• Macromolecular Research
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• v.15 no.6
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• pp.533-540
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• 2007

We designed and successfully synthesized UV curable, functional acrylate monomers having a polarizing group, i.e., an electron-withdrawing and/or electron-donating group for the optical materials of high refractive index. Optical polymer films made from the functional methacrylate monomers were achieved with photo crosslinking under UV illumination. A monomer having amino and cyano groups (Dimer-CN) exhibited the highest refractive index ($n_{TE}$=1.595 at 850nm) among the studied methacrylate derivatives, due to the large polarizability of the dipolar monomer structures with electron-donating and withdrawing groups. By controlling the compositions of the functional acrylate monomer of copolymers, the refractive indices of the polymers were readily adjusted within a wide range of 1.498-1.595. The copolymers showed a high glass transition temperature $(T_g)$ and good thermal stability, which are desirable for optical applications. $T_g$ and $T_{10%}$ (10%-weight loss occurred) of the copolymers ranged from $120-140^{\circ}C$ and from $329-387^{\circ}C$, respectively.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.637-642
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• 2016

In this study, we prepared and characterized a acrylate based UV-curable plastic scintillator. It was used co-polymers TMPTA, DHPA and Ultima $Gold^{TM}$ LLT organic scintillator. The emission spectrum of the plastic scintillator was located in the range of 380~520 nm, peaking at 423 nm. And the scintillator is more than 50% transparent in the range of 400~800 nm. The emission spectrum is well match to the quantum efficiency of photo-multiplier tube and the fast decay time of the scintillation is 12 ns, approximately. This scintillation material provides the possibility of combining 3D printing technology, and then the applications of the plastic scintillator may be expected in human dosimetry etc.

• Elastomers and Composites
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• v.51 no.4
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• pp.275-279
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• 2016

Additive manufacturing or 3D printing is a new manufacturing process and its application is getting growth. However, the product qualities such as mechanical strength, dimensional accuracy, and surface quality are low compared with conventional manufacturing process such as molding and machining. In this study not only mechanical characteristics of polymer sandwich panel having three dimensional core layer but also mechanical characteristics of core layer itself were analyzed. The shape of three dimensional core layer was pyramidal kagome structure. This core layer was fabricated by two different methods, injection molding with PP resin and material jetting type 3D printing with acrylic photo curable resin. The material for face sheets in the polymer sandwich panel was PP. Maximum load, stiffness, and elongation at break were examined for core layers fabricated by two different methods and also assembled polymer sandwich panels. 3D printed core showed brittle behavior, but the brittleness decreased in polymer sandwich panel containing 3D printed core. The availability of 3D printed article for the three dimensional core layer of polymer sandwich panel was verified.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.220-223
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• 2005

The rapid prototyping (RP) technology has been advanced for various applications such as verification of design, functional test. However, many RP machines still have low accuracy and limitation of applications for various materials. In this research, a hybrid RP system was developed to improve precision of micro parts. This hybrid system consists of deposition and material removal process by mechanical micro machining to fabricate nano composites using photo-curable polymer resin with various nano particles. In this work, using hybrid RP process with Multi-Walled Carbon Nano Tube (MWCNT) and hydroxyapatite, micro parts were fabricated. The precision of parts was evaluated based on the original CAD design, and to see the effect of nano particles on mechanical properties, tensile strength was measured. From the results of experiments, it was confirmed that the part made by hybrid process had higher precision, and the addition of nano particles improved mechanical properties.

• Journal of the Korean institute of surface engineering
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• v.55 no.3
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• pp.173-179
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• 2022

This study presents a roll-to-roll process which is capable of Ag nanowire (AgNW) transfer from polyethylene terephthalate (PET) film to polycarbonate (PC) film. We developed a roll-to-roll machine that consists of two film suppliers, a coater of photo-curable resin, a film laminator, an ultraviolet (UV) exposure unit, and a film winder to facilitate large-area electrode transfer between different flexible substates. Using the process, optimal fabrication condition was investigated by parametric experiments in terms of the UV exposure time, number of thermal cycling, and exposure time of high temperature and humidity. A fabricated AgNW on PC film showed sheet resistance of 52 Ω/sq and optical transmittance of approximately 80 % over a range of visible light.

• Polymer(Korea)
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• v.36 no.3
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• pp.315-320
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• 2012

Ultra violet (UV) curable pressure sensitive adhesives (PSA) were prepared by controlling both the structure of acryl copolymer and the functionality and content of multi-functional monomers. Acryl copolymer worked as the base polymer for giving the tackiness. Multi-functional monomers were used to vary the crosslinked structure and the degree of crosslink. Acryl copolymer showed the reduced peel strength after UV curing by decreasing the content of 2-ethylhexyl acrylate in the monomer composition. Both the peel strength of PSA and the content of residue found on silicon wafer decreased after UV curing by increasing the functionality of multi-functional monomers. UV curable PSA containing 20 phr six-functional monomer showed the higher peel strength before UV curing and the lower peel strength and the least residue on silicon wafer after UV curing.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.4 s.37
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• pp.275-280
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• 2005

We propose a new approach to greatly simplify the fabrication of conventional nanoimprint lithography (NIL) by combined nanoimprint and photolithography (CNP). We introduce a hybrid mask mold (HMM) made from UV transparent material with a UV-blocking Cr metal layer placed on top of the mold protrusions. We used a negative tone photo resist (PR) with higher selectivity to substrate the CNP process instead of the UV curable monomer and thermal plastic polymer that has been commonly used in NIL. Self-assembled monolayer (SAM) on HMM plays a reliable role for pattern transfer when the HMM is separated from the transfer layer. Hydrophilic $SiO_2$ thin film was deposited on all parts of the HMM, which improved the formation of SAM. This $SiO_2$ film made a sub-10nm formation without any pattern damage. In the CNP technique with HMM, the 'residual layer' of the PR was chemically removed by the conventional developing process. Thus, it was possible to simplify the process by eliminating the dry etching process, which was essential in the conventional NIL method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.269-270
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• 2009

The biased vertical alignment (BVA) liquid crystal (LC) mode shows a has a distinct advantage of lower manufacture cost due to the elimination of a lithographic process step to form either ITO-patterning or protrusions on the color-filter substrates. However, those devices have complex voltage conditions which is the respective induce voltage on common electrode, pixel electrode and bias electrode when positive and negative frame. In order to overcome the complex voltage condition, the pretilt angles is controlled by photo polymerization of the UV-curable reactive mesogen (RM). According to our studies, voltages to the cell are critical to achieve an optimized surface-modified quality BVA (Q-BVA) mode which provides the well defined reorientation of the LCs with respect to an electric field.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.221-226
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• 2016

Production of eco-friendly and biologically harmless materials is strongly required in all industries. In particular, reducing volatile organic compounds in coating processes is extremely important to secure worker's safety. During recent two decades, extensive research works on water-borne polyurethane dispersion (PUD) have been continuously developed as an alternative to solvent-borne polyurethane. However, PUD was shown inferior mechanical properties to the organic solvent-borne polyurethane due to a limit to the molecular weight increase, which resulted in the limit of applications. To overcome this drawback, several approaches have been examined such as polymer blends and thermal/radiation induced crosslinking. Among these methods, the radiation curing system was suitable for industrialization because of the high crosslinking density and fast curing speed. In this study, we overcame the drawback for PUD via introducing benzophenone radiation curable units to PUD. We synthesized PUD films which possessed good dispersion in water for 30 days, increased Tg and Td more than $5^{\circ}C$ after UV curing film as well as improved young's modulus more than double.