Surface modification of polyimide laser-drilled screen printing masks for low-viscosity liquids in print-and-imprint method

To lower a viscosity range of UV-curable liquid applicable to print-and-imprint methods, surface modification of polyimide (PI) laser-drilled screen printing masks with a hydrophobic and oleophobic surface modifier of tridecafluoro-1,1,2,2-tetrahydroocyltrimethoxysilane (FAS13) was investigated. The surface modification of PI surfaces with FAS13 was confirmed by measuring an increased contact angle for water after the surface modification. Three types of PI through-hole printing masks with a hole diameter of approximately 10 μm on a substrate-contact-side surface, named unmodified, surface-modified, and surface-and-hole-modified masks, were prepared by laser drilling using a picosecond pulse laser. The surface-modified mask only enabled selective screen printing of glycerol dimethacrylate (GDM)-based UV-curable liquid droplets onto a substrate surface. The mean volume of the printed and UV-cured droplets could be determined to be 0.55 pL. The comparison among the three PI masks in screen printing suggested that spreading of the low-viscosity UV-curable liquid on the substrate was suppressed by the surface-modified mask. The screen-printed droplets were molded by UV nanoimprinting with a fluorinated replica mold having 45 nm wide line-and-space patterns.