UV-Curable Solid Ink Composition for Low-Temperature Inkjet Printing
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Solution Overview
Problem
Conventional solid inks used in inkjet printing face challenges such as high temperature requirements, thermal degradation of dyes, poor image quality, smear resistance issues, and energy inefficiency, particularly in direct-to-paper applications, where they require high printhead temperatures and intermediate transfer drums, leading to limitations in robustness and substrate compatibility.
Innovation Solution
A radiation-curable solid ink composition comprising curable wax, monomers, non-curable wax, and photoinitiators that form a solid at room temperature and a liquid at elevated temperatures, allowing for jetting at lower temperatures, improved smear resistance, and enhanced hardness, without the need for post-fusing steps, using a combination of curable waxes, monomers, and photoinitiators that are free-radically polymerizable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If crystalline-wax based solid inks are used in conventional inkjet printing, then vivid color images can be achieved, but the printhead must be kept at high temperatures (120-140°C) which causes thermal degradation of dyes, dye diffusion, and poor image quality
Solution Approach 1:
The patent changes the chemical composition parameters of the solid ink by incorporating UV-curable components (acrylate-functionalized waxes, monomers, oligomers, and photoinitiators) alongside conventional wax components. This compositional parameter change enables the ink to cure via UV radiation rather than relying solely on thermal solidification, thereby reducing the printhead operating temperature and preventing thermal degradation of dyes and substrates
Solution Approach 2:
The patent substitutes the thermal curing mechanism with a photopolymerization mechanism. Instead of relying on high temperature to melt and solidify the ink, the invention uses UV radiation to initiate free-radical polymerization of the curable components, replacing the thermal field with an optical field to achieve ink solidification and image formation
2Productivity
If high temperatures are used for jetting solid inks, then the ink viscosity decreases for efficient jetting, but the dyes become susceptible to thermal degradation and diffusion leading to poor image quality and showthrough
Solution Approach 1:
The patent modifies the viscosity-temperature relationship by incorporating UV-curable components that allow the ink to be jetted at lower temperatures. The acrylate-functionalized waxes and monomers maintain adequate fluidity at reduced temperatures while the photoinitiator system enables subsequent curing, changing the operational temperature parameter from 120-140°C to a lower range that prevents thermal degradation
Solution Approach 2:
The patent applies preliminary UV irradiation to the printed image immediately after jetting, before thermal degradation can occur. The photoinitiator absorbs UV radiation and initiates polymerization of the curable components, locking the ink in place and preventing dye diffusion and degradation that would otherwise occur at elevated temperatures
3Device complexity
If conventional solid inks are used for direct-to-paper printing, then an intermediate transfer drum is required, but this increases device complexity and energy consumption
Solution Approach 1:
The patent removes the intermediate transfer drum from the printing system by enabling direct-to-substrate jetting. The UV-curable solid ink formulation allows the printhead to jet ink directly onto the final substrate without requiring a separate transfer medium, extracting and eliminating the unnecessary transfer drum component and its associated heating and mechanical systems
Solution Approach 2:
The patent introduces UV radiation as the intermediary mechanism for ink solidification and image fixation. Instead of using thermal transfer through an intermediate drum, the UV-curable components are activated by UV radiation that acts as a mediator to cure the ink directly on the substrate, enabling a simplified direct printing process
4Reliability
If crystalline-wax inks are used, then the ink solidifies on the transfer member, but the robustness (smear resistance) of the ink is insufficient for many applications
Solution Approach 1:
The patent creates a composite ink formulation combining conventional wax components (paraffin, microcrystalline wax, ester wax) with UV-curable components (acrylate-functionalized waxes, monomers, oligomers, photoinitiators). This composite structure provides both the solidification properties of wax and the crosslinked network formation of polymerized acrylates, resulting in enhanced hardness, toughness, and smear resistance that neither component alone could achieve
Solution Approach 2:
The patent changes the physical and chemical parameters of the ink by incorporating reactive wax and curable components that undergo polymerization. The resulting crosslinked polymer network fundamentally changes the mechanical properties of the cured ink, increasing hardness, elasticity, and resistance to smearing and abrasion compared to conventional non-reactive wax inks
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 solution enables inkjet printing at lower temperatures with improved robustness, reduced shrinkage, and enhanced hardness, providing superior print quality and adaptability to various substrates while minimizing environmental and health hazards, and eliminating the need for intermediate transfer drums and high-pressure fixing.
Implementation Method 1
at least one free-radical photoinitiator or photoinitiating moiety; curable by free radical polymerization; exposing the imagewise pattern on the final recording substrate to ultraviolet radiation
Data Source
AI summary
A radiation curable solid ink composition comprising at least one curable wax that is curable by free radical polymerization; at least one monomer, oligomer, or prepolymer; at least one non-curable wax; at least one free-radical photoinitiator or photoinitiating moiety; and a colorant; wherein the components form a curable ink composition that is a solid at a first temperature of from about 20 to about 25° C.; and wherein the components form a liquid composition at a second temperature of greater than about 40° C.