Silver Ink Composition for Fast-Cure Conductive Screen Printing
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Solution Overview
Problem
Conventional conductive inks face challenges in achieving high electric conductivity within a short baking time of 60 seconds while maintaining low material costs and ensuring appropriate screen printability, as they often result in agglomeration and reduced viscosity due to excessive surface coatings and low binder resin content.
Innovation Solution
A conductive ink composition using flake-shaped silver powder with a low tap density, a high molecular weight binder resin, and a controlled amount of oleic acid surfactant, along with a non-chlorine-based resin and suitable organic solvent, is formulated to achieve high viscosity and conductivity, allowing for screen printing and rapid drying at 150°C for 60 seconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional conductive inks use low molecular weight binder resin and high silver powder content to ensure screen printability, then printability is improved, but raw material cost increases and electric conductivity decreases due to oxidation
Solution Approach 1:
The patent changes the molecular weight parameter of the binder resin from low (conventional) to high (10,000 or more), which fundamentally alters the ink's rheological properties. This enables the formulation to achieve adequate viscosity and screen printability with reduced silver powder content (40-70 wt%), thereby reducing raw material cost while maintaining printability
Solution Approach 2:
The patent replaces expensive silver powder with a more cost-effective formulation by using high molecular weight binder resin as the primary viscosity-controlling component. This allows significant reduction in silver powder content while maintaining functional performance, effectively substituting expensive material with cheaper alternatives
2Reliability
If conductive metal powder surface is covered with long-chain fatty acids to suppress oxidation, then oxidation resistance is improved, but electric conductivity deteriorates due to formation of insulating oxide films
Solution Approach 1:
The patent extracts and removes the harmful long-chain fatty acid coatings from the silver powder surface through washing processes. By eliminating these coatings that cause oxidation and conductivity loss, the patent achieves both oxidation resistance and high electric conductivity without needing protective surfactants
Solution Approach 2:
The patent creates an inert environment by using high molecular weight binder resin to form a protective matrix that isolates silver powder particles from oxygen exposure. This physical barrier prevents oxidation without requiring chemical surfactants, maintaining both oxidation resistance and electrical conductivity
3Productivity
If Roll-to-Roll printing method is used to improve productivity, then production speed increases, but conventional inks require excessively long baking times that are incompatible with continuous production
Solution Approach 1:
The patent changes the thermal and rheological parameters of the ink formulation by using high molecular weight binder resin. This modification enables the ink to achieve adequate drying and adhesion properties with dramatically reduced baking time (60 seconds or less at 150°C), making it compatible with high-speed Roll-to-Roll continuous production processes
Solution Approach 2:
The high molecular weight binder resin performs preliminary binding and film-forming actions during the brief 60-second baking process, creating sufficient adhesion and structural integrity without requiring extended heating times. This preliminary action enables compatibility with rapid continuous production
4Quantity of substance
If silver powder content is increased to improve electric conductivity, then conductivity is improved, but viscosity decreases and screen printability deteriorates
Solution Approach 1:
The patent changes the molecular weight parameter of the binder resin to 10,000 or more, which fundamentally alters the viscosity characteristics of the formulation. This enables the system to maintain adequate viscosity and screen printability even with reduced silver powder content (40-70 wt%), reversing the conventional trade-off relationship
Solution Approach 2:
The patent creates a composite material system where high molecular weight binder resin and silver powder work synergistically. The unique molecular structure of the high molecular weight resin provides enhanced viscosity and binding properties that compensate for reduced silver content, achieving both good printability and high conductivity simultaneously
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 composition achieves high electric conductivity of 20 µΩ·cm or less with low raw material costs and maintains excellent screen printability, suitable for forming printed films on non-heat-resistant substrates like PET films.
Implementation Method 1
the organic solvent (C), which has a flash point of 75 to 110°C and is contained in an amount of 25 to 50% by weight with respect to the total ink composition
Implementation Method 2
a conductive metal particle (A) having an oleic acid surfactant
Implementation Method 3
a non-chlorine-based resin composition (B), and an organic solvent (C), wherein the conductive metal particle (A) is contained in an amount of 45 to 70% by weight with respect to the total ink composition, the non-chlorine-based resin composition (B) has a number average molecular weight of 50,000 or more and is contained in an amount of 5 to 15% by weight with respect to the total ink composition
Data Source
AI summary
Provided are: a low-cost and highly conductive silver ink composition; and a method for producing wiring using the silver ink composition. A conductive ink composition for screen printing contains a conductive metal particle (A) having an oleic acid surfactant, a non-chlorine-based resin composition (B), and an organic solvent (C), wherein the conductive metal particle (A) is contained in an amount of 45 to 70% by weight with respect to the total ink composition, the non-chlorine-based resin composition (B) has a number average molecular weight of 50,000 or more and is contained in an amount of 5 to 15% by weight with respect to the total ink composition, the organic solvent (C) has a flash point of 75 to 110°C and is contained in an amount of 25 to 50% by weight with respect to the total ink composition, and the ink composition has an ink viscosity of 10 to 25 Pa·s (23°C) at a shear rate of 100 s-1. A method for producing wiring uses the ink composition.