Transparent, photocatalytic, and self-cleaning TiO2 thin film is developed by TiO2 sol-gel coating on glass and polycarbonate (PC) substrates. Acetyl acetone (AcAc) suppresses the precipitation of TiO2 by forming a yellowish (complex) transparent sol-gel. XPS analysis confirms the presence of Ti2p and O1s in the thin films on glass and PC substrates. The TiO2- sol is prepared by stabilizing titanium (IV) isopropoxide (TTIP) with diethylamine and methyl alcohol. The addition of AcAcsilane coupling solution to the TiO2-sol instantaneously turns to yellowish color owing to the complexing of titanium with AcAc. The AcAc solution substantially improves the photocatalytic property of the TiO2 coating layer in MB solutions. The coated TiO2 film exhibits super hydrophilicity without and with light irradiation. The TiO2 thin film stabilized by adding 8.7 wt% AcAc shows the highest photo-degradation for methylene blue (MB) solution under UV light irradiation. Also, the optimum photocatalytic activity is obtained for the 8.7 wt% AcAc-stabilized TiO2 coating layer calcined at 450 oC. The thin-films on glass exhibit fast self-cleaning from oleic acid contamination within 45 min of UV-light irradiation. The appropriate curing time at 140 oC improves the anti-fogging and thermal stability of the TiO2 film coated on PC substrate. The watermark-free PC substrate is particularly beneficial to combat fogging problems of transparent substrates.

본 연구에서는 투명도와 기계적 특성을 향상시키기 위해 저온 공정의 졸-겔 법을 이용하여 하이브리드 복합체의 코팅 박막을 제조하였다. 하이브리드 복합체로는 ZrO2/TiO2/organosilane을 사용하였으며, 그 중 organosilane은 3-(trimethoxysilyl)propyl methacrylate을 사용하였고 이는 저온 공정의 광경 화 반응을 위해 도입되었다. 다양한 조성비로 합성된 복합체를 폴리 카보네이트 기판 위에 저온 공정의 졸 -겔 법을 이용하여 광경화와 열처리 공정을 거처 코팅 박막을 제조하였고 이 코팅 박막의 광학 특성 및 기계적 강도를 확인하였다. 코팅 박막은 가시광선 영역에서 97.5 % 이상의 투과도를 가짐을 확인하였고 기계적 강도는 9H 이상의 연필 경도를 가진 것을 확인하였다. 특히 ZTS-2-1 코팅 박막의 나노 압입 경도는 1.14 GPa로 가장 높게 측정되었다.

Anti-reflection coating films have used to increase the transmittance of displays and enhance the efficiency of solar cells. Hydrophobic anti-reflection coating films were fabricated on a glass substrate by sol-gel method. To fabricate an anti-reflection film with a high transmittance, poly ethylene glycol (PEG) was added to tetraethyl orthosilicate (TEOS) solution. The content of PEG was changed from 1 to 4 wt% in order to control the morphology, thickness, and refractive index of the SiO2 thin films. The reflectance and transmittance of both sides of the coated thin film fabricated with PEG 4 wt% solution were 0.3% and 99.4% at 500 nm wavelength. The refractive index and thickness of the thin film were n = 1.29 and d = 105 nm. Fluoro alkyl silane (FAS) was used for hydrophobic treatment on the surface of the anti-reflection thin film. The contact angle was increased from 13.2˚ to 113.7˚ after hydrophobic treatment.

ZrO2 films were coated on aluminum etching foil by the sol-gel method to apply ZrO2 as a dielectric material in an aluminum(Al) electrolytic capacitor. ZrO2 films annealed above 450˚C appeared to have a tetragonal structure. The withdrawal speed during dip-coating, and the annealing temperature, influenced crack-growth in the films. The ZrO2 films annealed at 500˚C exhibited a dielectric constant of 33 at 1 kHz. Also, uniform ZrO2 tunnels formed in Al etch-pits 1μm in diameter. However, ZrO2 film of 100-200 nm thickness showed the withstanding voltage of 15 V, which was unsuitable for a high-voltage capacitor. In order to improve the withstanding voltage, ZrO2-coated Al etching foils were anodized at 300 V. After being anodized, the Al2O3 film grew in the directions of both the Al-metal matrix and the ZrO2 film, and the ZrO2-coated Al foil showed a withstanding voltage of 300 V. However, the capacitance of the ZrO2-coated Al foil exhibited only a small increase because the thickness of the Al2O3 film was 4-5 times thicker than that of ZrO2 film.

In this study, the silica-based hybrid material with high barrier property was prepared by incorporating ethylene-vinyl alcohol (EVOH) copolymer, which has been utilized as packaging materials due to its superior gas permeation resistance, during sol-gel process. In preparation of this EVOH/SiO2 hybrid coating materials, the (3-glycidoxy-propyl)-trimethoxysilane (GPTMS) as a silane coupling agent was employed to promote interfacial adhesion between organic and inorganic phases. As confirmed from FT-IR analysis, the physical interaction between two phases was improved due to the increased hydrogen bonding, resulting in homogeneous microstructure with dispersion of nano-sized silica particles. However, depending on the range of content of added silane coupling agent (GPTMS), micro-phase separated microstructure in the hybrid could be observed due to insufficient interfacial attraction or possibility of polymerization reaction of epoxide ring in GPTMS. The oxygen barrier property of the mono-layer coated BOPP (biaxially oriented polypropylene) film was examined for the hybrids containing various GPTMS contents. Consequently, it is revealed that GPTMS should be used in an optimum level of content to produce the high barrier EVOH/SiO2 hybrid material with an improved optical transparency and homogeneous phase morphology.