Siloxane Oligomer with Random Structure for Use in Photosensitive White Decorative Coatings

A siloxane oligomer (Si-OLIGO-1) was produced by introduction of a bifunctional alkoxysilane into a silsesquioxane composed of a trifunctional alkoxysilane. The oligomer, which can form a thick film, was synthesized by a sol–gel method. This organic/inorganic hybrid material had good transparency and heat resistance. Infrared absorption spectroscopic analysis indicated that Si-OLIGO-1 had a random structure with many acidic silanol groups capable of alkaline development. A novel negative photosensitive white decorative coating that consisted of Si-OLIGO-1 as the base resin and 40 wt% TiO2 (particle size 250 nm) as a white pigment was produced. The coating enabled facile complex decoration. A white cured film of thickness 10 µm had the brightness (L*) and color (a*, b*) required for the white frame of a display product. Although the coating did not transmit straight light of wavelength 300–700 nm, it gave a good patterning performance (resolution and pattern shape) on irradiation with ultraviolet light at a dose of 200–250 mJ/cm2. This is because it transmitted both g-line and h-line scattered light.