Effect Pigments with Semiconductor Layers for High Chroma
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Solution Overview
Problem
Existing effect pigments exhibit low chroma effect, color flop, and high red hue shift when viewed from different angles, along with complex structures and high thicknesses that lead to orientation issues and reduced gloss and hiding power.
Innovation Solution
Development of an effect pigment with a layer stack comprising a metallic flake coated with a semiconducting material, such as Si(1-x)Snx or Ge(1-y)Sny, which enhances optical properties like flop index and color stability, combined with a PVD process for manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dielectric layers with thickness >50 nm are used to coat metal core, then the chroma effect is improved, but the structure becomes complex and the overall thickness increases
Solution Approach 1:
The patent changes the material parameter from dielectric to semiconductor and reduces the thickness parameter from >50 nm to 1-20 nm, achieving high chroma effect with minimal layer thickness. The semiconductor material's unique optical properties enable this parameter optimization.
Solution Approach 2:
The patent uses composite semiconductor layers combining multiple materials (e.g., SiO2, TiO2, ZnO) with specific refractive indices to achieve the desired optical effect. This composite approach allows tuning of optical properties while maintaining thin layer thickness.
2Illumination intensity
If multiple dielectric and semiconductor layers are added to achieve ideal chroma performance, then the chroma effect is improved, but the overall thickness increases rendering aspect ratios low which causes orientation problems
Solution Approach 1:
The patent dramatically reduces the layer thickness parameter from traditional multi-layer structures (>100 nm total) to ultra-thin semiconductor layers (1-20 nm total), maintaining high chroma effect while achieving high aspect ratios that prevent orientation problems in application media.
3Device complexity
If the metal content in effect pigments is reduced, then the structure becomes simpler, but the hiding power diminishes
Solution Approach 1:
The patent uses composite semiconductor layers with specific refractive indices (e.g., combinations of SiO2, TiO2, ZnO) to enhance optical effects, allowing reduced metal content while maintaining or improving hiding power through the semiconductor layers' optical properties.
4Device complexity
If traditional dielectric stacks are used, then the structure is simple, but color flop occurs due to path-dependent interference effects
Solution Approach 1:
The patent changes the material parameter from dielectric to semiconductor, which fundamentally alters the optical interference characteristics. The semiconductor material's properties eliminate path-dependent interference effects, preventing color flop while maintaining structure simplicity.
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 resulting effect pigments achieve a high flop index above 25, minimal color shifting with viewing angle, and excellent gloss and hiding power, while maintaining a simple structure and low thickness.
Implementation Method 1
semiconducting material having a band gap in the range of 0.1 to 2.5 eV
Implementation Method 2
path-dependent interference effects
Implementation Method 3
highly reflective metallic flake
Implementation Method 4
using a PVD process comprising the steps: depositing semiconductor layer 1 onto the flexible substrate
Data Source
AI summary
Disclosed herein is an effect pigment having a layer stack which comprises a highly reflective metallic flake having a first major interface and opposed to this first interface a second major interface, and at least one side surface and directly adjacent on one or of both of these major interfaces a layer of a semiconducting material having an average atomic composition of:a) Si(1-x)Snx, wherein 0<x<0.90 orb) Ge(1-y)Sny, wherein 0<y≤0.80 orc) Si(1-m-n)GemSnn, wherein 0<m<1.00, 0<n<1.00 and with the proviso that m+n<1.00.