Inkjet Recording Method for Flexible Packaging
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Solution Overview
Problem
Conventional inkjet recording methods face challenges with adhesion, flexibility, and odor issues when printing on plastic substrates like polypropylene, polyethylene terephthalate, or nylon, particularly in flexible packaging, where cracking occurs and uncured monomers can leach out, posing a problem for food packaging applications.
Innovation Solution
An inkjet recording method involving an undercoating step with a semi-curing process followed by overall curing under low oxygen conditions, using an ink composition with a high percentage of polyfunctional ethylenically unsaturated compounds and polyalkylene glycol diacrylate, and specific polymers or oligomers like polyester, polyurethane, or chlorinated polyolefin structures, ensuring covalent bonding and improved flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV curable inkjet method is used, then adhesion to plastic substrates and high speed drying are improved, but uncured monomer remains causing odor and leaching issues
Solution Approach 1:
The patent changes the chemical composition parameters of the ink by using polyfunctional ethylenically unsaturated compounds (95-100 mass%) with specific functional groups instead of conventional monomers. This parameter change ensures complete curing reaction while maintaining adhesion properties, eliminating uncured monomer that causes odor and leaching.
Solution Approach 2:
The patent uses composite ink composition combining polyfunctional ethylenically unsaturated compounds with specific polymers/oligomers having polyester, polyurethane, or chlorinated polyolefin structures. This composite material approach achieves both complete curing (no odor/leaching) and excellent adhesion to plastic substrates.
2Productivity
If conventional UV curable ink is used, then high speed drying is achieved, but cracking occurs in the image area when crumpled
Solution Approach 1:
The patent changes the molecular structure parameters of the ink composition by using polyfunctional ethylenically unsaturated compounds with specific functional groups and combining them with flexible polymers/oligomers. This creates a cured film that maintains flexibility and elasticity while achieving rapid UV curing, preventing cracks during crumpling.
Solution Approach 2:
The patent creates a composite cured film structure where polyfunctional ethylenically unsaturated compounds form a crosslinked network combined with flexible polymer chains from polyester, polyurethane, or chlorinated polyolefin structures. This composite structure provides both rapid curing and flexibility to prevent cracking.
3Object-affected harmful factors
If aqueous inkjet method is used, then safety is improved, but adhesion to plastic substrates is difficult and drying time is long
Solution Approach 1:
The patent replaces the water-based drying mechanism (evaporation) with a UV photopolymerization mechanism. The ink composition uses polyfunctional ethylenically unsaturated compounds that undergo rapid crosslinking upon UV exposure, eliminating the need for long drying times while maintaining safety through water-free formulation.
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 method achieves good image adhesion, flexibility, and suppressed odor on polypropylene, polyethylene terephthalate, or nylon substrates, preventing cracking and reducing odor issues, making it suitable for flexible packaging, especially food packaging.
Implementation Method 1
an overall curing step of carrying out overall curing of the semi-cured undercoat solution and the ink composition by exposure under an atmosphere having an oxygen concentration of no greater than 1 vol% after the image formation
Data Source
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AI summary
An inkjet recording method that comprises an undercoating step of applying an undercoat solution onto a transparent recording medium, a semi-curing step of semi-curing the undercoat solution, an image formation step of carrying out image formation by discharging an ink composition onto the semi-cured undercoat solution, and an overall curing step of carrying out overall curing of the semi-cured undercoat solution and the ink composition by exposure under an low oxygen atmosphere after the image formation, the undercoat solution comprising two or more types of polymers and/or oligomers from among polymers and oligomers having a structure selected from the group consisting of a polyester structure, a polyurethane structure, and a chlorinated polyolefin structure, the ink composition comprising at least 95 parts of a polyfunctional ethylenically unsaturated compound relative to 100 parts of the total content of ethylenically unsaturated compound, and at least 5 parts of a polyalkylene glycol diacrylate, and exposure in the overall curing step being carried out from both the image formation face and the reverse face of the recording medium.