UV-Curable Ink Composition for Metallic Gloss and Uniform Curing
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Solution Overview
Problem
Active energy ray curable ink compositions containing brilliant pigments face issues with deteriorating curability due to the reflective properties of these pigments, and increasing the content of polymerization initiators does not adequately improve metallic gloss.
Innovation Solution
An ink composition containing multiple types of polymerization initiators, including acylphosphine oxide, aminoacetophenone, and thioxanthone-based initiators, along with a specific content of brilliant pigments, is used to enhance curability while maintaining metallic gloss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of polymerization initiator is increased to improve curability, then curability is improved, but metallic gloss deteriorates
Solution Approach 1:
The patent divides the polymerization initiator system into multiple components with different absorption characteristics. By using a combination of initiators (e.g., Type I with peak absorption at 380nm and Type II with peak absorption at 480nm), the system achieves comprehensive UV-curing coverage without requiring excessive initiator concentration, thereby maintaining metallic gloss while ensuring curability.
Solution Approach 2:
The patent optimizes the absorption wavelength parameters of polymerization initiators to match the UV irradiation source characteristics. By selecting initiators with specific peak absorption wavelengths (e.g., 380nm and 480nm) that correspond to the emission spectrum of the UV-LED or UV-fluorescent lamp, the system achieves efficient curing with minimal initiator content, preserving the metallic appearance.
2Reliability
If a single broad-wavelength polymerization initiator is used to improve curability, then curability is improved, but curing uniformity deteriorates
Solution Approach 1:
The patent segments the UV absorption spectrum coverage by using multiple polymerization initiators with distinct peak absorption wavelengths. This segmentation allows different regions of the UV spectrum to be optimally absorbed, ensuring uniform energy distribution and consistent curing across the ink film without the non-uniformity associated with single broad-wavelength initiators.
3Ease of manufacture
If the amount of brilliant pigment is increased to enhance metallic gloss, then metallic gloss is improved, but curability deteriorates
Solution Approach 1:
The patent changes the spectral parameters of the polymerization initiators to ensure their absorption peaks align with the UV irradiation source emission spectrum. This parameter optimization enables efficient photopolymerization even in the presence of high concentrations of brilliant pigments that reflect visible and UV light, as the initiators effectively capture the specific UV wavelengths that penetrate the ink film.
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 composition achieves improved curability and maintains good metallic gloss, reducing curing unevenness and shrinkage, and enhances the overall quality of the printed matter.
Implementation Method 1
active energy ray curable ink composition... containing a polymerizable compound and a brilliant pigment... by being irradiated with active energy rays... includes an acylphosphine oxide-based polymerization initiator, an aminoacetophenone-based polymerization initiator, and a thioxanthone-based polymerization initiator
Implementation Method 2
brilliant pigments have properties of reflecting visible light and ultraviolet light
Data Source
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AI summary
Provided is an active energy ray curable ink composition capable of improving curability while maintaining excellent metal-tone glossiness. The present invention also provides a printed matter having high design properties and excellent metal-tone glossiness. This active energy ray curable ink composition is to be discharged using an inkjet method. The ink composition contains a polymerization initiator, a polymerizable compound, and a brilliant pigment. The contained amount of the brilliant pigment is 1.5 mass% or more with respect to the total amount of the ink composition. The contained amount of the polymerization initiator is 10 mass% or more with respect to the total amount of the ink composition. The polymerization initiator contains an acylphosphine oxide-based polymerization initiator, an aminoacetophenone-based polymerization initiator, and a thioxanthone-based polymerization initiator. The printed matter is provided with a brilliant layer containing the brilliant pigment. When incident light is incident on the brilliant layer at an incidence angle of 45° with respect to the brilliant layer of the printed matter, and when the angle of specular reflection light in response to the incident light and the angle of a normal line with respect to the brilliant layer are defined as 0° and 45°, respectively, the total L1 of L* values regarding a reflection angle of -15° and a reflection angle of 15° in the L*a*b* color system is 200 or more, the total L2 of L* values regarding a reflection angle of 45°, a reflection angle of 75°, and a reflection angle of 110° in the L*a*b* color system is 100 or more, and L1-L2 equals 90 or more.