This paper reports different routes combining photopolymerization of epoxy and acrylate monomers or photo sol-gel reaction yielding to organic or hybrid nanocomposites with enhanced thermomechanical properties. First homogeneous Interpenetrating Polymer Networks based on a dimethacrylate and an epoxide were straightforwardly synthesized by means of UV curing without any phase separation. Then, a dimethacrylate resin was mixed with a variable amount of a methacrylate trialkoxysilane precursor. Upon UV irradiation, a dual organic-inorganic polymerization occurred in one step leading to increased scratch resistance. The structural properties of the resulting coatings were investigated by FT-IR and ²⁹Si solid state NMR spectroscopies. In addition, their thermomechanical behaviour was characterized by Dynamic Mechanical Analysis and scratch tests.

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A palladium nanoparticle/silica nanoparticle/acrylic polymer hybrid negative pattern was formed on a flexible film by photolithography and then converted to a copper pattern by electroless deposition. The negative pattern of the hybrid was formed by UV-irradiation of the layer composed of acrylate monomer, palladium salt, and a photo radical initiator. The photochemically generated radicals induced the radical polymerization of the acrylate and also reduced the palladium ion to form palladium nanoparticles. A copper film was deposited on the surface of the hybrid pattern by electroless deposition, where the palladium nanoparticles work as a catalyst and the nanometer-scale roughness due to the silica nanoparticles increases the adhesion between the polymer and copper.

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In this paper, the ability of two photobase generators, 2-benzyl-2-dimethylamino- 1-(4-morpholinophenyl)-butanone-1 (PBG1) and tetramethylguanidine phenylglyoxylate (PBG2), to polymerize epoxides at room temperature was investigated. The polymerization, which proceeds at room temperature, was found to be speeded up in the presence of thiols. On the basis of the results, and taking into account that both photobases are released during photochemical processes that also generate radicals, interpenetrated epoxy-acrylate polymer networks were also produced. Finally, a polythiourethane polymer was obtained using the strongest photobase generator PBG2.

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Photoisomerization of azobenzene is a reversible photochemical reaction and has potential applications to reusable photo-functional materials. Azobenzenophane (macrocyclic azobenzene), possessing multiple azobenzene moieties in a macrocyclic molecular skeleton, have been of interest due to their unique strained structure, isomerization properties such as multi step isomerization, molecular motion, and potential application to photoresponsive materials. In this paper, from the viewpoint of material applications, physical and photochemical properties of azobenzenophane are reviewed and the uniqueness arising from the cyclic molecular structure is discussed.

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Polymers of substituted norbornenes were produced using palladium catalysts in the presence of silane chain transfer agents (CTA) which act to control molecular weight. Yields were dramatically increased by addition of hydroxylic reagents such as ethanol. Spectroscopic analysis of these polymers by 1H NMR and MALDI-TOF MS confirmed that hydrogen-terminated polynorbornenes are generated leading to extremely low optical densities at 193 nm. Negative tone compositions containing norbornene copolymers with aliphatic and fluorinated alcohol substituents have been demonstrated.

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A novel thiocyanate-free cyclometalated ruthenium sensitizer for solar cells is designed and developed. Upon anchoring to nanocrystalline TiO₂ films, it exhibits a remarkable incident monochromatic photon-to-current conversion efficiency of 83%. The solar cell employing a liquid-based electrolyte exhibits a short circuit photocurrent density of 17 mA/cm², an open circuit voltage of 800 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 10.1% at standard AM 1.5 sunlight. To understand the structural, electronic, and optical properties of the cyclometalleted ruthenium sensitizer, we have investigated using density functional theory (DFT) and time-dependent DFT (TDDFT). Our results show the HOMO is located mostly on ruthenium and cyclometalated ligand, while the LUMO is on 4-carboxylic acid-4’-carboxylate-2,2’-bipyridine. Molecular orbitals analysis confirmed the experimental assignment of redox potentials, and TDDFT calculations allowed assignment of the visible absorption bands. The present findings provide new design criteria for the next generation of ruthenium sensitizers and help foster widespread interest in the engineering of new sensitizers that interact effectively with the I^-/I₃ ^-redox couple.

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Tris(8-hydroxyquinolinato) aluminum (Alq₃) is known to induce negative interface charge in multilayer organic light-emitting diodes (OLEDs) because of orientation polarization when fabricated in dark. Recently, it was reported that light illumination during the deposition of Alq₃ induces bulk charge in addition. In this study, the illumination effect on the performance of Alq₃-based OLED was examined. In comparison with the device fabricated in dark condition, the slight increase of the current density was observed. Light emission is also increased for constant driving voltage, while the luminous efficiency showed decrease.

