• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.230-233
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• 2003

New photopolymers were designed and prepared using the photosensitive polymer binders. The photochemical reaction of the photosensitive polymer binder was studied by virtue of UV absorption and infrared spectroscopy. The holographic gratings were successfully fabricated in these photopolymer film samples by conventional optical interference method. We also investigated the effect of photocrosslink in the polymer binder on the diffraction behavior of the photopolymer. The dynamic behaviors of the grating formation were studied with the change of exposure intensity in terms of the diffraction efficiency. Particularly, we focused our efforts to observe the variation of the diffraction efficiency during post UV curing process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.421-421
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• 2008

Generally, the polymer thick-film resistors for embedded organic or hybrid substrate are patterned by screen printing so that the accuracy of resistor pattern is not good and the tolerance of resistance is too high(${\pm}$20~30%). To reform these demerits, a method using Fodel$^{(R)}$ technology, which is the patterning method using a photosensitive resin to be developable by aqueous alkali-solution as a base polymer for thick-film pastes, was recently incorporated for the patterning of thermosetting thick-film resistor paste. Alkali-solution developable photosensitive resin system has a merit that the precise patterns can be obtained by UV exposure and aqueous development, so the essential point is to get the composition similar to PSR(photo solder resist) used for PCB process. In present research, we made the photopatternable resistor pastes using 8 kinds of epoxy acrylates and a conductive carbonblack (CDX-7055 Ultra), evaluated their developing performance, and then measured the resistance after final curing. To become developable by alkali-solution, epoxy acrylate oligomers with carboxyl group were prepared. Test coupons were fabricated by patterning copper foil on FR-4 CCL board, plating Ni/Au on the patterned copper electrode, applying the resistor paste on the board, exposing the applied paste to UV through Cr mask with resistor patterns, developing the exposed paste with aqueous alkali-solution (1wt% $Na_2CO_3$), drying the patterned paste at $80^{\circ}C$ oven, and then curing it at $200^{\circ}C$ during 1 hour. As a result, some test compositions couldn't be developed according to the kind of oligomer and, in the developed compositions, the measured resistance showed different results depending on the paste compositions though they had the same amount of carbonblack.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.27 no.1
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• pp.119-131
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• 2001

Exposure of the human skin to UV-light can cause sun-tanning, photoaging and even photo-carcinogenesis. Melanin is important in protecting the skin against UV damage, but excessive or uneven melanin production can lead to the formation of freckles and aged spot. Control of hyperpigmentation is becoming even more important as aged population continues to grow. These needs led us to develop effective and safe depigmenting-agent, kojyl 3-aminopropyl phosphate (kojyl-APPA), called Whitegen. The development of whitegen was based on the fact that phosphate group of 3-aminopropyl phosphate can make kojic acid more compatible to the skin membrane and more stable. Instability of kojic acid has been a problem in cosmetic use. The insertion of phosphoester group has been recognized as a powerful tool to improve such physical properties as solubility and stability, because the phosphodiester residue is well characterized as a non-toxic moiety, having a high affinity for cell membranes. Kojyl-APPA showed no tyrosinase inhibition effect compared to kojic acid in vitro, but showed tyrosinase inhibition effect in situ. It means that kojyl-APPA is converted to kojic acid enzymatically in cells. Kojyl-APPA showed the inhibitory activity on melanin synthesis in mouse melanoma and normal humal melnaocytes and also showed long-lasting stability in comparison with its original form (kojic acid). Kojyl-APPA showed depigmenting effects when applied to UVB-induced hyperpigmentated region of guinea pig skin. Based on these results, kojyl 3-aminopropyl phosphate can be used as a safe and effective ingredient for the brightness and cleanness of skin.

