Silicon Watch Part Coating for Quiet, Deep Color Development

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Solution Overview

Problem

Existing watch designs face challenges in achieving quiet, deep color development due to variations in layer thickness and refractive indices of the light-reflecting layers, particularly when using silicon oxide as the third layer, which affects brightness and hue consistency.

Innovation Solution

A three-layer light-reflecting structure is employed, where the first layer is silicon oxide, the second layer is silicon, and the third layer is formed using a material with a refractive index of 1.7 to 2.7, such as aluminum oxide, aluminum nitride, silicon nitride, titanium oxide, or hafnium oxide, using the ALD method to control layer thickness and refractive index for precise hue adjustment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a three-layer light-reflecting structure with silicon oxide as the third layer is used, then favorable color developability is achieved, but it is difficult to realize quiet, deep color development since brightness is increased

Engineering Contradiction:
ImprovebrightnessVSAvoidcolor development quality
Core Design Contradiction:
Illumination intensityVSManufacturing precision

Solution Approach 1:

The patent changes the material parameter of the third layer from silicon oxide to materials with specific refractive indices (1.4-2.0), which fundamentally alters the optical characteristics of the light-reflecting layer. This parameter change enables achievement of quiet, deep color development while maintaining favorable color developability, resolving the contradiction between brightness and color quality.

Inventive Principle:
Principle #35Parameter changes

2Adaptability or versatility

If the layer thickness of the third layer is changed to adjust color, then color variation is achieved, but brightness is increased and quiet, deep color development is difficult

Engineering Contradiction:
Improvecolor adjustment rangeVSAvoidcolor development quality
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

Instead of adjusting only the thickness parameter of the third layer, the patent changes the refractive index parameter by selecting different materials (aluminum oxide, aluminum nitride, silicon nitride, titanium oxide, or hafnium oxide). This approach provides both color adjustment capability and achieves quiet, deep color development, resolving the contradiction between color versatility and color quality.

Inventive Principle:
Principle #35Parameter changes

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 approach enables the realization of a quiet, deep watch part with consistent and adjustable hues, such as red, green, or yellow, by controlling reflectance and brightness within specific ranges, enhancing design flexibility and durability.

Implementation Method 1

a light-reflecting layer stacked on the base material, wherein the light-reflecting layer includes a first layer, a second layer, and a third layer which are successively stacked

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 2

since three layers composed of the silicon oxide layer serving as a relatively-low refractive index layer and the silicon layer serving as a relatively-high refractive index layer which are alternately stacked

Methodology Applied
Scientific EffectOptical interference: Interference

Data Source

PatentEP4607288A1Watch part and watch
Publication Date: 2025.08.27 SEIKO EPSON CORP
  • EP4607288A1 patent drawingFigure 1
  • EP4607288A1 patent drawingFigure 2
  • EP4607288A1 patent drawingFigure 3

AI summary

A watch part includes a base material having a watch part shape and containing silicon as a primary component and a light-reflecting layer stacked on the base material, wherein the light-reflecting layer includes a first layer, a second layer, and a third layer which are successively stacked in this order from the base material, the first layer is formed using silicon oxide, the second layer is formed using silicon, and the third layer is formed using a material having a refractive index of 1.7 to 2.7.