Radiation-Curable Ink Surface Tension Control
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Solution Overview
Problem
Radiation-curable ink jet printing methods using inks with higher surface tension after applying those with lower surface tension fail to produce high-quality images with satisfactory color reproduction gamut, especially when using radiation-curable inks.
Innovation Solution
A radiation-curable ink jet ink set comprising a dark-colored ink and a light-colored ink, where the dark-colored ink has a higher surface tension than the light-colored ink, and both contain specific polymerizable compounds and polymerization initiators, such as acylphosphine oxide-based compounds, to enhance curability and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a radiation-curable light-colored ink with lower surface tension is applied after a radiation-curable dark-colored ink with higher surface tension, then color reproduction is improved, but ink filling in low-density regions becomes insufficient
Solution Approach 1:
The patent applies parameter changes by carefully controlling the surface tension values of radiation-curable inks. Specifically, it uses a dark-colored ink with surface tension of 28-35 mN/m and a light-colored ink with surface tension of 20-30 mN/m, ensuring the dark ink has higher surface tension than the light ink. This parameter control enables the dark ink to be applied first without preventing subsequent light ink application, while maintaining adequate ink filling in low-density regions and achieving satisfactory color reproduction.
2Productivity
If radiation-curable inks with conventional surface tension values are used, then printing speed is maintained, but image quality with satisfactory color gamut and filling is not achieved
Solution Approach 1:
The patent changes the surface tension parameters of radiation-curable inks from conventional values to optimized ranges. The dark-colored ink uses surface tension of 28-35 mN/m and light-colored ink uses 20-30 mN/m, with the dark ink always having higher surface tension. This parameter optimization enables both high printing speed and high image quality with satisfactory color gamut and ink filling to be achieved simultaneously.
Solution Approach 2:
The patent employs composite ink formulations containing multiple components including polymerizable compounds (acrylates, vinyl ethers), polymerization initiators (acylphosphine oxide-based compounds), and coloring materials. These composite radiation-curable ink compositions are designed with specific surface tension characteristics to achieve both high printing speed and high image quality, resolving the contradiction between productivity and manufacturing precision.
3Manufacturing precision
If multiple layers of radiation-curable ink are applied to achieve wide color gamut, then color reproduction improves, but droplet interaction increases degrading quality
Solution Approach 1:
The patent controls the surface tension parameter to minimize droplet interaction while enabling multiple ink layers. By setting the dark-colored ink surface tension (28-35 mN/m) higher than the light-colored ink (20-30 mN/m), the patent ensures proper wetting and spreading characteristics that prevent harmful droplet interaction. This enables application of multiple ink layers to achieve wide color gamut without degrading image quality from droplet interaction.
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 set produces images with improved color reproduction in high-duty regions and adequate filling in low-density regions, achieving a wide color gamut and high image quality through controlled surface tensions and UV irradiation.
Implementation Method 1
a radiation-curable dark-colored ink having a surface tension γ1 and a radiation-curable light-colored ink having a surface tension γ2. The surface tensions of the radiation-curable inks satisfy γ1>γ2
Implementation Method 2
a third UV irradiation step of irradiating at least one of the dark-colored and the light-colored ink on the printing medium with UV light. In the irradiation steps, the UV light is emitted from a UV light-emitting diode at 50.0 mJ/cm2 or more for every scanning of the printing apparatus
Data Source
AI summary
A radiation-curable ink jet ink set includes a radiation-curable dark-colored ink having a surface tension γ1 and a radiation-curable light-colored ink having a surface tension γ2. The surface tensions of the radiation-curable inks satisfy γ1>γ2.