• BMB Reports
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• v.44 no.11
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• pp.741-746
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• 2011

Tanning ability is important, because it represents the ability of the skin to protect itself against ultraviolet (UV) radiation. Here, we sought to determine genetic regions associated with tanning ability. Skin pigmentation was measured at the outer forearm and buttock areas to represent facultative and constitutive skin color, respectively. In our study population consisting of isolated Mongolian subjects, with common histories of environmental UV exposure during their nomadic life, facultative skin color adjusted by constitutive skin color was used to indicate tanning ability. Through linkage analysis and family-based association tests of 345 Mongolian subjects, we identified 2 potential linkage regions regulating tanning ability on 5q35.3 and 12q13.2, having 6 and 7 significant single nucleotide polymorphisms (SNPs), respectively. Those significant SNPs were located in or adjacent to potential candidate genes related to tanning ability: GRM6, ATF1, WNT1, and SILV/Pmel17.

• Textile Coloration and Finishing
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• v.25 no.2
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• pp.126-133
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• 2013

Although para-aramid fibers poss higher mechanical properties, they show very low resistance to sunlight exposure. This paper studied on the effect of nano-sol coated $TiO_2$ to improve the photo-stability of p-aramid fibers. Titanium dioxides were prepared by sol-gel method from titanium iso-propoxide at different R ratio ($H_2O$/titanium iso-propoxide). All samples were characterized by XRD, TEM and UV-vis spectrometer. The mechanical properties of p-aramid fabrics by $TiO_2$ nano-sol coating before and after sunlight irradiation were measured with tensile tester. XRD pattern of titanium dioxide particles was observed by mixing phase together with rutile and anatase type. The results showed, after sunlight irradiation, the decreased mechanical properties of the fiber. Furthermore, the sunlight irradiation obviously deteriorated the surface and defected areas of the fiber severely by photo-induced chain scission and end group oxidation in air.

• Toxicological Research
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• v.31 no.2
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• pp.97-104
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• 2015

The skin exposure to solar irradiation and photoreactive xenobiotics may produce abnormal skin reaction, phototoxicity. Phototoxicity is an acute light-induced response, which occurs when photoreacive chemicals are activated by solar lights and transformed into products cytotoxic against the skin cells. Multifarious symptoms of phototoxicity are identified, skin irritation, erythema, pruritis, and edema that are similar to those of the exaggerated sunburn. Diverse organic chemicals, especially drugs, are known to induce phototoxicity, which is probably from the common possession of UV-absorbing benzene or heterocyclic rings in their molecular structures. Both UVB (290~320 nm) and UVA (320~400 nm) are responsible for the manifestation of phototoxicity. Absorption of photons and absorbed energy (hv) by photoactive chemicals results in molecular changes or generates reactive oxygen species and depending on the way how endogenous molecules are affected by phototoxicants, mechanisms of phototoxcity is categorized into two modes of action: Direct when unstable species from excited state directly react with the endogenous molecules, and indirect when endogeneous molecules react with secondary photoproducts. In order to identify phototoxic potential of a chemical, various test methods have been introduced. Focus is given to animal alternative test methods, i.e., in vitro, and in chemico assays as well as in vivo. 3T3 neutral red uptake assay, erythrocyte photohemolysis test, and phototoxicity test using human 3-dimensional (3D) epidermis model are examples of in vitro assays. In chemico methods evaluate the generation of reactive oxygen species or DNA strand break activity employing plasmid for chemicals, or drugs with phototoxic potential.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.35-40
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• 1993

A FET(field effect transistor) type lipid sensor was fabricated uy immobilizing lipase enzyme on the gate of pH-ISFET($SiO_{2}/Si_{3}N_{4}$). A water soluble polymer, polyvinyl alcohol(PVA) was modified with 1-methyl-4-(formyl-styryl) pyridinium methosulfate(SbQ) to give a photosensitive membrane(PVA-SbQ) in which lipase was immobilized. The optimum photolithographic conditions were ; spin coating speed $5,000{\sim}6,000$ rpm. UV exposure time $20{\sim}30$ seconds, developing time in water $30{\sim}40$ seconds, and vacuum drying time 45 min. at room temperature with the suspension containing PVA-SbQ aqueous solution(SbQ 1mol%, 10 wt %) $200{\mu}L$, bovine serum albumin (BSA) 7.5 mg, and lipase 10 mg. The lipid sensor showed good linear calibration curve in the range of $10{\sim}100$ mM triacetin as a lipid sample.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.413-416
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• 2008

