Metal Dispersion Liquid for High Specular Gloss and Stability
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Solution Overview
Problem
Metal dispersion liquids with tabular metal particles of high aspect ratio face challenges in achieving both excellent dispersion stability and specular glossiness, as they tend to aggregate due to strong van der Waals forces, leading to degradation in film quality and tint.
Innovation Solution
A metal dispersion liquid comprising tabular metal particles with an average aspect ratio greater than 20 and a specific ratio of smaller aspect ratio metal particles, along with a dispersant like gelatin, to enhance alignment and prevent aggregation, resulting in a film with improved specular glossiness and suppressed tint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If tabular metal particles with large aspect ratio are used to improve specular glossiness, then alignment properties are improved and light scattering on side surfaces is suppressed, but dispersion stability is degraded due to strong van der Waals forces causing aggregation
Solution Approach 1:
A polymer dispersant with specific molecular weight (10,000-1,000,000) and functional groups is introduced as an intermediary between tabular metal particles. The dispersant adsorbs onto particle surfaces through its functional groups, creating steric hindrance that counteracts the strong van der Waals forces, thereby preventing aggregation while maintaining the high aspect ratio particles' alignment properties and glossiness-enhancing characteristics
Solution Approach 2:
The molecular weight of the polymer dispersant is optimized within a specific range (10,000-1,000,000) to balance steric stabilization effectiveness with solution viscosity. This parameter optimization ensures sufficient stabilization of high aspect ratio particles without excessive viscosity that would hinder processing, resolving the contradiction between particle stability and processability
2Use of energy by moving object
If metal particles with particle size less than or equal to visible light wavelength are used, then plasmon resonance occurs and light absorption at specific wavelengths is enhanced, but the film becomes tinted due to this selective absorption
Solution Approach 1:
The invention uses composite metal particles consisting of a core shell structure where a metal core (plasmon resonant material) is coated with a dielectric or semiconductor shell. This composite structure maintains the plasmon resonance of the metal core for efficient light absorption while the shell layer modifies the optical properties to reduce selective wavelength absorption in the visible range, thereby suppressing film tint while preserving light absorption efficiency
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 provides a metal dispersion liquid with enhanced dispersion stability and the ability to form films with high specular glossiness and suppressed tint, addressing the aggregation issues and optical properties of previous formulations.
Implementation Method 1
scattering of light on a side surface (that is, a surface other than two main planes) of each tabular metal particle is suppressed
Implementation Method 2
In the metal particles having a particle size less than or equal to the wavelength in a visible range, plasmon resonance occurs. Therefore, in the metal dispersion liquid containing metal particles, the metal particles absorb light having a specific wavelength in a visible range due to the plasma resonance
Implementation Method 3
Since the metal particles having a large equivalent circle diameter have a large surface area and a strong van der Waals force, the metal particles tend to easily aggregate
Data Source
AI summary
Provided are a metal dispersion liquid which includes tabular metal particles A having an average aspect ratio of greater than 20, which is a ratio of an average equivalent circle diameter to an average thickness, and an average equivalent circle diameter of 50 nm to 1000 nm, metal particles B having an average aspect ratio of 1 to 15 and an average equivalent circle diameter of 1 nm to 150 nm, and water, in which an average equivalent circle diameter A1 of the tabular metal particles A and an average equivalent circle diameter B1 of the metal particles B satisfy Expression (1), and a content a of the tabular metal particles A and a content b of the metal particles B with respect to a total mass of the metal dispersion liquid satisfy Expression (2); and an application thereof.A1>B1 Expression (1)0.0001≤b/(a+b)≤0.3 Expression (2)