Intermediate Layer Suppresses Interference Colors on Thin Metal Coatings

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Solution Overview

Problem

Thin transparent coatings on metallic components in household appliances can exhibit interference colors due to light interference, which are undesirable and difficult to prevent without increasing coating thickness or using costly and time-consuming methods, restricting design options and mechanical properties.

Innovation Solution

Applying an intermediate layer with a refractive index and absorption coefficient suitable for minimizing interference between the metallic surface and the transparent functional coating, allowing the functional coating to maintain its thickness and properties while suppressing interference colors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the layer thickness of the transparent coating is increased to more than 2000 nm to prevent interference colors, then interference colors are suppressed, but material costs increase and mechanical properties deteriorate (brittleness and cracking susceptibility)

Engineering Contradiction:
Improveinterference colorsVSAvoidmechanical properties
Core Design Contradiction:
Object-affected harmful factorsVSStrength

Solution Approach 1:

An intermediate layer with optimized refractive index and absorption coefficient is introduced between the metallic surface and the transparent functional coating. This intermediate layer acts as an optical mediator that suppresses interference colors by controlling light reflection and transmission, allowing the functional coating to maintain its optimal thin thickness (100-1000 nm) without developing mechanical defects.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the layer thickness of the transparent coating is increased to more than 2000 nm to prevent interference colors, then interference colors are suppressed, but coating time and production costs increase

Engineering Contradiction:
Improveinterference colorsVSAvoidcoating time
Core Design Contradiction:
Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The intermediate layer with specifically optimized optical properties (refractive index and absorption coefficient) enables suppression of interference colors in thin functional coatings (100-1000 nm), dramatically reducing the required coating thickness compared to conventional approaches (>2000 nm) and thereby significantly shortening coating time and production costs.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If physical or chemical roughening methods are used to suppress interference phenomena, then interference colors are reduced, but high-gloss reflective surfaces cannot be achieved and design options are restricted

Engineering Contradiction:
Improveinterference colorsVSAvoidsurface gloss
Core Design Contradiction:
Object-affected harmful factorsVSShape

Solution Approach 1:

The intermediate layer provides optical interference suppression while maintaining a smooth, high-gloss surface finish. Unlike roughening methods that alter surface topology, this intermediate layer approach preserves the aesthetic and functional properties of smooth metallic surfaces while eliminating unwanted interference colors.

Inventive Principle:
Principle #24Intermediary (Mediator)

4Reliability

If different coating methods (chemical CVD or physical PVD) are used for functional layers, then functional properties are improved, but process complexity and costs increase

Engineering Contradiction:
Improvefunctional propertiesVSAvoidcoating process
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The intermediate layer is designed to be compatible with standard CVD or PVD coating processes, allowing it to be applied using the same equipment and methodology as the functional coating. This multi-functional approach enables both the intermediate layer (for optical interference suppression) and the functional layer (for protective properties) to be deposited in a single integrated process sequence, reducing equipment requirements and process complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 method effectively prevents interference colors without increasing the functional coating thickness, maintaining mechanical properties and achieving a high-gloss, uniform metallic appearance with reduced production costs and time.

Implementation Method 1

interference effects lead to the formation of interference colors

Methodology Applied
Scientific EffectLight interference: Interference

Implementation Method 2

intermediate layer with a refractive index and absorption coefficient suitable for minimizing interference

Methodology Applied
Scientific EffectRefraction: Refraction

Implementation Method 3

intermediate layer with a refractive index and absorption coefficient suitable for minimizing interference

Methodology Applied
Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentEP3152344A1Method for preventing interference colors on thinly coated metal surfaces
Publication Date: 2017.04.12 BOSCH SIEMENS HAUSGERATE GMBH

AI summary

The invention relates to a method for finishing metal surfaces of components. The invention is characterized in that the method has the steps of coating the metal surface of a main part contained in the component with an intermediate layer and applying a transparent functional layer onto the intermediate layer. The transparent functional layer has a thickness ranging from 0 to 1000 nm. The invention additionally relates to components produced according to the aforementioned method, said components being characterized in particular by a pleasing homogeneous appearance without the formation of interference colors.