Perfluoropolyether Varnish for Security Document Soil Resistance
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Solution Overview
Problem
Conventional protective varnishes used on security documents, such as banknotes, suffer from poor oil, fat, or grease repellency, leading to reduced durability and circulation lifetime due to inadequate soil release characteristics and moisture resistance.
Innovation Solution
Radiation curable protective varnishes comprising cationically curable compounds and di-hydroxyl-terminated perfluoropolyether compounds, which form a durable, water/moisture and oil/grease repellent coating when cured, enhancing anti-soiling performance and fingerprint resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protective varnishes are applied to security documents, then the documents gain basic protective coating, but the oil, fat, and grease repellency remains poor
Solution Approach 1:
The protective varnish is formulated as a composite material combining a cationic polymer base with fluorinated surfactants (containing CF2 and CF3 groups). This composite structure provides both the protective coating function and superior oil/grease repellency, resolving the contradiction between basic protection and soil release characteristics.
Solution Approach 2:
The invention changes the chemical parameters of the protective coating by incorporating fluorinated compounds with specific surface energy characteristics. The fluorinated surfactants modify the surface properties to achieve low surface energy, which provides excellent oil, fat, and grease repellency while maintaining the protective function.
2Reliability
If conventional protective varnishes are used, then the documents receive a protective layer, but the resistance to moisture and environmental exposure is insufficient
Solution Approach 1:
The varnish forms a composite protective layer that combines the protective properties of cationic polymers with the moisture-resistant properties of fluorinated surfactants. This composite structure provides enhanced resistance to moisture and environmental exposure, extending circulation lifetime.
Solution Approach 2:
The fluorinated surfactants create a chemically inert surface layer that resists interaction with moisture and environmental contaminants. This inert surface provides long-term protection against degradation from environmental exposure.
3Ease of manufacture
If standard varnishing is applied, then the security document surface is coated, but fingerprint resistance and anti-soiling performance are inadequate
Solution Approach 1:
The invention changes the surface energy parameters of the coating by incorporating fluorinated surfactants. This parameter change creates a low surface energy surface that prevents fingerprint deposits and soil accumulation, while the cationic polymer base ensures proper adhesion and coating formation.
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 described varnishes significantly improve the anti-soiling characteristics and resistance of security documents to environmental exposure, extending their usable life by providing enhanced water/moisture and oil/fat repellency and maintaining performance over time.
Implementation Method 1
Radiation curable protective varnishes comprising cationically curable compounds and di-hydroxyl-terminated perfluoropolyether compounds, which form a durable, water/moisture and oil/grease repellent coating when cured
Implementation Method 2
enhancing anti-soiling performance and fingerprint resistance... significantly improve the anti-soiling characteristics and resistance of security documents to environmental exposure, extending their usable life by providing enhanced water/moisture and oil/fat repellency
Implementation Method 3
providing enhanced water/moisture and oil/fat repellency
Data Source
AI summary
The present invention relates to the field of the protection of security documents, in particular banknotes, against premature detrimental influence of soil and/or moisture upon use and time. In particular, it relates radiation curable protective varnishes comprising one or more cationically curable compounds and one or more di-hydroxyl-terminated perfluoropolyether compounds of the general formula HO-(CH2CH2O)c-CH2-CF2O-(CF2-CF2-O)a-(CF2O)b-CF2-CH2-(OCH2CH2)d- OH, wherein a and b independently are integers in a range between 0 and 50, wherein a + b≥ 1, and wherein c and d may be the same or different and are in the range of 1-20, and their uses for providing a protective coating or layer on a security document.