Discharge of viscous UV-curable resin droplets by screen printing for UV nanoimprint lithography

Abstract

We demonstrated a coating method of screen printing for discharging droplets of a high-viscosity resin on a substrate for ultraviolet (UV) nanoimprint lithography (NIL). Compared with a spin-coated resin film on a silicon substrate, discharged resin droplets on a silicon substrate were effective in terms of the uniformity of residual layer thickness (RLT) in contact with a mold with various pattern densities. Fluorescence microscope observations with a fluorescent-dye-containing UV-curable resin enabled the evaluation of the shapes of resin droplets discharged on a substrate surface. Widely used screen mesh plates composed of a stainless mesh covered with a patterned emulsion film caused defects of undischarged parts, whereas defects-free resin droplets with a narrow size distribution were discharged by mesh-free plates prepared with laser ablation. The pitch-to-diameter ratio in the configuration of 10-µm-diameter holes needs to be larger than 2.5 times for printing a resin having a viscosity of 12,800 mPa s.

Micro-print and nano-imprint methods combining laser-drilled screen printing and ultraviolet nanoimprint lithography: a review

“…The printed droplets have irregular shapes, and many printing defects are observed. 24) The printing defect arises from overlapping the entire hole of the emulsion mask with a cross point of the stainless wire mesh. The unshaped droplets are formed by covering a part of the printing hole with a stainless wire.…”

“…The lengths of the hole pitches are approximately SD0805-3 © 2022 The Japan Society of Applied Physics three times larger than the hole diameters for the displacement of the printed droplets with a regular shape. 24)…”

Selecting adhesive molecular layers with matched surface free energy and chemisorption for shape-fixed UV-cured thin films fabricated by laser-drilled screen printing and UV nanoimprinting

“…22) For UV-curable composite liquids with viscosities of higher than 1 Pa•s, laser-drilled screen printing and UV nanoimprinting have been proposed by the authors. [23][24][25][26] UV-curable composite liquids suitable for UV-NIL must have the following characteristics: the ability to handle quantitatively, low volatility, filling performance, low curing shrinkage, and excellent demolding. Because inkjet printing and laser-drilled screen printing quantitatively enable the placement of UVcurable droplets on a predetermined region of the substrate surface, the use of a mold having a mesa terrace with an area larger than the region of printed droplets prevents the formation of resin burrs that lead to unshaped defects of substrate surfaces after etching.…”

Design and Manufacture of a Novel Sunlight Guiding Panel

“…Among the conventional microprocessing or nanoprocessing technologies, nanoimprint lithography [10] has the advantages of high throughput and high-precision dimension control. Note that UV nanoimprint lithography has the excellent advantage of high-throughput efficiency because no heating and cooling processes are required and because of the minimal deformation of the imprint patterns realized using thermal expansion and contraction [11]. However, a mold with a pattern of the light-guiding structure has to be fabricated using nanoimprint lithography for manufacturing Coatings 2019, 9, 562 3 of 13 a light-guiding structure.…”