Silica-magnesium fluoride hydrate composite sols and process for their preparation

摘要

A sol comprising silica-magnesium fluoride hydrate composite colloidal particles used in an anti-reflection coating material for forming an anti-reflection coating and a process for its preparation are provided. A sol comprising silica-magnesium fluoride hydrate composite colloidal particles having a ratio of silica to magnesium fluoride hydrate MgF2.nH2O, n being in the range between 0.25 and 0.5, in terms of a SiO2/MgF2 weight ratio of from 0.01 to 5 and a primary particle size of 5 to 50 nm. A process for the preparation of an aqueous sol comprising silica-magnesium fluoride hydrate composite colloidal particles which comprises the steps of adding an aqueous fluoride solution to a mixture liquid of a silica sol and an aqueous magnesium salt solution to produce a slurry of an agglomerate comprising silica-magnesium fluoride hydrate composite colloidal particles and removing the salts formed as by-products. A process for the preparation of an ogranosol further comprising the step of replacing water in the aqueous sol with an organic solvent.