Hiroyuki Tomonaga

Ultraviolet ray absorbing coatings on glass for automobiles

Ultraviolet ray (UV) absorbing coating consisting of a complex oxide of cerium and titanium was deposited on glass via the sol-gel process. Addition of TiO 2 to CeO 2 changed the crystallinity and coordination state of CeO 2 and improved UV absorption. Formation of a double-layered coating comprised of outer CeO 2 -TiO 2 layer and inner TiO 2 -SiO 2 layer diminished the interference coloring and improved the adhesion of the coating to the glass substrate. The double layer coated glass shows high UV-shielding properties without visible light absorption and excellent durability against chemical and physical attacks. Therefore, it has been widely used in automobile windows.

Indium–tin oxide coatings via chemical solution deposition

Thin films of indium-tin oxide (ITO) were formed on glass substrate via a chemical solution deposition method. Indium nitrate coordinated with 2,4-pentanedione and ethylene glycol, and tin oxalate were used as the raw materials of the coating solution. Composition ratios of Sn/In were varied between 0 and 14 mol%. The solutions were coated on non-alkali glass substrate using a spin-coating process. Then, the coated glass was fired in air to thermally decompose the precursors and to densify the coating. The resistivity of the coatings fired in air at 300°C was 5.0 Ω cm and decreased at higher firing temperatures. The resistivity of the coatings fired at 700°C was 2.8 × 10 -3 Ω cm, which is more than 10 times higher than that of ITO coatings formed by the sputtering process. A post-annealing in non-oxidizing atmospheres such as vacuum, N 2 , Ar and H 2 /Ar after the firing lowered the resistivity of the coating. Treatment in hydrogen-containing atmosphere was particularly effective in lowering the resistivity of the coating to 6.2 × 10 -4 Ω cm. It was found that the decomposition of organic residues and formation of oxygen vacancies in the coatings were promoted by the hydrogen treatment.

Wet chemical functional coatings for automotive glasses and cathode ray tubes

Abstract Wet chemical coatings are applied to automobile glass and CRTs to provide new optical, electrical and chemical functions on their surface. Examples of the practically used functional wet chemical coatings are colored and water repellent coatings on glass for automobiles, and antireflective–antistatic and antireflective–electromagnetic wave shielding coatings on CRTs. Performance and composition of the various wet chemical coatings as well as the technology trends will be described in this report.

Photochromic coatings including silver halide microcrystals via sol–gel process

Abstract Photochromic coatings including silver halide microcrystals were formed on a glass substrate via the sol–gel process. 3-Glycidoxypropyltrimethoxysilane and methyltrimethoxysilane were used as starting materials of the ormosil matrices. The 3-chloropropyltrimethoxysilane and bromophenyltrimethoxysilane were added as halogen sources and silver colloidal dispersions were introduced into the precursor solution. The precursor solution was applied using a spin-coating process on a silica buffer layer which prevents Ag + migration into the glass substrate. The coated glass became transparent and photosensitive after Ag(Cl 1− x Br x ) microcrystals were precipitated in the coatings above 300°C. However, fading reaction did not proceed at room temperature. It was found that the deposition of a sensitizing layer including cuprous ions on the photosensitive layer was very effective in promoting fading reaction at room temperature. The cuprous ions in the sensitizing layer penetrated and diffused into the photosensitive layer during coating and firing. The cuprous ion located near or in the Ag(Cl 1− x Br x ) microcrystals acted as an effective sensitizer.

Photochromic Coatings Containing Ag(Cl1−xBrx) Microcrystals

Photochromic ormosil coatings containing Ag(Cl1−xBrx) microcrystals were formed on a glass substrate via the sol-gel process. Methyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane were used as starting materials of the ormosil matrices. 3-chloropropyltrimethoxysilane and bromophenyltrimethoxysilane were added as halogen sources and silver colloidal dispersion was introduced into the precursor sol. The coated glass became transparent and photosensitive after Ag(Cl1−xBrx) microcrystals were precipitated in the coatings above 300°C. Insertion of a SiO2 buffer layer between the substrate and photochromic layer was effective in preventing Ag+ migration into the substrate. Photochromic performances were improved by the substitution of Cl with Br and the incorporation of a minute amount of Cu.