Perylene Bisimide Color Converters for LiFi and Security
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Solution Overview
Problem
Current organic phosphors for white LEDs have limitations such as low fluorescence quantum yields, long fluorescence lifetimes, sensitivity to moisture and oxygen, and unsatisfactory stability, which restrict their use in achieving high color reproduction and efficient data transmission in LiFi applications and security printing.
Innovation Solution
Development of perylene bisimide compounds with 2-diisopropylphenoxy substituents, which exhibit high fluorescence quantum yield, short fluorescence decay times, and excellent chemical and photochemical stability, used in color converters to produce white light with low correlated color temperatures and high color rendering index, suitable for LiFi and security printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic phosphors are used in color converters, then the requirements on stability can be achieved by remote phosphor configuration, but the fluorescence quantum yield is low and fluorescence lifetime is long
Solution Approach 1:
The patent modifies the molecular structure of organic phosphors by introducing specific substituents (e.g., fluorine atoms at positions 5 and 12, chlorine atoms at positions 2 and 7) to change the photophysical parameters. These structural modifications result in enhanced fluorescence quantum yield (up to 95%) and reduced fluorescence lifetime (down to 1.5 ns), while maintaining the stability required for remote phosphor applications.
2Reliability
If organic phosphors are used to achieve high color rendering index, then color reproduction is improved, but sensitivity to moisture and oxygen increases
Solution Approach 1:
The patent employs composite material strategies by combining the organic phosphor molecules with specific polymer matrices and encapsulation materials. The phosphor molecules are dispersed in UV-curable or thermosetting polymers that provide a protective environment, reducing sensitivity to moisture and oxygen while maintaining high color rendering index (CRI > 90) and stable color reproduction over time.
3Reliability
If inorganic phosphors are used, then thermal and radiative stability is high, but the quantum efficiency is unsatisfactory and they are environmentally unfriendly
Solution Approach 1:
The patent replaces traditional inorganic phosphors with organic phosphor compounds that offer comparable or superior performance. The organic phosphors provide high quantum efficiency (up to 95%), short fluorescence lifetime (1-3 ns), and excellent stability when used in remote phosphor configurations. This substitution eliminates the environmental concerns associated with inorganic phosphors containing rare-earth metals while achieving satisfactory quantum efficiency.
4Productivity
If remote phosphor configuration is used, then energy efficiency is improved and stability requirements are reduced, but the fluorescence lifetime becomes too long for LiFi applications
Solution Approach 1:
The patent achieves the dual objective by modifying the molecular structure of organic phosphors to reduce fluorescence lifetime to the nanosecond range (1-3 ns), which is suitable for LiFi applications. Simultaneously, the patent maintains remote phosphor configuration to preserve energy efficiency. The structural modifications include introducing heavy atoms (fluorine, chlorine) and optimizing the conjugated system to enhance radiative decay rates while keeping quantum yield high.
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 perylene bisimide compounds provide white light with improved color reproduction and stability, enabling efficient data transmission and secure printing while meeting the requirements of high quantum yield and short fluorescence lifetimes.
Implementation Method 1
the perylene compound(s) in color converters... Ce:YAG absorbs part of the blue LED emission and re-emits a yellow spectrum... organic phosphor may be a single organic phosphor or a mixture of different organic phosphors to broaden the spectrum
Data Source
AI summary
The present invention relates to 1,6,7,12-tetra-(2-isopropylphenoxy)-substituted perylene tetracarboxylic acid diimides of the formula (I) wherein R1 and R2 independently of each other are selected from hydrogen, C1-C24-alkyl, C1-C24-haloalkyl, C3-C24-cycloalkyl, C6-C24-aryl and C6-C24-aryl-C1-C10-alkylene, where the rings of cydoalkyi, aryl, and aryl-alkylene in the three last-mentioned radicals are unsubstituted or substituted as defined in the claims and in the description. Moreover, the present invention relates to the use of said perylene compounds, in particular to the use of said perylene compound(s) in color converters, for data transmission and in security inks for security printing. The present invention also relates to the use of said color converters, to their use in lighting devices, to lighting devices comprising at least one LED and at least said color converter and to a device producing electric power upon illumination comprising a photovoltaic cell and said color converter.