Coffee ring-free inkjet printing using UV-curable quantum dot-acrylate solution for high resolution displays

Abstract

We report the coffee ring-free inkjet printing using a UV curable quantum dot (QD)-acrylate coating solution. The main objective of this study is to utilize UV curable acrylate monomers to prevent formation of coffee rings and hence to obtain uniform QD patterns using inkjet printing. For the UV curing reaction, cyclohexylmethacrylate (CHMA) was selected as the acrylate monomer, 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(o-benzoyloxime) (OXE-01), 2-isopropylthioxanthone (ITX), and 2,2-dimethoxy-2-phenylacetophenone (DMPA) were tested as photoinitiators (PIs), and pentaerythritol triacrylate (PETA) was used as a crosslinker. When the QDs were used with CHMA monomers without UV curing, inkjet printing resulted in the formation of coffee rings or cracks during monomer evaporation. However, UV curing with ITX as a PI produced inkjet droplets with uniform surfaces owing to the balance between evaporation and UV curing rates. By optimizing the compositions of the monomer, PI, and crosslinker, we successfully obtained uniform QD patterns on the micrometer scale using inkjet printing. We also demonstrated that this technique could be applied to inkjet printing of the 400 ×100 μm patterned epoxy molds. These results will be useful for the inexpensive and rapid fabrication of high-resolution QD displays using inkjet printing.