Contact-Angle-Guided Semi-Cured Slot-Die Coating Eliminates Air Entrapment in LED Multilayer Films

Zikeng Fang ¹, Jiaqi Wan ¹, Chenghang Li ²

⁰State Key Laboratory of High-Performance Precision Manufacturing, Dalian University of Technology, Dalian 116024, China.

Polymers +

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June 13, 2025

View abstract on PubMed

Summary

Researchers identified air bubble formation in LED polymer multilayer films during standard processing. A novel semi-cured slot die coating method was developed to create bubble-free films, enhancing LED quality.

Area Of Science

Materials Science and Engineering
Polymer Science
Optical Engineering

Background

LED polymer multilayer films offer superior properties like controlled particle distribution and spectral tuning compared to single-layer coatings.
The conventional "coat-dry-coat" method for fabricating these films frequently results in trapped air bubbles, compromising film quality and uniformity.

Purpose Of The Study

To investigate the underlying mechanism of air entrainment during the formation of LED polymer multilayer films.
To develop and validate a strategy for mitigating air bubble formation in these advanced optical films.

Main Methods

Utilized high-speed microscopy to capture and analyze interfacial dynamics during film formation.
Performed contact-angle measurements to quantify the wetting behavior of the polymer layers.
Employed numerical simulations, incorporating temperature-dependent viscosity, to model air entrainment and predict coating parameters.

Main Results

Identified low contact angles of cured bottom layers as a primary cause of liquid front destabilization and bubble formation.
Confirmed that reduced wettability and vortex formation are key drivers of air entrainment through simulations.
Demonstrated that a semi-cured slot die coating approach effectively modifies surface wettability and suppresses flow instabilities.

Conclusions

The developed semi-cured slot die coating strategy successfully produces reliable, bubble-free multilayer films.
Improved simulation accuracy by incorporating temperature-dependent viscosity significantly enhances the prediction of coating-gap limits.
This research enables the consistent fabrication of high-quality LED polymer films, advancing applications in light-emitting diode technology.

Keywords:

LED polymer multilayer films air entrainment mechanism interfacial wettability semi-cured slot-die coating