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This article gives an overview of reactive-monolayer-assisted thermal nanoimprint lithography (R-TNIL) for the fabrication of patterned metal thin layers on substrates by simple wet etching using a thermoplastic polymer resist layer assisted by photochemically grafted polymer layer. A photoreactive monolayer causing a photoinduced graft reaction on the metal surface anchors interfacial resist polymers, resulting in the suppression of thermally induced dewetting of the resist layer and the improvement of lateral pattern resolution of metal thin layers. Line widths of metal patterns could be tuned by controlled side etching. Enhanced adhesion of resist layers was revealed by lateral force curves measured by scanning probe microscopy. It was demonstrated as an application that transparent conductive substrates having metal mesh structures were fabricated by R-TNIL. We also demonstrated R-TNIL involving electrodeposition, which allowed the preparation of metal patterns with controlled aspect ratio. It was proved that the photoreactive monolayer played important roles to fabricate submicrometer patterns of metal thin layers.

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This contribution sheds light on typical challenges in UV-based nanoimprint lithography (UV-NIL) from the perspective of direct polymer patterning. Direct polymer patterning is an emerging NIL technique with structure dimensions being much different from those in high resolution nanoimprint lithography resulting in new challenges and resist behavior being also much different from established NIL techniques. Special focus was put on very high structure aspect ratios, their filling behavior and structural shrinkage. Filling of large structures proceeded via squeezed flow rather than capillary filling. Top line width shrinkage was identified as remaining challenge for a faithful structure replication. Stamp-and-repeat UV-NIL with spin-coated films is discussed as an efficient process for manufacturing of planar photonics.

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In recent years, utilization and reduction of pattern size are following nanoimprint lithography (NIL) quickly. Since nanoimprint is mainly contact printing, a higher separation force causes damages in the master mold and imprinting tool, and degradation in pattern quality as well. There is a mold-release characteristic of a master mold and mold materials as one of the biggest subjects in utilization. Then, we focused on release materials, and the new fluorinated polymers, based on α-chloroacrylate added to mold materials, were developed. In this paper, we report these synthesis methods, specific properties such as static contact angle as well as the segregation of fluorinated polymers on resin surfaces.

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Photo polymerization characteristics of UV curable resist in UV nanoimprint lithography are studied on monomer conversion ratio. The monomer conversion ratio is measured by Fourier Transform Infrared Spectroscopy (FT-IR) and polymerization velocity is theoretically investigated. The relation between monomer conversion ratio and UV intensity is investigated. Also, dependence of polymerization velocity on resist thickness is discussed. Monomer conversion rate is related to the product of square root of the UV intensity and exposure time. The reaction speed decreases in thin films.

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Nano-/micro-scale structures of transparent crosslinked polytetrafluoroethylene (RX-PTFE) mold have been fabricated by combined process which is thermal and radiation process for fabrication of RX-PTFE (TRaf process). The nano-/micro-fabricated RX-PTFE were attempted to be applied for the transparent polymer molds of UV nanoimprint lithography (NIL). The ability of the RX-PTFE mold for UV-NIL was evaluated by the imprinted patterns. The RX-PTFE molds and the imprinted structures obtained by UV-NIL were observed by a field emission scanning electron microscope (FE-SEM). As a result, imprinted structures of photo-curable resin (Trimethylolpropane-triacrylate: TMPTA) by UV-NIL using RX-PTFE mold were successfully obtained. The nano-scale L&S patterns, square (410 nm × 410 nm) and hole (φ 170 nm) array patterns were clearly obtained.

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The demolding forces for various molds are studied for thermal imprint process. Molds are fabricated by anisotropic KOH etching of (110) Si wafer and conventional plasma etching. Although the side wall roughness by the KOH etching is much smaller than that by the plasma etching, the demolding forces for the both molds are similar. The demolding forces for the molds with various cavity depths are measured, and it is found that the demolding force depends on the total side wall area. The demolding force for the mold with line and space pattern is about 50 times as large as that for the mold with no patterns. These results show that the demolding force from the side wall is dominant in the thermal imprint process.

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Waveguides for back lighting have been produced using roll-to-roll nanoimprinting. More than 1000 pieces were fabricated and every 50th device was analysed by confocal microscope, atomic force microscopy and luminance measurements. The properties of the devices are of commercial quality, confirming that roll-to-roll nanoimprinting has potential for high throughput production.

