Inkjet-Printed Encapsulated Quantum Dots for Micro LED Light Conversion
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Solution Overview
Problem
Conventional micro LED display panels using quantum dots light conversion units face challenges in achieving optimal color saturation and brightness due to difficulties in maintaining a light-shielding layer thickness greater than 5 μm and unequal filling of red and green quantum dots, leading to inadequate color gamut and visual recognition, especially in outdoor applications.
Innovation Solution
A method involving inkjet-printed encapsulated quantum dots, where a transparent substrate with a hydrophobic surface is used to form micro encapsulated QD structures through inkjet-printing of QDs solutions, creating a light conversion unit with balanced red, green, and blue QD distribution, enhancing color gamut and brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light-shielding layer with thickness greater than 5 μm is used to block light, then light blocking performance is improved, but the through holes become askew and fail to align with the micro LED components
Solution Approach 1:
The patent removes the light-shielding layer entirely from the structure. Instead of using a thick light-shielding layer with through holes, the invention uses a transparent substrate where the light conversion unit directly blocks unwanted light paths. This extraction of the problematic light-shielding layer eliminates the alignment issue between through holes and micro LED components while maintaining light blocking functionality through the quantum dot structures themselves.
Solution Approach 2:
The patent inverts the conventional approach by making the substrate transparent rather than opaque. Instead of using a light-shielding layer that blocks light and requires through holes for light passage, the invention uses a transparent substrate where light conversion units are strategically placed to block specific light paths. This inversion eliminates the need for through holes and their associated alignment problems.
2Ease of manufacture
If quantum dots material is filled into through holes to convert light, then color conversion is achieved, but the filling amount of red and green quantum dots becomes unequal leading to poor color saturation
Solution Approach 1:
The patent employs inkjet printing technology that deposits quantum dots material in a controlled manner directly onto the transparent substrate. The inkjet printing process inherently provides uniform distribution of red and green quantum dots through precise digital control of deposition parameters, eliminating the manual filling process that causes unequal filling amounts. The system self-regulates the filling uniformity through automated printing parameters.
Solution Approach 2:
The patent replaces the mechanical filling process (manual or automated injection of quantum dots into through holes) with an inkjet printing system that deposits quantum dots as liquid ink. This substitution transforms the mechanical filling operation into a controlled liquid deposition process, enabling precise and uniform distribution of different quantum dots materials through digital printing parameters control.
3Device complexity
If conventional LCD technology is used to display images, then device structure is simple, but color gamut is limited to 72% NTSC and brightness cannot exceed 1,000 nits
Solution Approach 1:
The patent changes the fundamental parameters of the display technology by transitioning from LCD to micro LED with quantum dot light conversion. This parameter change enables the display to achieve color gamut exceeding 100% NTSC and brightness over 1,000 nits. The invention maintains relatively simple device structure by using a transparent substrate with integrated light conversion units, avoiding complex multi-layer LCD structures while achieving superior optical performance.
4Manufacturing precision
If inkjet printing is used to deposit quantum dots solution on hydrophobic surface, then uniform droplet formation is achieved, but the coffee ring effect causes outward flow of solute
Solution Approach 1:
The patent acknowledges the coffee ring effect as an inherent phenomenon during inkjet printing but converts its harmful impact into a beneficial outcome. By controlling the drying process parameters, the outward flow of solute caused by the coffee ring effect is utilized to achieve uniform distribution of quantum dots across the droplet area. The controlled evaporation and outward flow prevent solute aggregation and promote even coating, transforming a typically harmful effect into a useful mechanism for uniform material distribution.
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 method achieves an excellent color gamut of approximately 110% NTSC, improving color saturation and visual recognition, particularly suitable for outdoor display applications.
Implementation Method 1
a droplet of the QDs solution is formed on the hydrophobic surface
Implementation Method 2
a solute having a cohesion force
Implementation Method 3
in case of letting the transparent substrate have a hydrophobic surface, so as to make the cohesion force of the solute greater than a driving force for impelling outward-bound flow that is induced by a coffee ring effect
Implementation Method 4
applying a drying process to the droplet of the QDs solution, so as to make a volume of the droplet shrink with an increase of a drying time
Data Source
AI summary
A method for making inkjet-printed encapsulated quantum dots and a light conversion unit using the inkjet-printed encapsulated quantum dots are disclosed. The light conversion unit comprises: a substrate, a light convertor carrying layer having several accommodating grooves, several first micro encapsulated QD structures, and several second micro encapsulated QD structures. In case of letting the substrate has a hydrophobic surface, at least one inkjet-printing nozzle is utilized for injecting a first QDs solution and a second QDs solution into the accommodating grooves by a form of droplet, such that one third of the accommodating grooves are formed with the first micro encapsulated QD structure, and another one third of the accommodating grooves formed with the second micro encapsulated QD structure. Moreover, a micro LED display panel having the light conversion unit exhibits a color gamut that is approximately 110% NTSC.