Lanthanoid Core-Shell Microparticles for Infrared Fluorescent Ink
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Solution Overview
Problem
Inorganic fine particles with up-conversion function suffer from energy outflow and poor water resistance, leading to reduced luminous efficiency and stability in wavelength conversion applications, particularly in infrared fluorescent inks used for security purposes.
Innovation Solution
A lanthanoid-containing inorganic material fine particle with a core-shell structure, where the core contains lanthanoids for light absorption and emission, and a shell layer with a rare earth element, optimized to prevent energy leakage and enhance water repellency, maintaining high emission intensity and retention properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a shell is formed on the surface of inorganic fine particles to prevent energy leakage, then energy outflow is reduced, but the shell layer becomes thick causing light scattering or absorption
Solution Approach 1:
The patent applies a thin shell layer (2-20 nm) of rare earth element-containing material on the inorganic fine particle surface. This thin film configuration provides sufficient protection against energy outflow while minimizing light scattering and absorption that would occur with thicker shells, directly resolving the technical contradiction between energy retention and optical transparency.
2Power
If the inorganic fine particle is a nanoparticle with large specific surface area, then up-conversion function is enhanced, but the particle becomes susceptible to oxidation and surface contamination
Solution Approach 1:
The patent creates a composite structure where a core inorganic fine particle (nanoparticle) containing lanthanoid elements is combined with a shell layer of rare earth element-containing material. This composite structure maintains the high surface area of the nanoparticle for enhanced up-conversion function while the shell layer provides protective coverage that prevents oxidation and surface contamination, thereby improving reliability.
3Illumination intensity
If conventional UV fluorescent ink is used for security printing, then visible light information is provided, but the print substrate deteriorates due to UV irradiation
Solution Approach 1:
The patent utilizes infrared-to-visible light up-conversion, where infrared light (non-damaging) is absorbed and converted to visible light emission. This phase transition approach allows the security ink to provide visible information while using infrared excitation instead of UV irradiation, thereby preventing substrate deterioration while maintaining the security printing function.
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 core-shell structure effectively reduces energy outflow and maintains high luminous efficiency and water repellency, ensuring stable emission intensity and pattern retention in wavelength conversion applications.
Implementation Method 1
These inorganic fine particles utilize a phenomenon called 'multiphoton excitation' caused by the energy level difference of these elements
Implementation Method 2
non-Patent Literature 1 proposes formation of a shell on the surface of an inorganic fine particle to prevent energy leakage
Implementation Method 3
amplification of light emission by complexing a noble metal nanomaterial that expresses surface plasmon resonance (SPR)
Data Source
AI summary
A lanthanoid-containing inorganic material fine particle having a function of converting a wavelength of light to a shorter wavelength, the lanthanoid-containing inorganic material fine particle including: a core particle; and a shell layer, the core particle containing a lanthanoid having a light-absorbing function and a lanthanoid having a light-emitting function, the shell layer including at least an outer shell containing a rare earth element, the total amount of the lanthanoid having a light-absorbing function and the lanthanoid having a light-emitting function in the outer shell being 2 mol % or less based on the amount of the rare earth element contained in the outer shell, the outer shell having a thickness of 2 to 20 nm, the core particle and the shell layer having no interface at a contact face to form a continuous body.