Primer-less Printable Coating for Adhesion
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Solution Overview
Problem
Current printable films, especially those using radiation curable ink, face issues with inadequate adhesion to the polymer film, particularly in extreme conditions such as freezing water and sterilization processes, leading to separation of the printed and cured ink from the film surface.
Innovation Solution
A printable film with a surface layer comprising a water-dispersible polymer, an ethylenically unsaturated compound that retains unsaturation for ink binding, and a crosslinker like aziridine or carbodiimide, which binds functional groups on the film surface without requiring a primer layer, ensuring strong adhesion and water resistance while maintaining printability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a primer layer is used to improve adhesion, then adhesion strength is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent removes the primer layer from the coating structure, extracting the problematic intermediate layer that caused complexity and adhesion failures. The surface layer directly contacts the substrate through chemically active sites that provide sufficient adhesion without requiring a separate primer layer.
Solution Approach 2:
The surface layer is designed to perform multiple functions simultaneously: it provides adhesion to the substrate, accepts the radiation curable ink, and cures to provide durability. This multi-functional surface layer eliminates the need for a separate primer layer while maintaining or improving adhesion strength.
2Productivity
If radiation curable ink is used for rapid curing, then productivity is improved, but adhesion reliability deteriorates under extreme conditions
Solution Approach 1:
The surface layer is pre-formed with chemically active sites (carboxyl, hydroxyl, or amine groups) that are ready to bond with the radiation curable ink before printing occurs. This preliminary preparation ensures that when the ink is applied and cured rapidly, strong adhesion is achieved without compromising reliability under extreme conditions.
Solution Approach 2:
The coating comprises a composite structure with a surface layer containing a polymer and chemically active sites that work synergistically with the radiation curable ink. This composite material system enables both rapid curing through radiation and reliable adhesion through chemical bonding mechanisms.
3Strength
If the surface layer is fully cured during manufacturing, then durability is improved, but ink receptivity deteriorates
Solution Approach 1:
The surface layer is pre-formed with chemically active sites that remain available for ink bonding. The layer is designed to be in a state ready for ink reception, with the understanding that curing will occur after ink application to maintain both ink receptivity and subsequent durability.
Solution Approach 2:
The coating system transitions from an uncured state during printing (allowing ink receptivity) to a cured state after printing (providing durability). This dynamic state change enables the coating to adapt to different functional requirements at different stages of the manufacturing and use process.
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 solution provides a cost-effective, easy-to-manufacture printable film with improved adhesion and water resistance, preventing ink separation under extreme conditions and enhancing printability without the need for a primer layer, resulting in a durable and functional printed product.
Implementation Method 1
a crosslinker comprising an aziridine or a carbodiimide, wherein said crosslinker is present in an amount such that it is able to bind the coating to the substrate, wherein the crosslinker binds functional groups on the film surface with functional groups in the components of the coating composition
Implementation Method 2
an ethylenically unsaturated compound which is aqueous-dispersible and miscible with or bonded to said water-dispersible polymer, wherein said ethylenically unsaturated compound retains at least some of its unsaturation after reaction with the crosslinker and is able to form a covalent bond with an ink
Implementation Method 3
After deposition of the radiation curable ink on the printable item, the print is exposed to radiation and hardens within a fraction of a second
Data Source
Figure 1
AI summary
A primer-less coating composition for facestock comprises: a binder being a water-dispersible polymer; an ethlenically unsaturated compound which is aqueous-dispersible and miscible with or bond with an ink; and a crosslinker, wherein said crosslinker is suitable for binding the coating to the facestock. The coating composition may be applied to a substrate to form a printable film, a printed film in accordance with the invention may be used in a label, for example for use on a container such as a bottle.