Security Element Silver Nanoparticle Wavelength Control

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Solution Overview

Problem

Existing security elements struggle to effectively control the maximum absorption wavelength of silver nanoparticles, which is crucial for achieving high protection against counterfeiting in documents like banknotes and credit cards.

Innovation Solution

A security element comprising a substrate with a metal layer, optionally a dielectric layer, and a layer of silver nanoparticles coated with a composition containing a solvent, surface stabilizing agents, and optionally a binder, where the amount of surface stabilizing agents and binder relative to silver nanoparticles controls the maximum absorption wavelength from 700 to 1600 nm.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the maximum absorption wavelength of silver nanoparticles is not controlled, then the security element lacks sufficient protection against counterfeiting, but controlling it requires precise control of stabilizing agent and binder amounts which increases manufacturing complexity

Engineering Contradiction:

Improveprotection against counterfeitingVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent controls the maximum absorption wavelength of silver nanoparticles by adjusting the amount of stabilizing agent and binder relative to silver nanoparticles. This parameter change approach allows tuning of the absorption wavelength (e.g., from visible to near-infrared range) while maintaining a relatively simple coating process, thus achieving high security protection without excessive manufacturing complexity.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the amount of stabilizing agent and binder is precisely controlled to tune absorption wavelength, then high security protection is achieved, but this requires precise manufacturing control which increases production difficulty

Engineering Contradiction:

Improveabsorption wavelength controlVSAvoidproduction difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent achieves precise control of absorption wavelength through parameter changes in the composition ratios of stabilizing agent and binder relative to silver nanoparticles. By establishing specific ratio ranges, the method enables precise wavelength tuning while keeping the manufacturing process relatively simple and scalable.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite material formulations combining silver nanoparticles with stabilizing agents and binders in specific ratios. This composite approach allows the system to achieve desired optical properties (absorption wavelength control) while maintaining ease of manufacture through conventional coating techniques.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If silver nanoparticles are used without stabilizing agents and binders, then the structure is simpler, but the nanoparticles cannot achieve controlled absorption wavelength and lack stability

Engineering Contradiction:

Improvestructure simplicityVSAvoidabsorption wavelength control and stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces stabilizing agents and binders as intermediary substances that mediate between the silver nanoparticles and the environment. These intermediaries enable controlled absorption wavelength and enhanced stability without significantly complicating the overall structure, as they function at the molecular level within the coating matrix.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite material system where stabilizing agents and binders work synergistically with silver nanoparticles. This composite structure achieves both simplicity and reliability by integrating multiple functions (stabilization, wavelength control) into a unified coating formulation that can be applied using standard techniques.

Inventive Principle:

Principle #40Composite materials

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 solution allows for a high level of protection against counterfeiting by varying the absorption wavelength, making the security element suitable for use in banknotes, credit cards, and other valuable documents.

Implementation Method 1

The maximum absorption wavelength of the silver nanoparticles in layer (d) is controlled by the amount of (surface) stabilizing agent(s) and optionally binder relative to the amount of silver nanoparticles to be preferably in the range of 700 to 1600 nm

Methodology Applied

Scientific EffectSurface plasmon resonance: Resonance

Data Source

PatentUS12296391B2Security element

Publication Date: 2025.05.13 BASF SE

AI summary

The present invention relates to security elements, comprising (a) a substrate, (b) on at least part of the substrate surface a metal layer, (c) optionally on at least part of the metal layer a dielectric layer, (d) on at least part of the metal layer, or the dielectric layer, a layer obtained by overcoating the metal layer, or the dielectric layer with a composition, comprising (i) silver nanoparticles, (ii) a solvent, (iii) (surface) stabilizing agent(s) and (iv) optionally a binder, and (e) a protective layer on top of layer (d). The maximum absorption wavelength of the silver nanoparticles in layer (d) is controlled by the amount of (surface) stabilizing agent(s) and optionally binder relative to the amount of silver nanoparticles to be preferably in the range of 700 to 1600 nm.