Transparent Coating for Security Paper Visibility
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Solution Overview
Problem
Security documents, such as banknotes, face challenges in maintaining high visibility of security elements and durability while achieving high print quality and resistance to circulation, particularly after printing, as existing solutions like mineral filler and polyurethane coatings hinder the visibility of security features.
Innovation Solution
A coated security paper with a transparent or translucent coating comprising colloidal silica and an elastomeric binder, specifically high-hardness polyurethane, is used, which improves visibility and durability without compromising print quality, with a preferred ratio of colloidal silica to elastomeric binder and optional crosslinking agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating made from mineral fillers and elastomeric binder (polyurethane) is used to improve resistance to circulation and printability, then the durability and print quality are enhanced, but the visibility of security elements such as watermarks and security threads is reduced
Solution Approach 1:
The patent changes the optical parameters of the coating by replacing opaque mineral fillers with transparent or translucent alternatives (such as transparent silica, barium sulfate, or titanium dioxide in specific concentrations). This parameter change maintains the coating's protective and printing functions while restoring light transmission to improve security element visibility.
Solution Approach 2:
The patent employs composite coating formulations that combine transparent fillers with elastomeric binders in specific ratios. This composite approach creates a coating that simultaneously provides durability, printability, and optical transparency, resolving the contradiction between protection and visibility.
2Strength
If a coating made from mineral fillers and elastomeric binder is applied to enhance durability and print quality, then the resistance to circulation is improved, but the transparency of the coating is reduced
Solution Approach 1:
The patent modifies the optical parameters of the coating system by selecting fillers with high transparency and controlling their concentration. This allows the coating to maintain adequate opacity for printing while remaining transparent enough to security elements, thus resolving the contradiction between durability and transparency.
3Reliability
If conventional opaque coating materials are used to ensure durability and printability, then the resistance to wear and tear is improved, but the optical effects of security elements are hindered
Solution Approach 1:
The patent changes the optical parameters of the coating by using transparent or translucent materials that allow light to pass through to security elements and reflect back, making them visible. This parameter change maintains wear resistance while improving detectability of security features.
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 enhances the visibility of security elements and significantly improves the resistance to circulation and print quality, making the security documents more durable and resistant to wear and tear.
Implementation Method 1
a transparent or translucent coating comprising at least one colloidal silica and at least one transparent or translucent elastomeric binder
Implementation Method 2
at least one colloidal silica
Data Source
AI summary
The invention relates to a coated sheet of security paper which includes security elements and has a high print rendition and a high resistance to circulation, which sheet is characterized in that at least one of its sides is coated with a transparent or translucent coating comprising at least one colloidal silica and at least one transparent or translucent elastomeric binder. In particular, the binder is a polyurethane.The invention also relates to the process for manufacturing the said sheet and to a banknote obtained from this sheet.