White Inkjet Inks Using Core-Shell Polystyrene-Titania Particles
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Solution Overview
Problem
White pigment particles, such as TiO2 and SiO2, are difficult to disperse in aqueous ink vehicles due to their high density, leading to settling issues and clogging in inkjet printheads, particularly in non-white media printing, where conventional solid pigment particles are challenging to handle.
Innovation Solution
The development of core-shell particles with a polystyrene core and a titania shell, coated with polyvinylpyrrolidone, which form stable and buoyant dispersions, offering improved opacity and stability in aqueous-based inkjet inks, and utilizing a combination of nonionic acetylenic and siloxane-based surfactants for enhanced image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solid pigment particles (TiO2, SiO2) are used in aqueous ink vehicles, then white pigment can be provided for printing onto non-white media, but the pigment particles are difficult to disperse and are prone to settling and clogging nozzles
Solution Approach 1:
The patent uses core-shell structure particles combining polystyrene core with titania shell, creating a composite material that leverages the low density of polystyrene for buoyancy and the high opacity of titania for white pigment functionality, resolving the contradiction between dispersibility and opacity
Solution Approach 2:
The patent changes the density parameter of the pigment particles by using hollow microspheres instead of solid particles, and optimizes particle size parameters (200-250 nm for titania, 100-1000 nm for polymer) to achieve both stability and dispersibility
2Ease of operation
If hollow microspheres of titania with particle size of 100 to 300 nm are used, then dispersibility is improved, but opacity is reduced compared to larger particles
Solution Approach 1:
The patent creates a composite particle system combining titania hollow spheres with polymer particles, where the polymer acts as an optical spacer to enhance light scattering and opacity while the titania provides the white pigment effect, achieving both dispersibility and high opacity
Solution Approach 2:
The patent introduces polymer particles as an intermediary between the titania particles and the ink vehicle, where the polymer serves as both a dispersing agent and an optical spacer that enhances light scattering, thereby improving opacity without sacrificing dispersibility
3Illumination intensity
If larger titania particles (200 to 250 nm) are used to optimize opacity, then opacity is improved, but dispersibility and stability are reduced
Solution Approach 1:
The patent combines titania particles with polymer particles to create a composite system where the polymer component provides steric stabilization and prevents aggregation, allowing larger titania particles to maintain both opacity and dispersion stability
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 core-shell particles provide high opacity and stability in inkjet inks, outperforming hollow microspheres in terms of opacity and cost-effectiveness, with optimal particle sizes between 500 to 900 nm, and improved image quality through surfactant interactions, addressing the challenges of pigment dispersibility and settling in thermal inkjet printing.
Implementation Method 1
the intrinsic buoyancy of the low-density core-shell particles
Implementation Method 2
The relatively larger polymer particles serve as optical spacers, which assist in scattering reflected light backwards towards the light source, thereby increasing opacity
Implementation Method 3
utilizing a combination of nonionic acetylenic and siloxane-based surfactants for enhanced image quality
Data Source
AI summary
A white inkjet ink includes: an aqueous-based ink vehicle and white pigment particles dispersed in the ink vehicle. The pigment particles are core-shell particles having a core comprised of polystyrene and a shell comprised of titania. Stable formulations producing good image quality include a first nonionic acetylenic surfactant having an HLB value in the range of 7 to 9 and a second nonionic acetylenic surfactant having an HLB value in the range of 12 to 14.