning. This parameter optimization resolves the contradiction between thinness for transparency and thickness for mechanical strength.
2Strength
If a thick protective layer (around 1 μm or more) is deposited to provide mechanical resistance, then mechanical stress resistance is improved, but the layer becomes visible on the substrate and interferes with visual appearance
Solution Approach 1:
The patent applies local quality by giving different regions of the protective coating different properties. The first layer has optical properties matched to the substrate (refractive index 1.7-1.9) to ensure transparency, while the second layer has enhanced mechanical properties (crosslinkable polymer with hardness 3-5 GPa) to provide mechanical protection. Each layer performs its specific function locally without compromising the other.
3Reliability
If an ALD thin film is used to provide chemical protection and invisibility, then chemical attack protection and visual appearance are maintained, but the layer is highly sensitive to mechanical stresses and cannot protect parts contacting external elements
Solution Approach 1:
The patent segments the protective coating into two distinct functional layers. The first layer (inorganic coating) provides chemical protection and optical matching, while the second layer (organic crosslinkable coating) provides mechanical resistance. This segmentation allows each layer to specialize in its intended function, with the second layer specifically designed to cushion mechanical impacts and friction.
4Ease of manufacture
If a PVD or CVD deposition method is used to deposit a protective layer, then coating application is achieved, but the layer either absorbs light (reducing transparency) or lacks sufficient mechanical resistance
Solution Approach 1:
The patent optimizes deposition parameters by controlling the thickness of the first layer to 1-5 μm and selecting materials with refractive indices matching the ceramic substrate (1.7-1.9). This parameter control minimizes light absorption and interference colors while maintaining adequate mechanical protection, resolving the contradiction between ease of manufacture and optical performance.
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 coating effectively protects ceramic watch components from abrasion and chemical attack while maintaining the intrinsic color and visual appearance of the substrate.
Implementation Method 1
The protective coating is applied using vacuum deposition methods
Implementation Method 2
The coating is configured so as to have a refractive index, at least at the interface with the substrate, substantially equal to that of the substrate for wavelengths in the visible range of the light spectrum
Data Source
Figure 1
AI summary
The invention relates to a covering piece (10) comprising a substrate (11) made of ceramic material on a surface of which is extended a transparent inorganic protective coating (12), said protective coating (12) being configured so as to have a refractive index substantially equal to that of the substrate (11) in the visible range of the light spectrum so that the covering piece (10) has a color substantially identical to the intrinsic color of the substrate (11), said coating (12) extending over a thickness chosen between 300 nm and 5 µm.