Optical Effect Layer Production via Substrate-Through UV Curing
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Solution Overview
Problem
Current methods for producing optical effect layers with magnetic or magnetizable pigment particles struggle to efficiently create motifs with high resolution and exact register, particularly when using photomasks that need to move concomitantly with the coating, limiting the production of complex patterns with different orientation patterns.
Innovation Solution
A process involving a photomask that moves in conjunction with the coating application, where a radiation curable coating composition with photoinitiators and magnetic or magnetizable pigment particles is applied, hardened through the substrate, and then oriented by a magnetic field, allowing for simultaneous or partial simultaneous hardening to fix the pigment particles' orientation, enabling the creation of motifs with distinct patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photomask is used to create motifs with different orientation patterns, then the resolution and register of the optical effect layer are improved, but the device complexity and process difficulty increase due to the need for concomitant movement between photomask and coating
Solution Approach 1:
The patent combines multiple functions into a single integrated system: the photomask is integrated with the substrate, the magnetic field generating device is positioned to act through the substrate, and the UV irradiation source is combined with the magnetic field device. This integration eliminates the need for separate concomitant movement mechanisms while maintaining high registration precision between different orientation patterns.
Solution Approach 2:
The substrate serves as an intermediary element that the UV irradiation passes through to harden the coating layer. This intermediary approach allows the photomask to remain on the substrate while enabling UV curing from the opposite side, simplifying the overall system architecture and reducing mechanical complexity.
2Manufacturing precision
If the coating layer is hardened through the substrate, then the pigment particle orientation can be controlled, but the production time increases due to sequential hardening steps
Solution Approach 1:
The patent employs periodic action by using sequential UV irradiation steps from opposite sides of the substrate. The coating is first hardened through the substrate in one direction, then additional UV irradiation is applied from the opposite side to complete the hardening process. This periodic approach ensures complete orientation control while optimizing production time by allowing parallel positioning of equipment.
Solution Approach 2:
The magnetic field is applied continuously during the UV irradiation process to maintain pigment particle orientation throughout the hardening sequence. This continuous action ensures that orientation control is maintained without interruption, while the UV irradiation steps are optimized to minimize total processing time.
3Productivity
If simultaneous or partial simultaneous hardening is used, then the production efficiency is improved, but the manufacturing precision may be compromised due to challenges in coordinating multiple irradiation sources
Solution Approach 1:
The patent segments the UV irradiation process into distinct steps: first hardening through the substrate, then additional hardening from the opposite side. This segmentation allows each irradiation step to be independently optimized and controlled, maintaining high orientation precision while improving overall production efficiency compared to purely sequential processing.
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
This process enables the production of optical effect layers with high resolution and exact register, allowing for visually distinct optical impressions that enhance security features by creating complex patterns with different magnetic or magnetizable pigment particle orientations, effectively protecting against counterfeiting.
Implementation Method 1
hardening one or more first substrate areas carrying the coating layer through the substrate, said hardening being performed by irradiation with a UV-Vis irradiation source
Implementation Method 2
exposing at least one or more second substrate areas carrying the coating layer which are in a first state due to the presence of the photomask of the substrate to the magnetic field of a magnetic-field-generating device thereby orienting the plurality of magnetic or magnetizable pigment particles
Data Source
AI summary
The invention relates to the field of the protection of security documents such as for example banknotes and identity documents against counterfeit and illegal reproduction. In particular, the invention relates to processes for producing optical effect layers (OELs) comprising a motif made of at least two areas made of a single hardened layer on a substrate comprising a photomask.