Metal Particle Ink Composition for Room-Temperature Conductive Sintering
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Solution Overview
Problem
Existing metal fine particle inks fail to achieve high electrical conductivity and ordinary-temperature sintering properties when forming a metal coating film on non-liquid absorbing printing substrates.
Innovation Solution
A metal fine particle-containing ink with specific compositions of polymer dispersant, low-molecular weight carboxylic acid, and aqueous solvent, where the boiling points and acid dissociation exponents satisfy certain relationships, allowing the ink to form a coating film that sinter at ordinary temperatures and exhibit high conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal fine particle inks are used, then metallic luster is achieved, but electrical conductivity and ordinary-temperature sintering properties are insufficient
Solution Approach 1:
The invention changes the chemical composition parameters of the ink by introducing a specific low-molecular weight carboxylic acid with controlled boiling point (higher than aqueous solvent) and pKa value (lower than polymer dispersant). This parameter change enables the metal fine particles to sinter at ordinary temperatures while achieving high electrical conductivity, resolving the contradiction between conductivity and sintering temperature.
Solution Approach 2:
The invention creates a composite ink system combining metal fine particles, polymer dispersant, low-molecular weight carboxylic acid, and aqueous solvent. The low-molecular weight carboxylic acid acts as a sintering aid that facilitates particle bonding at low temperatures, enabling both high conductivity and ordinary-temperature processing in the composite material system.
2Temperature
If the ink is designed for ordinary-temperature sintering, then sintering properties improve, but ejection stability and dispersion stability deteriorate
Solution Approach 1:
The invention carefully controls the pKa parameter of the low-molecular weight carboxylic acid to be lower than that of the polymer dispersant, and the boiling point to be higher than the aqueous solvent. These parameter constraints ensure that the carboxylic acid remains soluble and does not cause precipitation during storage and ejection, maintaining dispersion stability while enabling ordinary-temperature sintering.
Solution Approach 2:
The low-molecular weight carboxylic acid performs different functions at different stages: during storage and ejection, it maintains dispersion stability through its solubility characteristics; during sintering, it facilitates particle bonding. This local quality differentiation resolves the contradiction between sintering temperature and dispersion stability.
3Temperature
If low-molecular weight carboxylic acid is added to enable ordinary-temperature sintering, then sintering properties improve, but ink composition complexity increases
Solution Approach 1:
The low-molecular weight carboxylic acid serves multiple functions simultaneously: it acts as a dispersing agent for metal fine particles, a sintering aid for low-temperature bonding, and a solubility controller through its pKa relationship with the polymer dispersant. This multi-functionality reduces the need for separate additives, thereby limiting the increase in composition complexity while achieving ordinary-temperature sintering.
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 ink enables the formation of a metal coating film with excellent ordinary-temperature sintering properties and high electrical conductivity on non-liquid absorbing substrates, maintaining ejection stability and dispersion stability.
Implementation Method 1
a polymer dispersant B, a low-molecular weight carboxylic acid C and an aqueous solvent D... the polymer dispersant B contains a constitutional unit derived from an acid group-containing monomer (b-1)... an acid dissociation exponent pKa (C) of the low-molecular weight carboxylic acid C and an acid dissociation exponent pKa (B) of an acid group in the polymer dispersant B satisfy the following relational formula (II)
Implementation Method 2
a boiling point (C) of the low-molecular weight carboxylic acid C and a boiling point (D) of the aqueous solvent D satisfy the following relational formula (I)
Data Source
AI summary
The present invention relates to a metal fine particle-containing ink that contains metal fine particles (a) dispersed therein with a polymer dispersant B, a low-molecular weight carboxylic acid C and an aqueous solvent D, in which the polymer dispersant B contains a constitutional unit derived from an acid group-containing monomer (b-1); a content of the low-molecular weight carboxylic acid C in the ink is not less than 1% by mass and not more than 15% by mass; a boiling point (C) of the low-molecular weight carboxylic acid C and a boiling point (D) of the aqueous solvent D satisfy the following relational formula (I); and an acid dissociation exponent pKa (C) of the low-molecular weight carboxylic acid C and an acid dissociation exponent pKa (B) of an acid group in the polymer dispersant B satisfy the following relational formula (II), boiling point (C) > boiling point (D) (I), and pKa (C) < pKa (B) (II).