| 摘要 |
PURPOSE:To form a silicon dioxide film with excellent productivity by bringing a base plate into contact with the treatment liquid wherein silicon dioxide is made to a supersaturated state by adding boric acid to an aq. fluorosilicic acid soln. dissolved with silicon dioxide that is obtained out of silica glass, silicate glass and silicon chloride as a feed source. CONSTITUTION:An immersion vessel is constituted of an outer vessel 1 and an inner vessel 2 consisting of a front part 6, a middle part 7 and a rear part 8. Water 3 is filled between the outer vessel 1 and the inner vessel 2 and heated at about 35 deg.C with a heater 4 and an aq. fluorosilicic acid soln. dissolved with silicon dioxide which is obtained out of silica glass, silicate glass and silicon chloride is fitted in the inner vessel 2 and a base plate 9 is immersed in the middle part 7 thereof. The treating liquid is drawn out from the rear part 8 of the inner vessel in regular quantities by actuating a pump 10 and returned to the front part 6 through a filter 11. On one hand, an aq. boric acid soln. is dropped into the rear part 8 and silicon dioxide contained in the aq. fluorosilicic acid soln. incorporated in the inner vessel 2 is supersaturated and thereby silicon dioxide film is formed on the base plate 9.
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