Screen Printing Composition for Fast Drying and Uniform Conductive Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing screen printing compositions for printed electronics face challenges in achieving rapid drying, uniform dispersion of functional fillers, and optimal rheological properties, which are crucial for high-quality printed patterns and adhesion to substrates.
Innovation Solution
A screen printing composition comprising a specifically selected polymer vehicle and functional filler, such as silver flakes or a mixture of flake graphite with conductive carbon black, combined with a surfactant-treated filler and optimized milling process, results in fast-drying, uniformly dispersed layers with favorable electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If low-boiling solvents are used for rapid drying, then drying time is reduced, but rheological properties and adhesion deteriorate
Solution Approach 1:
The patent changes the chemical parameters of the binder by using a polymer graft copolymer with specific functional groups that enhance adhesion performance. This allows the formulation to maintain strong adhesion even with low-boiling solvents that enable rapid drying, thus resolving the contradiction between drying speed and adhesion quality
Solution Approach 2:
The patent employs a composite binder system consisting of polymer graft copolymer combined with specific additives that work synergistically. This composite approach allows the formulation to achieve both rapid drying through low-boiling solvents and maintained adhesion through the specialized polymer structure and additive interactions
2Loss of time
If low-boiling solvents are used for rapid drying, then drying time is reduced, but shear-thinning properties deteriorate
Solution Approach 1:
The patent modifies the rheological parameters by selecting a polymer graft copolymer with specific molecular weight and branch architecture that provides inherent shear-thinning behavior. This allows the composition to maintain proper flow characteristics during screen printing even when using low-boiling solvents for fast drying
Solution Approach 2:
The patent introduces specific additives as intermediaries that mediate between the low-boiling solvents and the polymer matrix. These additives help maintain the shear-thinning rheological profile by facilitating proper polymer-solvent interactions, ensuring printability is preserved despite rapid evaporation
3Stability of the object's composition
If functional filler is dispersed in organic vehicle, then uniform composition is achieved, but dispersion uniformity deteriorates
Solution Approach 1:
The patent uses surfactants and dispersing agents as intermediaries between the functional filler particles and the organic vehicle. These intermediaries reduce interfacial tension and prevent particle aggregation, enabling uniform dispersion of conductive or resistive fillers throughout the paste composition
Solution Approach 2:
The patent applies preliminary surface treatment to the functional filler particles before incorporating them into the organic vehicle. This pre-treatment with coupling agents or surface modifiers ensures better compatibility and uniform distribution within the paste, preventing clumping and achieving consistent electrical properties
4Reliability
If polymer content is increased for adhesion, then adhesion is improved, but drying time increases
Solution Approach 1:
The patent changes the quality parameters of the binder by using a polymer graft copolymer with optimized molecular weight, branch density, and functional group composition. This allows achieving maximum adhesion with minimal polymer content, thus reducing the time required for the organic vehicle to evaporate while maintaining strong substrate bonding
Solution Approach 2:
The patent employs low-boiling solvents that evaporate rapidly as the primary vehicle component, replacing traditional high-boiling organic vehicles. This approach uses the rapid evaporation of the solvent phase to achieve fast drying, while the polymer graft copolymer provides sufficient adhesion at reduced concentrations
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 composition allows for rapid drying of less than 15 seconds, uniform layer formation on rigid and flexible substrates, and achieves low sheet resistance and high reproducibility, with silver-based layers below 0.5 Ω/□ and carbon-based layers below 118 Ω/□, suitable for continuous printing on large areas.
Implementation Method 1
Due to the use of a low-boiling vehicle, the printed resistive and conductive layers dry in less than 15 seconds through flash evaporation.
Implementation Method 2
Dispersion is preferably carried out using a high-shear mixer with rotational speed gradually increasing to 14 000 rpm.
Implementation Method 3
The vehicle, acting as the binder matrix, plays a crucial role in screen printing compositions. It provides the rheological properties required for screen printing, including shear-thinning behavior, appropriate thixotropy, and viscosity adapted to the printing technique and screens used
Implementation Method 4
The vehicle, acting as the binder matrix, plays a crucial role in screen printing compositions. It provides the rheological properties required for screen printing, including shear-thinning behavior, appropriate thixotropy, and viscosity adapted to the printing technique and screens used
Implementation Method 5
The vehicle also influences adhesion of the printed structures to the substrate; the type and quantity of the vehicle largely determine adhesion.
Data Source
AI summary
A screen printing composition that includes a vehicle and a functional filler. The functional filler is selected from: (i) silver flakes or (ii) a mixture of flake graphite with conductive carbon black. The vehicle contains at least one solvent, present in an amount of 89-95 wt % of the vehicle, selected from α-terpineol, butyl diglycol acetate (BDGA), dibutyl phthalate (DBP), ethanol, and ethylene glycol, together with at least one binder, present in an amount of 5-11 wt % of the vehicle, selected from polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polyurethane (PU), styrene-butadiene-styrene (SBS), and ethyl cellulose (EC).