Antireflection film made of a CVD SiO2 film containing a fluoro and/or alkyl modifier

摘要

A low refractive index SiO₂ film is provided which uses a starting material for forming an SiO₂ film and has a lower refractive index than the conventional SiO₂ film. ;A starting material gas comprising a gas containing a fluorine atom, a gas containing a silicon atom and an alkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms with a part or the whole of hydrogen atoms substituted by a fluorine atom, and a gas containing an oxygen atom is subjected to plasma CVD in a vacuum chamber 1 to form an SiO₂ film on a web 2 in a plasma zone 5. The SiO₂ film thus formed has, introduced thereinto, at least one low refractive index element selected from a fluorine atom, an alkyl group having 1 to 4 carbon atoms, and an alkyl group having 1 to 4 carbon atoms with a part or the whole of hydrogen atoms substituted by a fluorine atom, and the SiO₂ film with the low refractive index element introduced thereinto has a lower refractive index than an SiO₂ film with the low refractive index element not introduced thereinto.