Aqueous Ink-Receptive Layer for Flexible Packaging
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Solution Overview
Problem
Aqueous pigment-based inks used in high-speed digital inkjet printing on plastic substrates face issues with adhesion and drying due to humectants, leading to defects like mottle, coalescence, and intercolor bleeding, and result in poor lamination bond strength in flexible packaging materials.
Innovation Solution
A method involving an aqueous-based ink-receptive layer with water-soluble salts of multivalent metal cations, polyvinyl alcohol or polyvinyl amine, and optional crosslinking agents and silica particles, combined with aqueous pigment-based inks containing anionically-stabilized pigment colorants and specific humectants, is used to improve adhesion and drying, eliminating the need for separate tie-layers and enhancing lamination bond strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If aqueous pigment-based inks with humectants are used for high-speed digital inkjet printing on plastic substrates, then printing speed and productivity are improved, but adhesion and drying performance deteriorate, causing defects like mottle, coalescence, and intercolor bleeding
Solution Approach 1:
The patent introduces a polymeric overcoat composition as an intermediary layer between the aqueous pigment-based ink and the plastic substrate. This overcoat acts as a mediator that facilitates proper ink adhesion and drying while maintaining the benefits of aqueous-based printing. The polymer matrix in the overcoat provides a suitable environment for pigment fixation, preventing defects like mottle and coalescence that occur with direct printing on plastic substrates.
Solution Approach 2:
The invention creates a composite structure consisting of the plastic substrate, the aqueous pigment-based ink layer, and the polymeric overcoat layer. This multi-layer composite material system combines the advantages of each component: the plastic substrate provides water impermeability and durability, the aqueous ink provides environmental friendliness and cost-effectiveness, and the polymeric overcoat provides adhesion enhancement and defect prevention. The composite structure resolves the contradiction between printing speed and print quality.
2Object-affected harmful factors
If aqueous pigment-based inks are used on water-impermeable plastic substrates, then health, safety, and environmental concerns are reduced compared to solvent-based inks, but adhesion and drying performance worsen due to ink beading and flowing
Solution Approach 1:
The polymeric overcoat composition serves as an intermediary layer that bridges the incompatible interfaces between aqueous-based ink and water-impermeable plastic substrate. This overcoat has properties that are compatible with both materials, enabling proper adhesion without requiring the use of harmful solvent-based inks. The polymer matrix provides a controlled environment for pigment deposition and fixation, ensuring reliable adhesion while maintaining the safety advantages of aqueous-based printing.
3Stability of the object's composition
If humectants are added to aqueous pigment-based inks to maintain stability during printing, then jet formation stability is improved, but drying performance worsens, resulting in sticky or tacky printed layers
Solution Approach 1:
The polymeric overcoat acts as an intermediary that facilitates controlled drying of the ink layer. It allows the humectants to perform their stabilizing function during printing while providing a pathway for subsequent drying. The overcoat's polymer matrix enables gradual moisture evacuation, preventing the sticky or tacky appearance that occurs when humectants slow down drying too much. This resolves the contradiction by decoupling the stabilizing function from the drying function.
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 enhances the adhesion of aqueous-based ink-receptive layers to water-impermeable substrates, improves lamination bond strength, and maintains stable jet formation, reducing printhead maintenance issues while producing high-quality, flexible inkjet-printed articles.
Implementation Method 1
aqueous-based ink-receptive layer disposed thereon
Implementation Method 2
improves adhesion and drying
Implementation Method 3
water-soluble salts of multivalent metal cations
Implementation Method 4
enhances adhesion
Implementation Method 5
polyvinyl alcohol or polyvinyl amine, and optional crosslinking agents
Implementation Method 6
optional crosslinking agents
Data Source
AI summary
A flexible inkjet-printed article is prepared by: A′) providing an ink receptive medium having a substrate and an aqueous-based ink-receptive layer. This layer has: (a) a water-soluble salt of a multivalent metal cation; (b) one or both of a polyvinyl alcohol and a polyvinyl amine (or a copolymer derived from a vinyl alcohol and a vinyl amine) at 0.5-30 weight %; and optionally, (c) a crosslinking agent and (d) silica particles. At least one aqueous pigment-based ink is deposited directly on the aqueous-based ink-receptive layer, each having: a) an anionically-stabilized pigment colorant; and b) a water-miscible humectant at 1-20 weight %, each having a carbon to oxygen atom ratio of ≥1.0:1.0 and only two hydroxy groups. After drying, a functional layer with adhesive composition is formed on the inkjet-printed image and a flexible material is laminated to the functional layer, to form a flexible inkjet printed article.