• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.53-54
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• 2006

• Proceedings of the Korean Fiber Society Conference
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• 2000.04a
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• pp.1.2-4
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• 2000

• Current Optics and Photonics
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• v.2 no.3
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• pp.286-290
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• 2018

We investigated the dependence of the retardation dispersion on the polarization direction of ultraviolet (UV) light during the photopolymerization of self-organized smectic reactive mesogen (RM) molecules. RM retarder film that was photopolymerized with UV light linearly polarized parallel to the layer plane showed negative dispersion (ND) of retardation for a wide range of UV polymerization temperatures. On the other hand, film that was photopolymerized with unpolarized UV light showed negative dispersion in a narrow range of UV polymerization temperatures. With a certain UV polymerization temperature, the dispersion of retardation was converted from positive to negative, depending on the UV polarization.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.299-309
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• 1999

The composite resin, due to its esthetic qualities, is considered the material of choice for restoration of anterior teeth. With respect to shade control, the direct-placement resin composites offer some distinct advantages over indirect restorative procedures. Visible-light-cured (VLC) composites allow dentists to match existing tooth shades or to create new shades and to evaluate them immediately at the time of restoration placement. Optimal intraoral color control can be achieved if optical changes occurring during application are minimized. An ideal VLC composite, then, would be one which is optically stable throughout the polymerization process. The shade guides of the resin composites are generally made of plastic, rather than the actual composite material, and do not accurately depict the true shade, translucency, or opacity of the resin composite after polymerization. So the numerous problems associated with these shade guides lead to varied and sometimes unpredictable results. The aim of this study was to assess the color changes of current resin composite restorative materials which occur as a result of the polymerization process and to compare the color differences between the shade guides provided with the products and the actual resin composites before- and after-polymerization. The results obtained from this investigation should provide the clinician with information which may aid in improved color match of esthetic restoration. Five light activated, resin-based materials (${\AE}$litefil, Amelogen Universal, Spectrum TPH VeridonFil-Photo, and Z100) and shade guides were used in this study. Three specimens of each material and shade combination were made. Each material was condensed inside a 1.5mm thick metal mold with 10mm diameter and pressed between glass plates. Each material was measured immediately before polymerization, and polymerized with Curing Light XL 3000 (3M Dental products, USA) visible light-activation unit for 60 seconds at each side. The specimens were then polished sequentially on wet sandpaper. Shade guides were ground with polishing stones and rubber points (Shofu) to a thickness of approximately 1.5mm. Color characteristics were performed with a spectrophotometer (CM-3500d, Minolta Co., LTD). A computer-controlled spectrophotometer was used to determine CIELAB coordinates ($L^*$, $a^*$ and $b^*$) of each specimen and shade guide. The CIELAB measurements made it possible to evaluate the amount of the color difference values (${\Delta}E{^*}ab$) of resin composites before the polymerization process and shade guides using the post-polishing color of the composite as a control, CIE standard D65 was used as the light source. The results were as follows. 1. Each of the resin composites evaluated showed significant color changes during light-curing process. All the resin composites evaluated except all the tested shades of 2100 showed unacceptable level of color changes (${\Delta}E{^*}ab$ greater than 3.3) between pre-polymerization and post-polishing state. 2. Color differences between most of the resin composites tested and their corresponding shade guides were acceptable but those between C2 shade of ${\AE}$litefil and IE shade of Amelogen Universal and their respective shade guides exceeded what is acceptable. 3. Comparison of the mean ${\Delta}E{^*}ab$ values of materials revealed that Z100 showed the least overall color change between pre-polymerization and post-polishing state followed by ${\AE}$litefil, VeridonFil-Photo, Spectrum TPH, and Amelogen Universal in the order of increasing change and Amelogen Universal. Spectrum TPH, 2100, VeridonFil-Photo and ${\AE}$litefil for the color differences between actual resin and shade guide. 4. In the clinical environment, the shade guide is the better choice than the shade of the actual resin before polymerization when matching colors. But, it is recommended that custom shade guides be made from resin material itself for better color matching.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.120-122
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• 1997

