Watch Coating with Titanium Carbide Undercoat for Scratch Resistance

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Solution Overview

Problem

Conventional watch coatings face challenges with scratch resistance, corrosion resistance, adhesion to the base, and allergic reactions, while maintaining a high-grade appearance and brightness, due to limitations in platinum, molybdenum, chromium, and tantalum carbide films.

Innovation Solution

A watch with a decorative member featuring a coating layer composed of a reaction compound or alloy of metals like Mo, W, Nb, Ta, Cr, Ti, Hf, and Zr, combined with nitrogen or carbon, providing a carbide, nitride, or carbonitride film with adjustable thickness and properties for enhanced scratch resistance, corrosion resistance, and adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a platinum coating is formed on the outermost layer to improve brightness and appearance, then the high-grade appearance is achieved, but the film thickness must be kept thin to suppress color change due to peeling, resulting in insufficient scratch resistance

Engineering Contradiction:
ImprovebrightnessVSAvoidscratch resistance
Core Design Contradiction:
Illumination intensityVSStrength

Solution Approach 1:

The patent uses a composite structure consisting of a titanium carbide undercoat layer and a platinum decorative coating layer. The titanium carbide layer provides hardness and scratch resistance, while the thin platinum layer provides brightness and appearance. This composite approach allows each layer to perform its specialized function without compromising the other.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The titanium carbide layer serves as an intermediary between the base and the platinum coating. It provides a hard, adhesive substrate that prevents peeling of the thin platinum layer, thereby maintaining both the brightness of the platinum and the scratch resistance of the underlying hard layer.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Strength

If the hardness of the titanium carbide layer is increased to improve scratch resistance, then scratch resistance improves, but the color tone is darkened

Engineering Contradiction:
Improvescratch resistanceVSAvoidcolor tone
Core Design Contradiction:
StrengthVSIllumination intensity

Solution Approach 1:

The patent applies different properties to different layers: the titanium carbide undercoat layer is designed with high hardness for scratch resistance, while the platinum outer layer provides the bright, light color tone. This local differentiation of properties allows each layer to optimize its specific function without compromising the other.

Inventive Principle:
Principle #3Local quality

3Strength

If the film thickness of the titanium carbide layer is increased to improve scratch resistance, then scratch resistance improves, but peeling of the film occurs due to increasing film stress

Engineering Contradiction:
Improvescratch resistanceVSAvoidadhesion
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent optimizes the thickness parameter of the titanium carbide layer to balance scratch resistance and adhesion. By carefully controlling the thickness within a specific range, the film stress is kept at acceptable levels while still providing sufficient hardness and scratch resistance.

Inventive Principle:
Principle #35Parameter changes

4Strength

If a Mo coating is used instead of platinum to improve brightness and scratch resistance, then brightness and scratch resistance improve, but corrosion resistance deteriorates

Engineering Contradiction:
Improvescratch resistanceVSAvoidcorrosion resistance
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent uses a composite structure where the titanium carbide undercoat layer provides corrosion resistance and the outer layer provides brightness and scratch resistance. This composite approach allows each layer to perform its specialized function without compromising the other.

Inventive Principle:
Principle #40Composite materials

5Reliability

If a Cr coating is used to improve brightness and corrosion resistance, then brightness and corrosion resistance improve, but scratch resistance deteriorates due to low film hardness

Engineering Contradiction:
Improvecorrosion resistanceVSAvoidscratch resistance
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent uses a composite structure where the titanium carbide undercoat layer provides high hardness and scratch resistance, while the outer layer provides corrosion resistance and brightness. This composite approach allows each layer to perform its specialized function without compromising the other.

Inventive Principle:
Principle #40Composite materials

6Strength

If a Nb carbide film or Ta carbide film is used to improve hardness and corrosion resistance, then hardness and corrosion resistance improve, but adhesion to base deteriorates and brightness is reduced

Engineering Contradiction:
ImprovehardnessVSAvoidadhesion
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent applies different properties to different layers: the titanium carbide undercoat layer is designed with high adhesion to the base and appropriate hardness, while the outer layer provides brightness and corrosion resistance. This local differentiation of properties allows each layer to optimize its specific function.

Inventive Principle:
Principle #3Local quality

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 achieves a watch with improved scratch resistance, corrosion resistance, and a high-grade appearance, while minimizing allergic reactions and allowing for control over film hardness, brightness, and color tone, enabling the formation of thick, durable coatings.

Implementation Method 1

a titanium carbide layer is formed on the surface thereof by a dry plating method

Methodology Applied
Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Data Source

PatentEP2829630B1Decorative member having white hard film layer, and production method therefor
Publication Date: 2023.09.27 CITIZEN WATCH CO LTD
  • EP2829630B1 patent drawingFigure 1
  • EP2829630B1 patent drawingFigure 2
  • EP2829630B1 patent drawingFigure 3

AI summary

A rigid decorative member of the present invention is a rigid decorative member comprising a base and a rigid coating layer laminated on or above the base, wherein the rigid coating layer comprises a reaction compound of raw metal, in which a metal M1 and a metal M2, and in addition, selectively a metal M3 are combined, and of a non-metallic element selected from one or two or more of nitrogen, carbon, and oxygen, or comprises an alloy in which a metal M1 and a metal M2, and in addition, selectively a metal M3 are combined; the metal M1 is selected from one or two of Mo and W; the metal M2 is selected from one or two or more of Nb, Ta, and V; and the metal M3 is selected from one or two or more of Cr, Ti, Hf, and Zr.