POS5-1365
Enhancing the EHD Jet Printing Stability of Optical Clear Adhesive (OCA) via Partial curing
When and Where
Nov 30, -0001
00:00 - 00:00
Presenter(s)
Yongsu Son (Dept. of Polymer Science and Engineering, Dankook University)
Co-Author(s)
Abstract
Optical clear adhesive (OCA) is a pressure-sensitive material that bonds the individual layers of display panels without optical loss, and it has conventionally been used primarily in film form. However, increasing demand for localized adhesion in Micro LED repair and semiconductor packaging requires a printing technology capable of precisely applying adhesive. Electrohydrodynamic (EHD) jet printing is a next-generation patterning technology that ejects droplets using an electric field, unlike piezo inkjet printing, which relies on pressure. It offers the advantages of applying to high viscosity inks and forming droplets smaller than the nozzle diameter.
In this study, an OCA was prepared by formulating a three-acrylate system (2-ethylhexyl acrylate (2-EHA), n-butyl acrylate (n-BA), and acrylic acid (AA)) with a dual crosslinker and a photoinitiator, and its printing stability was evaluated.
The uncured OCA had a low viscosity of 1.4 cP and, during EHD printing, was ejected as a dripping jet. The droplets spread widely toward the edges and evaporated rapidly, exhibiting unstable ejection behavior during continuous printing.
In contrast, the partially photocured OCA formed long molecular chains during curing, and entanglement increased via crosslinking reactions between chains, thereby raising the viscosity to 455 cP. As a result, it formed a stable cone-jet during EHD printing and ejected droplets smaller than the nozzle. Furthermore, by suppressing intra-droplet repulsion due to residual charge and excessive spreading, it exhibited delayed evaporation and superior printing accuracy compared with the uncured OCA.
These results demonstrate that the viscosity achieved through partial photocuring improves the printing stability of the OCA against the effects of residual charge, and they suggest the feasibility of achieving microscale precision bonding via EHD printing.
In this study, an OCA was prepared by formulating a three-acrylate system (2-ethylhexyl acrylate (2-EHA), n-butyl acrylate (n-BA), and acrylic acid (AA)) with a dual crosslinker and a photoinitiator, and its printing stability was evaluated.
The uncured OCA had a low viscosity of 1.4 cP and, during EHD printing, was ejected as a dripping jet. The droplets spread widely toward the edges and evaporated rapidly, exhibiting unstable ejection behavior during continuous printing.
In contrast, the partially photocured OCA formed long molecular chains during curing, and entanglement increased via crosslinking reactions between chains, thereby raising the viscosity to 455 cP. As a result, it formed a stable cone-jet during EHD printing and ejected droplets smaller than the nozzle. Furthermore, by suppressing intra-droplet repulsion due to residual charge and excessive spreading, it exhibited delayed evaporation and superior printing accuracy compared with the uncured OCA.
These results demonstrate that the viscosity achieved through partial photocuring improves the printing stability of the OCA against the effects of residual charge, and they suggest the feasibility of achieving microscale precision bonding via EHD printing.
