Security LEP Ink Composition for Invisible UV Detection
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Solution Overview
Problem
Conventional electrophotographic printing processes face challenges in creating invisible yet detectable security images that are transparent and colourless, especially when exposed to ultraviolet, visible, or infrared light, as existing inks either absorb or emit light in a way that is visible to the human eye or lack the necessary optical signals for secure detection.
Innovation Solution
A security liquid electrophotographic (LEP) ink composition comprising an absorber, a resin, and a carrier liquid, which is designed to be colourless and transparent, allowing it to be invisible to the human eye but detectable at a specific optical signal when exposed to radiation, such as ultraviolet, visible, or infrared light, by utilizing absorbers that absorb and emit radiation in a manner that provides a detectable optical signal without being visible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrophotographic inks are used, then the ink composition provides sufficient charge and adhesion, but the ink is visible to the human eye and lacks transparency
Solution Approach 1:
The patent applies color changes by selecting absorbers that are transparent and colourless in the visible spectrum (400-700nm) while maintaining strong absorption in UV (200-400nm) and/or IR (700-1000nm) regions. This allows the ink to be invisible to the human eye during application and drying, yet detectable under appropriate radiation for security verification purposes.
Solution Approach 2:
The patent changes the optical parameters of the ink by carefully selecting absorbers with specific absorption spectra that create transparency in the visible range while maintaining detectability in UV or IR ranges. The resin and carrier liquid parameters are also optimized to ensure proper charge adhesion and electrostatic properties without compromising optical transparency.
2Illumination intensity
If the ink is made transparent and colourless, then the ink becomes invisible to the human eye, but the detectability and optical signal for security verification is reduced
Solution Approach 1:
The patent moves the detection dimension from the visible spectrum to UV or IR spectral regions. By selecting absorbers that are transparent in visible light but strongly absorb in UV (200-400nm) and/or IR (700-1000nm) regions, the ink becomes detectable through specialized detectors in these alternative spectral dimensions, resolving the contradiction between transparency and detectability.
Solution Approach 2:
The patent replaces visual detection (mechanical/optical system relying on human eye sensitivity) with radiation-based detection systems that can detect UV or IR absorption. This substitution allows transparent, colourless inks to provide detectable optical signals through specialized detectors sensitive to non-visible radiation.
3Difficulty of detecting and measuring
If absorbers that absorb UV or IR radiation are used, then the ink provides detectable optical signals, but the ink may emit light visible to the human eye
Solution Approach 1:
The patent carefully selects absorbers whose emission spectra do not overlap with the visible range (400-700nm). By choosing materials that absorb UV or IR radiation but emit only in non-visible ranges, or that exhibit minimal visible emission, the ink provides strong optical signals for detection while remaining transparent and colourless to the human eye.
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 LEP ink composition effectively prints security images that are invisible to the naked eye but can be detected using appropriate radiation, offering a secure and visible optical signal for verification purposes without altering the appearance of the print substrate.
Implementation Method 1
an absorber... which absorbs and emits radiation in a manner that provides a detectable optical signal
Implementation Method 2
an absorber... which absorbs and emits radiation in a manner that provides a detectable optical signal
Implementation Method 3
The charged particles adhere to the image areas of the latent image while the background areas remain clean
Implementation Method 4
which can be a soft swelling blanket, which is often heated to fuse the solid image and evaporate the liquid carrier
Data Source
AI summary
Described herein is a security LEP ink composition comprising an absorber, a resin; and a carrier liquid for printing a security image.