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In this study, fabrication of microstructures was carried out using newly developed UV imprinting system named “Roller Press Scan^®”for large-area replication. Micro lens arrays were replicated using two types of UV resins and molds, onto quartz substrates. Microstructures have been replicated in uniform and have been confirmed high-throughput productivity.

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Continuous nano structures whose sizes 100 nm line and space were successfully fabricated using two step nanoimprint including oxygen (O₂) plasma irradiation on a silicon substrate in 8 × 56 mm² area. Silicon substrate surface condition is important property because fine and continuous pattern forming depend on photo curable resin uniform coating. O₂ plasma irradiation is realized to change into hydrophilic without damage for silicon substrate. The water contact angle was decreased to smaller than 40° after O₂ plasma irradiation. Therefore O₂ plasma irradiation has an advantage of treatment process for continuous nanostructure forming. Our activities on UV nanoimprint lithography are expected to be progress for large area continuous nano structures fabrication.

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Directed self-assembly of block copolymer polystyrene-block-polydimethylsiloxane by combining graphoepitaxy using nanoimprinted polyhedral oligomeric silsesquioxanes thin films as substrates and solvent annealing resulted in the BCP microphase segregation. For this purpose, the substrates for graphoepitaxy were fabricated by patterning the soft material POSS as thin films on silicon with nanoimprint lithography. The directed self-assembly of PS-b-PDMS resulted in the microphase segregation of PDMS cylinders with 25 nm pore diameter imbedded in a PS matrix. By modulating the hydrophobicity of POSS substrates, it was possible to control the orientation of the PDMS cylinders. For more hydrophobic POSS surfaces, the cylinders oriented parallel to the side walls surfaces whereas in more hydrophilic POSS surfaces the cylinders were oriented perpendicular to the side walls.

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The demplding forces for thermal imprint to polystyrene film are studied. Two molds with 0.4 μm and 4 μm pitch LS patterns are fabricated. The pattern heights are adjusted in order to keep the side wall areas of both the molds same. The demolding force for the 0.4 μm mold is much smaller than that for the 4 μm mold. The pattern height rather than the side wall area is important factor for the demolding force. The demolding force is increased by the UV/O₃ treatment. The effect is more obvious for the 0.4 μm mold than for the 4 μm mold, because the pattern density of the 0.4μμm mold is larger than that of the 4 μm

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It has been reported that the nano- /micro- fabricated crosslinked polytetrafluoroethylene (RX-PTFE) by focused ion beam (FIB) direct etching technique could be used as the polymeric molds for the ultraviolet nanoimprint lithography (UV-NIL) and electron beam NIL (EB-NIL). In this study, to evaluate the durability of RX-PTFE molds for repeating printing cycles, the RX-PTFE was spin-coated on two kinds of substrates; none-metal treated silicon wafer and 50 nm thick Al-layer deposited one. Then, RX-PTFE molds were obtained by FIB irradiation. 450 × 450 nm and 950 × 950 nm squares and φ 1000 nm circle were fabricated in 40 × 40 μm areas. Intervals of the squares and circle were 450 nm, 950 nm and 1000 nm, respectively. In the case of none-treated substrate, the 3rd imprinted pattern was distorted. On the other hand, the 10th imprinted patterns with UV-NIL were successfully obtained with the Al-layer deposited substrate. Though it is concerned about the mechanical strength of RX-PTFE degrading due to EB irradiation, EB-NIL was similarly succeeded with Al-layer deposited substrate. It is considered that the mold durability for printing would be improved due to high adhesion between Al-layer and RX-PTFE, because the fluorination of Al was caused by crosslinking treatment at high temperatures. Thus, it is suggested that the durability of RX-PTFE mold with Al-layer deposited substrate would be retained after 10 times UV- /EB-NIL processes.

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Polyimide (PI) has many advantages for microelectromechanical systems (MEMS) applications since it has flexibility, chemical stability, and thermal stability. However, one of major issues has been difficult in defining relatively large micro-patterns on PI surfaces using hot embossing. This paper presents improved hot-embossing processes to fabricate relatively large micropump patterns with dimensions between 100 and 5000 Μm and a depth of 200 Μm on a 360 Μm-thick PI film (Kapton JP, Dupont). Acceptably good shapes of the micropump structures were projected onto the PI substrate at a temperature range between 320 and 350 °C with a molding pressure of 1780 MPa using an anti-adhesion agent (HD-1100TH, OPTOOL) coating.

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