Aqueous Laser Markable Composition with Encapsulated Leuco Dye
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Solution Overview
Problem
Laser markable materials face challenges in terms of cumbersome non-aqueous production methods and poor daylight stability, particularly in security documents and multicolored applications.
Innovation Solution
An aqueous laser markable composition is developed, incorporating infrared absorbing dyes and pigments, encapsulated leuco dyes, and a color developing agent precursor, which allows for improved physical properties and enhanced stability through the use of an optothermal converting agent and a polymeric shell, facilitating a more environmentally friendly and efficient production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-aqueous coating solutions are used for laser markable layers, then colour formation and laser marking performance are achieved, but production becomes cumbersome and health and safety regulations are more difficult to comply with
Solution Approach 1:
The patent changes the fundamental parameter of the coating solution from non-aqueous to aqueous-based. This substitution maintains the functional performance of laser marking while dramatically simplifying the production process and improving health and safety compliance, as water-based solutions are easier to handle, dispose of, and regulate
2Loss of information
If laser markable layers are exposed to daylight for a long time, then background information is visible, but daylight stability deteriorates and background stains become pronounced
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 background. This absorber selectively captures UV energy before it can trigger unwanted colour formation in the background, thereby maintaining daylight stability while preserving the visibility of laser-marked information
3Adaptability or versatility
If multiple laser markable layers with different IR dyes are used for multicoloured articles, then colour versatility is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the multicolour functionality into separate laser markable layers, each containing a specific IR dye with a distinct absorption maximum. This allows each layer to be independently optimized and addressed by lasers at different wavelengths, achieving colour versatility while maintaining manageable structural complexity through modular design
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 aqueous composition enables simplified and environmentally friendly production while maintaining or improving physical properties and daylight stability, making it suitable for security documents and multicolored applications.
Implementation Method 1
an optothermal converting agent, wherein the core of the capsule contains a leuco dye... The colour laser markable article may comprise an infrared absorbing dye (IR dye) or an infrared absorbing pigment (IR pigment), 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
capsules composed of a polymeric shell surrounding a core; a colour developing agent and an optothermal converting agent, wherein the core of the capsule contains a leuco dye
Data Source
AI summary
A laser markable composition comprising (a) an aqueous medium; (b) capsules composed of a polymeric shell surrounding a core; (c) a colour developing agent or colour developing agent precursor; and (d) an optothermal converting agent; characterized in that the core of the capsule contains a leuco dye.