Multi-Layer Embossing Varnish for Security Elements
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Solution Overview
Problem
Existing embossing varnishes for security elements face challenges in being simultaneously flexible, metallizable, releasable, and providing adequate corrosion protection, with deeper embossed structures requiring higher layer thicknesses that often result in poor adhesion to films and mechanical stress issues.
Innovation Solution
A method involving a multi-layer embossing varnish where a first UV-curing layer is fully hardened before applying a second UV-curing layer, which is then embossed, ensuring no transfer to the embossing tool and improving interlayer adhesion through diffusion-driven mixing, with optional additional layers for enhanced properties like flexibility and metallizability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the embossing varnish layer thickness is increased to achieve deeper embossed structures, then the embossing depth is improved, but the adhesion to the substrate deteriorates
Solution Approach 1:
The embossing varnish is divided into multiple layers (first embossing varnish layer, second embossing varnish layer, and optionally a third layer) with different thicknesses and properties. The first layer provides adhesion and flexibility, the second layer provides the necessary thickness for deep embossing, and the third layer (when present) provides metallizability and corrosion protection. This segmentation allows each layer to be optimized for its specific function without compromising the others.
Solution Approach 2:
The patent uses a composite multilayer coating system where each layer has different compositional characteristics. The first layer contains components optimized for adhesion and flexibility, the second layer for embossing depth, and the third layer for metallizability and corrosion resistance. This composite approach allows the overall system to achieve both deep embossing and good adhesion simultaneously.
2Adaptability or versatility
If the embossing varnish is made more flexible to improve flexibility, then the flexibility is improved, but the metallizability and releaseability deteriorate
Solution Approach 1:
The coating is segmented into multiple layers where the first layer provides flexibility and adhesion, while the second and third layers provide metallizability and corrosion protection. This allows the flexible first layer to be metallized without compromising the metallizability of the overall system, as the subsequent layers contain the metallizable components.
Solution Approach 2:
Different layers are assigned different local qualities: the first layer is optimized for flexibility and adhesion, while the second and third layers are optimized for metallizability and corrosion protection. This local optimization allows each layer to fulfill its specific function without compromising the overall system performance.
3Reliability
If the embossing varnish formulation is changed to improve corrosion protection, then the corrosion protection is improved, but the flexibility and releaseability deteriorate
Solution Approach 1:
The coating system is segmented into multiple layers where the first layer provides flexibility and adhesion, while the second and third layers provide corrosion protection and metallizability. This segmentation allows the corrosion-resistant formulations to be applied in layers that do not compromise the overall flexibility and releaseability of the security element.
Solution Approach 2:
The patent uses a composite multilayer structure where each layer has different compositional characteristics optimized for its specific function. The first layer contains components for flexibility and adhesion, while the second and third layers contain components for corrosion protection and metallizability. This composite approach allows the system to achieve both corrosion protection and flexibility simultaneously.
4Reliability
If the embossing varnish layer thickness is increased to provide better corrosion protection, then the corrosion protection is improved, but the adhesion to the substrate deteriorates
Solution Approach 1:
The coating is divided into multiple layers where the first layer is optimized for adhesion to the substrate, while the second and third layers provide corrosion protection and metallizability. This segmentation allows the adhesion function to be performed by a thin, well-bonded first layer, while the corrosion protection is provided by subsequent layers that do not compromise the adhesion.
Solution Approach 2:
Different layers are assigned different local qualities: the first layer has properties optimized for adhesion, while the second and third layers have properties optimized for corrosion protection and metallizability. This local optimization allows each layer to fulfill its specific function without compromising the overall system performance.
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 improved mechanical resistance, adhesion, and embossing behavior without compromising overprintability, ensuring the security element's durability and visibility, even under mechanical stress and corrosive conditions.
Implementation Method 1
The individual layers are applied without complete curing of the previous layer, diffusion-driven mixing occurs at the interfaces of the layers. This process has a positive effect on the interlayer adhesion and results in improved interlayer adhesion.
Implementation Method 2
a) applying a first UV-curing layer, which is a Lacquer layer on the substrate; b) complete curing of the first UV-curing layer; c) applying at least a second UV-curing layer, which is a lacquer layer, to the fully cured first layer
Implementation Method 3
The resulting deposition of uncured layer material on the embossing tool can lead to a deterioration in the embossed image.
Data Source
Figure 1~3
AI summary
The invention relates to a method for producing a security element for a security paper, value document or similar, comprising a substrate (10) which is provided at least partially with an embossed coating (11) comprising at least two layers (1, 2). Said method comprises the following steps: A first UV-hardening layer (1) is applied to the substrate (10); the first UV-hardening substrate (1) is completely hardened; at least one second UV-hardening layer (2) is applied to the completely hardened first layer (1); the UV-hardening layer (2) applied second is embossed and the coating (11) is hardened.