Binder-less Electrostatic Ink for Non-absorbent Printing
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Solution Overview
Problem
Traditional printing techniques require complex processes to dry or fix each color separation on non-absorbent substrates, leading to issues like smudging, nozzle blocking, and incompatibility with food safety requirements, while existing digital methods struggle to produce high-quality images due to the use of solvent or water-based inks with soluble dyes.
Innovation Solution
A non-contact electrostatic printing process using binder-less inks with high pigment concentration, where all ink compositions are deposited before fixing, utilizing an electrostatic printhead to concentrate and eject chargeable marking particles, and a varnish is applied and cured to fix the image, allowing for independent decoration and fixing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional analogue printing techniques are used on non-absorbent substrates, then permanent impression can be formed, but complex drying or fixing processes are required between color separations to prevent smudging
Solution Approach 1:
The invention separates the decoration process (ink deposition) from the fixing process (varnish application and curing). All color separations are deposited first, then the varnish is applied and cured to fix the entire image. This segmentation eliminates the need for intermediate drying or fixing steps between colors, reducing process complexity while maintaining image stability.
Solution Approach 2:
The invention applies all ink compositions (color separations) to the substrate before applying the varnish fixative. This preliminary deposition of all colors followed by a single fixing step eliminates the need for intermediate fixing operations, simplifying the overall printing process while ensuring reliable image formation.
2Adaptability or versatility
If solvent or water-based inks with soluble dyes are used in CIJ and TIJ printers, then printing can be performed on non-absorbent substrates, but high quality images cannot be formed due to ink flow and smudging
Solution Approach 1:
The invention changes the physical parameters of the ink formulation by using binder-less ink compositions with high pigment concentration (6-40% by weight) dispersed in insulating carrier liquids. This parameter change increases ink viscosity and reduces flow, preventing smudging on non-absorbent substrates while maintaining substrate compatibility. The electrostatic ejection process further controls droplet placement precision.
Solution Approach 2:
The invention replaces thermal or piezoelectric ejection mechanisms with an electrostatic ejection system that uses applied electric fields to concentrate and eject chargeable marking particles. This substitution provides better control over droplet ejection, improving image quality while maintaining the ability to print on non-absorbent substrates.
3Ease of manufacture
If binder-based ink compositions are used in ink jet operations, then ink can be deposited on substrates, but nozzle blocking occurs and pigment concentration is limited
Solution Approach 1:
The invention extracts and removes the binder component from the ink composition, using only pigment particles (6-40% by weight) dispersed in insulating carrier liquid. This extraction eliminates the viscosity and flow characteristics that cause nozzle blocking, allowing higher pigment concentrations and faster print speeds while maintaining reliable ink deposition through electrostatic ejection.
4Reliability
If thermally cured electrophotographic imaging is used, then image fixing can be achieved, but required levels of adhesion cannot be met
Solution Approach 1:
The invention introduces a varnish as an intermediary fixative layer that is applied over the deposited ink compositions. This varnish acts as a mediator that provides strong adhesion to the substrate while securing the pigment particles. The varnish can be cured by various methods (thermal, UV, electron beam) to create a durable, adherent image that exceeds the performance of direct thermal curing methods.
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
This approach simplifies the printing process, enables high-quality image formation on non-absorbent surfaces, reduces wastage, and meets food safety requirements by separating the decoration and fixing processes, resulting in improved adhesion, durability, and reduced solvent usage, while allowing for faster print speeds and uniform finishes.
Implementation Method 1
an electrostatic printhead, which ejects chargeable marking particles dispersed in a carrier fluid by using an applied electric field to first concentrate and then eject the marking particles
Implementation Method 2
fixing the image on the substrate, wherein the fixing is by coating the ink compositions with a varnish, and then curing the varnish
Data Source
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AI summary
A process for forming an image on a substrate, comprises depositing ink compositions of at least two colours onto the substrate to form the image, and fixing the image to the substrate, wherein the ink is deposited using an electrostatic printhead, which ejects chargeable marking particles dispersed in a carrier fluid by using an applied electric field to first concentrate and then eject the marking particles, and wherein all of the ink compositions are deposited onto the substrate before the image is fixed. An ink composition suitable for use in the invention comprises: 45 - 95% by weight of a carrier liquid; 6 - 40% by weight of insoluble chargeable marking particles; and 0.4 - 10% by weight of a soluble dispersant, characterised in that the ink does not contain an agent that can fix the marking particles to a substrate.