UV-Curable Ink Composition for LED Curing and Adhesion
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Solution Overview
Problem
Active-energy-ray-curable inkjet recording inks face challenges with insufficient curing and adhesion when using LED lamps as a light source, particularly on non-porous materials like plastic films, and lack sufficient solvent resistance.
Innovation Solution
The ink composition uses a specific ratio of monofunctional and polyfunctional polymerizable compounds, including N-vinyl-2-caprolactam and isobornyl acrylate, along with a polymerizable compound having a vinyl ether group, to achieve effective curing and adhesion with LED lamps, while maintaining solvent resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive resins or reactive monomers are added to enhance adhesion on non-porous materials, then adhesion is improved, but viscosity increases which causes ejection instability and nozzle clogging
Solution Approach 1:
The patent changes the chemical composition parameters by introducing a silane-modified polymerizable compound with specific functional groups (acrylate/methacrylate and silane groups) that provides adhesion enhancement without significantly increasing viscosity. The compound's molecular structure allows it to maintain low viscosity while forming strong bonds with non-porous substrates through silane coupling mechanisms.
Solution Approach 2:
The patent uses a composite approach by combining the silane-modified polymerizable compound with other polymerizable compounds to create an ink composition that achieves both good adhesion and appropriate viscosity. The silane-modified compound acts as a coupling agent that bridges the gap between the ink formulation and the non-porous substrate, providing adhesion without requiring large amounts of traditional adhesive resins.
2Use of energy by moving object
If photopolymerization initiators absorbing 350-420 nm light are used with LED lamps, then curing is enabled, but pigment absorption at these wavelengths prevents sufficient curing
Solution Approach 1:
The patent changes the wavelength parameter of the curing light source from the conventional 350-420 nm range to a shorter wavelength range (200-350 nm, preferably 240-300 nm). This parameter change allows the photopolymerization initiator to be excited at wavelengths where pigments have lower absorption, enabling effective curing even in the presence of pigment particles in the ink composition.
Solution Approach 2:
Instead of trying to make the photopolymerization initiator absorb at wavelengths where pigments transmit (the conventional approach), the patent inverts the strategy by selecting a light source and initiator system that operates at shorter wavelengths where pigments are less absorptive. This inversion of the wavelength selection approach resolves the conflict between pigment presence and curing effectiveness.
3Power
If traditional high-pressure mercury lamps are used for curing, then sufficient energy is provided, but the equipment is complex and energy consumption is high
Solution Approach 1:
The patent replaces the complex mechanical and thermal system of high-pressure mercury lamps with a simpler solid-state LED-based light source. The LED system directly converts electrical energy to light at the required wavelength without needing complex ballast circuits, cooling systems, or high-voltage power supplies, thereby reducing device complexity while maintaining sufficient curing energy through the optimized wavelength match with the photopolymerization initiator.
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 composition ensures excellent adhesion and solvent resistance, even on non-porous materials, and maintains stability during storage, allowing for efficient curing with low light intensity and reduced viscosity, enhancing ejection stability and image durability.
Implementation Method 1
irradiating the image with an active energy ray having a peak wavelength ranging from 365 to 420 nm with an LED lamp to cure the image
Implementation Method 2
a photopolymerization initiator which can absorb light having a wavelength of around 350 to 420 nm
Data Source
AI summary
An active-energy-ray-curable inkjet recording ink composition is provided, in which a polymerizable compound having an active-energy-ray-polymerizable group and a polymerizable compound having at least two active-energy-ray-polymerizable groups are used in amounts of 60 to 95 mass% and 5 to 40 mass% relative to the total amount of the active-energy-ray-polymerizable compound, respectively; the polymerizable compound having an active-energy-ray-polymerizable group includes N-vinyl-2-caprolactam and isobornyl acrylate in amounts of 1 to 15 mass% and 1 to 25 mass% relative to the total amount of the active-energy-ray-polymerizable compound, respectively; and the polymerizable compound having at least two active-energy-ray-polymerizable groups includes a polymerizable compound having a vinyl ether group. Furthermore, a method for forming an image is provided.