Gold-Coated Flat Silver Particles Uniform Coating
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Solution Overview
Problem
Existing techniques for gold-coating flat silver particles often result in non-uniform coating, leading to aggregation and precipitation in high-concentration dispersions, and fail to maintain the desired particle shape, thereby compromising oxidative resistance.
Innovation Solution
The development of gold-coated flat silver particles with a gold coating layer thickness of 0.1 nm to 2 nm on principal planes and a ratio of 0.02 or higher on edge surfaces, achieved through a method involving a gold coating solution with a complexing agent having a reduction potential of 0.5 V or lower, and the addition of an organic component with a high solubility product and low reduction potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional gold coating methods are used on flat silver particles, then gold coating is achieved, but uniform coating on all surfaces (including edge surfaces) cannot be obtained
Solution Approach 1:
The patent applies local quality by using a thiol-containing compound that selectively adsorbs to edge surfaces of flat silver particles, creating different chemical environments on different particle surfaces. This selective adsorption enables preferential gold deposition on edge surfaces, achieving uniform overall coating through localized chemical modification
Solution Approach 2:
The thiol-containing compound acts as an intermediary substance that mediates between the silver particle surfaces and gold ions. It modifies the surface properties of edge surfaces to enhance gold affinity, serving as a chemical bridge that enables uniform gold coating without direct conventional coating methods
2Quantity of substance
If high-concentration flat silver particle dispersions are prepared using conventional methods, then particle concentration is increased, but aggregation and precipitation occur
Solution Approach 1:
The patent creates a composite structure where flat silver particles are coated with gold to form core-shell structures. This composite material approach prevents particle aggregation by providing steric and electrostatic stabilization from the gold coating and associated surfactants, enabling high-concentration stable dispersions
Solution Approach 2:
The patent changes surface chemical parameters by introducing thiol-containing compounds and gold coating, which modify surface charge and hydrophobicity. These parameter changes prevent particle aggregation and enable stable high-concentration dispersions that would otherwise precipitate
3Reliability
If silver particles are coated with gold to improve oxidative resistance, then oxidation protection is achieved, but non-uniform coating reduces effectiveness
Solution Approach 1:
The patent uses local quality modification through thiol-containing compounds that selectively bind to edge surfaces, creating zones of enhanced gold deposition. This ensures complete coverage including previously unprotected edge regions, achieving uniform protective coating throughout the particle structure
Solution Approach 2:
The thiol-containing compound serves as an intermediary that facilitates uniform gold distribution across all particle surfaces. It mediates the coating process by creating consistent surface conditions that promote even gold deposition, ensuring reliable oxidative protection
4Manufacturing precision
If galvanic replacement process is used for gold coating, then gold coating is achieved, but particle shape changes occur
Solution Approach 1:
The patent applies partial action by using controlled gold deposition that stops before complete galvanic replacement occurs. This partial coating approach maintains the original silver particle shape while adding protective gold layers, avoiding the excessive replacement that would alter particle morphology
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 ensures uniform gold coating, enhancing oxidative resistance and allowing for the production of high-concentration dispersions with improved productivity, resulting in a coating film and antireflection optical members with excellent durability.
Implementation Method 1
a gold coating solution with a complexing agent having a reduction potential of 0.5 V or lower
Implementation Method 2
the addition of an organic component with a high solubility product and low reduction potential
Data Source
AI summary
Provided are gold-coated flat silver particles, a dispersion including the gold-coated flat silver particles and a dispersion medium, a method of the dispersion, a coating film including the gold-coated flat silver particles, and an antireflection optical member. The gold-coated flat silver particles include flat silver particles and a gold coating layer, in which an average thickness of the gold coating layer on principal planes of the particles is 0.1 nm to 2 nm, and a ratio of the average thickness of the gold coating layer on the principal planes of the particles to an average thickness of the gold coating layer on edge surfaces of the particles is 0.02 or higher.