Photocurable Ink Composition for LED Curing and PVC Adhesion
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Solution Overview
Problem
Photocurable ink compositions for inkjet printing face challenges in achieving superior curability with LED light, adhesion to polyvinyl chloride-based sheets, prevention of cockling, and maintaining a high flash point while having low viscosity, as well as ensuring safety and stretchability of the cured film.
Innovation Solution
A photocurable ink composition containing benzyl acrylate, an acrylated amine compound with two photopolymerizable functional groups, and a photopolymerization initiator, which maintains a flash point of 70°C or higher, inhibits cockling, and provides superior adhesion and stretchability, while being suitable for low viscosity and LED curability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a photocurable ink composition is designed to form a tough coating for outdoor durability, then the coating hardness increases, but the adhesion to polyvinyl chloride-based sheet deteriorates
Solution Approach 1:
The invention changes the chemical parameters of the ink composition by incorporating specific compounds (ethylenic double bond-containing compound that dissolves polyvinyl chloride, amino group-containing compound, and carboxylic acid group-containing compound) to modify the interaction between the coating and base material, achieving both toughness and adhesion simultaneously
Solution Approach 2:
The invention uses a composite formulation combining multiple functional components: photopolymerizable monomers/oligomers for film formation, specific dissolving compounds for adhesion, and crosslinking agents for toughness, creating a multi-functional ink composition that resolves the contradiction between hardness and adhesion
2Reliability
If an ethylenic double bond-containing compound that dissolves polyvinyl chloride is added to improve adhesion, then the adhesion to polyvinyl chloride-based sheet improves, but the susceptibility to cockling increases
Solution Approach 1:
The invention balances the concentration of the polyvinyl chloride-dissolving compound with other components (amino group-containing compound at 1-10 mass%, carboxylic acid group-containing compound at 1-10 mass%) to control the degree of base material interaction, preventing excessive dissolution that causes cockling while maintaining adequate adhesion
Solution Approach 2:
The invention creates different functional zones within the ink composition: compounds that interact with the base material for adhesion, compounds that form the coating matrix for structural integrity, and compounds that prevent wrinkling by controlling drying and curing characteristics
3Ease of operation
If the ink composition is designed to have low viscosity for good dischargeability, then the dischargeability from discharge head improves, but the flash point decreases compromising safety
Solution Approach 1:
The invention selects photopolymerizable compounds and additives with specific viscosity and flash point characteristics, using low-viscosity monomers combined with high-flash-point oligomers to achieve the desired balance between dischargeability (low viscosity) and safety (high flash point)
Solution Approach 2:
The invention creates a composite ink formulation where low-viscosity components (for dischargeability) are combined with high-flash-point components (for safety), achieving a synergistic effect where the mixture maintains both flow properties and fire safety
4Reliability
If a high-energy light source such as metal halide lamp is used for curing, then the curability of the photocurable ink improves, but the generation of ozone and the size of the radiation device increase
Solution Approach 1:
The invention replaces the mechanical/optical system of metal halide lamps with LED light sources, using solid-state semiconductor devices that emit light in the wavelength range effective for photopolymerization, eliminating the need for large, complex high-pressure discharge lamp systems
Solution Approach 2:
The invention adjusts the photopolymerizable compounds and photopolymerization initiators to match the emission spectrum of LED lights, optimizing the absorption characteristics and curing efficiency for LED wavelengths while reducing device size and eliminating ozone generation
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 enhanced curability with LED light, improved adhesion, reduced cockling, and increased safety, with a flash point that meets Category 4 flammability standards, ensuring both practical performance and safety in inkjet printing applications.
Implementation Method 1
a photopolymerization initiator; and a sensitizer, wherein benzyl acrylate, N-vinylcaprolactam and an acrylated amine compound having two photopolymerizable functional groups and two amino groups in a molecule thereof are contained as the photopolymerizable compound
Data Source
AI summary
A photocurable ink composition for inkjet printing is obtained that has superior curability with respect to light from a light-emitting diode, has favorable adhesion to a polyvinyl chloride-based sheet, and is able to adequately inhibit the occurrence of cockling. The photocurable ink composition for inkjet printing at least has: a photopolymerizable compound; a photopolymerization initiator; and a sensitizer, wherein benzyl acrylate, N-vinylcaprolactam and an acrylated amine compound having two photopolymerizable functional groups and two amino groups in a molecule thereof are contained as the photopolymerizable compound, the content of the benzyl acrylate is 20 to 65% by mass in the photocurable ink composition for inkjet printing, a compound exhibiting an initiator function when irradiated with light having a wavelength of 450 to 300 nm is contained as the photopolymerization initiator, a compound exhibiting a sensitizer function when irradiated with light having a wavelength of 400 nm or longer is contained as the sensitizer, and a flash point as measured using a SETA closed-cup flash point tester according to a method in compliance with JIS K2256 is 70°C or higher.