Crack-Forming Coating for Fine Metallization in Security Elements
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Solution Overview
Problem
Existing methods for producing security elements with fine structuring of metallizations are complex and often result in unsatisfactory line widths, making it difficult to achieve line widths below 50 µm, and are costly due to the use of complex processes like photoresists and etching.
Innovation Solution
A method involving a transparent carrier substrate with an embossing lacquer layer, application of a crack-forming coating that forms a dense, coherent network upon drying, followed by metal deposition within the cracks, and subsequent removal of the cracked coating to create a densely meshed, conductive metallization network, allowing for fine line widths between 1 µm to 50 µm and improved chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photoresist lacquer and etching processes are used to achieve fine structuring of metallization, then manufacturing precision is improved, but device complexity and production cost increase
Solution Approach 1:
The patent changes the fundamental parameter of how metallization is structured - instead of using photoresist patterns to define areas to be etched, it uses a crack-forming coating that creates a network of fine cracks during drying. The metallization is deposited within these cracks, and the coating is subsequently removed, leaving behind fine metallic lines. This parameter change transforms a multi-step photolithographic process into a simpler coating-and-crack process that achieves comparable or superior line width precision without the complexity of photoresist application, exposure, and development steps.
2Ease of manufacture
If conventional printing processes are used to apply resist varnish, then ease of manufacture is improved, but manufacturing precision deteriorates due to minimum line thickness limitations
Solution Approach 1:
The patent replaces the mechanical printing system with a chemical self-organizing system. Instead of relying on the physical resolution limits of printing screens and ink viscosity to define line thickness, the crack-forming coating undergoes spontaneous crack formation during drying driven by tensile stresses. This mechanical-to-chemical substitution allows line widths to be determined by the crack formation process itself rather than by printing resolution, enabling line widths below the conventional 50 µm limit while maintaining ease of manufacture through simple coating processes.
3Ease of manufacture
If baffle or shielding plate is used during vapor deposition to create recesses, then ease of manufacture is improved, but manufacturing precision deteriorates resulting in coarse structuring
Solution Approach 1:
The patent introduces an intermediary crack-forming coating layer between the vapor deposition process and the final metallization structure. This coating acts as a template that directs where metal should be deposited - within the cracks - and protects areas where metal should not be deposited. After vapor deposition, the coating is removed, leaving the metallization pattern. This intermediary approach maintains the simplicity of vapor deposition while achieving fine structuring that would be impossible with direct baffle methods.
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 enables the production of security elements with fine, conductive metallic lines that are optically and electrically effective, providing higher chemical resistance and comparable conductivity to full-area ITO layers, suitable for use in transparent holograms and other security features.
Implementation Method 1
applying a crack-forming coating to the embossing varnish layer and drying the crack-forming coating, wherein the coating forms numerous cracks in the form of a dense, continuous network during drying
Implementation Method 2
applying a metallization to the carrier substrate obtained in step d), wherein metal is deposited within the cracks of the cracked coating
Data Source
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AI summary
The invention relates to a method for manufacturing a security element for a security paper or an object of value, in particular a document of value, said method involving the following steps: a) providing a transparent carrier substrate; b) providing a layer of stamping lacquer, which has a stamping structure, on the carrier substrate; d) applying a crack-forming coating to the layer of stamping lacquer and drying the crack-forming coating such that the coating forms numerous cracks in the form of a close-meshed, uninterrupted grid when drying; e) applying a metal coating to the carrier substrate obtained in step d); f) removing the coating having cracks along with any metal located on the coating such that a transparent, conductive metal coating in the form of a close-meshed, uninterrupted grid remains on the layer of stamping lacquer in the region of the coating that has cracks and has been be removed.