Silver Nano-particle Layers for Security Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing thin silver nano-particle layers on substrates require high curing temperatures, which can damage temperature-sensitive materials and are not suitable for high-speed printing processes, and they often result in conductive layers rather than non-conductive ones.
Innovation Solution
A method involving the application of a composition containing a metal complex of silver (Ag+L−) with specific ligands, a solvent, a reducing agent, and optionally a polymeric binder, heated to below 120°C or irradiated with electromagnetic radiation to form highly reflective, non-conductive or conductive silver nano-particle layers with controlled thickness and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high curing temperatures are used to form silver nano-particle layers, then the layers can be formed effectively, but temperature-sensitive substrates are damaged and high-speed printing processes cannot be used
Solution Approach 1:
The patent changes the curing temperature parameter from conventional high temperatures (typically above 120°C) to low temperatures (below 120°C, preferably 20-100°C). This is achieved by modifying the chemical composition of the silver complex and reducing agents, allowing the reduction reaction to proceed at lower temperatures while still forming high-quality silver nano-particle layers.
Solution Approach 2:
The patent replaces thermal energy input with chemical energy input by using specifically designed silver complexes and reducing agents that facilitate low-temperature reduction. Instead of relying primarily on heat to drive the reduction reaction, the chemical composition is optimized to enable the reaction to proceed at lower temperatures, thus protecting temperature-sensitive substrates.
2Ease of manufacture
If conventional silver ink compositions are used, then metallic layers can be formed, but the layers are conductive rather than non-conductive
Solution Approach 1:
The patent applies local quality by controlling the distribution, size, and spacing of silver particles to achieve different electrical properties in different applications. By adjusting particle concentration, size distribution, and spacing, the same silver nano-particle layer can be made conductive or non-conductive depending on the specific formulation parameters, allowing tailored electrical properties for different uses.
Solution Approach 2:
The patent uses composite material formulations combining silver complexes with specific ligands, reducing agents, and optional polymeric binders. This composite approach allows simultaneous control of particle formation, dispersion, and electrical properties, enabling the creation of layers with desired conductive or non-conductive characteristics while maintaining high reflectivity and optical quality.
3Stability of the object's composition
If room temperature stability is maintained for storage, then the composition remains stable, but fast printing processes cannot be achieved
Solution Approach 1:
The patent applies preliminary action by pre-forming stable silver complexes with ligands that prevent premature reduction during storage. The composition is designed to remain stable at room temperature during storage and handling, but upon application to the substrate, the conditions trigger rapid reduction and particle formation. This separation of stability during storage from reactivity during processing enables both long-term stability and fast printing.
Solution Approach 2:
The patent implements periodic action by designing a two-stage process: first, stable storage at room temperature where no reaction occurs; second, rapid activation upon substrate application where reduction and particle formation occur quickly. This temporal separation allows the composition to remain stable during storage while enabling fast processing when needed, effectively decoupling storage stability from processing speed.
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 allows for the production of highly reflective, non-conductive or conductive silver nano-particle layers with high gloss values and optically variable images, suitable for decorative and security elements, while maintaining stability at room temperature and enabling fast printing processes on sensitive substrates.
Implementation Method 1
heating the coating to a temperature below 120° C. and/or irradiating the coating with electromagnetic radiation, to form a highly reflective layer, containing silver nanoparticles
Implementation Method 2
irradiating the coating with electromagnetic radiation, preferably ultraviolet (UV) light or an electron beam
Data Source
AI summary
The present invention relates to a process for the preparation of thin silver nano-particles containing layers, which are produced directly on a substrate as part of a coating or printing process. The layers can show different colours in transmittance and reflectance. The invention further relates to decorative and security elements. When the layers are applied over a security element, such as a hologram, the obtained products may show different colours in reflection and transmission, an extremely bright optically variable image (OVD image). Depending on the thickness of the layer a more or less intensive metallic aspect appears.