Aqueous Laser Markable Composition for Security Documents
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Solution Overview
Problem
Laser markable materials face challenges in terms of cumbersome production due to non-aqueous coating solutions and poor daylight stability, particularly in security documents where health and safety regulations complicate production and long-term exposure to daylight leads to background staining.
Innovation Solution
Aqueous laser markable composition comprising a leuco dye, an optothermal converting agent, and a polymer particle capable of forming an acid upon exposure to heat, which includes infrared absorbing dyes and pigments, encapsulated in capsules to enhance stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If non-aqueous coating solutions are used for laser markable layers, then colour formation and laser markability are achieved, but production becomes cumbersome and health and safety regulations are complicated
Solution Approach 1:
The patent changes the solvent parameter from non-aqueous to aqueous medium, transforming the coating solution into a water-based system. This parameter change simplifies production procedures and eliminates the need to comply with complex health and safety regulations associated with organic solvents, while maintaining the essential laser markability and colour formation properties of the material.
2Reliability
If laser markable layers are exposed to daylight for long time, then information is stored inside the document, but background stain becomes pronounced reducing daylight stability
Solution Approach 1:
The patent introduces an intermediary substance - a UV absorber - that mediates between the harmful UV radiation in daylight and the leuco dye in the laser markable layer. The UV absorber captures and dissipates UV energy, preventing it from reaching and degrading the leuco dye, thereby eliminating the background stain problem while maintaining long-term daylight stability and information reliability.
3Adaptability or versatility
If infrared absorbing dyes are used with narrow absorption spectrum, then multicoloured articles can be produced, but production complexity increases due to multiple layers with different dyes
Solution Approach 1:
The patent employs a universal approach by using a single laser markable layer containing a leuco dye that can respond to different infrared wavelengths. Instead of requiring multiple specialized layers with different IR dyes, this single layer provides multi-functionality by enabling multicolour production through variable wavelength laser excitation, thereby reducing structural complexity while maintaining versatility.
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 simplifies production, improves daylight stability, and maintains or enhances physical properties, ensuring secure and durable laser-marked security documents.
Implementation Method 1
an optothermal converting agent, wherein the colour developing agent is a polymer particle capable of forming an acid upon exposure to heat... both absorbing the IR radiation and converting it into heat
Implementation Method 2
laser markable layers are used which are composed of colour forming compounds (also called ' leuco-dyes') which can change from essentially colourless or pale-coloured to coloured when exposed to for example heat
Implementation Method 3
the colour developing agent is a polymer particle capable of forming an acid upon exposure to heat
Data Source
AI summary
A laser markable composition comprising (a) an aqueous medium; (b) a leuco dye; (c) an optothermal converting agent; and (d) a colour developing agent, characterized in that the colour developing agent is a polymer particle capable of forming acid upon exposure to heat.