In this paper, the viewing angle characteristics of amorphous (a) - twisted nematic (TN) - liquid crystal display (LCD) on poly(viny)cirmamate (PVC) alignment surfaces were investigated. It was found that the threshold voltage is increased with increasing the polymerization on PVC surfaces. We suggest that the threshold voltage is affected to the surface anchoring strength with increasing the polymerization of the alignment film. Also, we obtained that the viewing angle of a-TN-LCD is increased with increasing the polymerization on PVC surfaces. Finally, we considered that the viewing angle of a-TN-LCD on PVC surfaces is large compared to TN-LCD on rubbed polyimide (Pl) surface.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.242.2-242.2
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• 2011

Molecularly imprinted polymer thin films were applied to develop a gas sensor based on the surface plasmon resonance phenomenon for small gaseous molecules such as toluene and xylene. The imprinted polymer films were synthesized via photo-polymerization method using various combination of templates, functional monomers and cross-linkers. The temperature of pre-polymerization solutions and the power of UV light were controlled for optimized performance of gas sensing. The morphology and porosity of the polymer films were controlled by varying the mixing ratios of the pre-polymerization solutions and confirmed by atomic force microscopy. By fitting the adsorption/desorption sensorgrams to conventional kinetic models, the effects of different templates and cross-linkers were interpreted in term of the structural differences of the polymer networks formed on the gold film. The sensitivity and selectivity of sensors were estimated for toluene and xylene, and also for humidity and other gaseous molecules such as formaldehyde and ammonia.

• Macromolecular Research
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• v.17 no.9
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• pp.651-657
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• 2009

This study examined the optimum compositions of binder, photo-acid generator (PAG) and sensitizer for the cationic ring opening polymerization of 1,3-bis[2-(3-{7-oxabicyclo-[4.1.0]heptyl})]-tetramethyldisiloxane in the presence of polydimethylsiloxane with four epoxide moieties as a co-monomer. When diffractive efficiency (DE) values were compared quantitatively to analyze the effect of the binder on holographic photopolymerization, DE was affected by the viscosity of the binders and miscibility with the monomer mixture. Extremely low DE values were observed when the immiscible dimethyl silicone was used as a binder. Therefore, methylphenyl silicone, which is miscible with the monomer mixture, was used as the binder for further studies. The optimal conditions were a binder viscosity between 250 to 390 cP, and contents of the binder, PAG, and sensitizer were 75-125 wt%, > 6 wt% and 0.05 wt% to the total monomer mixture, respectively.

• Proceedings of the Korean Fiber Society Conference
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• 2007.11a
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• pp.307-308
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• 2007

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.2
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• pp.46-56
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• 2014

The aim of this reviews is to introduce the information concerning design of the UV-curable jet ink composition in order to provide a good adhesive property on non-porous surface. In order to clarify the viscosity dependence of flying speed for the UV curable jet ink, rheological analysis and observation of the flying state of the ink were carried out. The relationship between ink formulas and adhesive property on non-porous surface was investigated. It was examined the adhesive property of radical polymerization type UV curable jet ink included hydrogen abstraction type photo-initiator, it was expected that the strong adhesive strength can be obtained between the ink and non-porous surface in this study. UV curable jet ink with a slight amount of water was prepared. Optimum ratio of the cationic polymerization type UV curable jet ink shows an adequate adhesive strength towards two kinds of non-porous surface such as glass, poly(vinyl chloride) when tests were conducted on the ink jet-printing test machine.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.172-178
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• 1992

The graft copolymerization of acrylonitrile(AN) onto chitosan film by using $F^{3+}(FeCl_3{\cdot}6H_2O)$ as a photosensitizer in an aqueous medium was carried out under ultraviolet(UV) irradiation. The grafted copolymer was identified by using IR spectroscopy and scanning electron microscope. The effects of various polymerization parameters involving monomer concentration, photosensitizer concentration, polymerization time and polymerization temperature were investigated. As monomer concentration and photosensitizer concentration were increased, the percent grafting was increased up to limiting value. And also the percent grafting was found to increase by increasing the polymerization time and temperature.