Recently, the results of vital tissue test showed that nitrosodimethylamine (NDMA) as a disinfection by-product (DBP), could be regarded as a carcinogen because a tumor was observed in organs. U.S.EPA indicated 0.7 ng/L as exposure concentration of NDMA based on a risk assessment target with a lifetime cancer risk of $10^{-6}$. Several recent studies have shown that UV oxidation could remove NDMA. However, UV oxidation is uneconomical and can reform NDMA after treating. In addition, the treatment mechanism of adsorption has not been founddue to the uncertainty of NDMA pathway. In addtion, NDMA has a radioisotope $^{14}C$-labeled which can be analyzed at low concentration of NDMA by Liquid Scintillation Counter (LSC). This study has investigated NDMA determination using LSC at an extremely low range from 1 to 100 ng/L and NDMA removal by powdered activated carbon (PAC) adsorption. For $^{14}C$-NDMA by LSC, the highest correlation over 99% between count number and NDMA concentrationwas obtained with possibility of $^{14}C$-NDMA concentration up to 1 ng/L. In the presence of PAC ranging from 50 to 10,000 mg/L, $^{14}C$-NDMA was removed from 18% to 97% for Sigma-Aldrich corporation (S-A co.) and from 9% to 93% by PAC for Daejung corporation (Dj co.). Hence it was found that the removal efficiency by PAC adsorption could vary depending on PAC types from different companies. For PAC adsorption capacity of $^{14}C$-NDMA using the Freundlich isotherm, $K_f$ and 1/n of PAC from S-A co. were $2.67\times10^{-3}$ ng/mg and 1.009, while those of PAC from Dj co. were $1.30\times10^{-3}$ ng/mg and 0.994, respectively. Thus, PAC from S-A co. showed twice higher adsorption capacity than Dj co.

• Food Engineering Progress
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• v.15 no.3
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• pp.257-261
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• 2011

Biodegradable plastics were developed using biodegradable pellets made of corn stalk and rice husk and their safety as food packages and their biodegradability against light (ultraviolet (UV)), heat, and fungi were evaluated. Four kinds of 50-${\mu}m$ biodegradable plastics were produced by extruding the mixtures of the biodegradable pellets, low-density polyethylene (LDPE), high-density polyethylene (HDPE), and linear low-density polyethylene (LLDPE) with different compositions. Developed biodegradable plastics were safe to be used as food packages. The initial tensile strength and percentage elongation of the plastics were similar to those of LDPE, but the values decreased with increased their exposure time to UV and heat. The fungal biodegradability of the biodegradable plastics was higher than that of LDPE. The biodegradability of the biodegradable plastics shows the potential for them to be used as sustainable food packages.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.77-81
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• 2020

Resistive RAM (ReRAM) is a strong candidate for the next-generation nonvolatile memories which use the resistive switching characteristic of transition metal oxides. The resistive switching behaviors originate from the redistribution of oxygen vacancies inside of the oxide film by applied programming voltage. Therefore, controlling the oxygen vacancy inside transition metal oxide film is most important to obtain and control the resistive switching characteristic. In this study, we introduced an applying electric field into photochemical metal-organic deposition (PMOD) process to control the oxidation state of metal oxide thin film during the photochemical reaction by UV exposure. As a result, the surface oxidation state of FeOx film could be successfully controlled by the electric field-assisted PMOD (EFAPMOD), and the controlled oxidation states were confirmed by x-ray photoelectron spectroscopy (XPS) I-V characteristic. And the resistive switching characteristics with the oxidation-state of the surface region could be controlled effectively by adjusting an electric field during EFAPMOD process.