Patent attributes
Glass can be synthesized and deposited at a high rate by the inside CVD method using a plasma burner in a manner such that unconsolidated portions or bubbles are little generated. The method includes a step of depositing a glass film on the inner wall surface of a starting pipe. In a first aspect, temperature the pipe is controlled not to exceed (1800 +100xd)° C., a temperature of (1100 +100xd)° C. or higher being continued for 20 seconds or more at each point of the pipe, where d (mm) represents the wall thickness of the pipe. In a second aspect, the burner includes at least two inlets and has an inner diameter of 80 mm or more, and the deposition step is performed in the relationship, 150 mm/s <(Total flow rate of the gases introduced into the burner)/(Sectional area of the burner) <600 mm/s.
