UV Watermark via Substrate Fluorescence Suppression
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Solution Overview
Problem
Existing methods for document security, such as UV ink watermarks, are costly and difficult to implement in digital printing environments, especially in variable data printing scenarios, due to high costs and incompatibility with standard electro-photographic or non-impact printing systems.
Innovation Solution
A method using a combination of non-overlapping primary colorants, particularly yellow and black, to create dot design patterns that suppress substrate fluorescence under normal light but reveal a fluorescent mark under UV illumination, leveraging common colorants and optical brightening agents in paper substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV fluorescent inks are used to create watermarks, then document security and watermark visibility under UV illumination are improved, but cost and compatibility with digital printing systems deteriorate
Solution Approach 1:
The patent utilizes the inherent fluorescent properties of standard paper substrates containing optical brightening agents, eliminating the need for special UV fluorescent inks. The substrate itself serves the dual purpose of being both the printing medium and the fluorescent source, making the system self-sufficient and compatible with conventional digital printers
Solution Approach 2:
Instead of adding fluorescent material to create visible watermarks, the patent inverts the approach by using non-fluorescent colorants (particularly yellow and black) to suppress the substrate's natural fluorescence in specific patterns. This creates visible watermarks under UV light through fluorescence suppression rather than fluorescence enhancement
2Reliability
If UV fluorescent inks are used for watermarking, then watermark visibility under UV light is improved, but cost increases
Solution Approach 1:
The patent replaces expensive UV fluorescent inks with inexpensive standard colorants (CMYK printing inks) that are already universally available. The solution uses common yellow and black inks to suppress fluorescence, eliminating the need for costly specialized materials while maintaining watermark effectiveness
Solution Approach 2:
The patent leverages the free fluorescent property already present in standard paper substrates due to optical brightening agents. By suppressing this inherent fluorescence strategically with common colorants, the system creates detectable watermarks without requiring any additional fluorescent materials, thereby eliminating material costs
3Reliability
If traditional UV watermarking methods are used, then security against counterfeiting is improved, but system overhead and storage requirements increase
Solution Approach 1:
The patent makes standard digital printing systems multi-functional by enabling them to produce both regular printed content and secure fluorescent watermarks using the same printing process and materials. The system simultaneously performs document production and security feature embedding without requiring separate specialized equipment
Solution Approach 2:
The patent extracts the security watermark function from the main printing process, allowing watermarks to be embedded as subtle variations in the normal printing output. The watermark information is encoded through slight modifications to standard colorant patterns, separating the security function from dedicated hardware while maintaining integration
4Manufacturing precision
If high paper coverage with non-overlapping colorants is used, then color accuracy under normal light is improved, but substrate fluorescence suppression increases
Solution Approach 1:
The patent applies different colorant patterns in different spatial locations to achieve local optimization. Areas requiring fluorescence suppression use high coverage patterns with yellow and black colorants, while other areas use lower coverage patterns, creating a mosaic that balances color accuracy and fluorescence suppression locally across the printed surface
Solution Approach 2:
The patent employs selective application of colorants, using yellow and black inks at varying concentrations and coverage levels depending on the specific watermarking requirements. Rather than uniformly applying maximum coverage, the system uses partial coverage in strategic locations to achieve the desired balance between color fidelity and fluorescence suppression
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
This approach provides a cost-effective, secure method for detecting document counterfeiting and alteration in digital printing by creating a UV-visible watermark without requiring special materials or physical modifications to printing devices, ensuring security without increased system overhead or storage needs.
Implementation Method 1
substrate containing optical brightening agents, such that the resultant printed substrate image suitably exposed to an ultra-violet light source, will yield a discernable pattern evident as a fluorescent mark
Data Source
AI summary
The teachings as provided herein relate to a watermark embedded in an image, and methodology for same, that has the property of being relatively indecipherable under normal light, and yet decipherable under UV light. This fluorescent mark comprises a substrate containing optical brightening agents, and a first dot design printed as an image upon the substrate. The first dot design has as a characteristic, the property of strongly suppressing substrate fluorescence. A second dot design having a property of providing a differing level of substrate fluorescence suppression from that of the first dot design such that when rendered in close spatial proximity with the first dot design image print, the resultant image rendered substrate suitably exposed to an ultra-violet light source, will yield a discernable image evident as a fluorescent mark.