Wavelength Conversion Film Quantum Dot Aggregation Control
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Solution Overview
Problem
Existing methods for forming wavelength conversion films using quantum dots often result in aggregation during solvent evaporation, leading to reduced emission efficiency, and have limited design freedom due to the use of polymerizable compounds with restricted viscosity and curing methods.
Innovation Solution
A wavelength conversion film-forming composition comprising quantum dots, a volatile component, and a binder or binder precursor that is soluble in the volatile component, which is gellable, allowing for controlled mobility and aggregation prevention through viscosity manipulation during the coating process, using techniques like cooling, heating, light irradiation, or shear force treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If quantum dots are dispersed in a polymer matrix and molded using a cast method with solvent removal, then a wavelength conversion film can be formed, but quantum dots aggregate during solvent volatilization leading to reduced emission efficiency
Solution Approach 1:
The patent changes the physical-chemical parameters of the binder by using a polymer with specific glass transition temperature (Tg) range (0°C to 100°C) and specific functional groups. This parameter control allows the binder to maintain appropriate viscosity during coating and prevent quantum dot aggregation during solvent removal, while still enabling proper film formation. The Tg parameter is specifically selected to balance between maintaining quantum dot dispersion and allowing solvent evaporation.
Solution Approach 2:
The patent utilizes the phase transition properties of the binder through its glass transition temperature. By selecting a binder whose Tg is within 0°C to 100°C, the material undergoes a controlled phase transition that affects its viscosity and flow characteristics during the coating and drying process. This phase transition behavior helps prevent quantum dot aggregation while maintaining film-forming capability.
2Reliability
If a polymerizable compound is used as binder precursor with curing by heating or light irradiation, then quantum dot aggregation is suppressed, but the viscosity suitable for coating is limited and design freedom is reduced
Solution Approach 1:
The patent expands material design freedom by changing the selection criteria from specific polymerizable compounds to polymers with controlled Tg and functional groups. This parameter-based approach allows selection from a broader range of materials that can achieve both proper coating viscosity and quantum dot dispersion stability without being limited to compounds suitable for curing reactions.
Solution Approach 2:
The patent extracts the essential requirements for preventing quantum dot aggregation (viscosity control, solubility, stability) from the specific mechanism of polymerizable compounds and curing reactions. By focusing on these extracted requirements and implementing them through Tg-controlled polymers, the solution removes the limitation of needing specific polymerizable compounds while maintaining the benefit of aggregation prevention.
3Reliability
If the binder has high viscosity to prevent quantum dot aggregation, then emission efficiency is maintained, but coating processability is reduced
Solution Approach 1:
The patent uses the glass transition temperature as a control parameter to achieve temperature-dependent viscosity adjustment. Below Tg, the polymer maintains higher viscosity to prevent aggregation; during coating, the temperature can be elevated temporarily to reduce viscosity for better processability, then returned to normal to restore the protective high-viscosity state.
Solution Approach 2:
The patent introduces dynamic control of binder viscosity through temperature management relative to the glass transition temperature. The viscosity is not fixed but dynamically adjusted during different process stages: higher viscosity during storage and final drying to prevent aggregation, and temporarily reduced viscosity during active coating for better processability.
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 solution effectively suppresses quantum dot aggregation, enabling the formation of films with high emission efficiency and increased design flexibility by controlling the mobility of quantum dots during curing, resulting in improved color reproduction and reduced power consumption in liquid crystal display devices.
Implementation Method 1
a binder or a binder precursor which is soluble in the volatile component and forms a gel
Implementation Method 2
by performing at least one treatment of a cooling treatment, a heating treatment, a light irradiation treatment, or an energy ray irradiation treatment so as to cause the coating film to gel
Implementation Method 3
removing the volatile component from the gel film
Implementation Method 4
quantum dots that are excited by excitation light to emit fluorescence
Data Source
AI summary
Provided is a wavelength conversion film-forming composition which forms a wavelength conversion film by being applied to a substrate to form a coating film and curing the coating film, the wavelength conversion film-forming composition including at least quantum dots, a volatile component, and a binder that is soluble in the volatile component and/or a binder precursor that is soluble in or compatible with the volatile component, in which the wavelength conversion film-forming composition is gellable in the presence of the volatile component.