Morphological Changes in Ultraviolet-Nanoimprinted Resin Patterns Caused by Ultraviolet-Curable Resins Absorbing Pentafluoropropane

Abstract

In this article, we revealed the maximum values of pentafluoropropane (PFP) absorbed by acrylate-type monomers and UV-curable resins causing radical photopolymerization and measured the viscosities in a state saturated with PFP. We described the influences of PFP condensable gas effectively used in UV nanoimprinting on the morphologies of resin patterns fabricated by UV nanoimprinting. The weights of the resins and monomers were increased by exposure to a PFP atmosphere, while the viscosities were reduced markedly. The absorption of PFP depended on the chemical structures of the monomers. The solubility parameter calculated by the Hoy method clearly suggested that the monomer with a solubility parameter of 20 (J cm-3)1/2 absorbed the most PFP. The UV-curable resin composed of the monomer absorbing a large amount of PFP resulted in morphological changes in nanoimprinted resin patterns where the height was lowered and the outermost surface became rough. The UV-curable resins having hydroxyl groups play an important role in preserving the size fidelity of UV-nanoimprinted resin patterns.

Surface Segregation of 1H,1H,9H-Hexadecafluorononyl Acrylate in Dimethacrylate Resin Films Cured by Exposure to Ultraviolet Light

“…12 Although there have been several studies on lowering the surface free energies of cured resins by searching for the most effective fluorinated additive to a certain resin, 13,14 general knowledge of what type of main monomer causes surface segregation of a certain fluorinated additive in a UV-curable resin is still lacking. In this communication, we demonstrated that Hansen's solubility parameter 15,16 was useful in searching for a suitable methacrylate monomer that decreased the surface free energy of a cured resin by adding 1H,1H,9H-hexadecafluorononyl acrylate (16F-AC).Glycerin 1,3-dimethacrylate (GDM) and 1,3-butanediol dimethacrylate (BDM) were used as the base monomers because of their similar chemical structures, in addition to their low viscosities, which are required for UV-NIL.17 16F-AC was chosen as the fluorinated reactive additive because of its good miscibility with the base monomers and according to the previous report that an outermost surface occupied by difluoromethyl groups shows a low surface free energy. 18 The concentration of a photoinitiator, Irgacure 907, was adjusted to 5.0 wt % for mixtures of each base monomer with 16F-AC.…”

“…15 We used Hansen's solubility parameter, calculated using the group contribution method proposed by Hoy,22 because the Hoy method is widely accepted. 16,23,24 Hansen's solubility parameter ¤ is expressed as shown in eq 1,…”

“…12 Although there have been several studies on lowering the surface free energies of cured resins by searching for the most effective fluorinated additive to a certain resin, 13,14 general knowledge of what type of main monomer causes surface segregation of a certain fluorinated additive in a UV-curable resin is still lacking. In this communication, we demonstrated that Hansen's solubility parameter 15,16 was useful in searching for a suitable methacrylate monomer that decreased the surface free energy of a cured resin by adding 1H,1H,9H-hexadecafluorononyl acrylate (16F-AC).…”

“…In this communication, we demonstrated that Hansen's solubility parameter 15,16 was useful in searching for a suitable methacrylate monomer that decreased the surface free energy of a cured resin by adding 1H,1H,9H-hexadecafluorononyl acrylate (16F-AC).…”

Breakthrough Achievement In Nanoimprint Lithography Using PFP Condensable Gas

“…The mechanism due to absorption of PFP by the liquid UV-curable resin was recently clarified. We demonstrated a solution strategy [48]. The volume of uncured resin before UV-exposure increases due to the absorption of PFP, while the volume of cured resin after UV-exposure decreases due to the release of PFP.…”